Posted by: eric anderson on March 11, 2005 at 14:58:49:
Current rules pertaining to materials in hulls and Planks.
The current rules prohibit using carbon fiber or Kevlar as reinforcements in building hulls and Planks, (and booms). I think the time has come to change this rule.
Today, when you look at the costs of carbon fiber cloth and carbon unidirectional it is not prohibitive for home building. On strength per dollar is as cheap or cheaper then unidirectional S glass or cloth. I am going to break this down into 3 sections, plank, hull, and boom.
Plank. Currently, state of the art is spruce or basswood 2-piece planks cnc routed to an airfoil shape and covered with prepreg S glass mostly unidirectional. Alternatively more conventional planks can be 3-piece ash- basswood-ash. Plank stiffness varies all over the map. The min weight for a plank is 20 lbs. The prepreg glass planks would benefit from carbon because you can use a heavier wood (like poplar) and a lot less carbon then you need S glass = cheaper construction. The homebuilder gets an advantage also because he can build a min thickness plank and use the carbon uni to stiffen it. It takes a lot less carbon to stiffen the plank then uni S glass Materials costs for equivalent amount stiffening are less now with carbon. No one can gain an advantage by building a super lightweight plank because the min weight is still 20 lbs. The end result of allowing carbon is to decrease costs slightly and to allow easier tailoring of stiffness.
Hull. Traditional hull construction was spruce, basswood, etc sideboards. Built carefully the boat can be at minimum weight. There is an ongoing debate about how stiff or flexible the hull should be. Today it is much tougher to find quality lumber and it is not cheap. A slightly lower quality wood with a layer of carbon on both sides would be a good substitute. Hell you could start with 1X8 clear pine from home depot and it would work just fine. Alternatively, if you have a mold for making sideboards, end grain balsa with a layer of biaxial carbon fiber and a little uni at the top and bottom would make awesome sideboards. Right now you can make end grain balsa sideboards with Biaxial S glass and also S-2 Uni on the top and bottom of the board. This turns out to require quite a bit of uni on the top and bottom so it does not flex. It would be easier and cheaper to use carbon fiber in this application. Considering what the availability of high quality wood products may in the future, plantation grown end grain balsa might be a good long-term solution. Keeping the min hull weight at 46 lbs eliminates any advantage a super high tech boat would have
Booms. Today it is hard to build a boom out of wood that is the same weight as an aluminum triangular type boom. Allowing a carbon reinforced wood boom would allow you to attain the same weight as an aluminum boom in home buildable form. If you want to prevent high tech keep the wood requirements or better yet, just set the min weight to that of the lightest aluminum sections available.
My objective is not to get into a high tech war or up the costs of competing, in fact it is just the opposite. I think the decrease in costs of carbon and other composites makes them attractive for DN construction. Considering the cost vs. benefit of carbon, I think it should be allowed anywhere fiberglass is. I know there is a feeling many share that composite construction is beyond the scope of most homebuilders, but I don’t think it has to be.
What do other people think?
Eric Anderson
US 5193