A new wooden yacht build, strip planking technique technique impresses

[Rumars]

Treating veneers as reinforcement over a core is nothing new, de Havilland did it in 1938 with a balsa core and birch veneers. Durakore is another such product, mahogany veneers over end grain balsa. COVE uses foam for core, and in some cases replaces some of the wood with fiberglass or carbon.

From your description I expect Amati to have something like this for a layup: woven finish cloth, biax +/-45° glass, 0° wood, uni 90° glass, foam, repeat. The wood is not treated as a core, it's just another reinforcement layer. Arranging the different fiber orientations in a stack is done the same as for an all glass or carbon skin that uses unidirectional fabrics.
Cold molding uses the same principles using only wood, just like a monolithic glass or carbon build. It's seldom used to full advantage because you run into material handling problems, the individual skins are either to thick and require steam bending, or to thin wich requires a lot of layers. There comes a point where it's simpler to substitute some of the thinner layers with something else, like glass or carbon, just like there comes a point where a semi-monocoque is lighter then a true monocoque.
You have to consider wood for what it is, an anisotropic composite material, cellulose reinforced lignin if you want it simple. Using it is like dealing with cured man made composites or a very thick and stiff prepreg.

 

[baeckmo]

..........You have to consider wood for what it is, an anisotropic composite material, cellulose reinforced lignin if you want it simple. Using it is like dealing with cured man made composites or a very thick and stiff prepreg.

Excellent engineering definition, Rumars!

 

[gonzo]

what wood was used for the one tonner?

True mahogany. It came from Brazil.

 

[Paul Scott]

Treating veneers as reinforcement over a core is nothing new, de Havilland did it in 1938 with a balsa core and birch veneers. Durakore is another such product, mahogany veneers over end grain balsa. COVE uses foam for core, and in some cases replaces some of the wood with fiberglass or carbon.

From your description I expect Amati to have something like this for a layup: woven finish cloth, biax +/-45° glass, 0° wood, uni 90° glass, foam, repeat. The wood is not treated as a core, it's just another reinforcement layer. Arranging the different fiber orientations in a stack is done the same as for an all glass or carbon skin that uses unidirectional fabrics.
Cold molding uses the same principles using only wood, just like a monolithic glass or carbon build. It's seldom used to full advantage because you run into material handling problems, the individual skins are either to thick and require steam bending, or to thin wich requires a lot of layers. There comes a point where it's simpler to substitute some of the thinner layers with something else, like glass or carbon, just like there comes a point where a semi-monocoque is lighter then a true monocoque.
You have to consider wood for what it is, an anisotropic composite material, cellulose reinforced lignin if you want it simple. Using it is like dealing with cured man made composites or a very thick and stiff prepreg.

Which is exactly how Steve described COVE. And which also begs the question: how do you factor in the weight/strength differences of varying species of wood? For example, the true mahogany of Gonzo’s 1 tonner example is ~32lbs per cubic foot, Port Orford Cedar ~27 per cubic foot (assuming roughly the same moisture content?), and both exhibit different strength characteristics, resistance to rot, resilience to bumps, ease of fairing, etc etc., which all enter in to the design/build calculu$.* Having had a boat built, and being exposed to the wildly varying cost differences of different build methods was bracing if nothing else, but cultural attitudes towards different build approaches within the industry was even more complex and even bruising at times, even ignored or assumed (?) during initial design stages.

*And how man made materials complement wood to achieve design/budget goals- for example: mahogany 1 tonner weight/ cubic foot vs COVE weight/ cubic foot for what kind of performance goals. We also had an Ultimate 20, which was built at Ron Moore’s shop, which was Santa Cruz style construction- balsa core, which was lovely, stiff and light, no water ingress problems, but it was assumed, IIRR that it needed a mold, and even finding a balsa core boatbuilder at that time who wanted to build Amati seemed weirdly problematic. One foam/glass boatbuilder that Bob wanted to use, after an interview with me over the phone, decided he didn’t like me enough to build her (to which I am sure some here are nodding their heads in agreement). Delicate dance!

 

[jehardiman]

I concur with Rumars; the wood is a much better composite than we can build. See John Guzwell's book Modern Wooden Yacht Construction.

 

[Paul Scott]

I concur with Rumars; the wood is a much better composite than we can build. See John Guzwell's book Modern Wooden Yacht Construction.

Endangered Species is a 10 minute walk away- always inspiring! His son did the teak work on Amati.

 

[jehardiman]

Endangered Species is a 10 minute walk away- always inspiring! His son did the teak work on Amati.

I used to work with Dave Mancebo (out of the Wylie Design Group) who designed/built (cold moulded) CRITICAL MASS (MORA/IOR mini-tonner) and BLOOM COUNTY (well known SF Bay MORA winner) in the 1980's. We both believed that for a one-off couple sized yacht, cold moulding was the way to go.

 

[Paul Scott]

More modern wood

Traditionally futuristic - Seahorse Magazine https://www.seahorsemagazine.com/current-issue/188-content/february-2023/1279-traditionally-futuristic

 

[gonzo]

That is mostly sales hype. There is nothing revolutionary about the design or construction.

 

[Rumars]

And which also begs the question: how do you factor in the weight/strength differences of varying species of wood? ...

You want to know how the sausage is made? Actually no so different from all the others. After you have done the math for the loads and specified other requirements that might be important for you, like for example puncture and rot resistance, you start playing the weight vs. stiffness vs. strength game.
There is a bewildering array of wood species, but first you look for what's actually commercially avaliable to the builder, what glues well, and anything else you defined. This will usually reduce the choice to manageable proportions, and you can start running simulations. For example, for strength X you can use 1mm of purpleheart or 3mm WRC. Now it's a question of what's more important, weight or stiffness, since in this example the WRC weighs more but beeing thicker is a lot stiffer. Let's say stiffness is excessive, so now you look at sitka spruce, where 2mm satisfy the strength, stiffness and is lighter. But spruce isn't rot resistant, so you look at Port Orford Cedar to see what can be done with that. In the end you arrive at a compromise between mechanical properties, other factors and building praxis. Using 1mm thick veneers isn't really practical, especially if you have to use a lot of them, since the adhesive quickly builds up weight. Once stiffness is satisfied, weight is the point where you go to other fibers, a single layer of glass or carbon can provide the needed strenght.

Using end grain balsa without a mold is normally done only on multichine boats, as exemplified by all the Durakore builds. With compound curves it becomes a messy and time consuming affair, it's more practical (read cheaper) to use foam, either thermoformed or stripped vertical.

 

[Paul Scott]

That is mostly sales hype. There is nothing revolutionary about the design or construction.

My apologies, I meant only to point out that they are doing it, and it is working for them.

FWIW, for my small boat projects, because of allergic reactions, I can’t use epoxy, Gorrilla Glue, Resorcinol, a bunch of other glues, balsa, or any type of cedar. Less reactive woods (like Hemlock and Ocume) have become my go to, as well as Titebond 2 or 3. What I discovered in all this is how heavy cloth and epoxy are (as in all wood structures can be lighter, if I’m clever), and how difficult it is to get non epoxy hulls not to leak. I really don’t want to go back to carvel planking , Resorcinol (which I believe eventually killed him), cotton and goo like we used on my dad’s boat projects. But the really fine woodworking necessary for watertight wood boats is a time sink pain in the butt, and I was a piano tuner/tech for 42 years, so that’s saying something. Sometimes ya just wanna go sailing.

 

[wet feet]

That is mostly sales hype. There is nothing revolutionary about the design or construction.

I would describe it as promoting their methods as there was nothing other than the truth of the matter expressed.It does no harm to remind people that wood is not only available and easy to work with,it can produce a very sound boat that fulfills it's owner's requirements.I'm not too sure about how many designers without exposure to the material in recent times would have made the leap of faith to go with the material that Noah used.

 

[DCockey]

Brooklin Boat Yard in Brooklin, Maine has built numerous boats with diagonal layers of veneer over strip planking. It's a fast, efficient method to obtain a fair, light hull. They start with a set of CNC cut cross-sectional molds which they can erect in a day or so. The molds are checked for fairness and typically no adjustment is needed. The layer of strips naturally fairs fore-aft. The diagonal layers and possibly layers of glass/epoxy can be designed to provide the desired strength and stiffness. In the Shop — Brooklin Boat Yard https://www.brooklinboatyard.com/in-the-shop

 

[wet feet]

Six or seven years ago I was watching a fellow doing some work on a boat which looked fast and from a different era.It was about a 36 footer and seemed to be in excellent condition.I complimented him on keeping it in such good cosmetic condition and asked what it was built from.He told me it was a Dick Carter One-Tonner from the late 1960's and it was cold moulded.there wasn't a hint of a plank seam and it looked like a well finished glass boat.Such things could be done and it didn't need to be sheathed or held together by epoxy.I often think the fixation with epoxy for every conceivable use has gone too far.It can be a great material,but for adhesion once you have a glue that is stronger than the wood it is bonding,why go further?
The Uffa Fox boats mentioned earlier were hot moulded in Fairey Marine's autoclaves and have survived exceptionally well.Possibly because the heat of the process destroyed any destructive life forms in the wood,even if the vacuum didn't suffocate them.

 

[Rumars]

I often think the fixation with epoxy for every conceivable use has gone too far.It can be a great material,but for adhesion once you have a glue that is stronger than the wood it is bonding,why go further?

Please provide the name of the glue that is: structural, waterproof, gap filling, requires low clamping pressure, has a long open time, is reasonably cheap and widely available.