I thought it looked familiar. It needs the ama design update. http://sarasota.craigslist.org/boa/5792085107.html
I found this container ship trimaran in Pacific Maritime magazine. KNUD E. HANSEN A/S was design office proposing these con/ro ships. By eyeball it looks like that would be too much weight to get in under 1/10 magic fineness ratio on the main hull. And I can’t believe that those tiny amas so close in would help much in a beam-on wave situation. it sure seems like a catamaran would be a better choice.
I see that the Choy catamaran ImiLoa is for sale. http://www.ebay.ca/itm/CATAMARAN-SAILBOAT-43-CSK-Rudy-Choy-Design-ImiLoa-/232058125191?hash=item3607bdfb87:g:HnEAAOSwj2dXj8UL#viTabs_0
ImiLoa was kind of famous here in the PNW back in the old days. First, let me explain who Larry Christensen is. Back in the 60s he designed and built a 37′ trimaran that was years ahead of it’s time. Invictius had a huge dagger board, was wide, and had big amas way out there. And it was rigged to excel upwind, for its time. Unlike the famous Atlantic ocean trimaran designers who were using 3 strand halyards and had huge forestay sag, back then.
Larry basically schooled a whole generation of builders and sailors here in the PNW, including me. And he did every race he could, including a couple of Transpacs. Am doing this from memory. Anyone actually knows more, do share.
So ImiLoa came to the PNW to do the Swiftsure. They were bragging that they were going to clean everybody’s clock, including Larrys. “Wait,” Larry said, ” You are telling me that you don’t have boards on that boat?” “No.” “You won’t even finish on the same day that I do.” They didn’t.
I see on the specifications and the boat, that it has boards now. Larry must have taken them to school also. Does anyone recall what year that was?
Wood Boatbuilding Fusion
Some time ago I was invited to give a lecture to the Seattle Central Community College school of wooden boat building.
I advisd them that their futures were not in steamed knees and nuances of refastening a hull. I told them that the future of wood boatbuilding was in fusing wood/epoxy technology with composite technology. Together they offered advantages that neither can separately
I don’t know if they were impressed, but some of my fusion samples never made it back to me. I guess that is good.
Wood and plywood have many advantages that many composites don’t have. Woods, for example, have a fatigue strength that is only matched by carbon fiber and is more than double that of E glass. After some 10 million use cycles, plywood and carbon have about 50% of the strength they started with. E-glass has about 22% of the strength that it had initially.
Plywood has an industrial smooth surface finish that composites can only achieve after hours of finsh work or a large bagging table. It comes that way right out of the factory. One should try to use those advantages given by the economy of mass production wherever possible.
A fusion composite part probably will not need a mold. The plywood appearance face can form the part. When I built the composite lunar lander, if I would have had a big budget, I might have infused the parts with triaxial roving and pvc or sen core. I would have needed molds or at least a bagging table. I did not have the budget so I vacuum bagged my own SIP panels by vacuum bagging ply faces onto foam core.
By itself wood or plywood is too heavy to be efficient against out of plane loads or to be restrained against global loads. Composite cores like pvc, sen, or balsa can make a very strong panel by bagging the core to the plywood and in turn, bagging more plywood or composite fabric onto the opposite face. The result can resist out of plane loads and or, restrain a structure against global loads at much much less weight than a solid plywood or even plywood and stringers can do.
All wood used as an engineering material must be encapsulated in epoxy. That not only improves the wood’s mechanical properties, but it protects it against moisture and rot. The epoxy also becomes the bond with the core and or fabric that is used. Epoxy is also much easier to get right, especially if the temperature of the workspace changes during the day. Polyester or vinylester initiators and catylists must be mixed accurately to often fractions of a per cent. And that measure must change as a function of temperature. I always say that you can be almost brain dead and still get epoxy right.
Plywood has extra benefit from combining with carbon fiber. Plywood and carbon fiber both have a stretch to failure of about 1%. They work very well together. In comparison, E-glass has a stretch to failure of about 5% to 6%. So if the combined part of plywood and E-glass is loaded to failure, the plywood will fail while the glass is onIy contributing about 20% of its strength. I have seen plans of catamarans by famous multi designers, who charge much more than I do, who design beams with plywood and E-glass combined. With enough glass, it works, but is very inefficient. And I remember one set of plans I saw with something like 20 layers of e-glass uni was called for. The schedule not only had no cross laminates, but the contact surface with the plywood was minimal. Those each are a failure waiting to happen. Combined? Wow.
E-glass does have a place with fusion products, but not against global loads. Glass cloth is great at providing damage protection and a vapor barrier for plywood. Glass cloth or biaxial roving are ideal for joining parts where global loads are not involved. The extra give that glass has can do very well to prevent the energy of crack initiation on a plywood free edge. Like a ripstop.
Ideally the carbon fiber is vacuum bagged to the plywood with the warp in the same direction as the plywood 0 degree. In general you can replace about 10 thicknesses of plywood by one thickness of carbon fiber, for bending strength. Note that many other factors enter in, but in general that’s true.
Plywood, lumber and composites combined can create products that are synergistically better than the different parts that were combined. Fusion.
So I’m off to the Port Townsend Wooden Boat Show again. The list of topics is mostly traditional stuff. I see fellow designer Richard Woods will be presenting.
I should have offered my program on plywood/composite fusion that I presented at Seattle Central Community College School of Boatbuilding. I thought it was at the website but I see not. I will post it in next post.
I did print up a splashy T shirt for the show. Will be on a black shirt.
This sad project took a turn for the worse and remains another example of the need to sort out your mission statement before you build the hulls. And I spent dozens of hours hand-holding these guys. They bought plans to the 32 ferry and wanted it stretched to 38. But would only pay for the hull lines revision.
Years later they started again, demanding that it now carry 44 pasengers and cargo. The hulls were already built, about the size of a 40′ trimaran amas, but weighed 1500 lbs each (3.5 lbs/sqft) so it was already in a huge payload deficit. I talked them down to 40 seats and no cargo.
I 3D modeled the new design, sent ortho drawings of the new design, did new weight study, designed added laminates for impacts, structural updates and all the hand holding to try to save the project. I gave them a minimal fee.
I just got word that if I didn’t agree to more design work at no cost to them, they would find a new designer. Corrosive when they got so much. Remind me not to do more work than is paid for, in the future.