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Slanting forward retracts! - 11/21/2011 4:42 PM   
skillet92


 

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Status: offline 		Hey guys I have a ESM Mustang that I have installed Sierra retracts and wanted to see what you guys thought or if you had any Ideas. It wants to nose over on takeoff and if I apply to much elevator it will jump off the ground before it is up to speed. I have tilted the retracts forward by placing washers under the back 2 screws on the retract mount. Not a lot but enough to move the wheel out closer to the leading edge. I have not flown it like this yet. Have any of you done this or anything different?


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RE: Slanting forward retracts! - 11/21/2011 4:47 PM   
MinnFlyer



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Status: offline 		I do that all the time - No prob

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RE: Slanting forward retracts! - 11/21/2011 5:15 PM   
acerc



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Status: offline 		I had to do the same on a Hanger-9 corsair. Worked great.


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RE: Slanting forward retracts! - 11/21/2011 5:39 PM   
BobH


 

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Status: offline 		I think the solution would be to not apply to much elevator on take off. Try using Expo instead.. it should help.

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RE: Slanting forward retracts! - 11/21/2011 7:45 PM   
Thunderbolt47



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Status: online 		Try releasing the elavator as the plane picks up speed.

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RE: Slanting forward retracts! - 11/24/2011 4:09 PM   
Firebar


 

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Status: offline 		I agree with the flying technique suggestions listed. I don't have the ESM Mustang and am not familiar with the gear setup. I have flown lots of tail draggers though.

The rule of thumb that I have always heard is that if you look straight down on the leading edge of the wing with the plane in flying attitude, you should see one half of the wheel. Less wheel and it will be difficult to keep from nosing over without lots of up elevator. More wheel showing and there will be a lot of weight on the tail wheel possibly making the plane takeoff prematurely.

Charlie

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RE: Slanting forward retracts! - 11/25/2011 1:07 PM   
carlbecker



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Status: offline 		I have issues like this with my Bf-110 flying off of grass. The problem may end if you can learn to control the elevator better. As soon as the rudder is effective I try to get off the elevator. When I control the elevator properly all is well. I don't use expo or a lot of elevator throw, enough to control landing flair and that is about it. I try to fly warbirds in a scale fashion.

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RE: Slanting forward retracts! - 11/25/2011 2:30 PM   
da Rock



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Status: offline 		We've pretty much covered this problem from one side, now look at the other.

Moving the wheels forward looks at the "front half" the solution. Look at the rear half of the solution, the location of the CG.

The footprint of the tires is the front, the CG is the rear.

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RE: Slanting forward retracts! - 11/25/2011 2:39 PM   
da Rock



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Status: offline 		If you are someone who thinks the CG should be "a bit more forward to make the plane fly better", you'll probably be surprised how far aft it can go. You'll probably also be surprised how much better it flies when you try moving it aft.

Moving the CG aft really isn't the terrifyingly dangerous acts many of us modelers think it is. With out 60 size models, the bankvault safe CG range is often over an inch wide. When you're working with a taildragger warbird, that's a real good thing.

Consider moving the CG back some. Want to be safe doing it? Measure your model with a yardstick and input the numbers into geistware.com's CG locater app to get a bankvault safe CG range: http://www.geistware.com/rcmodeling/cg_super_calc.htm

Moving the wheels forward is only half the possible solution. But it is a decent solution, especially when so many full scale birds had forward slanting gear and doing it makes the model look more realistic.

Here's my Hellcat after 90degree retracts were replaced with Wingspan 100 degree retracts:

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RE: Slanting forward retracts! - 11/25/2011 2:52 PM   
da Rock



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Status: offline 		Here's an example of a model that has the opposite problem. It porpoises on landing as soon as the tires hit. They're so far forward, when they hit they push up and the CG pushes down. Nose up results and unless it's below flying speed it takes back off.... with the engine at idle.

How to cure it? Either move about 4 ounces aft (elev/rudder servos) or move the gear back about the radius of the tires.

Notice the designer put funny gear on it to begin with? To begin with, I bet that designer was using what we'd consider normal gear. I bet that sucker bounced like a superball.

The present angle on the model, as illustrated in the attached, is about 25 degrees and all I've seen or flown better be going slow when the tires hit, very slow.

BTW, the igniter in the picture is sitting on the MFG's recommended CG location. That also happens to be WAY FORWARD from where the formulas suggest. In fact it's an inch forward the range you discover after measuring the model. The "scientific" range is about an inch and a quarter wide, and about an inch aft the MFG's suggested location. Yes, that model is on rails in the air.



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RE: Slanting forward retracts! - 11/25/2011 3:45 PM   
Lifer


 

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Status: offline 		A lot of good ideas and observations here. C/G movement is a proven solution as well. Nose heavy planes really don't fly well at all. Determine the c/g and then convert to a percentage of the chord and you can duplicate the balance point on future aurcraft. 28 to 32 percent is my favorite.

As far as shimming the retracts, I do it all the time. Put a 3/16ths to 1/8th inch thick spacer under the rear retract mounts and tighten back up. Nose overs are pretty much a thing of the past....and nobody knows but you.

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