Impact Resistance—How Hull Materials Respond to Impacts

yacht crash on the rocks

I have a confession to make: I've run boats aground on several occasions. Granted, it's always been at dead-idle speed when poking up shallow rivers. And the damage, thankfully, has so far been limited to a few nicked propeller blades and shredded rubber hubs. But, despite all precautions, it happens. If we were to rank groundings and collisions on the scale of skippers' worst fears, I suspect they'd fall somewhere between an engine room fire and the pirates' scene from Captain Ron.

Hitting something in a well-built boat is usually survivable, but is still a scary and potentially life-threatening situation. In this chapter, we will take a look at how some common hull materials respond to impacts.

  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. Five Ways That Bad Boats Happen
  8. The Two Biggest Lies Yacht Brokers Tell
  9. Learn From The Designers
  10. You May Need a Bigger Boat Than You Think
  11. Sail Area: Overlap, Multihulls, And Racing Rules
  12. 8 Tips For a Great Cruising Boat Interior Arrangement
  13. Of Cockpits, Wheelhouses And Engine Rooms
  14. Cockpits—Part 1, Safe and Seamanlike
  15. Cockpits—Part 2, Visibility and Ergonomics
  16. Offshore Sailboat Winches, Selection and Positioning
  17. Choosing a Cruising Boat—Shelter
  18. Choosing A Cruising Boat—Shade and Ventilation
  19. Pitfalls to Avoid When Buying a New Voyaging Boat
  20. Cyclical Loading: Why Offshore Sailing Is So Hard On A Boat
  21. Cycle Loading—8 Tips for Boat and Gear Purchases
  22. Characteristics of Boat Building Materials
  23. Impact Resistance—How Hull Materials Respond to Impacts
  24. Impact Resistance—Two Collision Scenarios
  25. Hull Materials, Which Is Best?
  26. The Five Things We Need to Check When Buying a Boat
  27. Six Warnings About Buying Fibreglass Boats
  28. Buying a Fibreglass Boat—Hiring a Surveyor and Managing the Survey
  29. What We Need to Know About Moisture Meters and Wet Fibreglass Laminate
  30. Offshore Sailboat Keel Types
  31. US$30,000 Starter Cruiser—Part 1, How We Shopped For Our First Cruising Sailboat
  32. US$30,000 Starter Cruiser—Part 2, The Boat We Bought
  33. US$30,000 Starter Cruiser—How It’s Working Out
  34. Q&A, What’s the Maximum Sailboat Size For a Couple?
  35. At What Age should You Stop Sailing And Buy a Motorboat?
  36. A Motorsailer For Offshore Voyaging?

Matt, Engineering Correspondent, is a Professional Engineer and true renaissance man, with a wide range of expertise including photography and all things boat design. He has a unique ability to make complex subjects easy to understand and he keeps an eye on the rest of us to make sure that we don’t make any technical mistakes. Working as M. B. Marsh Marine Design, Matt designs innovative powerboats of all shapes and sizes.

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Wally Moran

I thought we were talking about cruising boats here, so your comment: “It is for this reason that aluminum is the material of choice in the uncharted, rock-strewn lakes of Northern Ontario” leaves me a bit bewildered.
You see, I happen to come from Northern Ontario – and I can assure you, the cruising boats I see in the 30,000 Islands, Georgian Bay or in the North Channel of Lake Huron, are just about 100% fiberglass. Just like the cruising boats on the Hudson River and all the way down the US east coast in fact.
Now if you’re talking small boats, yes, there are lots of aluminum boats – 12 – 20 foot recreational fishing boats, and they are everywhere. That’s because about 90% plus of the boats made for this market are made out of aluminum due to the economies of scale and the fact they can be built cheaply, like the one in your photo – not because they are tougher. I tow a 12 foot aluminum as a dinghy, because of its durability and because I cruise some pretty remote places.
France, which has NO rock strewn lakes with cruising boats on it, is known for aluminum cruising boats however. For whatever reason, Europeans and especially the French, have accepted aluminum as a material for cruising boats.

Wally Moran

No edit function, so I’ll add to my post here – the problem with aluminum is that it is very costly, especially in comparison to fiberglass. In part, that’s due to the availability of fg boats – there’s simply an awful lot of them.
Additionally, while accidents do happen, the likelihood of being holed is fairly low – and can certainly be made less possible with proper training and care while cruising. Does that nullify the advantages of aluminum? No, of course not, but essentially, the availability of aluminum cruising boats along with their cost, puts them out of consideration for most voyagers.

Wally Moran

I grew up in Sudbury, worked as far north as Wawa region – so I’m familiar with the areas you’re talking about. Generally, locals are familiar enough with where they boat to avoid a lot of problems even on the unmarked lakes. A lot of the damage one sees on the bottom of these aluminum boats is from beaching them, or dragging them ashore across a rock bottom. Which, of course, makes aluminum a good choice.

Hans

Hi Matt,
as a steelboat owner I’m well aware that she has certain disadvantages when compared to the same boat in aluminium, the main and only worth mentioning for me being the weight issue. But I always thought I had an advantage when it comes to impact resistance, and I’m a bit shocked about this statement of yours: “Mild steel is somewhat more fracture-prone in impacts than marine aluminum, …” Isn’t it the other way round? Steel has a considerably wider range of flexibility than aluminium, so that it can absorb more energy by deforming itself before being fractured. I just assured myself that this is still the case at http://www.kastenmarine.com/alumVSsteel.htm

Hans

which of course I don’t. Thank you for the clarification. Otherwise it would have robbed me of my main argument in favour of steel. Its hard enough to drag around all that weight of a steel hull only 33ft. long, but being without argument is harder I suppose.
But tell you the truth: even the weight doesn’t bother me much. And the rust issue is almost non existing, provided there is good construction, proper insulation, a good paint system and some vigilance involved. It surely is as you say: Every material has its strenghts and weaknesses and , John, I didn’t accuse Matt of putting one material above the other. Thanks for sharing your knowledge.

John Harries

Hi Hans and Wally,

I’m sure Matt will answer your questions and concerns, but I just wanted to step in here and point out that Matt has never said that one material is better than another.

In fact, in his last post in this Online Book his base hypothesis was that all the common boatbuilding materials have advantages and disadvantages and that any attempt to pick a “best” material is futile.

Matt is simply sharing his engineering training to explain what the trade offs of each material are.

Trond

Hi this is interesting, i hava a quistion. What is the best material for a cruising boat if i want too go realy north and ice can bee suspekted (alminium?)
Trond

Erik Snel

Matt, of abrasion is a concern for using composites in ice-infested area’s, could this not be solved by using an outer layer of kevlar in the composite?

Regards,

Erik

John Harries

Hi Trond,

I can jump in here. Having spent years in the north, much of it around ice, my thinking would be that aluminium (as long as only the bottom is painted) wins over steel for a high latitude sailboat that might push a bit of loose ice around but won’t be ice breaking, due to the fact that it does not corrode when the paint is abraded and that maintenance of an aluminium boat is much cheaper and easier than steel.

(It is interesting to note that both Skip Novak and Hamish Laird went with aluminium for their later boats after years of maintaining the first Pelagic that is built of steel.)

If you are going to break ice, then steel is the winner due to the abrasion resistance (as Matt points out), but very few yachts (none?) actually break ice, if for no other reason than that activity takes tremendous weight and size.

Erik de Jong

My personal preference for operating in ice infested waters is steel. If you were to build a vessel officially ice-classed and certified, aluminium would not even be allowed, and in my opinion for a good reason.
Both Mild Steel and 5000 series Alu will get bridle when exposed to sub zero temperatures, but for steel, there are special alloys available to make it “sub zero proof”, something that is much harder to achieve with aluminium.

Opposite to what John mentioned, I do not feel that steel is more expensive to maintain IF the proper paint was applied when the boat was built. There are special paints for steel boats in ice waters, and is generally sold under the name “ice-breaker paint”. I have sailed on Steel boats in icy waters since 1989, and own my own, specially designed and built, steel “polar boat” since 2008.

I personally would not consider any other boats but steel for serious cruising in the (Ant-)Arctic, especially if you consider spending some off-seasons there as well. Although this opinion is contradicted by a lot of highly respected sailors, including the people mentioned by John, and John himself.

John Harries

Hi Erik,

All good points. Probably what I should have added to my comment is that its a close run thing between steel and aluminium. For me, it would be aluminium, for you steel.

I do stick by my assertion that an unpainted aluminium boat is the easiest and cheapest to take care of. Painting metal boats is very labour intensive, as I know all too well having lived with a painted aluminium boat for 22 years. And even with the best paint system in the world, you will be repainting every ten years or so.

I would also question the brittle from the cold assertion in that the water will be around zero until it turns to ice, and as far as I know aluminium does not experience any substantial brittleness at that temp. Matt?

John Harries

Hi All,

For those that are thinking about the steel or aluminium decision, you may wish to read Colin’s excellent Online Book Why Not Steel, which clearly details what it takes to properly paint a steel boat.

For me at least, its a daunting prospect, particularly when you take into account that a paint failure on an aluminium or fiberglass boat is a cosmetic issue, on a steel boat it is, at least potentially, a structural issue—the stakes are high when painting steel.

Trond

Hi John, and thanks too all of the answers. I hope that i not will need too break ice, but too sail in to small ice that can bee poosh away, whith no damish on the boat, is what i want.
In my mind a sailing cruiser abaut 40 – 45ft, whith engine power only 50-75 hp is no icebreaker.
Do you, or anybody else have a tips for the best boat? Rigt now am i looking at some of the france boats. And i like too sail as fast as possible whith a cruiser (the normal thing).

John Harries

Hi Trond,

If I were looking today for a boat to make the voyages we have made over the last 20 years the Boreal 47 would be at the top of my list.

richard s.

there was an article in ocean navigator magazine at least 20 years ago that recounted the experience of a typical blue-water fg sloop about halfway between bermuda and virgin gorda barreling along one night and suddenly crashing into something unseen that brought everything to a screeching grinding halt as if hitting a brick wall…the crew had barely enough time to escape with their liferaft before their main life raft (sloop) sank…they never saw any trace of whatever they hit…the skipper’s later research revealed there was a navy sub in that area at that time but never could pin down whether or not that was the object possibly cruising close to the surface…sobering article…talk about hitting something hard ! doubtful any sloop could have survived that

John Harries

Yikes Matt, do we Canadians—well, I’m almost one—really want to let on about that one. If for no other reason than it’s an admission of how badly we got took by the Brits! 🙂

FAIVET DANIEL

Bonjour
Cet article est exceptionnel, par son analyse technique sur la déformation des matériaux : acier, allu, composites et bois
Les echouages bien évidement font partie des accidents, impondérables de la vie de marins confirmes, il convient donc d attacher une importance particulières au choix du matériaux
J ai bien note l anecdote du vendeur vantant la ” dureté ‘ de son bateau et sa technique de démonstration , qui s est avérée fausse, cette histoire me rappelle un grand constructeur de bateau connu actuellement et que nous connaissons bien qui pour vanter la solidité de son bateau en exposition avait mis un MARTEAU qui cognait sur le rouf et coque il y a de nombreuses années ? c etait impressionnant ce qui lui a permis de réaliser de nombreuses ventes
En matieres d’ échouages talonnages ( la photo est remarquable de réalité) nous connaissons bien puisque nous avons echouer 2 fois directement sur les rochers pour cause de pannes moteur ( voir article blog HANSE échouages) et une autre fois il y a des années sur un Beneteau qui fut reparé en Martinique
J ai lu attentivement l analyse de l auteur sur l acier et son pouvoir déformant lié a son élasticité, c est très juste évidement, j ajouterai la facilite de réparation et la sécurité pour les grandes traversées ou l on risque de rencontrer des OFNIS ( engins flottants non identifies)
Pour terminer, cet articles fait la synthèse du choix des matériaux de fabrication qui doit etre associer a la conception du bateau qui a fait l objet d un précédent article dans ce forum pour exemple simplifié les epaisseurs des parois de coque le varangage , raidissage etc qui modifie la capacité de résistance a l impact des coques, l ensemble construit doit etre cohérent et fonctionnel et c est tout l art et la compétence de l architecte naval concepteur …….choix des materiaux, calculs de resistance des materiaux, statique des forces mecanique des fluides etc
Cordialement Ulysse

Alan

No doubt some have been waiting for my response, well here goes. Somewhat of a long read.
Firstly Matt – my apologies if my comments have caused you hurt. My original statement was about you needing to be careful about how other people represent you, I had omitted the words “by others” so my mistake for thinking these implied words were apparent to other readers (Paul’s posting is very true). I wish you well to attain your professional status and receive the “iron ring”.
John –It was my view you were not accurately portraying Matt’s background by omitting which discipline his engineering training related to and hence left the implied suggestion that his engineering training related to the subjects being discussed on this site. I accept you have sort of acknowledged this and that it was not intentional.
So I am making the effort to be conciliatory and suggest we now all move on.
Moving onto to my issues about Matt’s article on “Impact resistance” and my view that it lacked balance. I think this article might have better been titled “Puncture Resistance” because that was the subject being discussed, at least until the reader reached the section about cored hulls where it seemed to turn into a general condemnation of cored hulls by the generalisation about engineers and other selective examples quoted without qualification. To me this is a bit like taking the following selective facts:
1. Richard Branson’s aluminium Virgin Atlantic I (the cat) hit something near the end of its run and sank off the English coast;
2. A 30m aluminium yacht being built in Thailand was relocated to New Zealand, inspection of the hull in NZ found the welding totally deficient and all welds had to be ground out and re-welded; and
3. The bad batch of 5083 Aluminium from Alcan which was faulty, due to a change in the heat treatment process, and drawing the conclusion that aluminium is a bad material to use in construction of boats. Not true of course, but this is much the same logic path Matt has used.
I do not have a particular axe to grind about cored construction, only believing it to be a good form of construction when properly executed, just like any other medium. My experience ranges from assisting in the build of, I believe, the second only foam sandwich boat of any size built in NZ in the 70’s, using Airex foam, polyester resin and woven rovings/CSM (those were the days when you washed your hands in acetone, horrifying to think about that now) – this boat is still sound in spite of being somewhat neglected and having been washed ashore several times due to mooring failure. Since then I have owned a balsa cored power boat and now a foam (Klegecell) cored yacht. I have also been involved in quite a lot of industrial fibreglass applications including project managing the construction of possibly the tallest (120m) fibreglass chimney flue in the Southern Hemisphere. This does not make me an expert but certainly provides some firsthand experience. I am not a big fan of using balsa or honeycomb as a core, because of the possible rot issues if there is water intrusion with balsa and the lack of skin bonding area with honeycomb. My preference is a foam either of the PVC or SAN (Corecell) groups and used in the right applications eg we all know have to be careful about the grade of foam used for deck construction due to heat issues. That being said there are many successful boats built using balsa and honeycomb. Derek Kelsall, who has many years of experience with conventional foam core construction, has written a good article, http://www.kelsall.com/TechnicalArticles/KCTheCoreOfTheSandwich.pdf
There is another interesting discussion (opinion based) about the various fibreglass construction options here:
http://www.sailnet.com/forums/boat-review-purchase-forum/16517-hull-construction-print.html
Here is an article about how an owner who considered both aluminium and fibreglass arrived at his choice:
http://www.newmorning.info/page12/page15/page20/page16/page16.html
Coming back to Matt’s article, as I said earlier, I felt in principle it was more a theme about “puncture resistance” (happy to be corrected by Matt about his intent) and in that respect I would not disagree that the metals and properly constructed solid glass should have superior properties to cored fibreglass in this situation.
However in the other area of “Impact resistance” , ie “slamming resistance” I believe a cored fibreglass structure to be superior to solid glass because of the low shear loads on the glass to core bonds compared to the much higher shear loads between the glass skin and its framing, which is typically a secondary bond with its ensuing issues. An interesting case study is the powerboat Ermis2, a 30m power boat designed for a top speed of 60kts. Originally a solid carbon laminate was envisaged but they could not make that work and High Modulus (the structural engineers) finished up specifying, after testing panels, a cored carbon laminate.
I had another read of Dave Pascoe’s articles to refresh my mind in where he was coming from. He makes it clear that he is not in favour of cored construction for underwater parts of a hull primarily due to the possibility of water intrusion (I agree with him on Balsa, not on the correct foams). But it should be clearly noted much of his criticism for all forms of GRP construction comes down to one or a combination of poor engineering, cutting corners on material selection, bad work practices both in construction of hulls and their fit out, and finally ( as Matt has subsequently noted) poor or non-existent QA/QC. Basically all driven by the bottom line. We all know about the hull blisters on Valiants built by Uniflite from a resin which turned out not to be suitable for long term immersion, however I think this was more a case of unintended consequences. Uniflite had used the same resin in their Mekong Delta patrol boats and saw its fire resistance as being a selling point.
Consultant Bruce Pfund http://bpspecialprojects.com/ (see his Pro-Boat Articles) has written some excellent articles analysing problems and practices in GRP construction
In respect of specific items in Matt’s article, I question specifically
1. “Engineers become nervous” – which engineers was/is my question, this is an unsupported generalisation? To give an analogy, my wife is a respiratory specialist but even though she is a doctor she would never give advice on say neurology or any other specialty. Similarly you would not normally ask an engineer who designs supertankers for a professional opinion on composite structures for small craft, or vice-versa. Pascoe himself said in his opinion that a contributing factor to the many of the issues he identifies is that it appeared engineers with a naval architecture background were being replaced by industrial engineers with no applicable marine experience by the big manufacturers. A problem I see in my own industry is CAD draftsmen (& women), they know how to drive the software but they really do not know what they are drawing. You go to the people who have the experience in the medium under consideration and there is now a depth of experience available where cored fibreglass is concerned. The trap of NIH (not invented here) needs to be avoided as well – think back to the 1987 America’s Cup in Perth, Connor’s technical advisors and engineers had told him a fibreglass 12m could not be built in compliance with Lloyd’s requirements, yet NZ proved it three times over (KZ3, 5 and 7) and it was all about a matter of attention to detail in the engineering and rigorous QA/QC during construction to ensure weight compliance.
Dashew, who as we know is a fan of aluminium, has also overseen a number of yachts built from cored fibreglass (I believe all balsa) under his Deerfoot and Sundeer brands. These include his father’s original Deerfoot and Wakaroa (both built in NZ in the late 70’s and still looking good today) Deerfoot 61’s, 2-62’s (eg Moonshadow) and most significantly the Sundeer 56 and 64 production series, built by TPI. His Ocean Cruising Encyclopedia has a very good discussion about how they arrived at the hull laminate specification for the Sundeers including the areas they decided should be beefed up to protect from localised impact.
2. In relation to the Claw Hammer story, as Matt says that is probably apocryphal, then I ask what is the relevance – maybe it occurred (maybe it did not) but under what circumstance, what type of boat etc? I have seen pictures of core test panels subject to this very test which showed no damage.
3. The Bertram 63 which lost its outer laminate – there is an article on Pascoe’s site about this and you can sum up the failure as a combination (but not being sure which had the greater weighting) of poor laminate specification – he said the uni-directionals were only running fore and aft, nothing transverse – and poor building practice in that the laminate and core were not properly bonded. Do you condemn the construction method because of poor workmanship?
4. The Pascoe article on Cores – to quote Pascoe in one of this series in respect of a Sea Ray “Here’s fine illustration of what is meant by the laminate being comprised of an extremely small amount of fiberglass reinforcement. The only glass you see here is a single layer of Roving on the inside of the hull, with the exception of a very, very thin layer of mat against the gel coat. Otherwise, the major part of this Sea Ray hull is comprised of some kind of very porous material. Notice how huge chunks have broken away. This would never happen with fiberglass laminate”. Once again coming back to design, material selection, work practices and QA/QC, not a condemnation of the method.

In summing up it keeps coming back to all the previously mentioned requirements, ie proper design and engineering, appropriate materials selection, correct work practices with the supporting QA/QC are essential to ensuring a good product in any medium, but in particular any form of fibreglass construction (or for that matter a multiple-skin wood laminate). This is because there is less opportunity for “post construction” visual inspection or verification (unlike say metal or traditional single skin wood) and NDT is not typically conclusive, although in saying that there are some promising new techniques using thermal imaging. For example it is very difficult to verify if a Taiwanese “leaky teaky” with its 30mm thick hull actually has any woven rovings in the laminate, or is it all CSM with very little tensile strength.
I have said I like cored hulls but they must of course use the correct build method(s). In my view the only acceptable way to laminate a cored hull in a female mould is by Resin Infusion, there is no way you can be sure of having a full core bond using core bonding putties between the outer skin and the core material. Furthermore the kerfs in the core have to be carefully considered to ensure they are filled with resin, otherwise there is a potential moisture path. My preference, and obviously this is for custom boats, is the way my yacht was built – male mould with the core first put in place and then glassed over externally which ensures the best possible bond because you are pressing down on the core (either manually or using vacuum) and you do not have to use the kerf’d core. Then turn it over and glass the inside. Chuck Paine in his recent book of designs makes this same specific comment. Kelsall’s KSS system achieves much the same result by his process using infusion on a laminating table, however this method has its shape restrictions being limited to slim hulls ie cats or tri’s without too much compound curvature.
Aluminium has its own set of issues to consider for construction. Just one example – consider an aluminium hull being welded in a warm environment, the welder is getting hot so he opens the shed door to get a breeze thru and what happens, the shield gas for the MIG welding process is blown away and you are left with a sub-standard weld. Maybe that’s what happened with the Thai boat I mentioned previously.
I could write a lot more, but this has become rather longer than intended. Hope readers gain an understanding of some of the issues involved and this promotes further discussion, might even give John some thoughts in relation to the Adventure 40
Regards
Alan

John Harries

Hi Alan,

Just to clarify, nowhere in his three part series on hull materials did Matt express any preference for aluminium over GRP. All he said was that he did not like or approve of cored laminates under the waterline on voyaging boats–an opinion I agree with.

You might want to re-read the first part of the series in which his whole premise was that there was no best material for sailboat hulls.

Matt Marsh

Hi Alan,

I do agree with you that cored construction can and should play a role in many applications. I don’t think this technology should be categorically dismissed; foam- or balsa-cored fibreglass is often an ideal choice for decks, topsides and bulkheads, and one would be hard pressed to build a competitive modern raceboat without cored composites.

The only place where I will unequivocally reject cored construction is from the waterline down on a cruising boat. This is for two reasons: the risk of long-term water damage to the core, and the tremendous difficulty in creating a cored structure that can survive an impact with a hard object. (Once you’ve designed the structure and are confident in the design, there’s still a big gap between being confident in the final product of skilled craftsmen making a one-off under a class surveyor’s eye, and being confident in the final product of $10-an-hour labour laying up a hull a week.)

There has been a point raised about my technical training and qualifications, to which I respond: My formal training is in engineering physics, an R&D-oriented discipline that includes most of what mech eng and physics students would take, a fair chunk of what elec eng and math students take, and a few other random scatterings. My experience in things directly related to the cruising boats discussed here at AAC include 20 years driving and fixing boats and roughly 5,000 hours of academic study and shop time in hull and rig design, fluid dynamics, advanced composite construction, DC power systems, engine and drivetrain, and structural analysis. I do not, and will not, write about topics which are outside my realm of experience and knowledge.

Philip Waterman

I stumbled upon this interesting photo:

comment image

A picture is worth a thousand words as they say!

I presume that this is an aluminum hull looking at the apparent malleability.

John Harries

Hi Philip,
Yikes, that must have stung! Good advert for aluminium though.

Matthew Clark

This is a fascinating, and somewhat confounding discussion for someone who is following all of the design, construction, budgeting and planning articles carefully as we research, consider, and inspect various boats in our quest for a relatively affordable cruising boat that we can refit and enjoy for years to come. Without getting too far into the weeds on personal selection criteria, two of the boats on our list for consideration are the Tartan 41 and Ericson 39, there are certainly several others but I want to use these two as an example here because I think they illustrate my question well and relate to topics brought up here. The Tartan generally seems to have a better reputation and by all accounts is built like a tank by a reputable builder who is still in business. I’ve come across no accounts of structural issues in them yet. The Ericson generally seems to be considered more lightly built in more production focused environment, and I’ve read accounts of the hull flexing and tabbed bulkheads breaking loose over time with hard sailing, similar to people’s experiences with Cal 40’s and some other uncored GRP boats. I’ve come across some laminate schedule info on the Ericson that shows 7/16” thick sections at either side of the glassed in keel and 5/16” at the bow. Unfortunatly there is no info about other parts of the hull, or the keel to hull transistion area. The T41s I’ve inspected have full balsa coring, all the way under the waterline, ending somewhere before a very heavy duty over 1” thick keel stub area to accept the bolt on lead keel. Some of the very first boats might not have had this but it sounds like they were trying to lower the weight pretty soon in the build cycle as they came out heavier than intended as designed. Leaving out the obvious possibility of removing both of these boats from consideration, and knowing that they both enjoy a pretty dedicated following and have sailed all over the world, if you (John, Matt, and others with informed opinions) had to choose in this sort of situation, which criteria would you weight higher? I tend to want to favor the repution of Tartan and the generally heavy duty build of the T41 in particular but this discussion on coring has given me pause. Maybe this is just to big, and at the same time too specific of a question but any thoughts are appreciated.
Thanks again for all that you do, Matt

John Harries

Hi Matthew,

Unlikely that Matt will answer: https://www.morganscloud.com/2013/11/10/aac-comment-guide-lines/ (#5)

I like the Tarten 41 as a boat, although it does have a very funky IOR stern that makes them a bit squirally off the wind.

As I understand it, only some were built with balsa in the core. Given that this was very early days for this technology and that the boats are now 40 years old, I would probably avoid those hulls.

On the other hand as I remember, the Ericsons where not, as you suspect, built to a very high standard, although that did, I think vary a lot. I do remember the keel fell off one being delivered to Bermuda, although admittedly, that was when a tow rope got around it.

Bottom line, the key to all of this is going to be a really good survey, not an opinion you get from me, or anyone else. See our online book for more on how to make sure you get that: https://www.morganscloud.com/category/boat-design-selection/book-how-to-buy-a-cruising-boat/