Dennis, Frank, & Jeff:
Thanks for your kind comments guys. Proof is in the flying and as of right now its still unproven. Tonight, however, I did some quantitative testing on the rigidity of the structure. For this test I used 3 models, the new C-14, an Ultraproducts Nobler, and a Brodak SV-11 arf. I wanted to be able to measure if this was a quantifiable improvement. I chose these models to compare to because they are well known standards to compare to. The wing area of the C-14 is closer to the nobler than the SV but the moments of the C-14 are more comparable to the SV.
For my test I placed each model on a Robart model stand. I removed the pivoting arms so that they would not influence the results. I placed the wing spar on the solid 1/2 inch wide foam support on one of the stand, and the aft fuselage rested on the back cross piece of the stand. This does place a slight advantage to the two full fuse ships as the width of the aft fuse which was about under the elevator hinge line could support the width of the fuse while on the C-14 it was a point contact at the bottom of the fuse radius. I measured out the horizontal stab from the center line of the fuse 12 inches. On the nobler I had to add a slight extension to get the line but not much. I wanted to place a one pound weight on each horizontal stab at this location and measure the deflection of the stab from level. The closest I could get to a pound in a shape I could get stable was a one pound one ounce lipo. The following deflections were measured:
C-14 carbon fuselage model 3/8 inch
UHP nobler 5/8 inch
Brodak SV-11 3/8 inch
I think this shows some validity to the concept of using large diameter thin wall carbon tube in combination with balsa wing cradles to produce a profile structure that measures comparable aft fuse rigidity to a full fuse model. Most likely an improvement in the carbon fiber version could be attained by using the same carbon balsa composite laminate for the wing cradles as I did for the nose motor mount section. However I do not think it would be substantial and the workability of getting an accurate fit would be decreased. Still, for a scratch build where I was assembling the wing and stab and had completely accurate patterns for both I would have done it. As for trial fitting two layers of carbon fiber and two layers of epoxy with a half inch end grain balsa sandwhich was not my idea of a fun time where the wings and stab were already built. This way I had no trouble getting accurate fits, alignments, and angles of attack with minimal work.
Most likely first flights will be this coming Friday. I will report on flight expereince after that though obviously trimming will go on for some while.
bob branch