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Old Nov 10, 2012, 02:24 PM
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Alter control surface

I have the Tiger 60 kit and studying this plane there was mention of aileron flutter as a result of it's narrow length and the use of one center mounted control arm.

Question: can the length of aileron be cut in half and width doubled without effecting performance. I use digital servos and useing two of them to eliminate flutter and added battery drain is'nt a good remedy from my point of view

Good experienced advice would be well recieved, thank you, Leroy
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Old Nov 10, 2012, 04:02 PM
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Hi Leroy
The major snag here is not so much the aileron length as the wire torque rods. Using those torque rods - the wire lengths bent to stick into the ailerons and then upwards to give leverage points for the servo - is about the oldest way to move ailerons going. It dates back to when advanced radios had four channels and servos were big and expensive.

Quick way round. Lose the torque rods, keep the kit ailerons - they will do you fine, this is a well regarded and proven model. Use two servos, one per aileron. Use either 'standard' servos, or the likes of Hitec's HS225 mini servos. Mount those servos out near half span into a mounting based on wing ribs, run their leads, with extensions if needed, through paper tubes going through round holes you add to the ribs. At the centre, you can either join these leads with a Y connector or to two receiver channels for tranny mixed control.

I could show some pics of how to do this,but due to circumstances involving house painting, I can't get to my real computer and photo files right now. Loosely, there's two tidy, efficient ways to mount servos inside the wing profile or they can hang out under the wing with the servo arm and aileron horn moving at ninety degrees to each other.

Changing the aileron span and chord will require a fair amount of structural redesign around the wing TE and two servos would still be the easier way to waggle them.

Real cheap suggestion . Do the research and figure out how you want to proceed before starting to build your model. It's much easier in the long run.

Good luck with your project

D
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Old Nov 10, 2012, 07:02 PM
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Derick thanks and I am doing the research, thats what prompted the question. I may have mislead you with the two servos. One artical used two on each aileron to stop flutter. I realize that gaposis on controls will cause flutter. There has been so much good said about this plane that that is why I bought it. When I see issues with it I just like to get opinions from many of you whom have built and or fly it.

I'm going with the tail dragger version, doing some bashing ( minor ) and a DLE 20, more to deal with weight issues than power needs. 1/2 throttle, small gas tank equals long flight times.

Thanks again, Leroy
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Old Nov 11, 2012, 01:29 PM
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If you go to two aileron servos, it is best to always put the control horn at some odd multiple of the length of the ailerons; like 1/3, 2/3, 2/5 or 4/5 as this will eliminate some of the possible frequencies that might initiate flutter. Also, use a very stiff materiel for the ailerons, the stiffer the better in so far as flutter goes.
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Old Nov 11, 2012, 01:41 PM
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i agree with Dereck 100%. Using 2 separate aileron servos is the best choice. You then also have additional options like spoilerons, flaperons, and the best one is aileron differential

Old_dude
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Old Nov 11, 2012, 04:32 PM
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But to answer the other part of the question,building buddy Don and myself regularly kit bashed those strip ailerons into 'barn doors' as a matter of course.

We halved the length and doubled the chord to arrive at the same area.
We swore aileron response was better with the narrower ones,closer to the tip.

We used single servos,(one per aileron), and offset the horn closer to the inboard end....about 40% out..
And we always 'sealed' them..
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Old Nov 11, 2012, 04:59 PM
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I've had great luck with converting during the building to proper wide outer style "barndoor" ailerons as well. I found that they improved things just as Earl says.

In your case instead of widening the existing ailerons which makes them MORE prone to flutter at the same time it increases the stiffness I'd go with horn style mass balances. This is where you put a wire whisker onto the ailerons that extends forward and down at an angle off the lower side or forward and up along the upper side and stick a littel lump of lead on the end. The idea is that this moves the chord wise balance point of the aileron forward closer to or even right to the hinge line. This acts to raise the flutter speed up above what you can achieve with the model. I've had to do this on two models over my modeling career and both time it produced excellent results.
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Old Nov 12, 2012, 01:56 PM
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Ok' now we are getting some where, Rodney, old_guy and Earl thanks' kinda what I wanted to hear. I was just out looking at the 60" wing of a Cherokee I have which is similar to the Tiger wing. I'm trying to get the perspective of aileron size to wing size. Probably a formula for this but I never had geometry so will have to come up with size another way. One thing do not want to do is have too much or too little.

On the Cherokee, which has flaps 1 1/2" X 12" and ailerons 2 3/8" X 12 1/2" or about 1" wider and may be a good gauge for the Tiger wing perportionally(spelling?) do you think ?. I don't mind doing the reconstruction to accomplish it and like the built up aileron anyway. I dont have flutter problems on any of my planes, propper mounting of control surfaces pretty much eliminate that.

BMatthews I'm sorry but I havent a clue what you said in your post so I probably won't be doing that, however I am greatfull for your attempt to help

Earl I see many of your posts and you have some good experience to offer, so goes to the rest of you. Any other comments are surely welcome, can't learn too much and I am planning some other changes (minor) on this plane like the viertical stab and increasing cowling aera for DLE 20 and a larger fuel tank. want to cowl the engine (fiberglass) so you see I have some things to work out.

Thanks again, Leroy.
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Old Nov 12, 2012, 02:21 PM
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Mr. Matthews has the right idea....Have you ever seen a Lockheed P-38 ? in the middle of the Elevator is the very thing he describes...Lead weights on a rod that locates them ahead of the hinge line...The weights accomplished two things-they balanced the Elevators ahead of the hinges,and since the weight was considerable,they fought the efforts of the flutter to a great extent.....They wouldn't move as fast as the wave wanted to,so it cancelled the flutter.
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Old Nov 12, 2012, 02:58 PM
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Some full scale use a "spade". It is a weight and also helps counteract the aerodynamic forces present on the aileron.

Search Google images for "aileron spade" You will get a ton of photos.

Ken
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Old Nov 12, 2012, 07:57 PM
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Yep, "spade" shaped or shaped like a teardrop....





As you can see from the second picture the P-38 had two such mass balances. I'm guessing that they wanted to keep things symetrical.

Another way is to cut a small opening in the covering and use one which fits into and moves in and out of the fixed portion of the wing such as this one;

(EDIT- OK, Jim Markse's web page won't let me grab an image. So go to http://www.continuo.com/marske/pione...oneer%2011.htm and about 1/3 of the way down the page is some pictures of a more "inline" style of mass balance)

For our model speeds simply cutting a small and clean cornered opening in the covering out at about 60% of the span from the center and adding an arm with a weight on the front that is roughly situated at the covering surface with enough clearnace in the arm to avoid mechanically binding with the trailing edge would do the job.

If you chose to re-do the controls to extend to separate wider flaps and ailerons that will certainly work too. But it's a lot more work and the addition of outboard "barn door" ailerons most certainly requires relocating servos or fitting internal pushrods. All of which require more modifications to the wings.

On the other hand the mass balances as shown are a simple fix that only requires a simple add-on and no covering removal or other mods.
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Old Nov 12, 2012, 11:12 PM
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BMathtthews, tip stall is what you were talking about in reguards to ailerons and stalls, need to use the rudder and most of that can be prevented.

Beaitiful P-38 and yes I can see what your talking about. I've seen them on the real plane but never knew what they were for, I don't recall seeing them on any sport planes but I'm learning something new today. Like said, I have'nt had flutter problems with my planes but suppose some air foils could lead to it even with a tight control fit. Always something to learn, one of the reasons I ask questions. I'm always greatfull for those of you who have the answers.

Thank you Leroy

Oh, Ken I'll check that out and Earl you always have something to offer. Really don't know what I and other guys would do without you

While I'm in the learning mode could you guys elaborate some on wing tip spoilers, what they do and if they are helpfull on a Tiger 60 type plane. Are they applied in such a way that the trailing edge is the same on both sides of wing or just upper.

As a one time airframe and engine mechanic, private license flier and now RC plane builder just baffles me at how little I know about air flow. We really never got into it much and those old airplanes I worked on and flew some 50 plus years back were nothing like these of today. Besides all that they were alot easier to fly from a seat than from the ground, a learning curve here also. Some of you may be in the same boat with me. Thanks for all the help I get here, Leroy
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Old Nov 13, 2012, 02:34 PM
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One more thing,while we're teaching you stuff-Those large "spades" you see on aerobatic aircraft are NOT for balancing !.....If you look closely,they don't weigh all that much,considering......
They are the airborne equivalent of power steering.In level flight,they are aligned with the airflow. -But when the ailerons are deflected,they reduce muscle effort from about 80 lbs. to 10lbs.,to allow that incredible roll rate.The spades actually 'grab' the air and try to deflect the aileron to the limit.-make them too large and you can't over come the deflection,and you'll go 'SPLAT%#@!!@#$%^
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Old Nov 13, 2012, 09:44 PM
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I got "caught" by the mention of "spade" balances thinking it was the flat airfoil shaped ones rather than the aerodynamic balances.

Up to now all my replies have been aimed at adding a quick mass balance aimed at a cheap and easy way to fix or avoid a flutter issue such as is sometimes found on narrow, thin and flexible strip ailerons. Tip stalling and spoilers are a whole other topic.

To avoid tip stalling the classic method is to simply add some washout to the wing panels so the tips are flying a few degrees lower for angle of attack.

Another way, but which isn't as good, is to reflex the outboard "barn door" ailerons slightly. But since the Tiger uses strip ailerons that's not really an option. Besides, it's not as effective a method as properly washing out the whole wing panel.

As for spoilers? Are you sure you didn't mean "turbulators"? Spoilers require an additional movable surface. And besides, spoilers don't delay tip stalling. Quite the opposite in fact. Unless you intended to say "spoilerons". That's where the ailerons are deflected upwards equally to change the airfoil to add in some washout. But again, with strip ailerons that isn't an option. It only works if you have regular outboard "barn door" ailerons.

On the other hand properly done turbulators on some airfoils can aid in delaying the pre-stall separation bubble and thus delay the final stall point. So in SOME CASES adding a turbulator over the outboard 1/3 of the wing can aid in delaying or avoiding tip stalling. The thing is that there's no magic number for a turbulator. You need to play with the style, thickness and chord position to find out if it works or not.
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Old Nov 14, 2012, 11:49 AM
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Spoilers, well I had to laugh at that one, I used them on a dragster to keep it on the groung, now I'm doing stuff to keep it in the air. Turbulators, I know that they used them on war birds it's all about dinamics of air flow some of which I don't fully understand. I do know, where there is a positive effect there is also a negative related to it and that leads to flutter.Turbulence and drag are the enemy of airplanes.

I basically got part of what I was looking for and I can figure out the rest. Thank you all, Leroy
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