Tip stalling Chippie.

[Maurice Dyer]

Blackhorse 65" Chipmunk . I/C motor. C of G in the place where recommended, 100mm back from leading edge, I've reflected the ailerons slightly up by 1-2 mm up for washout. I've cut the down going aileron movement to half the upgoing. Land with or without the flaps, unless you come in like an express train, she tip stalls left. 

 

Why I'm giving up with it is there's a gentleman (obviously a better pilot than me) who flies the same model on YouTube and lands like a  feather every time. 

 

Radio and engine is coming out.........

 

[J D 8]

 Black Horse Chipmunks at our club always look to be good flyers.  Have you checked for warps in the wings ? 

[Denis Watkins]

We transformed one of these Maurice, to fly and land OK 

1. Tickover, get this to 2200-to -2500, to get good idle braking, and

2. C of G is too far back still. Go for 90mm or 95mm if you have to, ours is 90mm

Edited August 15, 2021 by Denis Watkins

[Maurice Dyer]

I wasnt too sure about the c of g Denis, does an aft c of g cause this or ??

JD8, cannot see any warps, thanks.

[Denis Watkins]

As others will note Maurice, aft C of G causes multiple problems with both control authority and ability to fly with the tail up.

As speed reduces, we stand a better chance of lift with a good balance.

Sometimes lads want aft C of G to do the likes of harriers.

I just know at 90mm from leading edge we transformed the model.

Just practice for the time being, flying in to " wheels touch" until you get used to it,

And do get a good 2000 ish idle on the motor, to aid landing

[Jon H]

I am slightly doubtful regarding the c/g issue. A tail heavy model will tip stall no more than a normal one as the angle of attack at which the wing stalls is the same. The only difference is a tail heavy model tends to be pitch sensitive making it easier to over pitch. However, 10mm movement of the c/g position will make less difference than the engine draining the tank so i really doubt that is the issue. 

 

I would check your rudder trim. Is the model flying in a straight line? This is often neglected and left yaw will always result in a left spin. 

 

Also, how are you trying to land? Are you doing a fairly steep approach with power off and full flap, or a flat approach with power? 

 

If its the latter, its not recommended for a scale model. The nose high attitude is asking for trouble and the power on will also cause a torque swing to the left. I recommend you try steeper approaches using the flaps as dive brakes. WIth the model trimmed using elevator flap mix (up usually required) it should parachute down nicely without needing any elevator input at all. 

 

 

Edited August 15, 2021 by Jon - Laser Engines

[Maurice Dyer]

5 hours ago, Jon - Laser Engines said:

I am slightly doubtful regarding the c/g issue. A tail heavy model will tip stall no more than a normal one as the angle of attack at which the wing stalls is the same. The only difference is a tail heavy model tends to be pitch sensitive making it easier to over pitch. However, 10mm movement of the c/g position will make less difference than the engine draining the tank so i really doubt that is the issue. 

 

I would check your rudder trim. Is the model flying in a straight line? This is often neglected and left yaw will always result in a left spin. 

 

Also, how are you trying to land? Are you doing a fairly steep approach with power off and full flap, or a flat approach with power? 

 

If its the latter, its not recommended for a scale model. The nose high attitude is asking for trouble and the power on will also cause a torque swing to the left. I recommend you try steeper approaches using the flaps as dive brakes. WIth the model trimmed using elevator flap mix (up usually required) it should parachute down nicely without needing any elevator input at all. 

 

 

Jon

flat approach with power. Regarding c of g, wouldnt aft c of g make the model 'drag its backside ' lower in all flight, including landing ?

Maurice

[Jon H]

1 hour ago, Maurice Dyer said:

Jon

flat approach with power. Regarding c of g, wouldnt aft c of g make the model 'drag its backside ' lower in all flight, including landing ?

Maurice

 

Not exactly, and not always. The tail dropping is all related to the way the tail generates lift vs the wing at different speeds. Its not uncommon for a tail heavy model to drag its booty, but even so i can be overcome with down trim or forward elevator pressure. Not all models do drop their tails so it is not always representative. Many models ( piper cubs, SE5a etc) drop their tails in turns even when correctly balanced so dont let tail dropping be the only signpost. 

 

Most of my warbirds are balanced 'tail heavy' by most standards. This has a number of advantages, one of which is keeping the blasted thing on its wheels and not ending every landing with its nose in the dirt. The down side is they become even more pitch sensitive than normal so very low elevator rates are needed. For reference, i can loop my Sea Fury on about 3mm elevator deflection. Most models are flown very nose heavy due to excessive elevator rates being used. If you reduce the rates, you can move the c/g and have a model that is actually more enjoyable to fly as you took some weight off it. 

 

When it comes to landing bin the flat approach, its not a great idea.

 

i set up an elevator flap mix on the tx and leave the menu open when i fly. I then drop gear and flaps, then keep adding elevator up trim (up is normally needed on heavy scale models) in the flap/ele mix menu until the model is at the limit of stalling in level flight with power used as required. If flying and button beeping is too much get an assistant to beep the buttons for you while you fly. With this point found i dial back the ele flap mix a few % and we are all set for landing. The procedure is to drop flaps and line up in a high approach. As the model is trimmed for just over stall speed if you chop power it will descend at the trimmed airspeed without needing to touch the elevator. If you are coming up short of the runway add power, if you are long reduce power. It cant possibly tipstall as its trimmed for a safe pitch angle/speed and you arent touching the elevator so the pitch remains the same. All you have to worry about is the last few feet. Add power and gently pull out of the descent at a few feet off the ground. Once level at a few inches chop the power and wait for the stall. By the time it happens you will already be on the ground. 

Edited August 15, 2021 by Jon - Laser Engines

[Don Fry]

Side mounted motor, wing not balanced? Long shot.

[SIMON CRAGG]

I have just built and flown the same model, with no tendancy to drop a wing.

c/g as per manual @ 100mm.

I had one wing heavier, which required a small amount of lead in the opposite wing tip.

Flies beautifully on 5s.

Try and persevere with it..........they are great models!.

[Maurice Dyer]

Just in case anybodies interested, solved the problem. Two more ounces of lead in the nose. I know all the aerodynamics say it shouldn't mattelr. And I don't know why it does. But it does..... Now lands and flies much better.

Maury