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Montague -> RE: New Twin Tail SSC Design (3/31/2008 2:31:24 PM)
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I do like the plane, you'll have to let us know how it flys.
I'm curious, why only 60" span and not 64"? foam only available in 7foot-6in sheets there? [:D].
I've never tried running the flutes across the fuse you like you did, so I can't say what it does for rigitity of the fuse. I would worry about a tear starting and running around the fuse instead of along it, but I just don't know.
On the MkIII version of the Rapier (the current version is Mk IV), I used 2mm coro for the fuse sides, and glued the rods into slots cut into the foam core, and against the coro sides. The fuse died when a hard hit caused the coro to delaminate from the foam and the rods popped loose in the foam slots, like when you get a loose spar in a wing. I could have fixed it, but by that point I'd gone to the Mk IV fuse anyway (which is 1/4" wider and has the much-improved tail). Anyway, I don't know if glueing rods into the corner folds would work or not, but it sounds like a good idea.
What anchors your wing hold down dowls, or how are you holding on the wing? My wing dowls go under the rods in the flutes, so while they often tear oval holes in the coro and slide around a little, they can't pull out of the top of the fuse. That did happen to one of the earlier Mk II fuses, which had the rods located lower in the fuse side (and shorter rods).
How are you holding your vstab and hstab on? I find they get hit a lot during combat, so I find that a quick-change tail group is really handy. Your verticals should be easy to mount by screwing to a hardpoint in the fuse, which would be a real win at a contest. Same with your horizontal.
I think your verticals are a bit small. They are large enough for normal flight and for handling a streamer or two on the wingtip, I think. Twin tails do well in that regard. And I like the verticals in front of the horizontal, I think that gives a tighter turn. (I got a noticeable improvement in turning radius when I increased the vertical tail size on the Rapier and moved the LE of the vertical out in front of the horizontal stab. Lots of vertical tail in clean air at high alpha seems to keep the nose pointed and delay the snaproll by a couple of degrees, and that means higher-G turns.)
But in your case it also reduces the moment arm on the vertical area. I suspect that you might have trouble with getting out of impact-induced flat spins. Twin tails seem to blanket each other, making the tail almost half as effective when in a fast spin. You'll have to see if you have trouble getting out of low altitude spins. Let us know how that tests out, your fuse is wide, so the tails might not blanket like I've seen with other twin tail planes. If nothing else, when you're flight testing, be sure to point the nose straight up until you run out of airspeed, then give it full aileron and elevator and see what it does. You'll get some kind of stall-snap-spin, but the question is how fast is the rotation and how quickly can you get out of it.
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