- Jul 29, 2005
- Orange County, California
Agreed. However, it's morning here and I'm procrastinating about a brochure that I've designed and had approved, but now have to do the not-fun part of stamping out copies with differing text. Hoist one for me, will 'ya? :gig:I guess that I read your text differently (as in: about the ensuing discussion about piano hinges). Darn text indeed, we should discuss this with a cold beer in the sun. (Yes, it's evening here)
What I meant was that it's easy to make something like designing aileron hinges too complicated. Piano hinges have quite obviously worked just fine in many an airplane, so in similar applications and with the same reasonable amount of design effort you'd use for anything else in the airplane, they ought to work fine elsewhere. As I mentioned, my dad's old Aeronca had aileron hinges that were just a couple of bolts in single shear. Optimum design? Hardly. But the airplane was forty-something years old when we got it, and the ailerons worked just fine.
I think I'm following you. And I highlighted 'mold warp', thinking "mold warp as in thermal expansion, for example?" I see what you're getting at, but I don't think I'm quite convinced. I agree that setting it all up and fixing it before infusion is better than the alternative I mentioned earlier, but the infusion process is going to put a lot of forces through the system, and I can see things moving around, if only a tiny little bit. Which might be enough to require scrapping the part. The great big expensive part.By not doing that.
Simply put the full-span piano hinge in a dry mold. Align both ends and align the rest with a laser, then fix it to the mold (some screws or glue) and seal the hinging middle part, such that you can later cut the wingskin over there and not wet and glue the hinging part. This way you can align it perfectly, without any time constraint or worrying about creating a mess. By the time you're laying up (or in my case infusing), there's nothing than can be ruined anymore, except maybe mold warp. It's fairly easy to cut away a major part of the piano hinge later if one would want to.
I guess I'm a great skeptic about processes that require near-perfection in execution, particularly as applied to the shop of an amateur constructor like you or I. I'd much rather attach the piano hinge to the aft spar with small bolts, and then oversize the bolt holes in the hinge slightly, allowing them to be adjusted to perfection during assembly. YMMV, of course.