Im new to Swaylocks, This is my second post and my first topic. I am currently building a hollow wood fish. I have some experience shaping foam boards, I have made 5 clark foam surfboards and about 30 foam-core skimboards (I live in Tampa FL so I’m lucky if I can catch some good swell on the gulf, but there’s a lot of good skim waves to be had)
my main hobby is radio controlled airplanes, I design and build my own airplanes. This has given me lots of experience working with balsa, plywood, carbon, kevlar, fiberglass and foam. And most of all I concider myself an expert on building light hollow structures that are capable of withstanding rediculous loads!!!
Check out my avitar I designed that airplane. It weighs 4.5 lb, The eingine gets over 1 hp at 15,500 rpm. It is capable of 120 mph and can pull over 15 G’s. That equals 67.5 lbs on a wing that weighs less than 1 lb.
I was about to shape a new fish but Clark foam went out of buisness so I can no longer get a good blank. I then decided to combine my skills and make a hollow wood board. I plan on making my board like I would make a wing on an aircraft. I am Inspired by Paul Jenson’s boards, however, No offense to you Paul, but Ive checked the specs on your boards and they seem very heavy. 13 lbs for a fish wich is under 6’0" seems excessive to me!!
After carefully examining the construction of other’s hollow wood boards, I have come across one MAJOR flaw. The loads from the deck are NOT distributed through-out the board properly. The gaps between ribs and stringers are way too large. In order to keep the board from crushing, Thick wood skins are used to bridge the large gaps between the stringer , rails and ribs. I don’t care how many lightening holes you cut in that plywood frame, it just looks SOOOO heavy!!!
I plan on making a much denser framework (tighter rib spacing and a second stringer between the center stringer and rails) A tighter framework will distribute the load across the board more efficiently, thereby allowing me to use a much thinner skin (veneer laminated at 45 degree angles) The thinner skin will be major source of weight loss. The frame’s structure will be made entirely out of plied balsa, carbon tubes and carbon and kevlar laminates. I will also use generously sized lightening holes to further reduce every last ounce. In addition, The rib spacing and strength of the materials within the board will change through out the board to eliminate as much unnecessary material as possible. for example the ribs will be packed tight and highly re-enforced where my feet are, but the spacing will double and ribs will be less re-enforced tward the front of the board
The board is designed to transfer all loads directly to the carbon and kevlar parts. The wood is mearly used to keep all carbon and kevlar parts in allignment, and to give shape to the board. This will allow me to use the least amount of wood possible.
The deck’s cross section will be able to support weight by working like an arch crossed with a bow and arrow (sounds confusing I will explain) Pressure on the deck will be absorbed by spruce strips running rail to rail under compression like an arch. When a load is applied to the top of the board, the arch will push the rails away from the center of the board. Directly under the arch, imbedded in a 3 ply balsa rib is a 1/8" carbon tow under tension (imagine the arch and tow forming the bow from a bow and arrow) The spruce translates the load to the carbon and keeps the board from collapsing without heavy ribs, thick sheeting and the excessive weight plywood ribs and rails!!
So far I have made the subframe for the stringer and I have finished the rear 2 ribs. I am being delayed because all my carbon parts are running late in the mail. Pics coming soon. I plan on fully documenting the construction of this board on this thread so stay tuned. It may take a while because there are a RIDICULOUS number of tiny intricite parts that go into the construction of just one rib. (Thats on thing that plywood’s got on me!! - low parts count)
