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Old Jul 11, 2012, 06:35 PM
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United States, GA, Atlanta
Joined Feb 2011
39 Posts
Help!
Scratch built Super Cub... very first RC build

Hi all,

I'm almost finished with my first RC build, but I ran into an issue with the throw of the ailerons. The measurements are as follows: Right Aileron down:1/2" up:9/16"
Left Aileron down: 1/2" up:9/16" . I can't seem to get the up and down throw equal and it's driving me nuts. I made sure the ailerons were centered in the wing with all my trims at zero. Then I tried to use sub trim and travel adjust to equalize the trow up and down but to no avail. I have a DX6i Tx and I'm using a Y connector for the ailerons and the AUX port for the flaps.

Here is a video of what I did on the scratch build...
RC Super Cub Scratch build_2 (7 min 23 sec)
Ignore the issue I explain at the end of the video, I already solved that.

I'm also posting some pics of my progress just for fun. Let me know what you think!

Thanks











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Old Jul 12, 2012, 11:57 AM
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molond's Avatar
Australia, SA, Adelaide
Joined Oct 2011
253 Posts
I would just say go with it, since the differential is actually in your favour.
Normally when a plane banks it creates 'adverse' yaw, which is yaw in the opposite direction from bank. To fix this you can use rudder in a turn or differential. Differential is basically just more up compared to down which evens out the drag on both sides of the wing minimising adverse yaw.

If you really want to fix this move your control horns closer to the control surface axis. Your problem it probably cause by the fact that the linkage between the rod and horn is not "exactly" (my rule is lose enough is good enough) over the axis.

Edit: Just looked at your photos again, but that is not good enough. When I said that I was thinking millimetres not centimetres! (centi=10*milli)

But that my 4 cents (2 opinions * 2 cents)

Darcy
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Old Jul 12, 2012, 04:03 PM
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United States, GA, Atlanta
Joined Feb 2011
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Darcy, thanks for the reply. I'm going to be brave and fly this weekend (weather permitting) The photos I have up are slightly out dated. I redid the aileron and flap hinges and they are now flush with the wing. I also read that the throw differential is actually a good thing for this type of plane. Wish me luck, I'll be sure to post a maiden flight
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Old Jul 12, 2012, 04:52 PM
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dedStik's Avatar
United States, VA, Virginia Beach
Joined Feb 2012
5,475 Posts
I like it. Some will say it's not true scratch build, but being your first build and I'm guessing your first RC, it's the way to go. You will have infinitely more fun going this route and you will know your plane inside and out.

Your throws are unequal due to your placement of the control horns.



If you look at that image the eye of the horn (where the push rod connects) should be directly over the joint of the trailing edge of the wing and the leading edge of the control surface. The same holds true for rudder and elevator control horn placement.

The impact of your placement is negligible though and should not have any ill effects in flight.
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Old Jul 12, 2012, 05:25 PM
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dedStik, thanks for the advice! I have much to learn
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Old Jul 13, 2012, 11:27 AM
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molond's Avatar
Australia, SA, Adelaide
Joined Oct 2011
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Quote:
Originally Posted by Dionatron View Post
Darcy, thanks for the reply. I'm going to be brave and fly this weekend (weather permitting) The photos I have up are slightly out dated. I redid the aileron and flap hinges and they are now flush with the wing. I also read that the throw differential is actually a good thing for this type of plane. Wish me luck, I'll be sure to post a maiden flight
sorry I probably explained it wrong or you didn't understand me but that's ok as dedStick was able to put the exact same point in a more clear and consice manner.
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Old Jul 13, 2012, 01:48 PM
Damn this gets addictive.
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United Kingdom
Joined Oct 2011
530 Posts
Nice job on the build. Good luck with your maiden.
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Old Jul 17, 2012, 08:09 AM
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United States, GA, Atlanta
Joined Feb 2011
39 Posts
Well my first flight didn't go very well. The plane took off almost instantly with about 20% throttle and after that it was all a blur. I couldn't control the plane very well at all. It felt like the plane was "fish tailing" My aileron throw's were way too much and I just wasn't prepared for that. Eventually I crashed into a fence with minimal damage and it is already fixed. I'm going to setup dual rates for my ailerons/rudder/elevator and see how that goes.
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