The Offshore Voyaging Reference Site

Hull Materials, Which Is Best?

As Phyllis and I think about what our next boat might look like, one of the primary decisions is hull material.

We have several chapters in this Online Book about the characteristics of the four general available options, steel, aluminum, wood and fibreglass (see Further Reading below), but that still leaves the question: Which is best, not just for Phyllis and me, but for you, too?

As usual, the answer is the oh so annoying: it depends on what we plan to do with the boat.

But what I can say, is that there are two materials that are pretty easy for Phyllis and me to drop from the hull materials prospect list. So let’s start with that, and then move on to the two left standing to pick a winner.

Hull Material We Won’t Consider

We will not even be looking at boats made of steel or wood—not quite true, we might consider a good wood epoxy saturation build—and that’s also our advice to most of you.

Why neither of those two materials? Both are intrinsically unstable. Or, to put it another way, no matter how well the boat is built, if left to their own devices, wood will rot and steel will turn into a pile of iron oxide.

OK, before you take me to the woodshed in the comments, let me make clear that I understand that good boats can be built of both wood and steel.

One of my good friends has a wooden boat that has given great service (including a bunch of ocean crossings) for decades, and will continue to do so for many more. But he built her himself, has cared for her meticulously, and has incredible skills. But I’m not Wilson (that’s his name) and, in all likelihood, neither are you.

The same applies to steel. If you built the boat yourself, or supervised every step of the build, and then cared for her yourself, it can work. Just look at the amazing voyages made by AAC contributor Trevor Robertson in Iron Bark.

But we are talking about second-hand boats for most of us, so steel and wood are out because it’s difficult to be reasonably sure in a pre-purchase survey on either material that something horrible is not going on deep within the structure. Something that, when discovered, can turn our new-to-us boat into a worthless pile of junk—we are talking the risk of serious wealth destruction here.

Still not convinced? Let’s dig deeper.

There’s another big problem with wood. If we find say a rotten stern post, or any other structural member after purchase, the skills and time to replace it are prodigious. Heck, just replacing a single plank in a way that will actually be watertight takes great skill and perseverance. Way beyond practical DIY for most of us. And I have seen professional replacement of just a few rotten members in a wooden boat cost over US$100,000.

What about steel? Well, on the positive side, repairs require less skill than wood. But the problem is it is very difficult to build a boat of steel under about 45 to 50 feet that will sail or motor well. The reason is that steel plating must be of a certain minimum thickness to be workable and not deform, regardless of boat size, so small steel boats are pretty much always too heavy, at least for the performance that Phyllis and I want.

And, finally, the maintenance of a steel boat is simply no fun—unless you have some perverted love of chipping rust and working with toxic chemicals—and to make that worse, any breach of the coating must be dealt with promptly and properly.

The bottom line is that I know a lot of people who own a steel boat, or have done so in the past, but I have never met anyone who has owned a second steel boat.

All that said, I guess purchasing a steel or wood boat with a history like those I mention above, from someone you really trust, would be OK—particularly if you make clear that if they have lied to you, you will hunt them down and… And the advantage of this course is that you can often get a lot of boat for very little money.

But be careful…really, really careful. And know that you have consigned yourself to a heavy maintenance burden for as long as you own the boat, as well as taking on a boat with a resale value that could easily go to near zero.

Hull Materials We Will Consider

Where does that leave Phyllis and me, and probably you, too? Yup, with fibreglass and aluminum. Both are intrinsically stable—assuming we don’t do something stupid, and, when built right, a hull of either does not deteriorate just because of the passage of time.

And both can be surveyed prior to purchase to make fairly sure (there is no certainty) that there is not something horrible lurking. Yes, I know there are many horror stories (I have one of my own) about fibreglass boats with hidden faults, but that’s a survey failure, not a material one. (More on how to avoid survey failures coming soon.)

So which is best, aluminum or fibreglass? Brace yourself. I’m going to do it to you again. It depends on what you want to do. Let’s look at each.


As a 30 year aluminum boat owner, I love the material. And if Phyllis and I were planning to go to seriously hazardous places (as we have in the past), aluminum would be our only choice.

There is simply no other material that can match the combination of strength-to-weight ratio, impact survivability, stiffness, and keeping those characteristics for decades, all without the horrible maintenance load of steel. This is probably the reason that by far the majority of experienced high latitude sailors that we have encountered over the years have aluminum boats.

But on the other hand, aluminum is a bitch to keep paint on, an expensive bitch. And, by the way, don’t think for a moment that leaving the hull bare solves that. Prepping and painting the deck and cabin of an aluminum boat to the yacht standard that many owners want and want to maintain, will, if done right by professionals, cost as much or more than painting an entire fibreglass boat.

The point being that if you are considering aluminum, you need to do as I do: take your glasses off when you see the paint bubbling. Or, better yet, seriously embrace the industrial look and have no paint on deck or hull, other than non-skid.

Also, although there is no question that most of the horror stories you hear about aluminum are just that—stories—the material does require caring for, including closely supervising anyone who works on the boat. Most boatyard professionals are dangerously ignorant about aluminum and many will make that worse by not appreciating their own ignorance.

All that said, if you want the ultimate voyaging boat built in the ultimate material, and you have some big bucks to spend, buy a Boreal 43/47 in aluminum, and be happy. And you may be able to buy a good used Garcia or Ovni for much less.


So that leaves fibreglass. And for Phyllis and me, who now want a boat that we can safely leave unattended far from home—we are now part-time cruisers—that’s the way to go.

Also, as we age further, we will be paying boatyards to do more and more for us, another plus for fibreglass, since it’s more resistant to unsupervised ignorance—boats with core in the hull, particularly balsa, not so much—than aluminum.

Bottom line, if you are not willing to learn the basics of aluminum boat care and won’t be constantly present to rigorously enforce that knowledge on others, choose fibreglass. On the other hand, the good news is that said aluminum boat care is not hard, and not magic. See Further Reading for our complete guide.


So, to wrap this up, when buying a second-hand boat, good old frozen snot is the baseline and aluminum the ultimate, but with caveats. As for steel and wood, the great majority of us should not go there.


I’m guessing that many of you steel boat owners are now seething and reaching for your keyboards to tear me a new one. Feel free to disagree and tell me why steel is great, but be realistic.

And please keep in mind that we have a lot of readers who do not have a lot of boat ownership experience. So if you blow sunshine about the issues with steel boats, particularly old steel boats, you may make yourself feel better, but you may also tip someone into a life altering decision with substantial negative consequences. Not something any of us need on our conscience.

Further Reading

More Articles From Online Book: How To Buy a Cruising Boat:

  1. The Right Way to Buy a Boat…And The Wrong Way
  2. Is It a Need or a Want?
  3. Buying a Boat—A Different Way To Think About Price
  4. Buying a Cruising Boat—Five Tips for The Half-Assed Option
  5. Are Refits Worth It?
  6. Buying a Boat—Never Say Never
  7. Selecting The Right Hull Form
  8. Five Ways That Bad Boats Happen
  9. How Weight Affects Boat Performance and Motion Comfort
  10. Easily Driven Boats Are Better
  11. 12 Tips To Avoid Ruining Our Easily Driven Sailboat
  12. Learn From The Designers
  13. You May Need a Bigger Boat Than You Think
  14. Sail Area: Overlap, Multihulls, And Racing Rules
  15. 8 Tips For a Great Cruising Boat Interior Arrangement
  16. Of Cockpits, Wheelhouses And Engine Rooms
  17. Offshore Sailboat Keel Types
  18. Cockpits—Part 1, Safe and Seamanlike
  19. Cockpits—Part 2, Visibility and Ergonomics
  20. Offshore Sailboat Winches, Selection and Positioning
  21. Choosing a Cruising Boat—Shelter
  22. Choosing A Cruising Boat—Shade and Ventilation
  23. Pitfalls to Avoid When Buying a New Voyaging Boat
  24. Cyclical Loading: Why Offshore Sailing Is So Hard On A Boat
  25. Cycle Loading—8 Tips for Boat and Gear Purchases
  26. Characteristics of Boat Building Materials
  27. Impact Resistance—How Hull Materials Respond to Impacts
  28. Impact Resistance—Two Collision Scenarios
  29. Hull Materials, Which Is Best?
  30. The Five Things We Need to Check When Buying a Boat
  31. Six Warnings About Buying Fibreglass Boats
  32. Buying a Fibreglass Boat—Hiring a Surveyor and Managing the Survey
  33. What We Need to Know About Moisture Meters and Wet Fibreglass Laminate
  34. US$30,000 Starter Cruiser—Part 2, The Boat We Bought
  35. Q&A, What’s the Maximum Sailboat Size For a Couple?
  36. At What Age should You Stop Sailing And Buy a Motorboat?
  37. A Motorsailer For Offshore Voyaging?
  38. The Two Biggest Lies Yacht Brokers Tell
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Henry Rech


What are the hull and deck panel thicknesses on MC?

Ernest E Vogelsinger

I hear your warnings about steel, and I know this might be a complicated route to go.
My main reservations about fiberglass boats is that the majority of them come with external keels which is fine for me for a one or two weeks charter but something I absolutely do not want for my own future boat.
Encapsulated keel structure (or welded on as with steel hulls), a deep V forefoot, and a rugged skegged rudder, are characteristics that can more often be found with steel hulls as with “plastics”.
When going for my survey I plan to come with a fiber optic to inspect all those remote places, and would certainly rule out a boat where I would not have access to most if not all hull places.
That said, if I were to buy now, my current favourite on the market is a fiberglass ketch 😉

Patrick Kelly

Hi John—

Agree with everything you say about steel boats. When I got back from Vietnam in 1969, I took all of my savings and bought a steel 45 steel schooner and lived on her. I went to work at the Naval base in Pensacola, FL and left my wife to chip, sand and paint the rust spots that seemingly appeared almost every day inside and outside ( no wonder she divorced me! ) I finally sold the
boat to a “know it all” and bought a Hinckley 50 fiberglass yawl — problem solved!

Eric Klem

Hi John,

I totally agree with your conclusions on this. No material is perfect but fiberglass has a lot to be said for it overall and aluminum is great when a bit extra is required. Aluminum is actually the only material you have listed that I really don’t have much experience with beyond little skiffs so it is the one I can’t properly comment on but I like the concept.

I have had a lot of interactions with wooden boats including having a good sized one in the family and working aboard several. While I love these boats and think they look great, our boat is fiberglass and that is intentional. For that matter, our boat doesn’t have any wood on deck at all. With wooden boats, like most things, it really comes down to who the owner is. An owner who gets it and stays ahead of maintenance puts in surprisingly little time (still a whole lot) dealing with rot and paint that won’t stick. An owner who is a little less vigilant and deals with a deck leak by hanging a diaper under it rather than getting out their irons to fix it will find the boat falls apart on them incredibly quickly. In my experience which is all salt water based, deck leaks are the biggest killer of these boats by far and they are actually comparably one of the easiest to track down and fix. Even for an owner who farms out the wood work, I would say that if you can’t fix a deck leak and don’t have oodles of money, then it is a disaster waiting to happen.

With steel boats, all I have to say is that I hate the sound of a needle scaler. If you have a ton of money, there are great examples like the Columbia replica but that is not attainable for most of us.

I realize that there are a lot of people who get very nervous with keel bolts (and bolts in general in anchors and other things) and while it is something to watch, I think that it is a good trade-off given the other options. I think that a lot of the issue is that the average person does not know how to evaluate whether a bolted connection is a good connection and there have been an awful lot of poor connections built over the years. An example of a good connection is most connecting rod bolts which have enormous numbers of cycles, vibration and other factors to contend with but yet basically never fail unless there is another underlying issue such as the caps being mixed up. By getting the bolt stretch length long enough, using appropriate materials, having appropriate mating threads and using enough torque/tension, you end up with bolts that don’t back out and do not fatigue. Keels are a bit tricky as very few materials won’t suffer from some sort of corrosion if there is any water and fiberglass creeps so it is difficult to maintain constant tension but I think that you would find an extremely low failure rate on well designed connections and that most of the failures were on connections where an analysis would have shown that the margins were low and best design practices were not followed.


Matt Marsh

I would make no such assumption about the keel bolts. They may be seized, in which case you’ll see the correct reading on the torque wrench but the pre-load tension in the bolt will be wrong. They may also be partially corroded, in which case they may withstand the torque but still be capable of failing in tension if the boat were to, for example, ground on a reef.

If it’s possible to get at them to check their torque, it shouldn’t take much longer to completely remove the nuts, one at a time, to check the studs or the cavities for signs of corrosion before re-torquing them to the proper specs. If it’s not possible to do this, then it’ll be difficult for *any* non-destructive examination to reveal what you want to see.

Rob DesMarais

Pull a few and inspect is probably the only real way to to be sure. At least this is done on a woodenboat.

Eric Klem

Hi John,

Ignoring whether a seller will or should allow retorquing keel bolts, the theory is good but the practice is somewhat more problematic. Proof testing is a well established industry practice that has proven to be pretty effective. Periodic hydrotesting of pressure vessels such as boilers, tanks, etc is just one example of something that has been successful at eliminating a lot of dangerous failures.

The first practical issue is what torque do you apply. I design capital equipment not sailboats so don’t know exactly what is done as there are multiple schools of thought but if I were designing one of these joints, I would figure out my worst case loads, choose a preload of ~2X and then upsize the bolts from there a bunch to give a corrosion allowance but not increase the preload any more. The question is, what was done on the boat you are looking at. The average person does not have the knowledge to calculate what the maximum per bolt load is and then we don’t know the factors from there. I suspect that there are some boats out there where the torque value from the factory is 75% of yield just like most bolts are but I also suspect there are a lot of boats out there where the preload will be more on the order of 30% (I have it written down at home but I believe this is approximately what I calculated for ours with the assumptions I made). In the case where the designer did not leave a corrosion allowance, then a torque to 75% of yield is entirely appropriate but on other boats, you could break a bolt which while corroded was actually still well within allowable parameters or you could crush the laminate if there is insufficient load distribution for the higher tension. All of this can be calculated with fairly simple calculations but having anybody without training apply it is problematic and even then, you are really doing a proof test not just a retorque as you likely won’t know the original torque. If anyone knows of a standard that all designers hold to so a way to avoid the guessing game of the factory torque, I would love to know it.

The other practical issue that comes to mind is the imperfect relationship between torque and tension. Engineers refer to this relationship as K factor which is basically friction between the threads and the faces. When tension is really critical, the standard thing to do is to actually use oil or grease which are more repeatable and represent a lower K factor. If there has been any galling at all which is a real problem with stainless, all bets are off and you could even break the bolts before bottoming out if it is really bad. This is really the long way of saying that it is really inexact if you do it dry, you would really want to clean everything well and then oil the threads. Of course, if you are NASA, then you can actually measure tension on the bolts but everyone else is left using torque as a proxy.

Given all of this, I am not sure that most sellers could be made to agree to a specific torque number unless original build documentation can be found with a number which I don’t think that I have ever seen (unfortunate and kind of scary). Retorquing is definitely not a bad idea and I have done it on our boat, I just don’t know how to implement it simply and quickly unless someone knows that all keel bolts were originally torqued to some % of yield or something equivalent.


Ernest E Vogelsinger

John, you just elaborated very wisely the reasons why I will certainly not be looking for a boat with an external keel. You just can’t look inside (and I doubt even industrial xray could reliably see cast-in bolts). It is just like playing lottery, and what I learnt is at least that I will never win 😉
You’re right that encapsulated ballasts have their own issues, but at least they cannot fall off during a passage.

Rob Gill

Hi John,
Your question highlights for me that another valid comparison (apart from hull material) might be long run production boats vs short run / custom boats.
Long run production yachts of course favour fibreglass of course and tend to have more than a few things worked out over time – one of which is to make them as “charter friendly” (aka idiot proof), as possible. But am I right in my supposition that for this reason, most long run production boats will have steel keels, secured with stainless bolts tapped down into the metal keel? And short run designs (not generally being for charter markets) take advantage of the performance gain with lead keels, but have studs penetrating up through the hull, with securing nuts?
Reading between the lines of Matt and Erics’ responses, it seems you must remove the keel to really check the studs on a lead keel and even then there could be something lurking deeper inside.
Conversely, to check the keel bolts in a steel keel yacht, you could simply specify removing say 25% of the bolts at pre-purchase survey time. For total peace-of-mind, replacing all the keel bolts on our Beneteau 473 with original OEM bolts costs about $200 US, available ex-stock from the Beneteau Spares web-site (as are most other parts by the way, even now 15 years since launch).
Now I get there are pro’s and cons of lead vs steel keels. But the simplicity and integrity of a steel keel is really hard to beat. I know of a Beneteau 473 that hit a rock doing 8-9 knots under motor, coming to a crash stop. The only damage the surveyor could find on the Monday (up on the hard) was a fleck of anti-foul chipped off. No gap in the hull joint, no weeping at the keel / hull join, no cracking in the anti-foul. Internally, no damage to the lay up or the supporting girders either. No harm, no foul as they say in America.
So how about a long run production boat, John?
br. Rob
ps – no, it wasn’t our B473!

Matt Marsh

I think you could get pretty good contrast and detail of a set of keel bolts in cross-section via X-ray, given sufficiently high quality X-ray equipment. And if the X-ray crew has access to a megavoltage source like Co-60, you’ll be able to see the bolts cast into the lead quite clearly.

This is not going to be cheap, however. And whether it tells you anything useful will really depend on the exact design of that particular boat.

You could try ultrasound, but that’s highly dependent on the technician’s skill and on the access situation for that hull.

If stainless steel, or galvanized mild steel, bolts are cast into the keel (forming studs that protrude into the boat), and there’s evidence of water intrusion, then I think dropping the keel a few inches is the only reliable way to tell the extent of damage.

With lead keels, bronze bolts are definitely the correct choice; the bronze/lead combination is basically indestructible for more than the life of the hull.

Galvanized mild steel bolts with a cast iron keel also seem to be OK as long as the bolts are accessible for periodic replacement, and I’d definitely undo one or two to check during pre-purchase survey. Stainless makes me nervous. Bronze bolts with a cast-iron keel make me nervous.

Don Casey has a good article on assessing keel joint issues here:

Henry Rech


Thanks for posting link to Don Casey’s article.


Eric Klem

Hi John,

I was worried what you would ask what to do about it. Unfortunately, I don’t have great ideas beyond actually taking a look. I work on the design side of things and so don’t know a lot about non-destructive testing other than where I need to make allowances for it to be done (this is something that is definitely not done in the design of these joints). My experience with X-ray is limited to inspection of welds and castings and I am not sure how it would work on keel bolts so I can’t really add anything beyond what Matt said. I believe that there are also design solutions to make this a much smaller concern that could involve changing materials, designing to be inspectable, designing to be repairable (iron keels that are tapped and bolted from the top being an example), etc but that doesn’t deal with the already built boats.

In my case, there are a few things that made me feel comfortable with our boat. Looking at the ISAF statistics compiled in 2013, of 72 recorded keel failures, only 3 could be attributed to the bolts (important to note that 40 were undefined so the actual number could well be higher). Weld failures, and internal structure failures both had a more than double incidence ratio. I actually find this failure rate pretty low given the number of poorly designed (or designed with low margin for racing), poorly maintained and poorly repaired joints out there. Our boat has a pretty conservative keel attachment, the lever arm is small and the attachment is wide in both directions and the bolts are large. Given that, I calculated the required bolt strength and then looked at the bolt size on our boat and concluded that the designer had been appropriately conservative in upsizing to allow for corrosion. Next, our boat did not show any of the problem signs such as large rust streaks, signs of grounding damage, etc. Finally, I did exactly the test that you were hoping to do which is a torque test on all of these bolts (note, this and all the calculations were done post purchase) to values I calculated and felt comfortable with. Obviously this is not perfect but has mitigated the risk to a level where I feel there are other more important places to put my efforts.

Actually pulling the keel in a properly equipped yard is not that big of a deal, often on the order of what people spend on electronics for the boat. What becomes really problematic is if the bolts are found to be compromised to the point where they must be replaced. Given our location, I would contact Mars Metals if I ever got to this point. For people who do not live near a facility like this, it gets more tricky. I have limited experience installing bolts from the bottom of a keel and I could see it working in some instances but not all.


Rob Gill

Hi John, thought I should address the keel questions for anyone considering a Beneteau cruiser and reading this.
Cheeki Rafiki, was a Beneteau First designed primarily as a racer / cruiser. They have light hulls and rely on a structural liner for much of their hull rigidity, with bulkheads and “furniture” glued in. In the main, the boats are fit for purpose and they don’t have a history of losing their keels, even though there seems to be a serious question over the keel to hull design. I personally wouldn’t sail one offshore but would have no hesitation in owning one around the NZ coast, if I raced more.

The Beneteau Oceanis 473 was designed by Beneteau as their offshore model and as I have heard it told, the model was built to help alter their “bendy Beneteau” reputation. The Clipper Oceanis range (of which the 473 is one), are the last of the all hand laid fibreglass models before European regs changed to enforce epoxy, vacuum bagging and sandwich construction. The hulls were built super-thick of solid glass fibre and more so around the keels and other high stress areas. 473s then have massive supporting girders glassed into the bottom of the hull. The bulkheads are also glassed in not glued. The flanges of these girders are wide to improve the hull bonding and spread the keel load. Around the front and back of the keel area, the girders are only about 250 mm apart. The keel bolts go through both the girder flanges and the hull. Unlike the First, the 473 in particular has a much wider keel base and a double row of bolts (single row on the First). Comparing the two boats for offshore use, is like comparing a Toyota MR2 with a Toyota Land Cruiser – built for two very different things. My experience with owning a Beneteau is the QA processes were (are?) excellent, but I must add inspecting one or two bolts a year to my maintenance list. I haven’t so far because we run a dry bilge and the bolts are like new.
And John, therein lies an opportunity for an astute buyer – there are gems in most production yacht manufacturer’s ranges, just as there are bad’uns. It is finding those good’uns that can pay off – the 473 is an absolute diamond.
best regards

Richard Elder

Hi John,
Why do sailboat keels smile? Because they are thinking about how much fun it would be to swim freely in the ocean like the dolphins, free of the heavy burden on their backs!

Chris Fedde

Of course we all know that GRP is forever. Even after you scrap the damn thing it’ll still be recognizable land fill or artificial reef for the next thousand years. Still there is one other material that deserve a passing derisive remark: Concrete. It’s a material used exclusively by amateur builders that never seems to survive the first owner.

Andre Langevin

Insurance company do not underwrite concrete boats in Canada. Not sure of USA. Since they need civil responsibility, place are limited for an owner. Altough it was a most decent material, well insulated, cheap, partially insulated.

Philip Wilkie

For what it’s worth Joe Adams (the designer of our boat) had his first big success with the original Helsal that was a ferrocement boat. It smashed up records for the Sydney Hobart classic and was forever known as the ‘Flying Footpath’.

Andre Langevin

Ask any physicist about the stability of Aluminum alloy and they will say ; the aluminum stability derive from its oxyde layer which is the strongest material on earth after diamond. Thus any object built of aluminum alloy should make sure that oxyde layer is preserved. A simple piece of wood on an aluminum plate staying outside in the rain will get holed in a few months and will prove you that it can be attacked easily once the Al2O3 layer is depleted in oxygen poor environment. And aluminum is born of electricity and can be destroyed by electricity.

The ebook should have started with the french joke: Circumnavigators knows that 50 % of the boat going around the world have a metal hull, the remaining are US boats.

Each aluminum boat is a unique closed loop battery and had to be kept under cathodic state under all conditions. Some boat well builts have it naturally, some others don’t and with maintenance mistakes, this is were horror stories come from.

I am not found of polyester boats because the environnmental cost of getting rid of those tons of plastic polluants at the end of life have never been taken into consideration is the first price. Polyesther fiberglass is not recyclable. We are just pushing the problem forward to the next generations. One day not to far someone will wake up and put environnemental cost on the new GRP production boat and people will realise its not cheap.

Wood as said before, is only up to the maintenance made. My marina neighbor has a magnificient wood boat that he built himself, on the plan of Joshua. He told me last weekend, 6000 to built and 6000 hours to maintain since 30 years. A tribute to those brave men.

Steel… if only the genius of the french architects who recommended to build hulls in steel and the deck and infrastructure in stainless would have been more commonly communicated, we would have less steel boats relics today. 95 % of the paint maintenance of a steel boat is on the deck. A steel hull/stainless deck has about 1 hour of touch up maintenance every year (for all those logs and obstacles hit on the water)

Thus for metallic boats ultimately the material is not the problem, its the way it has been put together and maintained. A production aluminum sailboat could be the perfect boat for circumnavigators. For some specific usage, only steel can survive. This special boat is quite an achievement, almost 20 years in the polar sea:

(Of course i am biased i have a year of mechanical engineering classes in material resistance and my full welding certification for both Aluminum alloys, Steel and 304 and 316 stainless on conventional SMAW and also on GMAW and GTAW.)

Andre Langevin

Hi John at the marina were my boat is (Québec city) we had to get rid of an old 30 feet fiberglass sailboat unused and leftover. The city environmental personnel came in and said we could not use the city garbage service and it had to be destroyed on site and buried in a special area (city owned) for about 100$ per ton. It ended up costing us 2000$ to get rid of this boat. If it would have been alu or steel people would have paid to pick it up.

If course Quebec is very serious with garbage and landfill management and not all jurisdictions are equal. But the trend has started here…

As for alu alloy indeed 5083 is a magic material if properly maintain. I did own a 34 feet powerboat for 6 years in my auxiliary coast guard previous life and there was a corrosion meter on the dash of it (silver anode isolated under water connected to the hull) and the owner book went to great lengths explaining the potential issue. At sea no problems because electrolytic voltage are low. But I had a AC current leak from the battery charger once and I noticed a month later(boat in water) tiny droplets of water appearing at the inside of the hull in the engine room just over the propeller. I wiped it everyday and when I hauled the boat out it could be seen from outside that the aluminum was severely pitted at 3 places… almost 1/8 depth. I had to replace and reweld the plate… it was full of tiny holes. I had magnesium anodes on the boat ant they were untouched. So it was galvanic corrosion at its worst. One season…

I agree it’s a worst case scenario but I was a first line witness of it. In this case the corrosion meter didn’t showed any problem although a problem was occurring.

Do you have a corrosion meter on MC?

This being said I would not be nervous of having another aluminum boat built of marine grade alloy by professionals- it’s is certainly the best boat material if properly built and maintained.

Philip Wilkie

Having a strong electronic/electrical background like John, I’d like to reinforce his point on isolation transformers. It’s my view they should be mandatory on all metal boats, and considered highly desirable on all others. They serve at least three safety critical purposes:

1. The obvious one is that they isolate the ground loop to the shore power ground. Essential to prevent electrolysis and ensuring swimmer safety.

2. They provide inherent shore power reverse polarity protection. This is often an overlooked and not very well understood benefit.

3. The secondary of the transformer effectively becomes a ‘local power source’ and the neutral bonded to the boat hull ground. This provides a rock solid ground path for the boat that is independent of the shore power ground. This is essential to ensure any Earth Leakage/Residual Current Balance protection devices will work reliably. Depending on a shore ground loop that may have multiple cables and connectors, all subject to corrosion and miswiring, is a hidden and underestimated danger.

While the first attribute is highly relevant to metal boats, the second and third are common to all. Probably most boats don’t have an isolation transformer, and if they all were beautifully wired to a high standard it’s a compromise I’d be more sanguine about. But isolation transformers aren’t expensive in the wider scheme of things, and from an electrical perspective I regard them as the single most valuable investment you can make.

Andre Langevin

Hi John indeed it didn’t had an insulation transformer, and i took care of installing a Victron one on my steel sailboat. The anodes barely work on my boat i have the same since 2011 🙂

Alastair Currie

GRP is recycled in Europe and on an industrial scale. Additionally GRP boats are deposited in land fill, cut up, as it is considered inert. In the UK land fill sites are now sealed for future reclamation as well as the avoidance of leaching. Regarding recycling, it is not commercial for smaller batches but tends to be the waste streams from large GRP users.

Andre Langevin

Thanks Alastair for the information, Europe is in advance on us ! Indeed fiberglass is most inert … but 10 000 years later we don’t know… probably it would still be there !

Fair winds


You have [predictably] left out Ferro Cement – order should be (I owned a Ferro Cement yacht for many years so speak from experience)

Ferro Cement

Donald Joyce

As my wife reminds me every time I look at a “beautiful” steel boat: “Rust never sleeps”

Andre Langevin

Donald that is also true for everything apart gold, platinum,titanium and a few other incorruptible elements.

We human live in the bottom of an air ocean and the O2 is a powerful oxydant. By chance is it diluted in nitrogen because otherwise we would have all burned including everything around.

Oh and that brings a point. A steel and férocement boat would survive a fire but others not. GRP is like a gallon of gasoline waiting for its match…

Richard Hudson

Hi John,

I’ve had three steel cruising boats, two of which I’ve cruised extensively with. Each were bought used, 20 or more years after they were built. If I was in the market for another boat, I’d definitely consider a steel one.

Everything depends on how the boat was built and maintained.

My current steel boat was built very well, with no longitudinals to trap water, and–more importantly–flame-sprayed with zinc inside and out (properly-prepped & applied epoxy coatings can be almost as good as this). Rust is not a problem with this boat.

Yes, there are poorly built and/or maintained steel boats that will require a lot of work to go sailing (and may not be worth restoring). I think that holds true for any hull material–a couple of years ago I was offered a once-beautiful boat, professionally-built of fibreglass, effectively for free. I turned the offer down. The boat had been neglected, and while the solid fibreglass hull was undamaged, the plywood bulkheads and most of the interior had rotted due to water sitting inside the boat (it was left unattended in a boatyard for a few years).

A steel boat with:
* properly-applied coatings,
* easy access to most areas (to all areas would be best, but realistically, you’re unlikely to remove tanks to inspect the plating under them unless you suspect a problem),
* few or no areas where water can sit,
shouldn’t be a maintenance problem.

Everyone I’ve met with a stainless steel deck, as Andre mentioned above, has had good things to say about them (none of my boats had stainless steel decks, so I don’t speak from personal experience, here).

It is true (and important) that damaging the coating on a steel boat requires fixing it promptly (how promptly depends on temperature–corrosion happens very slowly below freezing). Zinc coatings on the steel have some advantage here (if underwater), as the zinc migrates to the bared area electrolyticly, but this is only for small scratches. POR-15 (buy some small cans before leaving North America, as it isn’t all that widely available), a coating developed for the antique car restoration market (which deals with thinner steel plate), makes maintenance painting of damaged areas much easier, since it doesn’t require sandblasting before applying.

>This is the reason that by far the majority of experienced high latitude sailors have aluminum boats.
Are you sure of that? When I went thru the NW Passage, there were more steel boats than aluminum boats. In Antarctica, I don’t recall aluminum boats outnumbering steel boats. In Patagonia, I saw more fibreglass boats, and roughly equal numbers of steel and aluminum ones.

Steel probably isn’t suitable for you, because you are looking at buying a considerably smaller boat than the one you have. But for someone looking to cruise long distances, high latitudes and remote places, a used steel boat could be a good choice. It all depends on the construction and maintenance that has been done, and that’s something that mostly can be determined before buying.

Best regards,

Richard Hudson

Hi John,

Yes, two professional, high-latitude sailors, Skip Novak & Hamish Laird have moved to aluminum charter boats after extensive experience with steel ones. I think most people who own steel boats would consider or have considered aluminum boats.

I don’t think there is any definitive list of boat types that are out doing high-latitude cruising. Records are kept of vessels that go through the NW Passage. I did a quick search of the sailboats that went through the NW Passage in 2017. I counted 4 of aluminum, 4 of steel, 3 of fibreglass, 2 of wood, and 8 that I was unable to determine the construction of. Of the two sailboats that went thru in 2018, one was ferrocement, and I don’t know about the other one. The NW Passage is very much a high-latitude trip, and anyone who has gone through it has at least that much high-latitude experience (and, I would greatly hope, a lot more experience than that before they attempt it!). Those NW Passage numbers are pretty recent, and are in accordance with what I have observed while cruising. So I respectfully disagree with the statement, which the article puts in bold print,
‘by far the majority of experienced high latitude sailors have aluminum boats’.

Some people considering a metal boat will find themselves in the situation of feeling they can afford to buy a steel one, but can’t afford to buy an aluminum one, and see their choice being to own a steel boat or not own a boat. I would encourage people considering a steel boat to read books about them (‘Steel Away’ and Tom Colvin’s ‘Steel Boatbuilding’ were both of much use to me when I was a beginner), talk to people who’ve owned steel boats, and talk to boatbuilders, yards and surveyors that work with them. I don’t know of any particular site on the internet to recommend for information on steel boats.

I agree that steel boats are not for everyone, but disagree that they are only suitable for those who have owned them before–steel boats can be learned about.

Best regards,

Richard Hudson

Hi John.

Thanks, now we’re in agreement.

Best regards,

Alastair Currie

Jut some musings.

There is an aluminium boat from 1936 still floating around and the oldest aluminium boat builder started building aluminium hulls in 1898, Savage Aluminium Boats. I think there are GRP hulls from the early ’50s still pottering about today.

I read that a typical, modern 40’ish GRP yacht has around £5000 worth of materials to make it. Today we see new and old GRP yachts sailing around the globe frequently, managing the stresses and strains of the Souther Ocean and plenty of arctic and antarctic voyages. A colleague ran his Contessa 34 onto a boulder lee shore, F5, big damage, the boat dragged off and significant repairs; owner of a Sigma 41 ran into a rock and snapped the steel toe of the hull flange from the keel all theta through, as well as significant hull damage, I too rammed a ledge at spring tides at speed and busted GRP stringers etc, none of these yachts sank. One thing that GRP has going for it, is that it flexes considerably on impact before it yields, although the area will have been significantly stressed and weakened. The same for aluminium, recently at Ardfern Marina, a modern aluminium yacht was on the hard, after the owner ran her over rocks and bashed the hull significantly at the turn of the bilge, I guess the aluminium though would have maintained a lot of it’s strength. The skills were not available to fix and she was being prepared for road transport back to the builders yard in France when I saw the boat; GRP on the other hand can be fixed easier, I suggest. The point I wish to make, is that GRP is a strong material, it has resilience and a history of surviving neglect and abuse. This is what makes it a superior material in my opinion. Sailing is a minority pastime, the vast majority of participants will have reasonable funding and GRP has proved to be very cost effective and allowed some fantastic low cost, extreme voyages to be made by amateurs. I don’t particularly value steel or aluminium for their strength in hull choice as avoiding the sort of impacts that damage hulls should be the name of the game for any serious voyager. If one is in a situation that impact damage is happening, then it is luck that is stopping the hull from foundering. I think hull design with collision bulkheads and water tight compartments is more relevant for security against foundering than GRP v aluminium v steel. It is this sort of design feature that buys time and allows options to be worked. There are always exceptions of course.

John, I think your reasons for going GRP are very valid. I am a lazy hull cleaner, preferring to let the waves do the washing. But about every 3 years I polish and wax the hull and it comes up beautifully.

Marc Dacey

We chose steel because we saw the boat we purchased had been prepared properly and we were aware of the need for prompt maintenance. Everything in “adventure cruising” being a compromise, the key to happiness is, we feel, this awareness. We are a few weeks from leaving on what we hope will be a five-year circ with an emphasis on independence from the shore and the ability to do our own repairs save for major refitting. Few people get to do this, irrespective of hull material. The wisdom of our choice will soon reveal itself, one way or another. Now, if you’ll excuse me, I have to wire up a fridge compressor…

Richard Elder

Hi John,
A few vignettes;

Bernard Moitesser’s Joshua;
Washed ashore in a hurricane in Cabo San Lucas– filled with sand. Given away to two guys walking on the beach. Pumped out and motorsailed all the way up to the Pacific Northwest where she became a dock mate to my Cape George 36. Every fiberglass boat that washed ashore on the same beach was cut up and hauled away.

Brewer Atlantic 45:
Built by a well know Canadian yard. Sailed around the world and arrived in Trinidad with several overlaid hull patches. Spent a year being “completely” re-plated and re-decked while sitting outside as is the practice there. (and rusting all over again) Repainted and looked “smooth as glass.” Sold to a naive young couple who panicked the first time they hoisted sail. I was offered it for $15,000 and turned it down.

Classic 110 ft. Feadship
In our yard for a complete restoration. Hull built with overlapping strakes — every overlap rusted out. Re-plated the majority of the hull, re-powered and restored interior to new. Fixable, but at tremendous cost.


John Guzzwell was one of the earliest pioneers of cold molded wood boat construction. I met him when he hauled his Laurent Giles ketch out in our interior storage area. It was built in the days before epoxy— he used resorcinal glue just like the Spruce Goose. Planking was mahogany rather than the more rot resistant Alaskan cedar. And the hull sheathing was Dynel in polyester resin. John spent the winter removing the old sheathing and replacing it with glass cloth and epoxy out of concern over moisture penetration from the resin. I made it a point to chat frequently to pick John’s brain and learn everything possible about cold molding. When he finished bringing “Treasure” back to bare wood there was only a small area of discolored wood— the planking was as sound as new and she was ready to receive her new modern sheathing.

I built my Cape George 36 deck without fasteners, epoxy bonded over an epoxy/glass base over Port Orford Cedar. Lived for 36 years outside with no covering and little care by multiple owners, but was still watertight and serviceable.

So yes, properly built wood boats can be durable.

At the same era the PT Shipwrights Co-op worked on a caravel planked boat that was built in 1898. She required a new stem timber and about 40% of the bow planking replaced. The repairs probably cost little more than all the Beneteaus that were being peeled and glassed under warranty at the same time.

So yes,traditional wood boats that have been properly built can be repaired over and over again so they last forever.


A J130 that has a perfect black paint job, new carbon sails, the latest electronics, and a custom $30,000 factory upgrade interior just sold for $15,000! Underwater delamination and extensive wet core. My proposal was to completely re manufacturer the hull bottom with epoxy resin infusion and close spaced foam/carbon ribs and stringers and no core. The end result would be the best J 130 in the world.. Some extensive rebuilds actually make sense!

And not all fiberglass boats last forever! Especially if they have a balsa core underwater.

Richard Elder

Hi John
My little stories weren’t chosen as examples of good projects for do-it-yourself dreamers! What I was trying to illustrate is that good (and bad) boats can be built of all materials. I could have included an aluminum Italian motor yacht with black AC current “peppercorns” in the hull that you could push a screwdriver through, or a 90′ fiberglass motor yacht where the underwater exhaust outlets had burned all the resin completely away from the adjoining area and was a single wave away from sinking.

The skill level required to undertake repairs runs the entire range:

John Guzzwell’s 24 year preventive maintenance project required a strong back and weeks of work with a heat gun and scraper, but technically anybody could learn how to do it with a couple of weeks of practice. The guys who nursed the battered Joshua up the Pacific coast were adventurers, not shipwrights. Hundreds of graduates of wooden boat schools know how to re-plank a traditional wood boat– that skill has not entirely disappeared. A teak deck originally built like my Cape George only takes a day with a grinder to be ready to be glassed over, unlike the can of worms in a screw fastened fiberglass, aluminum, or (heaven forbid) steel boat teak deck.

On the other hand, the hull rebuild I suggested for the J 130 is probably more technical than building an entirely new boat and requires engineering and solutions not found in the typical professional boat yard.

Andre Langevin

All in all, i am not sure the hull material is a strong discriminating factor in a purchase. If i my boat would be lost and have to shop for another one, the first criteria for me would be a metallic hull. Because it is a metallic hull it can have also a safe swing keel and a flat bottom to go on the beach or where there is tides. Shopping for a boat is a matter of luck for the availability of what we want. And age is important also. i have 58 and plan to use my boat for another 20 years if God helps. But suppose my boat would be lost and i would be 70 – knowing that in 6 to 8 years the boat will have to be sold back would mean a very important criterion would be to be able to sell the boat rapidly and profitably. For this reason i would opt for a good aluminium sailboat or if a catamaran then GRP. Not because technically they are better (in my humble opinion) but rather because its easy to sell. I thinks its also the thinking of many prospective buyers….

Kevin McShane

I submit that it is possible to find a world cruising sailboat for under $100K that is not a project boat:
This is also a not too subtle plug for checking out Cruisers Forum when researching said topics.
Full disclosure, this has been my beloved boat for nine years, and AAC is the first site I recommend to not only aluminum hull boaters, but every boater.
Thanks John, Phyllis and crew

Jonathan Perret

Hello John,
I guess I’d like to also throw in my little “grain of salt”. I am one of those “idiots” who is on to his second steel boat…The first one, a 1975 van de Stadt ketch, I spent 10 years rebuilding, while living on board and working full time, in the heat and humidity of the Florida Gulf coast. I never finished! However, my second boat, a one-off Treworgy 38 built in 1995, is of a combination you haven’t mentioned, but which is used in a large proportion of the luxury mega-yachts, as well as military and work ships: Steel hull and aluminium deck and superstructure. They are built using a flatbar, called a Datacouple, that has one side of steel imploded onto the other side of aluminium. This is welded to the steel hull and the aluminium deck, and the junction being a very fine micro-line, presents absolutely no electrolytic corrosion problem whatsoever, is 100% watertight, maintenance free, and very strong. It allows the eternal problem of maintaining steel horizontal surfaces to disappear, and lowers the weight topsides.
Isolation transformers: Obviously a must, although most GRP boats can get away with a galvanic isolator. One thing to be careful of: The Marinco deck receptacles for the AC connection, as they come out of the box, have a small chromed metallic jumper that connects the ground terminal with the casing. Pleas make sure this is removed!
Last but not least, no one has mentioned lightning! With 20 years working professionally on boats in the Tampa Bay area, which is also know as the lightning capital of the US, I can assure you that when you are living aboard full time, and have these daily and very scary lightning storms pass right over you, such that you know is a lottery and at any moment one of those blasts will be right on top of you, having a metal boat is a big reassurance. It won’t keep equipment from being damaged, but it will certainly keep you from being damaged if inside the boat. Very cozy!
Best regards and thanks for the great website. Jonathan

Andre Langevin

Dear John your comment is not scientific… the sample of steel boats you might have seen doesn’t necessarily represent the reality. We should not compare amateur built steel boat versus commercial built aluminum boats.

When I built my boat I visited a professional alu boatbuilder who had learned in French yards his skills. Although I had welding skills I find out that I was not capable of building correctly without experience a first aluminum boat. I turned to steel with the compromise of a stainless steel deck and superstructure and using commercial Amercoat primers and finishing paints + a certified paint inspector. The sandblast + paint costed me 18000$ CAD in 2008 which account to approximately 3 % of the total cost of the boat.

And frankly unless the builder as in your example as strictly adhered to products and applications guides an as proof or it we should not even consider it in a fair comparison.

This being said, almost all semi professional and professional yards have turned to aluminum in the last 20 years.

In the commercial world, steel boats, freighters, petrol carriers, liners etc.. all got a paint system valid for their 50 years of life. We don’t have the number but I guess that if we count all the ships in the world the number of square feet built of aluminum would be less than 0.01% (probably even less) of the worldwide commercial fleet.

Demonstrated valid protection system exist for steel immersed in sea water with 50+years of useful life.

1-We should compare apples to apples in our discussion otherwise we get lost in armchair stories.

2-Shopping for an amateur built steelboat should involve much more scrutiny than a professional made steel or aluminum boat.


Richard Elder

Hi John
Judging from what I’ve seen, a really good paint job on an aluminum boat is not that common either! The difference with steel construction is that the most important area for protection is on the inside where perfection is the hardest to achieve and recoating is difficult or impossible. Thats’ why steel boats rust out from the inside. And why there are so many home built rust buckets.

re aluminum boat structures:
As you mentioned in an earlier comment, an aluminum design with multiple frames and stringers covered by relatively thin plate like MC and aluminum race boats is stiffer per pound than one with thick plate. However I’ve never seen that method of construction result in a surface with so little distortion that it doesn’t require fairing and paint to look decent. Isn’t that the reason you’ve never stripped MC back to bare aluminum?

I’ve worked on two heavily framed aluminum boats— a 12 meter designed to Lloyds scantlings and a 300,000# motor sailor where the owner insisted that the longitudinals be continuously welded on both sides “to make it stronger.” The 12 meter had 3/8″ of mud in some places, and the megayacht had so much accumulated welding stress that it crushed the decks and engine room overheads.

At the other extreme of aluminum construction, my friends Garcia Passoa was built with 12mm plate up to the waterline because they wanted to be able to set it down on rocky bottoms in Patagonia without damage. Back in those days Sr. Garcia used a massive roller to shape 50′ long curved aluminum panels that were so fair you could paint directly onto them and it would look like molded fiberglass. Or you could leave them bare and marvel at his craftsmanship. As I recall the ribs were over a meter apart, and served more to attach bulkheads to than to add stiffness. Different boats for different folks– and purposes.

Wilson Fitt

Thanks, John, for featuring a lovely photo of us and our boat at the beginning of this post. However, and with great respect for all the contributors, I think that the discussion of the “best” hull material misses a couple of essential points.

Most of us build, own and sail boats simply for the pleasure they give. For me at least, a large source of pleasure lies in the boat’s look and feel. Does the boat look good from afar and up-close? Is it pleasing to your eye and comfortable under your bum as you sit in the cockpit with drink in hand? Is the cabin warm, dry, and cozy? Do passers-by offer compliments? Does it perform well under way and at rest?

Hull material strongly influences the look and feel of the boat. Metal boats tend to the industrial strength go-anywhere-any-time look that can be very impressive and pleasing if well executed. Wooden boats tend to fall into the fussy, look-but-don’t-touch category or, at the other extreme, the hairy old, gaff and baggy-wrinkled character boat group, irresistible to some, anathema to others. Fibreglass is the most adaptable of materials but seems to be dominated by a white desert of angular shapes and shiny metallic trim.

My suggestion is to consider “best” material in the context of the ways in which you expect to gain pleasure from your boat. Don’t buy/build something that is built of a material that can survive pounding on lee shore rocks or banging into ice floes unless the resulting look and feel and knowledge of its strength will please you every time you climb aboard.

Our boat is made of wood because that’s what I know and like. I have confidence in its strength and durability for the type of sailing we have done and dream of doing. Countless times we have had folks say to us something along the lines of “what a beautiful boat, but it must be a lot of work”. Well, it is a lot of work, but keep two things in mind. First, I enjoy the work and annual rhythm of varnishing and painting (at least most of the time). If I didn’t like that work, I would have a different boat. Second, structure and finishes that attract onlookers’ initial response are relatively small parts of the whole boat in terms of initial cost and ongoing effort. Our wooden boat has the same needs as any other boat in terms of underwater paint, rig, sails, electrical and mechanical systems, ground tackle, safety, and other gear.

So, my advice is to get a boat that will give you pleasure in the overall scheme of things and consider hull material within that context, not as a starting point.

Dick Stevenson

Hi Wilson,
Nicely put and a wise way to look at things.
My best, Dick Stevenson, s/v Alchemy

Richard Elder

Hi John,

No disagreement from me. I was just trying to point out that there are always connections: in this case the relationship between how an aluminum boat is engineered and whether it is a good candidate for bare aluminum finish.

Eric Klem

Hi Wilson,

You make a very good point. I have never enjoyed the boat part of cruising so much as when sailing on an extended family member’s beautiful wood S&S. As someone who has worked on several nice wooden boats, I always felt a bit awkward when I would answer the inevitable question of which yard takes care of the boat and I would explain that it was not yard kept and also that no, I couldn’t claim credit for most of it either, I was just lucky enough to get to enjoy it.

When getting our current boat, we really thought hard about whether we should take over stewardship of that boat. In the end, we went to the opposite end of the spectrum and decided to get as low a maintenance fiberglass boat as possible. We certainly have given up something that is hard to describe but the design is much more suited to the actual sailing we do and we can keep up with doing all the maintenance ourselves. I am someone who enjoys metalwork but does not enjoy the more artistic elements of woodwork which means that while I can spile a plank just fine, I have trouble motivating making elements that require an “eye” and as a result they don’t come out very well. Every time I see a picture of that boat, I wonder whether we made the right call as the feeling of being aboard was just so wonderful despite it lacking the creature comforts of newer boats.


Richard Elder

Hi Wilson

Great way of describing the Real Purpose of owning a boat! If she doesn’t warm your heart every time you row out to her at anchor, perhaps it would be best to invest in a motor home with the obligatory wavy graphics on the side!

While talking to Larry Pardey years ago on the dock a passerby commented: “what a beautiful boat, but it must be a lot of work” LOL Larry didn’t say anything for a minute, having heard the same comment a thousand times in a hundred harbors. “Well, we don’t have anything else to do” he said. (having just crossed the North Pacific from Japan in a self-built wooden boat with a 24′ waterline)

Andre Langevin

Nobody has raised the difficulty of getting a good antifouling for an aluminum hull, when i was building i remember the ban on TBT taking place in Europe. Is there good protection available today ? (this article is old) for current owner of alu boats what is the current state of the art antifouling ?

Steel hull is very easy to protect with a simple copper oxide suspension.

Dick Stevenson

Hi Rob,
I find your report of a Beneteau 473 hitting a rock at 8-9 kn and then a surveyor finding no damage extraordinary. I know you were discussing lead vs steel keels, but, less others think that sailboats can get away with that, I will share a couple of observations.
For years I lived near a boatyard in a town with a very seductive rock a few miles away. Most every year, boats would limp in having hit that rock. Every one (or almost every one, I can’t remember) that hit that rock at hull speed with an external keel was considered a total write off by surveyors and the insurance companies.
Usually the killer was structural damage of the fiberglass just aft of the keel, sometimes forward, as the keel tries to lever its way off the hull. Beyond that there always was near to the keel bulkheads pulling their tabbing from the hull and furniture etc. being dis-lodged. That was usually enough for the complete insurance write-off.
Now, a steel keel would, I would think, transmit the forces more abruptly/directly into the hull as lead has a bit more “give” to it. I suspect the difference altogether may not be all that great. It is my understand that the average boat will not survive a keel to rock grounding at hull speed.
I have been told, by those who know about these things, that it would be very hard (read expensive) to have a boat that could withstand an external keel to rock grounding at hull speed (I suspect full keels and some shoal draft could come closest).
My best, Dick Stevenson, s/v Alchemy

William Newport

We saw a Beneteau 50 (2004 ish) hit a rock at speed last year and damage the hull with water ingress. Damage was as described, fore and aft of keel, stringer damage. I think after removing the interior, reglassing and putting everything back, it was around 50-70k ish which the insurance company paid.

Rob Gill

Hi William,
Absolutely horrible thing to witness as a sailor I’m sure.
I think I am right in saying the Beneteau 50 you refer to above is a completely design to the B473 I referenced above. I have never sailed one, but from the pieces I have read, it seems to share the hull liner design of the lighter First models, like Cheeki Rafiki. I am sure the hull would be thinner, too.
That doesn’t in anyway detract from your corroboration of Dick’s point about many boats being massively damaged or written off by such impacts. It just doesn’t mean that well designed production boats and in particular the Beneteau 473s and their smaller sister-ships 423 and 393 have the same issue with their external steel keels.
br. Rob

Matt Marsh

Would it really be that hard to engineer a keel joint to survive routine impacts at hull speed?

Today in 3 Minutes of Rough Physics Approximations:

Say it’s an 8 knot boat…. round that to 4 m/s. Displacement 10,000 kg. Draught 2.5 m (of which 0.5 m is hull and 2 m is keel). The keel tip hits a rock, the boat pitches forward, she comes to a dead stop in half a metre (measured at the waterline), average acceleration 16 m/s2. About 80 kJ of kinetic energy needs to be dissipated. Impact forces are on the order of 160 kN at the keel tip, for a pitching moment of 320 kN.m. Couple that through a keel root joint with a 2 m chord length that’s already supporting maybe 5 tonnes of keel, and simplify to pseudo-point loads at leading and trailing edges, assuming the middle part does nothing. That looks like about 190 kN of tension shared among the leading keel bolts and 140 kN of compression on the trailing edge of the keel root joint.

So the question “is it possible to make a 10,000 kg fin-keel boat with a 2m keel survive an 8-knot hard grounding on solid rock” is reduced to “is it possible to share 19 tonnes of tension among the first few keel bolts, and carry 14 tonnes of compression from the trailing edge of the keel joint into the hull, plus appropriate safety factors”. 19 tonnes is below the proof load of four M16x2.00 – Class 5.8 bolts, which seem considerably undersized for a boat of this class. 14 tonnes from a point load can easily be spread through a tapered U-shaped rib/frame about 20-30 cm in moulded depth, or a partial bulkhead, spanning most of the beam of the boat.

I think it’s not a matter of “that’s hard” or “that’s expensive”, but rather a matter of “we build to the scantlings in the class rules and they don’t consider this load case to be routine”. But it seems to me like, at build time while the hull is still in the mould, you’re talking maybe a three-digit dollar figure for this kind of reinforcement.

Rob Gill

Hi Matt, how right you are!
The boat in question (Beneteau 473) has internal “U” shaped tapered beams almost exactly as you describe, but with thick, wide flanges. The beams are probably slightly over 30cm at their deepest, in the centre, near the bilge and the keel bolts, tapering to not very much at the turn of the bilge (fairly flat bottom especially around the back of the keel). The beams are very close together at the front and back of the keel and about 20 cm wide.
These beams are so tough that during our pre-purchase inspection, the surveyor’s hammer bounced off them like they were steel. He called me over to remark on their size and thickness and how many there were around the keel area. Being an ex-yacht designer, offshore sailor and boat builder he didn’t seem the sort to be easily impressed. We both thought they might have a steel core, but I later discovered they are 100% moulded fibreglass.
Matt, I think these beams may have cost a little more than a three digit number more, but as you say – not a lot. But I have heard that due to EU heath regulations, such hand lay-up techniques can’t be used anymore, and that most large items like beams would be epoxy injected and vacuum bagged, then cured and simply glued in. I wonder if this is not as inherently impact resistant. Do you have a view on this?
br. Rob

Jordan Bettis

This is my biggest problem with modern fiberglass boats. Boatbuilders that still exist are exceedingly good at value engineering. The ones who weren’t went bankrupt decades ago.

Value engineering requires warranty claims for its feedback mechanism: make something weaker, and if there aren’t any claims then it’s still too strong.

But most pleasure craft spend nearly all their time floating next to a dock, plus an occasional few hours underway in Force <5 conditions.

So value engineering is walking boats down to the point where they're good at floating next to a dock and occasionally sailing in benign conditions—plus Class.

But Class is controlled by manufacturers, and they'll continuously make the case that real world experience shows that Class is too conservative. So Class is value engineering with a delay, and that's how we end up with (for instance) brass thru-hulls and glued matrix liners.

Alastair Currie

If you go to YouTube and search for “Crash Test – Dehler 31 yacht” you can see Dehler ramming their yacht against all sorts of objects at hull speed. It’s a GRP hull with a standard fin bolted to the hull, not a bonded in grid or encapsulated. The video is worth watching all the way for all the ramming scenarios this boat is going through, including a keel strike against a breakwater base. I am not doubting your observations. My position is that GRP hulls can be designed strong enough for extreme loads at sea, and that inherently makes them strong enough for many types of impact. As design changes over time we now see hull designs with very efficient keels that meet a performance criteria with some sacrifice in strength and are less resilient. I do agree that steel can be stronger but I think GRP can be relied on as safe and secure material, where the design demonstrates that. I won’t post the link here as I am not sure if that is allowed.

Dick Stevenson

Hi Alistair,
I fully agree that fg hulls can be built to withstand almost anything the sea may challenge it with. I also agree that fg hulls can be built strong enough so that the keel to hull joint is not compromised by anything the sea has to offer. In fact, it is my take that most are. It is a non-sea event that I was referring to: hitting a rock at speed low down on a conventional keel. It is a predictable event for a certain (hopefully small, like lightening) percentage of those who put significant miles on their boats.
It is my take and observation that the average sailboat can’t tolerate hitting a rock down low on a keel (possibly excepting shoal draft and full keel where the lever arm is mitigated to a large extent) without substantial damage and often leading to total loss.
As to the video, you cited: hitting floating wood objects and log booms should leave only a dent and did leave gauges as shown in the video. But that should be all the damage. I believe the video shows the boat hitting the rock wall with the underbody leading up to the keel high up on the keel, not low where the lever arm is most powerful. This is augmented by the video of a keel placed well aft and the boat rising at first and then largely stopping dead with very little tipping forward.
A boat hitting the bottom of their keel at hull speed looks like it will pitchpole. It is incredibly dynamic and looks to eject the people in the cockpit into orbit. This hitting the breakwater was gentle by comparison and says they were sliding up the hull, absorbing the loads till they got to the keel. Very little was shown of keel dents or evidence on the forward underbody where I suspect there was contact. Also, the keel to hull footprint is one of the tiniest I have ever seen on a fin keel boat: harder still to believe it could survive unblemished a bottom of the keel rock grounding at hull speed.
Your Dehler video was not, to my observation telling or compelling: it was an advertising stunt. (Reminded me of the old Hunter destruction tests done back in the day: I am not a fan of manufacturer testing.)
Now, I am largely unfamiliar with Dehler boats and they may make great boats, but I am not impressed by the video as evidence that a conventional fin keel boat can survive a bottom of the keel rock grounding at hull speed.
My best, Dick Stevenson, s/v Alchemy

Rob Gill

Hi Dick, that was my understanding entirely, so I fully understand your note of surprise. This was also the owner’s expectation at the time – the boat was rushed back to the nearest haul out facility, with crew in life jackets, coastguard on standby and bilge pumps primed.
Most people are reticent about admitting things like going aground, never mind crashing into a rock at full tilt. So I have no reason to doubt a first hand account of the incident, from the owner to me, on board their boat some months later. At the time of the impact the owner was down below, having handed over the helm to a friend to check something. The rock concerned is well marked by a beacon and for some inexplicable reason, the EXPERIENCED sailor and friend took the beacon on the wrong side – hey stuff happens. The crew were lucky to avoid injury.
Please see my answer to John above, on the way Beneteau Oceanis 473s are built for the reason why I think they could withstand such force, without any visible damage. Not that I am looking to test it mind. Inside the hull the keel bolts, girders and hull are all completely visible by simply removing a few floor boards. All easily checked by an experienced surveyor. I have to say if it was me, I would have insisted the insurer pay for the keel to be removed, keel bolts changed and the whole thing re-seated at a minimum, and this may well have been done – I don’t have the detail of that.
By the way, I do wonder that marine insurers don’t sponsor more marine buoyage. We have a notorious rock near us, that collects about four launches a season.
br. Rob

Dick Stevenson

Hi Rob,
It sounds like you have a very solid boat and you must be re-assured to have it validated especially if you were not the one doing the testing. My interest in responding to your initial letter was primarily to point out that, in my experience and in talking with others, most of the regular sailboats out there could not survive unblemished what you described.
And I concur with your thought of further examination of the keel. Internal furniture etc. are one thing, but I would also be concerned about the shock load’s effects on the rig, chainplates etc.
My best, Dick Stevenson, s/v Alchemy

Dick Stevenson

Hi John,
I am not convinced that the average offshore boat buyer need be so pessimistic and precautionary about keel to joint integrity. For those boats being considered for offshore use (for ex., Malo, Hylas, Rival, Valiant, J Boats etc.), I would think that a good survey, boat history (no evidence of groundings), general consideration of the quality of boat construction (including details on the keel to hull joint, caulking, bedding etc.) and the history of sister ships would reveal a lot and make it likely that the keel would stay attached during her sailing life. I think for most boats nowadays (including those mentioned above), all bets are off for untoward events like groundings. That said, I think there is a good long way to go ensuring that new builds are better done in this area and in inspecting those that have been around awhile.
My best, Dick Stevenson, s/v Alchemy

Svein-Erik Lamark

Hi Dick,
I agree with your conclusions. However I have some interesting information, several fg yachts with fin keel in Scandinavia are built so strong that they can tolerate to hit a stone with the keel in good speed. The ones I have sailed are X Yachts of Denmark, Arcona Yachts of Sweden and Baltic Yachts of Finland. The keel construction of this three are all different, but looks very strong and stiff. You can find the drawings on the net. They all sail well. I like to sail in uncharted waters and then you must be prepared to meet this problem every year. Then it is not so difficult, but most fin keeled fg boats are not built to handle this difficulty.

Dick Stevenson

Hi Svein,
Thanks for the info. When sailing your part of the world, I saw those boats pretty regularly and thought they looked fast and well built, like J boats from the US, but had no other contact with them. I was unaware they were robust enough to tolerate hitting a rock at cruising speed unscathed.
My best, Dick

Richard Phillips

I have just bought my *third* steel boat – so there you go, you do know of at least one person who has bought more than one!

One of these is coming up to 100 years old and has not had a spot of rust on the undersides in the last 15 years – though to be fair, she sits in freshwater.

The game changer for steel is proper grit blasting and professionally applied two part epoxy paints. Done properly, it lasts for decades.

Steel is a nightmare if not maintained and if poor quality preparations / coatings are used. A pure DIY life of grinding and painting rust is indeed a mugs game. With proper blasting and painting however, you have an extremely strong, durable and low maintenance system.

My latest steel boat is 30 years old and the paint failed about five years ago so there is some remedial work. With that done and a visit to a Dutch yard for an SAE3 blast and glass flake epoxy paint job (when I can afford it!) – I expect it to go another thirty years. How many fiberglass boats can confidently expect to last 60 years?

Andre Langevin

Hi Richard well said. Here in USA/Canada people are afraid of steel boat..European are not and they have made plenty still traveling the globe. We should not forget “attainable” in the adventure cruising. I’m talking of used boats of course as I made it clear that all professional yards have turned to aluminum and I’m fine with this.

People look after non metallic boat as a magic bullet for secure world traveling but there are all sort of dangers awaiting: rocks, corals, UFOs, containers, fire, and the most dreadful and invisible… the 1 million cycle of flexing in the ocean after a few years. Attainable cars still have their coil-springs and chassis made of steel. Every polyester boat owner have experienced the need tighten up the rig after a rough passage…

I would have no problem of buying another steelboat if mine one day would be lost. You are right that with proper preparation steel in marine conditions can go many decades – just look at the oil rigs they are built for 40 years up.

Thanks for the informated post!

Philip Wilkie

As a steel boat owner I understand why people have their reservations. The way in which an old steel boat can crumble before your eyes is disheartening and if that kills your confidence in it then that is that. And as another person mentioned, the fear of old steel boats does seem more prevalent in North America than elsewhere; there may be good reasons for this.

Personally I’d love a good aluminium hull, but all the ones I could access in Australia were well out of my budget. And many of the fibreglass ones came with other problems, osmosis, cracks, delamination, water logged cores and so on. Or they were really heavy old designs that sailed like slugs.

Plus I really wanted rigidity, as an engineer this attribute seemed fundamental to me, so in the end I went with steel despite knowing full well that rust never sleeps. And truly modern coating systems really are remarkable and quite surface tolerant. They’re designed for aggressive industrial applications where ideal surface preparation isn’t possible or economic.

If I could build new it would be a steel hull with no horizontal stringers, stainless deck, integral tanks, total bilge access and a full noise Jotun or International paint system. Thirty year life easy.

Still I don’t feel any pressing need to defend steel; it’s not as good as aluminium and it will never be as popular as fibreglass. Besides there aren’t that many really good steel hulls out there and those of us who like them wouldn’t want to see them become too much in demand 🙂

Charles Kanieski

I would love to meet and talk hulls, but that would ruin your “I never met” a second steel boat owner.
I am on my second steel boat. I have owned steel, fiberglass and wood boats in my sailing life.
My first steel boat was an Ebbtide 36, built like a brick shithouse as they say, in the UK. As a newbie to cruising, I read Jimmy Cornell’s “Ocean Cruising Survey” where most long term cruising boat owners preferred metal. I sailed it hard across the Atlantic and Pacific and points in between (over 35k passage miles in 5 years). I even had the opportunity of living through an experience of driving it ashore in a strong wind. My (now ex) wife fell asleep on her watch and let us drive it directly into a rocky shore of an island in the Caribbean at about 7 knots. The boat was eventually hauled off and the dents in the hull needed to be repainted. No leaks, no lost keel, and after, no rust.
My current steel boat is a Folkes 42. I had the electrical system completely rebuilt after my purchase. On a trip from WA state mainland to the San Juan islands, we had a voltage regulator (brand new, just installed Balmar regulator) fail, start on fire and allow two batteries to explode before the fire suppression system blew the fire out. We had to abandon ship into our dinghy. The boat did not sink, but was totaled per our insurance company. After many months negotiating with Balmar they finally admitted fault and paid for a complete rebuild of our boat. As we gutted the interior to bare steel we got a chance to check for interior rust and found none. Now (three years later) we are back on the water sailing again.
With modern coatings and a minimum of maintenance chasing after any scratches a properly built steel boat offers an inexpensive (relative to the other metal choice-aluminum) safe and strong boat. I think the boat has to be properly built originally (professionally) and then properly coated inside and out. One other advantage of steel is that it can be repaired anywhere in the world.
Charley s/v Hongvi

Ernest E Vogelsinger

As I am still considering buying some (used) steel boat in a couple of years time this tells me one important lesson – access to the inside of the hull must be able _everywhere_, at least good enough for proper inspection using some fiberoptic or the like. Even (and especially) below tanks, or similar built-in structures. It is quite easily possible to blast and recoat the outside, and doubtful areas on the outside can be easily spotted. But it must absolutely be possible to routinely inspect the complete hull area from the inside as well, without too much ado. If (heaven forbid) there would be some blasting and recoating necessary it is still a chore removing parts of the internal structures, but you need to be able to detect it first.

And the story about your exploding batteries makes me shiver. What had you done if your boat was from plastics?

Marc Dacey

There would be a different ending to the story.

Andre Langevin

Very good advice John, all boat need total inspection capability. Unprotected steel can rust, aluminum should be kept free of any standing water (wood is terrible in contact with bare alu) that can attack the oxyde and start up a crevice corrosion.

On any metal boat the bilges should be dry all the time.

Aluminum corrosion protection is not a simple science…if only aluminum could be alone but the problem start when attached to another metal or with itself sometime.

On the periodic table of element Aluminum is a much more active element (less stable) than iron. But neither are used on a boat, it is rather in alloy: Alu 5083 is an alloy, Steel is an alloy and the same for 304 and 316 stainless. All have their corrosion issues and can be attacked with the proper conditions/oxidant.

I have read on Collin post that his Alubat seacocks are in plastic…what are yours John on MC ? Mine are stainless steel and for the plastic speed and depth transducer i have built a safety chamber over it. I would NEVER leave a plastic seacock alone (without side impact protection or safety chamber) on a metal hull.

William Koppe

Hi John,
I also have had 2 steel yachts.
The first had no corrosion issues as it had only paint on a rather bare internal fitout.
Surprisingly, in Sydney Australia it had almost no condensation due to adequate ventilation. It was 6 t, and 20 years old.
The second yacht had a full internal fitout but the hull was done in corten steel which only ever showed minor surface rust. However the mild steel frames in the anchor locker were rusted out to half their original size. It was 20 t , and 28 years old.
It should be noted that Lloyds would not let me build in Corten due to its brittleness in subzero temperatures.
If I were looking to buy another yacht I would look for another steel one with these provisos.
1/ a good design. Backyard builders don`t pay for a high quality design
2/ The price has to allow for a total strip out, sandblast and paint ,and refit, rewire etc.
3 If the insulation is sprayed on foam then walk away.
According to the US Navy their paint systems are good for 25 years.
My third yacht was an alloy 55 ft 1969 racer. At 14 t it always felt fragile and it`s motion too lively. In asking what alloy they used I could not say, but probably not the modern 5083 and not the old duralium.

Jordan Bettis

Lloyds is out to lunch. Old Corten A was brittle (which is why USS sold Corten B) but modern A588/A606 has excellent cold notch toughness for an HSLA and is significantly better than A36.

A588 is sold primarily for bridgemaking and is an excellent structural material in most conditions.

To be fair to your mild steel frames: they almost certainly sacrificed themselves to the corten, which is more noble than mild steel.

Maxime Gérardin

what about plywood builds? Would you consider them an option? What would your conditions be, what would you survey?
My first reaction when I read your specifications for your next boat was “that’s a RM1200!”. I’m not stating that they are perfect: they definetly have some drawbacks, and I wouldn’t be able to assess if one is a safe buy. But their twin keels are well-designed (just as the twin rudders of the Boréals, maybe!), and make for boats that are quite good upwind, despite being roomy, light, and of moderate draft.

Maxime Gérardin

Ouch, plywood without epoxy? I don’t even want to know about this!

Sorry for the mistake regarding Boreal: I meant “aft daggerboards” and not “rudders”, of course. The point being that, as far as I know, the RM were the first twinkeel boats on which the keels are properly angled, so as to reduce leeway when sailing upwind.

Maxime Gérardin

Thanks for the information! I didn’t know about tortured plywood.

I see on the internet that the best trade-off for an auto-jibing 505 centerboard is around 2.5-2.8°. And something I didn’t suspect: if the daggerboard is well-made, slightly lifting it brings it back to the centreline! Which would be ideal downwind. The keel angle on RMs and similar designs is less than that (around 2.0°?), but keels have to be kept in place when not sailing upwind!
In my experience, the advantage of this is not that you could point higher, but that, for the same angle between the wind and your route, the hull can point a little further from the wind, yielding 1) a better hull shape through the sea (there is another saying about sharp edges: when the sharp edge opens the way, it works better!) and 2) a little more distance between the two sails, which seems to help, too. I know it may sound like I’m overmaking this, and 2 degrees may not seem that important, but the difference is quite visible, especially with 15kts of wind and a flat sea (it becomes all the more visible if you heel too much, but that’s not advisable anyway).

Richard Elder

Hi John

Tortured Plywood? A Kamanu catamaran built with the Hughes Cylinder Mold process has been in daily commercial service in the rough Hawaiian waters for THIRTY YEARS. That is perhaps equivalent to 100 years use for the average full time cruising yacht.

Fairly recently an entire half hull of a 70′ CM catamaran was built in the Philippines in a single day using the process. It is a full curvature hull shape, not a chine boat like Rags.

A few years ago I met the skipper of a 55′ CM cat built 20 years ago for Lake Tahoe. It sits outside in the snow every winter and carries passengers every summer. The best story over beers was about the time a jet ski hit it at full throttle and ended up inside of the hull. Sailed it to the dock, pulled the jet ski out, scarfed in a new hull section, and went back to work carrying tourists.

Marc Dacey

Tortured plywood, a phrase you won’t hear anywhere but AAC!

Richard Elder

Thought all you metal heads would like to know that a new process for refining wood has been developed in the lab. All the lignin is chemically removed, and then the remaining fiber massively compressed. The resulting material is stronger than steel on a weight basis. May never be a boat building material, but who knows!

William Koppe

Hi John,
As a metal head, my perfect hull material is SAF 2205 ( DUPLEX ) stainless steel.
It has a yield strength 3 times that of mild steel and excellent corrosion resistance, as well as great fatigue resistance. See sv tanielle
Thanks Jordan Bettis for the update on Corten