New Memeber with a question

Hans has bigger balls than I do! Sailing that hand hewn beast across open oceans with strips of conveyor belt to seal it is admirable as hell, for those who can do it! I am not familiar with the asymmetric hull concept, esp pointed into one another at the bow. Very interesting link, thanks much! A composite version of that vessel might be perfect.

 

Which marine plywood? I am not sure if the old school, old growth fir and larch (tamarack) plywood is still available, and not so sure about panels with okoume cores either. You have any recommendations? I have done some initial research and the results I found were that some species of bamboo are actually quite rot resistant, and resist boring worms while featuring great strength to weight characteristics. But I absolutely agree old school marine ply is good stuff. Second growth softwoods are a fraction the quality of old growth materials.

 

European builders always used hardwood plywood, now it's okoume for light weight or sapele or khaya for rot resistance. There is also good ply in the meranti group, but it's highly manufacturer dependent. Birch ply is an option, but heavy. In the past maufacturers used even real mahogany and other rot resistant tropical species for ply.
There is no bamboo ply made to marine standards that I know of (wich does not mean it does not exist). But bamboo ply is heavy as hell, makes birch look like a lightweight.

To be fair, hull material costs are location dependent. Plywood is only cost effective if not sheathed, the moment you start sheathing both sides it's not cheaper than strip plank composite. Foam/polyester can also be cheap.

For what you want I would take Woods Ondina design.

 

For solid wood and low grade plywood, that would be true. Second growth trees are younger, grow faster and have more branching because they are not competing for sunlight the way old growth trees do. This makes them knotty and not so straight in their grain. However, the standards for marine grade plywood dictate that the flaws that make this wood inferior have to be corrected or not used. No knots or voids internally and the quality of the glue is better than ever. I'm no expert, but I think you are not done with your research.

Steel, by the way, does great in marine environments if handled with knowledge and forethought. Better than aluminum.

-Will (Dragonfly)

 

The density, pitch content and tight grain of old growth softwoods are what make them so much stronger and stiffer than second growth. Douglas fir used to be used for hand split roof and siding shingles when old growth was abundant. Don't try that with second growth A single deep V hull 50' long and approx 7' deep/wide weighs over 4000 lbs. That is just for the skin no bracing, ribs or longitudinals. And that is 1/10" thickness, just barely thick enough to weld without offensive distortion (if you are careful) and to be stiff enough to take any abuse. Steel is the only choice for building ships. Too heavy for small vessels. And steel hulls can look like crap and be very high maintenance after 5-10 years. Not a prob for professionally maintained commercial vessels with budgets for that. But even commercial steel ships have a 20 year average working lifespan anymore.

 

Thanks for the inputs. I did some googling around and found somebody who had all of those species except BB and was able to compare prices. The only two that are reasonably rot resistant were doug fir and sapele, which cost 5 times what the fir costs. Found lots of other hardwood products but they were decorative with thin hardwood veneers over okoume or some other substrate. White oak was surprisingly cheap, just twice the cost of fir while stronger, harder and more rot resistant than second growth fir. But I am sure it is heavy. I haven't located marine grade bamboo plywood, just some quality veneers in China and a wide variety of bamboo panels. All different orientations. But marine grade mainly means free from voids and knots and splits. Bamboo is a completely manufactured product it has no flaws at all in the finished sheets. Practically homogeneous. It is so tough and strong it could make great layups in composite arrangements with lighter cheaper core material. But so could white oak.

 

I'm guessing, from your name, you are familiar with Harryproas? They would seem, on the face of it, to answer a lot of your requirements.

 

HPs are all about performance and have to compromise everything else around that.

 

Where exactly are you envisioning to build the boat? I ask because you have Spain as location and I don't know anyone selling douglas fir plywood in Europe.

 

hopefully in Portugal but not certain yet. Locals here tell me it can be sourced but it may be pine not fir, my language skills are not sufficient to differentiate.

 

In Europe "fir" always means a true fir, namely silver fir (abies alba), not Douglas Fir, wich is called either douglas(ie) (usually means european grown wood) or Oregon pine (imported from Canada or the PNW, often old growth timber and differently priced).

"Fir plywood" is an undiferentiated mix of spruce (picea abies) and true fir (abies alba). Then we have "pine plywood" wich is usually made out of scots pine (pinus sylvestris). Highest commercial grade available with exterior glue for both is B/BB. Due to market demands A/A and A/B qualities are only interior rated.
Then there is maritime pine (domestic) and elliots pine (imported) ply, wich is only good for packing crates.
You will only find good grades at specialized timber merchants not the local DIY store.
Then there are the various okoume/khaya/sapele/etc. ply manufacturers, from mixed quality up to Lloyds rated.

For a big boat like you want, monolithic fiberglass (polyester resin) with top hat stringers is always a possibility, and cheap. Another option is strip planked with a tropical wood (african wood is cheap in the EU) or black locust (domestic) or larch (domestic or siberian). If you want it lighter, strip composite with a non durable local wood (spruce, fir, douglas, pine).

As for sourcing don't panic, you are in the single market, it does not matter where in the EU you buy, transport is cheap.

 

Rumars said it best.

 

thanks for all of that. I hadn't even considered buying outside my local region. Will look into that.

 

Here, fits all your criteria, 15m long, 6t max. load, open deck, plywood on stringers, CNC cut kit available, no compound curvature, basic interior, living designer to change what you want, one has been buildt and is available for charter.
Balta Patrick, Architecte naval, motor yacht, catamarans http://balta.fr/CATP.html