control horn wire size

Happy 4th guys,
On a .60 sized stunter (GEO XL) can 3/32 music wire be used to construct the flap and elevator horns, or shold 1/8 wire be used?
Jim

>Happy 4th guys,
>On a .60 sized stunter (GEO
>XL) can 3/32 music wire
>be used to construct the
>flap and elevator horns, or
>shold 1/8 wire be used?
>

Lots of them were made with 3/32. As long as you weld/silver solder them properly, strength is not an issue.

Flexibility *is* an issue. I would recommend 1/8 on at least the flaps, if not both. The span is larger than the tail, and the load is greater, so the flap would tend to flex more.

Brett, Please tell me where I've got this wrong.

Total tailplane area, Stab and Elevator, is usually 20--25% of wing area. Elevator 40--50% of total tailplane area. Flaps about 10--15% of wing area. Is this correct?

If tailplane were 25% of wing, elevator 50% of tailplane and flaps 12.5% of wing, why would load on elevator be less than flaps?

Brett is off to the Nats, and I am heading out myself in a couple of minutes, but I think he is talking about the total tortional load. The flaps are longer and will have more leverage to twist (which means we have to keep them solid, also. If they twist, we have lost their effectiveness.)

In other threads and magazines, conventional wisdom is 1/8 flap and 3/32 elevator on everything .35 or larger. Brett and the other top flyers don't take chances on controls, so trust them.

This is a classic "Snapping your fingers keeps elephants away" issue. (If you snap your fingers every hour, your house will not be invaded by elephants.) Point is, using those sizes, no one has ever reported a problem. No one has failure data on lesser sizes that I am aware of. Go with conventional wisdom in this case. You don't want to be the first to find that not snapping your fingers caused an elephant invasion. You don't want to be the first to find that 3/32 flap horns caused a control problem.

The "snapping your fingers" reminds me of a time recently I bypassed using epoxy on a bellcrank mount. I had never had one break free, so I figured I had been overbuilding them. Well, I hadn't. First lap on the SkyRay without epoxy and the bellcrank pulled right out. When in doubt, overbuild.