The Offshore Voyaging Reference Site

One Tough Old Aluminum Boat

It is amazing how often people look surprised, and even mildly alarmed, when I tell them that we own an aluminum boat. The next tentative question(s) is almost always about electrolysis and the general longevity of the material.

For some reason there seems to be many stories of disaster, particularly on this side of the Atlantic, around aluminum as a boat building material. These stories normally go like this: “I have a friend, who knows a guy, who has a cousin, that bought an aluminum boat, and after a week in the marina the bottom fell out of her”.

The funny thing is that after 20 years of aluminum boat ownership and ten years of being a fairly high profile proponent of the material, I have yet to meet one of these mythical aluminum boat victims.

The fact is that as long as the boat is built out of the right aluminum alloys, and the right welding wire is used (all well documented), aluminum boats last longer and stay stronger and more stiff than boats built of any other material you can think of.

Which brings me to Carina, a McCurdy and Rhodes Custom 48—same designer as our own Morgan’s Cloud—that has just won the Newport Bermuda Race for the third time. Thing is, the first time Carina won, the leisure suit was in fashion…the year was 1970.

Carina won again in 2010, exactly forty years after her first win. And then again this year. And you know what Carina was doing between her second and third win? She sailed around the world clocking up 42,000 miles. And while she was at it, she did a few races…like The Trans-Atlantic, The Sydney Hobart and The Fastnet—not exactly known as walks in the park.

One tough old bird that aluminum boat…fast too.

I spoke with Rives Potts, who is not only Carina’s owner and skipper, but also runs Pilots Point Marine. Rives has been involved in building and repairing many aluminum boats over the years. He had this to say:

  • If an aluminum boat is built of the right alloys and the right welding wire is used, she will last essentially forever.
  • The great thing about aluminum is that what you see is what you get—if you have a problem, you can see it.
  • He has not had to make any structural repairs to Carina. And she shows no significant corrosion.
  • She is still incredibly stiff and strong after 43 years of hard voyaging and racing.
  • And because Carina is stiff, she is still fast and it is much easier to keep the deck fittings and hatches watertight than it would be on a boat that flexes more.
  • When he has seen corrosion damage on aluminum boats—usually the result of a wiring problem or an inaccessible area where debris has lain for years—it is confined to a small area and is easy to repair as good as new by cutting out the plate with a skill saw and welding in new plate. Just make sure you use the right alloy plate and the right welding rod.
  • Repairs and modifications to an aluminum boat are easier [that means cheaper too] than they are on boats built of most other materials.
  • The only real drawback of aluminum is keeping paint on it. But if the paint job is done right even that issue can be overcome.

So if you are looking for a boat to take you offshore safely and comfortably, don’t look past that old aluminum boat. She might have a few years and miles left in her…or a few decades and a few circumnavigations.

And if you are crazy enough to embark on a major refit, at least if  you are restoring a well built aluminum boat, you will know that you are investing in a good hull, unlike poor stupid Bob.

Comments

We are cruising the south coast of Newfoundland, where internet availability is scarce, so it may be some time before we can respond to comments.

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Michael Shea

Very true. As a fellow 40-year old McC&R (Luke-built) aluminum sailboat owner, I couldn’t be happier. There is simply nothing as secure, quiet or comforting as racing through the ocean in a metal. No flex, no squeaks, no leaks, no oil canning…just pure power and smooth sea motion. Mine ws refit with a ‘wooden boat interior’ for the best of both worlds. Of course, most of this credit is due to her designer but there is no question that aluminum is a terrific material from which to craft a boat. Commom sense prevents all the rumors.

C. Dan

And yet… not for the Adventure 40?

Jean-François

Dear John,

I confirm your figure for deck and bottom for a Adventure 40 with a simple deck shape and if the welding job is done correctly so you don’t have layers and layers of filler to applicate.

But for a hull you would need to add much more than the additional 5000 you mention…. Mostly to the get the hull ready to paint.

I understand what you say about the willingness to have an unpainted hull but at the same time painting the hull would be – in my eyes – against the philospohy of the Adventure 40 and the idea of low maintenance

And the first scratch is a very expensive one…

Jean-François

Bruno

Hi,
i have actually a question on that one, and more specificaly on painted decks, as i have to remove the many layers of different ugly paints and the antislip on good old “Moscatel”,
i will sandblast it first, and i’m actually considering leaving those decks blank, or at least where it does not need antislip,
what would be yr feelings abt that ?
next question is of course which antislip to apply after that …
The hull would remain as it is, as it was originaly faired by epoxi resins and painted, and repainted epoxi.

Jean-François

Hey Bruno,

It seems like you have a Romanée…

One thing : You don’t know what you will discover under your paint. There might quite some filler… If you sandblast you have to remove everything.

On our first boat, we sandblast the deck to remove everyhting. It took us much more time and sand than we tought. At some place we had several cm of filler…
As the paint was ugly but ok when we had removed the 20 year old treadmaster, we would have been better of with just a new layer of paint and new Treadmaster or a (Sicomin) anti slip paint…

After sanding we did ourselves a complete cycle of paint on some part of the saloon (and the hull) because of ethetics. 12 years later the paint is still perfect.

Jean-François

Hi John,

There are different answers to your question. Some elements which contributed to our choice :
– esthetics : general look of the boat. We did not want an all “grey” boat.
(But note that at the same time, we did not want any paint on the hull. This has determined the way we build the hull)
– esthetics : we wanted the look of the deck and the saloon to be tight and tidy. Said in another : we wanted way to hide the imperfections of the boilerwork. Therefor we wanted filler, therefor we have paint…
– antislip : we do not discuss the effectiveness and the qualities of Treadmastesr, but esthetics is another question. Moreover the day you have to remove it, it is a very very hard hard job (Bruno will confirm). You can also say that walking barefoot on it is not very pleasant. We use as anti-slip paint made by Sicomin Deck Line (bi component). The constitution of the paint makes it is “elastic”. It is either sprayed or applied with a roller. The way you apply it will determine its final aspect.
So under the antislip we apply the whole cycle of paint all over deck and deckhouse.

Note that the traditional paints are mechanilly bonded on the aluminium.
Now there are paints coming up which are bonding chemically tothe aluminium. This does make the process “lighter” because the surface oxide is not a problem.
There is a Swedish boatyard which is doing some tests with it. It is (at least here in Europe) pretty new and there is no feedback yet.

I hope this helps…

bruno

Hi,
many thks for yr feedback on antislip and deckpaint, and yes, the good old Romanée needs some efficient cosmetics, foreseen for next winter, you are both right, and a choice will have to be made, after blasting,
i’m also really convinced by antislip paints, as i use them since 25 years on my (job) oceangoing steelships, we just mix antislip slints during our epoxi-polyurethane cyclus, and this work great and easy, nice surfaces, good holding,
But as you say, the chemical bonding is usually a bit of a problem on aluminum, and i hate to re-do things too fast …
I have now no choice but to sandblast, i’m quite confident on the surface condition, as she is a 1979 (they started to build them in 1973), and hopefully used less filler 6 years later (i might check with builder G.Fillon), some even sandblasted the hull after years and left it blank,
After that, i’ll have to make a (fast) choice, as for so many (good) things in life …
thanks again !

Abel van Staveren

Great post and reassuring comments from you experts for greenhorn Alu owners like us. We acquired a 23 year old alu Koopmans 48 last year and so far have nothing to complain about. Amazed at the speed considering her weight. We carry 8 tons of lead due to the lifting keel having no ballast so she weighs twice as much as the tupperware equivalent. Hull lines look fairly similar to the Carina
Cheers
Abel

Petter

hello Abel,
it appears that we sail very similar vessels. might be both fun and useful to connect. I see that you plan to enjoy Norway – and my Koopmans is one of two currently based there. Feel free to reach me at moc.liamg@smrettep
rgds, Petter

Colin Speedie

Not only a great material, but a great looking boat too – lovely sheerline.

A boat to gladden the heart of any owner – no wonder he’s hung on to her!

Best wishes

Colin

Bill

What is the correct aluminum alloy and rod?

Matt Marsh

Hull plating is usually done in strain hardened alloys 5083 or 5086 (also common are 5456 and the slightly weaker 5054).

Framing could be 5000-series but is more commonly of 6061-T6.

I’ve never seen anyone stick-weld aluminum; it is usually welded by MIG (with a 5000-series electrode) or TIG techniques, with an argon or helium/argon shielding gas.

Aluminum is tricky to weld correctly and is very prone to fatigue around bad welds. When you combine a knowledgeable designer and a skilled welder, you can end up with aluminum hulls that will last almost indefinitely. If you give incorrect detail drawings to someone who isn’t quite so good with a MIG torch, you’ll get stress risers, poor returns and poor penetration, and you’ll find yourself wondering why the boat’s full of fatigue cracks in her second season. If you want to use aluminum, it’s really important that everyone involved takes the time to learn how to use it correctly- this means a lot of reading, and a lot of practice on bits of scrap.

Bill Stine

Great info, this is the first I have seen this list of aluminum types, Is there a way to find which aluminum types were/are used by the companies that build aluminum sailboats?

Jean-François

Hi Matt,

Absolutely perfect information. I’m happy I had not to answer this one as you express things in a much clearer way than I can do.

Note that theoretically all alumiunium with the same denomination (5083 or 5086) should be exactly the same.

According to our insurance they have on regular base claims from non conform aluminium coming from some countries.
In our contract we commint our Aluminium is coming from Norway, Holland or France.
Each plate is marked and you can track the origin…

Bill : the constructor should mention in his technical description which aluminium he uses for what. During the construction you should be able to see it on the plates…

Andrew Troup

The preferred electrode/filler wire grade for MIG and TIG is 5356: this *can* be used to weld 6061 as well as the 50xx alloys for the plating.
(Incidentally, it *should* be used for 6061 for any weldment which will be anodised.)
Opinions differ on whether there’s any electrochemical issues when combining 6061 framing or welded thru-hulls etc vs 50xx plating
If there are problems, it seems likely they’re either very subtle, or only arise under highly unusual circumstances.
Some builders hedge their bets by preferring to avoid this combination below (heeled) waterlines for thru-hulls, or in the bilge-water zone for interior framing.

Andre

I’ve seen an experienced boat builder making a Philippe Harlé boat, and he explained to me that the secret of fabrication is 1) the welding equipment that MIG has to be water cooled for better precision and 2) the hammering process after welding to rebuild the strenght loss in the HAZ (Heat Affected Zone) where aluminum alloys loose all their mechanical and structural properties. If someone doesn’t hammer correctly the hull, it will not be possible to have it without paint as all the defects will appear. So not easy for an amateur to do a first time boat in aluminum.