I think Eduardo's idea is the strongest, incorporating the best of both construction methods.
This could help keep ones cost down if wood is hard to get ++++++++++++++++++++++ Acceptable grade plywood is a problem for me - Eduardo's method really appealed to me as a cost effective solution that also produces a pretty elegant fuselage - BUT, the concern I have with this relates to the difference in relative stiffness between the wooden structure and the glass /epoxy skin(s). Extract from Zeke Smith (On Composites): This illustrates a principle that carries into practical composite aircraft design. Some designs which use mostly E-glass fiber make use of carbon (graphite) fiber for spar caps. Carbon is much stiffer than glass, so the carbon will carry nearly the entire spar cap load. If any glass is used in parallel with the stiffer carbon, the glass component is essentially wasted because it will never experience enough strain to carry a useful load - the carbon fiber gets nearly all the load ...... Eduardo created a wood structure that (I think) is potentially as strong as a regular KR boat except that he replaces the ply skin with a pseudo composite structure. To what extent will the difference in stiffness here cause the inadequate wooden structure (no plywood skin) to take the load - as suggested by Zeke Smith? Even if the composite component is actually strong enough to do the job without the wood - maybe the wood takes the load first due to "stiffness". Something here is certainly along for the ride contributing only weight. The Vision fuselage is based of a Last a Foam core with glass skins to form a classic 6mm (1/4") sandwich structure. The wood structure, as you know, is purely a "mould" that is discarded after the fuselage shape is established - thus no embedded wood. My own idea of getting the "best of both worlds" is to follow Eduardo's method but pursue the Vision end result by using a lighter wood structure (3/8" square) that will remain embedded (like Eduardo) but without any gussets or blocks - for that matter, even using lighter white Pine or Poplar, but with an adhesive that will allow the joints to flex or stretch later. Filling in with 1/2" core material leaves some surplus to sand and the result is a fast, straight, smooth, rounded shape (as per Eduardo). The skin thickness is selected as if there was no wood. We are taught that a thicker composite sandwich is stronger for a given skin strength, so the resultant KR fuse of 3/8" sandwich should be stronger (than a 1/4" sandwich) plus the embedded wood (3/8" sq) will improve the mean shear strength of whatever core material we use. It sounds like loads of extra work, but it suits my workshop and my style - the question is - will it work??? Steve J
