Guys, I'm going through this decision again for fuselages. I have a limited basis for comparison, since recent different methods I've used have gone into three different profile fuselage types - and one laminated landing gear set. However, what I have seen indicates that, as has been written on SSWF more than once, the matrix material - epoxy, dope, or whatever, is very important to the stiffness.
I have used silkspan - even the newer garbage - with success, to the extent that finish and stiffness are noticably better than bare wood. Also, with wood alone, laminations of two 1/4" sheets with some grain variance is significantly stiffer than a single 1/2" sheet for fuselages. From what I've read, I'm also convinced that fiberglass or CF are better for stiffness than silkspan.
However, on my last plane, I used butyrate dope to adhere light fiberglass, without feeling that I achieved the fiberglass advantage. The glass went on great with thinner application over an understrata of clear on the wood; conformation to compound curves was great. However, progressive dope shrinkage left surface weave pattern difficult to smooth, and the increased stiffness was disappointing. I think that dope elasticity allows too much movement of the fibers and that epoxy, used correctly, would have been superior and no heavier, since the dope seemed always to get underneath to some extent, "floating" the fabric. Proper, economical application of epoxy would have eliminated this problem, and I'm sure the harder epoxy would hold the fibers or threads more stationary. This would cut down on much more of the fuselage twist.
I think too that Ron Burn is correct over "yonder" in stating that the carbon fiber veil is better for stiffness in epoxy, because of the varied fiber orientations.
One thing I encountered with epoxy though - probably through ignorance or inexperience - was that epoxies seem to vary a lot in their properties. I used "Smooth 'n Easy" epoxy finishing (and 'laminating') resin to laminate up some carbon veil gear legs last year, but despite more robust than usual thickness, they came out spongy and useless; the poor P-Force looked drunk and would have dug up some serious turf with its prop. I can't believe all my lay-ups were mixed wrong, since they set up in reasonable time anyway. So I can't see this resin working well to stiffen a fuselage.
My present project will probably have CF veil and 30-minute, or perhaps West Systems epoxy rolled on. I may even tak it on and then roll a secondlayer into the veil and sand smooth.
I know the Al Rabe mentioned his own technique with epoxy resin a couple years ago on SSWF, and I think that a search will dig up some good information, INCLUDING some good responses on my previous queries on fuselage stiffness. Cap'n Curt posted a picture of his triangular trussed CF cloth technique, among others. Much of this seems relevant to flap stiffening, per the original post. Comments?
SK
Topic: Carbon veil and flaps ? (Read 1765 times)