Satsloader

Greetings,

After being away from the sport for 15 years I've purchased a new radio ( 7CAP ) and ARF ( Seagull Models PC-9 ). The plane is known to tip stall at low speeds, so my first actions are to remove weight via carbon pushrods, smaller/lighter servos for the ailerons ( Futaba 9601's ), a micro servo for the throttle, sealing the moving surface hinge lines with tape, etc.

I've also considered cutting the "strip" ailerons just inboard of the aileron servo position to create flaps, which will be driven by Hitec HS-65HB's, one on each flap ( although a small servo, the low flight speed and relitively small surface area of the flaps shouldn't overload them ). I will also add additional hinges on all moving surfaces as flutter at higher speeds is another known bug in the model.

My question to you fine folks is whether you feel the addition of the flaps will allow lower safe landing speeds given the added weight to impliment them? If it does, would a very slight up position of the ailerons with the flaps down be feasible for more insurance against tip stalling while landing?

Thanx,

Bill

Mikel-t

My Feedback: (12)

Bill, sounds like a lot more work for the effect your after. Can you program in for flaperons from your radio? I think you should try that 1st then try taking the plane apart. That plane has a tapered wing like a warbird does'nt it? So slow flying on the wing type landings are not going to be happening anyway. Well whenin doubt do the easiest thing first.......take a nap!

mcarleno

Flapperons will help with landing speed, but with strip ailerons probably will not help with tip stall issues. This aircraft has a slightly tapered wing and flaps help with tip stall as they increase the angle of attach at the wing sections where deployed. This allows the tips to remain effective. If your worried about tip stall and want to add something to help, then split the ailerons with 1/3 inner being flaps. Or, you can add droops to the tips or add at the root traingle stock which will allow the center of the wing to always stall first.

Personally though, I would leave it as it and just keep your landing speed up. Use flapperons on a wing with a constant cord and strip ailerons (JM2C).

Marc

Satsloader

Thank you for the replies.

I will definetly keep the landing speed up.. Fortunately adding flaps on this bird would be extremely simple . I'm calculating approx. 23oz./sq.ft. wing loading with them, so will most likely give it a go.. My goal is to have the plane fly as close to scale as I can get it.

Cheers,

Bill

da Rock

What do I think about flaps curing tip stall?

Nope.

Before trying to redesign and rebuild the airplane, do something dead simple and plain easy. Twist some washout into each wing. It'll take you about 5 minutes. It won't require any building or modification. It will work. It will directly address the problem you expect from your model. Unless the wing is wood covered foam, all it will take is 5 minutes with your iron.

nickj

darock is correct. Flaps increase lift at the root, but do nothing for the tips. And reflexing the alierons decreases lift at the tips, exactly what you don't want. Flaperons will increase lift the entire length of the wing, but depending on design may be more effective at the root, increasing tip stall tendencies. The surest cure for tip stalls is washout.

Flaps are fun, though.

Satsloader

Just found my way back to this thread, thank you for the replies.

I think I'll definetly keep this bird moving fast enough to not worry so much about stalling, but in regards to washout at the tips, how much adverse affect, if any, does it have on inverted flight for sport/semi scale rc aircraft like the PC-9?

Thanx again,

Bill

Richard L.

My Feedback: (24)

Flaps increase lift at the root, so when the wing stalls, the root will stalls first. Read the thread on flaps in the aerodynamics forum. Whenever I land my Top Flite P-40 with full flaps, the plane has no tendency to tip stall, even at slow speed. I tried landing the plane once without flaps at a slightly higher landing speed, and the left wing dropped. Please explain that to me.