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Archive for May, 2010
Posted by A Useless Geek | May 31, 2010 @ 06:35 PM | 6,700 Views
Well, anyway, I wanted a very crashable airplane for a newbie product. Something that they can essentially drive into the ground repeatedly without damage. I figured it has to be a mid pusher, with dihedral, and RET. My first pass at this sucked pretty badly, but this one less so.

Only the front end is EPP for the test bed. I wanted to see how I could eliminate flex as much as possible without braces. The dihedral and KFm2 wings are plenty stabilizing, and have all the lift you can shake a stick at. The wide center section going back to the tail is hefty enough to prevent torquing, which was a problem on the first unit. The long, tall tail fin prevents flex in the vertical axis.

So far the Crashable isn't working out too badly, but there are some issues with it that I don't like. Let me gather some more data and flight experience and I'll let you know what I'll try next.


Well, this is lousy.

The Crashable is junkable. It's just too flexible along the longitudinal axis to be of any real value. There are lots of ways I can reduce the flex, but all of them get away from the basic concept of a low cost, indestructible trainer. This was a nice try, but goes into the ashcan.

Next up I'm gonna try a variation on the Trainer One concept and see if that gets me anywhere.
Posted by A Useless Geek | May 25, 2010 @ 01:33 AM | 6,546 Views
I built another one to make sure I could do it the same way again. Details here.
Posted by A Useless Geek | May 13, 2010 @ 04:59 PM | 6,097 Views
So the guys at Slot and Wing (http://www.slotandwinghobbies.com) showed up for the SRCB Swap 'Til You Drop in April. They had piles of inexpensive goodies, including a barnload of static display models of the Swarm. These kits had no motor, no electronics, nuthin' -- perfect for scratch builders. I grabbed a couple, got another naked airframe for zero, and won another kit in a club raffle.

These are great planes to start from. 780 mm wingspan and 610 mm overall length. Wing chord is 125 mm. Lots of room inside to put electronics and batteries. Good structural design with enough bulkheads to keep it stiff but not too much structure to add mass.

The airframe is a two piece affair with the top and bottom halves held together with some form of RTV. A fresh #1 blade will zik right through the bond and split the fuselage halves cleanly.

The wings, horizontal stab, and vertical stab are all made of 2 mm foam that is kinda crusty with the color (ink or paint, I can't tell). The graphic stickers are all kinda wrinkled, though, so I just peeled most of them off. You can see from the picture that the wings end up looking like some post-modern op art piece, but that's okay by me.

I got rid of all the hard plastic pieces that are attached to the plane, including the motor mount and the whole front bulkhead. Even the cowl is too heavy (8.4 grams by itself). By hacking off the whole front end I removed 18 grams per plane! The other plastic parts aren't so heavy, but they have...Continue Reading