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TF P-40 tip stall

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TF P-40 tip stall

Old 01-26-2017, 07:31 PM
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mashp39
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Default TF P-40 tip stall

Do all TF P-40 60 size kits have a tip stall problem?Is there a way to remedy this problem after the plane is built?Has anyone else had this problem.Do the P-40's need to be landed a a high speed?
Old 01-27-2017, 08:32 AM
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jetmech05
 
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A tip stall is a stall. You should always stall a new airplane at altitude to see how she will behave.
in the mean time keep the speed up on approach
Old 01-27-2017, 12:18 PM
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There seems to be a general consensus that they will snap or tip stall as it were, more easily than others. It gets pretty hard to fix after building because is is a fully sheeted wing. If you followed the plans and built in the correct amount of washout in the tips you should be fine. Warbirds in general need to flown to the ground like a real airplane and if you are used to floating in a trainer or sport plane you are going to have trouble with it. You need to maintain enough speed to keep the aircraft flying until just before touchdown. Practice higher speed landings with a sport plane until your comfortable with approaching at a higher rate of speed and using the throttle to manage the landing speed and the elevator to control the stall point. You want to maintain forward speed until just before touch down then chop the throttle and feed in the elevator until she settles onto the runway. You don't need to come in like a rocket but you can't float it in. Good luck.
Old 01-29-2017, 03:54 PM
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mashp39
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On another site it was suggested to raise both ailerons a couple degrees and this will help the tip stall. Anybody ever try this?The plane was built by someone else and I don't know its build history. The plane flies very well but but does do a quick turn to the left if the speed it cut. Do planes tip stall to the right? I will check the washout amount but have not yet.
Old 01-30-2017, 06:28 PM
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They could stall in either direction and you can even stall at high speed if the angle of attack is to great the wing just quits flying. Have you done a stall test yet? take it up a couple hundred and reduce speed and increase elevator until it stalls and see which way it goes. Are you saying it goes left when suddenly decelerating?
Old 01-30-2017, 07:49 PM
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mashp39
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Yes it has gone left both times it has been landed. One time at some altitude as it was turned to land and it ended up in a tree. The next time it was about 25 feet up on a landing approach 1/3 throttle and I thought to cut the throttle and let it come on down. It snapped very quickly to the left and did some good damage.It can be repaired but I will wait to get it back into the air. A friend has an electric P40,foam, with about a 50 inch wing span and his tip stalled to the left at about 4 ft. altitude when he cut the throttle on landing.Is this common on P-40s? I wonder.
Old 01-31-2017, 07:38 AM
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JohnBuckner
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Originally Posted by mashp39
On another site it was suggested to raise both ailerons a couple degrees and this will help the tip stall. Anybody ever try this?.

Yes, yes, yes! Reflexing both ailerons up a few degrees at neutral and at this point with that airplane is the key to its survival.

First let me say it is my belief that the so called 'tip stall' is the most over used catch phrase in model aviation. In the full scale world it is rarely used. A stall is a stall it can also be an Accelerated stall as described by one of the responders above. The term tip stall is merely used to describe a stall that starts at the wingtip and propagates inward toward the wing root. Now a stall can also start at the wing root and propagate outward toward the tip. This last is not a tip stall.

Always if one is going to stall the airplane it is most desireable for the stall start at the wing root not the wing tip. The reason for this is to delay the loss of aileron control up to the point that the 'entire' wing becomes stalled.

The reason in your situation getting perhaps slower on landing approach that when the stall occurs it starts at the wing tip and aileron control is lost then if power is being maintained to control the approach or is increased for go around at the point of the stall the torque will tend to roll the airplane left at the break and the "P" factor will case the Yaw to the left.

Now normally this problem (and the problem is making the wing root stall first) is handled by several methods and the most common is first the actual airfoil itself of the wing and the second is a built in twist of the wing with the wing tips at a lessor angle of attack than the wing roots intended to cause the stall to start at the roots.

Two other methods that are easy for us to do is simply reflex the ailerons up full time. Also another it to simply tape short pieces of triangle stock to the wing roots the idea here is the sharp leading edge will trip the stall at the wing root first.

Now in the RC jet world since most turbine airplanes have dedicated flaps (not flaperons) it is common to mix in aileron up reflex when the flaps are applied. This does indeed work.

I have indeed used the stall tripper strips and or aileron reflex on P-40's of some folks I was helping and indeed these airplane were tending to tip stall. I do not recall which brand ARF's they were.

Please do not fly the airplane agine until you at least adjust so up reflex of both ailerons perhaps two to three degrees .

John

Last edited by JohnBuckner; 01-31-2017 at 07:42 AM.
Old 01-31-2017, 01:32 PM
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mashp39
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Thank you very much for you reply. Before I fly this plane again I will add some up to both ailerons. I saw this on another web site and you confirmed it for me.I did use the term "tip stall" to describe the quick movement to the left just to be descriptive.The plane is in storage until another day but not forgotten.
Old 02-01-2017, 09:37 AM
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Nice explanation John, I have the ARF version of this plane and it seems TF resolved that issue because it will basically stall forward, that is at the root. Good idea adding aileron up to help with this issue. Also using the rudder instead of the aileron to correct for the P factor is far more effective.
Old 02-01-2017, 11:16 AM
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JohnBuckner
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Originally Posted by raptureboy
it Also using the rudder instead of the aileron to correct for the P factor is far more effective.

Thank you fella's. Yes indeed raptureboy that is absolutely correct and the rudder is the proper way to correct for P factor.is rudder.

Most all propeller aircraft do require right rudder thought out the climb and you either have to hold it or trim it out. Curiously I once owned a full scale aircraft witjh an European engine that rotated in the opposite direction and unlike most other aircraft this one required left rudder at rotation and for the duration of the climb (this one had no rudder trim and took a bit of getting use to.

John

Last edited by JohnBuckner; 02-14-2017 at 06:06 AM.
Old 02-01-2017, 06:49 PM
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DavidAgar
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Speed is your friend for War Birds. You need to adopt the fly it to the runway theory. My War Birds clear the threshold at 1/4 power at 10 to 15 feet altitude. When I am over the runway the power comes down and all I do is keep the plane flying in a straight line. When I have my fun planes out at the field, I practice flying to the Runway by doing high speed touch and goes with the wheels actually being on the runway. Over the years the P-40 has a rap of being the worst Gold Edition kit for stalls over any of the rest of them. They all will stall if they get to slow, so as I said, speed is your friend. Good Luck, Dave
Old 02-03-2017, 10:32 AM
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I'm on my 2nd GE P-47 and they fly beautifully with no bad habits. Lost the 1st one to radio failure but it was fun while it lasted.
Old 02-03-2017, 01:53 PM
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mashp39
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My TF P-40 flies well but has some problems on landing. I will try the 2 degree upturn on the ailerons but am now wandering about the use of flaps. If I were to use the flaps , what would be the affect on the landing? Would flaps help to reduce tip stall?
Old 02-04-2017, 09:12 PM
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BobH
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Flaps create extra lift until they create drag.
15-20 degrees will create lift.. more may just create drag and slow the plane down.
Old 02-05-2017, 08:02 AM
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Flaps will also give you a washout effect because they are inboard from the ailerons, so when you deploy them you have effectively a higher angle of attack near the fuselage, which is good. Drag issue mentioned by BobH is good to remember, might need to hold a little more throttle coming in so you don't slow down too much.
Old 02-05-2017, 08:19 PM
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mashp39
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This is good advice. The flaps will be used the next time the plane is flown. This plane was built by someone unknown to me and used for the fun of it. It wanted to stall both times it was flown and repaired after the hard landing. I have built one with flaps and retracts and will fly the other again to work out problems before the new one.Thanks for the reply.
Old 02-10-2017, 11:24 AM
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Well if you were trying to land without flaps, that is most likely why it stalls out. I have flown my P-51 several times and had to use flaps to land it, or it would just flip over. I also discovered that it uses very little elevator, too much and it snaps over in a high speed stall, which wrecked it once. The only heavy metal plane that lands without flaps is my H9 P-47, it has such a huge wing that it lands like a trainer(as long as a building doesn't leap out and smack it). I also have a Twin Otter and that one needs flaps for landing too.

So do the aileron trick, verify that the elevator is at low rates while flying, and use flaps when landing and you will find the plane lands a lot easier. If you have never flown with flaps, suggest the 3 mistake high approach. Drop flaps and slow the plane down until you see it get flaky then increase throttle until you have it slow but fully under control. When testing the speed, make sure you have your finger on the flap switch so you can get them back up quickly to increase speed, if you slam the throttle open with flaps deployed it could balloon on you and cause it to further stall. Once you get comfortable with the planes speed with the flaps and gear down, then try your landing approach at the same settings, and when just a few feet above ground, chop throttle and let it land.
Old 02-10-2017, 12:57 PM
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mashp39
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Thanks. The longer this runs the more knowledge that comes along. I have never used flaps so the ones on the P-40 were not used and were made to not work. I am now building a Great Planes Cherokee that has flaps that will be used as a training aid. When I get used to flaps I will fly the P-40. This is a work in progress and one of the reasons to enjoy RC.I have a simulator but it just doesn't seem to give total real life playback.Time will tell.Flaky is an excellent term.
Old 02-12-2017, 10:31 AM
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JohnBuckner
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Originally Posted by mashp39
Thanks. The longer this runs the more knowledge that comes along..

Yes indeed I agree






Here is an example of the point I was making in post #7 about the up reflexing of ailerons and/or flaps to effect a reduction in lift with out the drag and its set up on my Great Planes Cherokee arf in the top set of pictures. The flaps are set up on a three position switch and the positions are in full trail - down (about 30 degrees) - and up reflex about 5 degrees. There is a flap to elevator mix that applies a slight down elevator when the down position is selected. The up reflexing is just for fun to experiment with and not needed on the Cherokee but illustrates the spoiler action without the extra drag.

Now the next set of pictures you might find interesting. The airplane is my turbine Super Viper and the flaps are two position First there is takeoff flap just a bit over 20 degrees and of course there is an elevator mix that applies just a bit of down elevator when the takeoff flaps are set, now things get interesting when full flap is applied for landing even a bit more down elevator is applied but with this three way mix about 5 degree of up aileron mix is applied!

This is most needed on this airplane an enables it to operate on smaller fields with lots of drag provided by the full down flap and a reduction of lift provided by the spoiler action of the ailerons. This enables the airplane to maintain a small amount of throttle throughout the approach and vital because of the typically slow throttle response of the turbines.

Hope you find this interesting mashp39

John
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Last edited by JohnBuckner; 02-12-2017 at 10:40 AM.
Old 02-12-2017, 07:13 PM
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mashp39
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Very interesting. A picture confirms what your words say. My Cherokee isn't quiet finished but maybe in the next couple of weeks I can give it a try.
Old 02-12-2017, 08:13 PM
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tailskid
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John, I like the way you store your planes.....you even have two of the same model? One for the odd numbered days, the other for even numbered days....cool....
Old 02-13-2017, 03:32 PM
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JohnBuckner
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Hey mashp36 I think you will like the Cherokee it a fine scale sport model and the flaps can be educational. I acquired mine as a 'deal' sweetener. Didn,t want it at first, I am constantly doing barters but glad I got it and has been fun.

Well now thanks Tailskid, actually I think I have stuff stashed and stored just about every way possible. OK now, ya can't just leave it hanging there (pun intended). Which two airplanes do we have in common? I am guessing we have more than just those two of the same.
Old 02-13-2017, 04:11 PM
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tailskid
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Planes 3,4 5,,,,4 AND 5 SURE DO LOOK SIMILAR! Going from L to right.....
Old 02-13-2017, 09:39 PM
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JohnBuckner
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Hmm, left to right:

#2 GP Proud Bird EF-1
#3 Vargas Racer II 424
#4 GP Viper 426
#5 Vortex 428
#6 GP Viper (no engine) and
#7 Jim Allen Quick 'V' (no engine)

John
Old 02-14-2017, 09:25 AM
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tailskid
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Well get them down and fly'em then <g> Your planes go too fast for me, so I'll "let" you fly them FOR me

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