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Thread: Stabilizer Leading Edge

  1. #1
    Aeronut's Avatar
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    Stabilizer Leading Edge

    I‘m about to start jigging up the stabilizer of my PA-18 build and the kit presented me with two options for the outboard portion of the leading edge. I can either keep the leading edge diameter the same on the outboard as the inboard or I can flatten the outboard portion to the same thickness as the elevator at that location.

    Does anyone have an opinion of one over the other? If I flatten that portion of the leading edge, what process do you recommend?

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    skywagon8a's Avatar
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    Piper drawing #12769 says to flatten starting 6" from the end. They don't say how. You could use a couple of 2x4s squeezed with a big C clamp.
    A3310071.pdf (supercubproject.com)
    N1PA
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    Aeronut's Avatar
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    Ah! I didn‘t realize this was an original piper thing. I‘ll take a look at that drawing. I like the idea of 2x4s and a C clamp.

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    Take care to squeeze equally on the top and bottom. If you don't the stabilizer, will have a twist on the tip which could effect the flying characteristics. It may not be much, but every little bit counts. Be certain both stabilizers are the same. It is possible to end up with a twist from the tip of one side to the tip of the other. If you end up with a twist on one stabilizer, make sure the twist on the other one is the opposite. Then the twist (error) will offset the other one.
    N1PA
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    Aeronut's Avatar
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    Good point, Skywagon! I'm going to put some thought into it and then set up a jig/clamp so that I can get consistency.

    Drawing 12769 states to flatten to 3/8" an area on the outboard portion of the leading through 6". I assume that after 70 years this hasn't resulted in any problems but it does seem like a bit much of unnecessary stress at the transition from 3/8" to 1". I'm plannig on setting it up so that it tapers from 1" to 3/8" if I can get that working.

    I'll try to remember to post pictures on this thread in the next week or two when I have it all set up.

    Thanks for the tips!

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    CubCrafters flattens the leading edge. Here is my FX-3 stab as I assembled it in the welding jig:


    Click image for larger version. 

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  7. #7
    Aeronut's Avatar
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    I like that taper. I'm going to see what I can to duplicate that.

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    If you have a mill with a Kurt vice on it you can use that vice. Works better than a C clamp. Easy to make a couple tapered wood blocks, one for each side of the tube, and cut the desired tube profile into that. Put the tube between the blocks and smush with the vice.
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    Aeronut's Avatar
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    I do have access to a Kurt vice. I'll need to double check the depth but I think it might even be greater than 1". I like that idea but I think the challenge would be getting both leading edges on the same plane since on a mill it would be hanging off to the side.

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    skywagon8a's Avatar
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    Quote Originally Posted by Aeronut View Post
    it does seem like a bit much of unnecessary stress at the transition from 3/8" to 1". I'm planning on setting it up so that it tapers from 1" to 3/8" if I can get that working.
    You can always warm it up with a torch to soften it.
    N1PA
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  11. #11

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    A good size bench vise with flat boards works well.
    Put a spacer, dowel, drill bit, metal or wood stock or something at the thin end as a stop to help with parallelism and reduce over compression. You can add clamps as needed to spread the compression easier.
    I am starting my taper at the near rib.
    My outer end is not flat since the rib has an airfoil shape.

    If you have access to a bench press consider that as well. Vises and C clamps are not designed with the proper threads to draw allot of load.
    Regards, Charlie
    Super Coupe E-AB build in process
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    Aeronut's Avatar
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    I like those pointers, Charlie, in particular the one with the spacer. I'll need to incorporate that.

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    Here are some pictures of the press dies I made to flatten the end of the leading edge. I set up a 3 degree slope on the milling machine and made each half of the die. The intent is to press the tube ends using my end vise. In order to keep the leading in plane I have a tool I made that should allow me to keep the leading 90 degrees to the horizon during pressing using bubble levels. I did a practice run a scrap piece of 1" tubing and I'm pretty confident this will work on the actual piece.

    Click image for larger version. 

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