Steve Steinbring

I'm building up a Spectra kit wing I was given for a fuselage I have. My plan is to add ailerons then program spoilerons in for additional control. Its my intent to remove all or most of the dihedral from the center section of the wing. My question is should I leave a small about dihedral in the center or just rely upon the wing tips being kicked up?

Your thoughts please..............

da Rock

The combined dihedrals are what turns the airplane when it's rudder/elevator only. The ailerons will be doing that if they're adequately sized and you actually won't need the outer dihedral.

Ailerons are usually placed as far out as possible for efficiency.

BMatthews

Some dihedral will aid in stability in the turns. So I would leave all the center angle in and just drop the tips to line up with the center panels. Also you'll gain some added stability in the turns by making the rudder smaller to reduce the overall vertical stabilizing area. I'd suggest cut the rudder down to 2/3's of the stock width and be prepared to cut a little off the top if the model still seems to want to tighten the turns unless you use some "top" aileron. Maybe make the built up portion about an inch shorter for the fin and rudder and glue on a sheet cap to the stock height so you have some area that is easy to prune later on.

If from this you are thinking that I'm saying that less dihedral requires less vertical tail area you're right. Too much vertical tail area for the amount of dihedral makes the model spirally unstable and you'll see this if the model wants to tighten into the turns when doing a constant radius turn. Taken to extremes too large a tail will make it so the model will want to fall off into a spiral dive even from almost nearly level flight.

The opposite is where the model shows signs of a wandering tail where it tracks the wrong way when banking into a turn and hangs tail low in a steep turn.