22Ryan22

hey guys. I was just wondering if I could take my weekend-flier Nexstar to a whole new level. Let me first explain that I KNOW that it is a TRAINER, and that i AM not a newbie. I REALIZE that the PLANE was MADE to TEACH people how to fly, and not do ACROBATICS. however, i believe that this little plane is capeable of much more. I have adjsted all the throws to get the maximum deflection that is possible, and trust me, I can handle acrobatics!

My question is: is it possible to successfully make control surface extentions with perhaps a sheet of thick lexan? I was considering extending the control surfaces so they further impact the flight characteristics of the plane. I know that i would have to adjust the cg and all other balencing of the plane, but is there any way to make extentions easily????

thanks, Ryan

da Rock

We used to cut stiff paper, very stiff paper, and tape it to the control surface we were testing. It worked like gangbusters for the tests. It worked for 125mph CL combat stabilators on models pulling 10X the g's RC airplanes pull.

That'd be for initial tests. And I'd suggest you do some testing first. It takes more than larger surfaces to change the personality of most models.

da Rock

Oh yeah.........

What made the stuff strong enough was that we basically folded it at the TE of it, and taped it to both the top and bottom of the surface. It quite elegantly formed the thickness that was appropriate had it been the original surface. It also picked up more than enough strength from that triangulation. And it wound up being taped to both sides of the original surface, so it had twice the tape to hold it.

da Rock

Oh yeah......

And a couple of times, we used a slightly porous paper and glued it instead of taping. And then painted it with fuelproof dope. It then became basically a new, perfectly adequate retrofit to the original (which was hidden inside).

The kind of paper used in rifle/pistol targets works great for that. I've used it recently and painted it with surfacing resin. It cures out with more strength than most would think. And is more than light enough. However, anytime you increase the size of a control surface you have to consider flutter. Make doubly sure your connections are slop free and the servo is strong enough.

BMatthews

Try moving the CG back in small increments until it's a handful but will still fly without pitch divergence. I think you'll find that this sharpens up a lot of the aerobatic abilities.

What's wrong with just adding extensions of balsawood? Cut then a bit shorter to get a square and blunt edge and glue on an what you cut off plus a little more.

22Ryan22

wow you guys have great advise. Thanks alot. I will definately try these

mesae

I know it's not as easy to do, but adding span is much more effective than adding chord. Increases in chord are likely to only marginally increase pitch authority, or possibly even decrease it (if the servos stall as a result), while greatly increasing the load on the servos.

Diane Hakala (US acro team) showed me her early Staudacher in 1996 at a full-scale acro contest in Chandler, AZ and explained that she was having the chord on her elevators reduced by 3" to lighten the stick-force-per-gee, without decreasing their effectiveness noticeably. So, if you have two elevators with the same area, but one has a large chord/small span and the other has a longer span/short chord, the longer span elevator will be more effective and require less force to deflect.

If you have an abundance of available servo torque, increasing chord might work for you. It's jut more efficient in terms of servo and battery life to do it the other way.

Control surfaces on racing airplanes are generally made as small as is safe in order to reduce drag. I know your objective isn't overall minimum drag but this illustrates the point that deflecting large control surfaces requires a lot of energy.

I'd use something lighter than lexan, like balsa per BMatthews. Or I'd build new elevators with large counter-balances.

da Rock

If you wonder about the results you'd get from increasing the chord, it takes about 5 minutes to tape the stiff paper around the control surfaces. The rudder takes less. And you can fly the sucker almost right away and find out in one session.

We were originally worried that what we thought was going to look like a lashup wasn't going to be strong enough. So some of the first trial setups had small balsa ribs to hold the paper's shape. We discovered they weren't needed if the paper was stiff enough.

BMatthews

Folded over card stock is easily strong enough to test as you mentioned. Just fold so it's an open V shape and masking tape it for the trial. It should extend up onto the existing surfaces by a good 1/4 to 3/8 inch and then tape in place. The oil will make a mess of it after a few flights but by that time you will know if it helps or not.

The CG location is a biggie though. Try it.

Also to greatly enhance the rolling speed on these trainers get used to adding in some rudder along with the aileron. That REALLY snaps 'er up!

22Ryan22

haah thanks guys. thats a good project for tomorrow [8D] really, thanks

-ryan

da Rock

BTW, one of the guys decided before we'd actually done this lashup deal, that the paper wasn't going to be strong enough. So the night before, he spray painted some paper to use after creasing it.

We wiped the test planes down with thinner, acetone, alcohol, whatever was good enough, and taped 'em up. Every one of the rigs held up for the tests. But he decided that his tape was going to get oil soaked. (the stab he was testing was directly behind a combat engine back when we didn't use mufflers) So he shot the tape with a quick thin coat of fuelproof paint. Aerogloss in a can was sort of trick at that time. His airplane flew better than anything he'd built up until then. He started doing that to just about everthing from then on. We used to kid him about it. Told him we expected any day that he'd drive up with a big fold of paper taped to the back of his car so it'd "turn better" or at least get better gas mileage.