installing Flaps?
 

Hey Guys I have a cap 21 with 83" wing span this plane is huge the more I read about the cap 21 being hard to fly and the bad tip stall the more I think I should try to install flaps can anyone tell me how? how much of the ailerons I should keep can I just cut the aileron and install servos for flaps they are ca hinges now so it would be fairly easy to just cut off and build any suggestions would be very helpfull thanks Mike !:D Ps anything at all you can tell me about this cap 21 would be very cool [8D] Oh I'm going with a sachs 3.7 what do you guys think about that [:-]

RE: installing Flaps?
 

The answer for taming a CAP isn't going to be installng flaps. While they might help some... you'll be making a change that will eliminate part of the airplane's designed performance... no torque rolls and hovers. (need the inboard part of the ailerons to hover... and to help stabilize torque rolls)

The answer is... learn the performance of the Cap... and fly it the way it is designed to fly. Keep the speed up a bit at landings. (practice slow flight when WAY up to see what it looks like when its about to stall and snap into a spin...)

And definitely... its not a trainer.

RE: installing Flaps?
 

Besides, flaps can lead to a tip stall. Slowing the plane down with flaps probably isn't the answer.
Dennis-

RE: installing Flaps?
 

FLAPS don't lead to tip-stall. Full span flaperons do. the primary purpose of small deflection flaps is... prevent tip-stall.

RE: installing Flaps?
 

I don't think that flaps lead to tip stall. The primary purpose of flaps is not to prevent this (although it is a by product). Flaps are there to increase drag, increase the angle of approach, reduce stall speed and usually produce a better view (in the case of a full size aircraft)

Tip stall is reduced by washout which reduces the angle of attack at the wing tip.

As FHHuber says the answer is probably learning its performance. Practice applying aileron near the stall speed at height and see what happens. Land with a little speed and don't turn too quickly after take off and you should be fine.

RE: installing Flaps?
 

Another suggestion I have heard is to make sure the plane is perfectly balanced latterally. Make sure your rudder is at dead center and hold the spinner and rudder and see if a wing tips. If it does, add some weight to the wing tip to ballance it. I did this to my cap 232 and it will almost fly as slow as my trainer and will not wing stall.

Dave

RE: installing Flaps?
 

Reflex your ailerons upwards about 5 to 10 degrees in the flaperon mode of your radio to increase the washout of your wings. This will reduce the onset of a stall/tip stall and permit slower landings.

Better yet, learn to fly your plane within the envelope in which it was designed. Caps are not for beginners.

RE: installing Flaps?
 

Sorry, I should have been more clear, but flaps can lead to tip stalls. Flaps add lift, but also add considerable drag, and slowing the plane too much with or without flaps, will lead to a tip stall.
Dennis-

RE: installing Flaps?
 

Or a regular stall.

Technically, there's no such thing as a tip stall, it's just that sometimes, one wing stalls before the other.

In either case, without doing some wind-tunnel testing, or finding someone with the same plane who HAS installed flaps, we won't know what they will do to the flight characteristics. But don't try to land it like it's a Piper Cub! It was never designed to fly that slowly.

RE: installing Flaps?
 

I sure appreciate everyones input here Im still a little unclear what to do the ailerons are 41" long one friend of mine said that he wouldnt do it flaps are not the answer but I was reading a thread from a guy on here that knows alot about these cap 21's and he recomends flaps so I think I will just wait to get the general concensus from you guys :D by the way what do you guys think about the sachs 3.7 on this plane would that be ok ? and if anyone knows of a web-site that I can check out a real cap 21 ? I cant figure out the cowl on this bird I'm trying to build one :eek: thanks in advance This website is invaluable to rookies Thanks Guys !!!!!:D

RE: installing Flaps?
 

Here is a picture of the cap 21 ( makes Me thirsty !:D)

RE: installing Flaps?
 

Are those pictures blurry, or am I having another 60's flash-back?

RE: installing Flaps?
 

I also wouldn't bother with flaps on a Cap 21. Yes, they have a nasty stall, but that's half the fun of flying a Cap.

RE: installing Flaps?
 

ya the pictures are blury I dont know what happened there ? And I am not going to put flaps on it I will just wait until I can fly the way it is. That seems to be the way to go what about that sachs ? no replys on that yet Thanks guys !

RE: installing Flaps?
 

All comes down to flying within the limitations of the aircraft. This is true from Full Scale on down. Know your stall speed, and fly above it. With many sports models, that means a hotter/faster landing profile than what you may be used to. Flaps will reduce the speed at which stall occurs, but it won't change "tip stall". If you don't want tip stall, avoid turns when flying just above or at stall speed.

RE: installing Flaps?
 

Bear with me as I'm not 100% on this but.......

I thought that the deployment of flaps increased the angle of attack (similar to a down going aileron). Therefore, with inboard flaps the root angle of attack is higher than the tips when the flaps are deployed. This means that as you slown down the root will reach the critical angle of attack before the tip. This will obviously reduce the chances of tip stall in a similar way to washout. It does not guarantee that you will not get a wing drop at the stall but it should be less severe.

The only time that this will really cause you a problem is just after take off or on the approach. The take off problem is easy, just don't turn until you have built up a little speed. On the approach you will just have to keep the speed up a little.

I flew my new staudacher a couple of days ago. I took it to height and stalled it. It has quite a marked wing drop. It is not a problem because I now know it is there and make a concious effort to keep the speed up when landing.

RE: installing Flaps?
 

siclick33:

You are correct. The main purpose of SMALL DEFLECTION flaps is to prevent tip-stall (prevent a wingtip stalling before the root) That is why the full scale P-51 specifies 7 deg flap for takeoff. (so the pilot has a larger safety margin when pulling on the stick)

Tht increased AOA effect of flaps is also why full span flaperons can be dangerous. Yu get a false sense of security thinkng the flap effet will improve low speed performance. Well, yes it does improve low speed performanc BUT it can take a gentle stall characteristic and create a violent characteristic that has no warning.

Caps tend to stall wingtip first on puropse. They are designed to SNAP fast for better snap-rolls and other maneuvers that need the airplane to rotate. The trade-off is... you have to beware of unwanted stalls.

You can find similar effects of desin in other models of highly aerobatic aircraft. Some give more warning about thier stalls than the CAP... but all planes made to fly the same maneuver schedules will have a tendancy to drop a wing when they stall.

RE: installing Flaps?
 

I want to add flaps to my 80" h9 piper cub, how wide should they be (from fuse to ailerons or shorter) any help apreciated. cub flys beautiful with the os 91 surpass and a 14X6 prop, just want to make it more scale like .

RE: installing Flaps?
 

On the cub, the flaps should be from the aileron to just short of the cabin wall.

RE: installing Flaps?
 

thanks for your input, went from 3/4 inch of cabin to the aileron, they work perfect, I have a 8103 radio and tried flaperons.... they dont work , caused it to go into an instant 90 deg. dive. with the flaps it pitched up like its supposed to, easy modifcation on a h9 80" piper cub and well worth the extra work. 5 deg take off works great, with only 15 deg for landing its noticeably slower havent tried any more than that yet.