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Thread: One Lucky Fox

  1. #41
    Senior Member efwd's Avatar
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    Jun 2015
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    Yorba Linda, CA
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    2,817

    Default Re: One Lucky Fox

    When I was building my RV-4 back in 2000 I was on the phone with MR Vansgruven who stated "your not building a space shuttle". What you have there is not a problem whatsoever. Just wait until you go to hook up the first hinge to the flapperon control horn. It will likely be so out of alignment that you may need to bend the bracket into a slight S shape for the bolt holes to line up. It all works fine in the end.
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

  2. #42
    Senior Member Delta Whisky's Avatar
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    Dec 2017
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    Amissville, VA
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    Default Re: One Lucky Fox

    What Eddie said is good, general guidance. You'll get a chance to help with some of the alignment issue you have detected but in so doing you might run into a short edge distance issue with the aluminum reinforcements that go on the trailing end of the ribs. Then, you will try to eliminate some of the SED issues by placing the flapperon horn on either the outside or inside of the bracket vs. sandwiching the horn(s). One or two horns might have to be spaced with a washer from the bracket to make sure the horn does not rub on the skin of the flaperon. You might have to make one or two passes thru these steps so don't drill all of the bracket holes until you feel comfortable with the alignments. And, as Eddie said, some of the issues will be eliminated with a little scientifically applied force de jure. It might be challenging but fun and rewarding when complete. A bunch of tolerances are stacking up and the end steps have to tolerate that fact.

  3. #43

    Join Date
    May 2020
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    Boise, ID
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    98

    Default Re: One Lucky Fox

    Thanks guys for the sage advice and resetting my expectations correctly. It certainly ain't a space shuttle, that's for sure.
    Building N137DF
    STi, Rotax 915is, Airmaster

  4. #44

    Join Date
    May 2020
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    Boise, ID
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    98

    Default Re: One Lucky Fox

    The bends of the flaperon brackets are mere suggestions. 😂

    You need to bend them properly so the bends are square and the right and left bracket pieces are square to each other.

    before:

    2BFF0E97-3B37-405F-8F83-5B9C92566A73.jpg

    after:
    CD2E5151-1AA7-4BCA-9932-F7CF02FC6767.jpg

    the batch:
    761504A4-7747-48B0-80C8-5CB67629ED8F.jpg
    Building N137DF
    STi, Rotax 915is, Airmaster

  5. #45

    Join Date
    May 2020
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    Boise, ID
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    98

    Default Re: One Lucky Fox

    Stopped by the factory in Homedale a few months ago and a gent was passing through after fabricating carbon fiber flaperon ends which I thought were pretty neat so I made my own.

    I also discovered the #1 best way to dull a flat file. Use it on carbon fiber! 🤣😖

    5DFEC08F-1506-4969-ADC3-EC884199A768.jpg
    Building N137DF
    STi, Rotax 915is, Airmaster

  6. #46

    Join Date
    May 2020
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    Boise, ID
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    98

    Default Re: One Lucky Fox

    I have a small workshop - too small to put the wings on and take them off repeatedly - so I bought the pre-rigged wing option from Kitfox.

    The pre-rig option sets 4 things:

    * dihedral
    * washout twist
    * wing sweep
    * distance between rear and front spar attach points

    The construction guide instructs the builder to attach the wings to the fuse prior to installing the root rib, rib #1, and the tanks.

    As I said, I have a small shop, so after some thinking I figured out how to install the root rib and tank without installing the wings in the fuse. The solution is simple: a steel jig that sets the distance and hole angle the same as the fuse mount points.

    First clamp a length of angle iron on the lower side of the fuse mounts and drill through the points with a size N drill bit and ream with 0.1325” reamer:
    image1.jpg


    Next, place the angle on top of the fuse mount points, insert the AN 5-31 long bolt through the rear hole, clamp tightly and drill up through the the front mounting hole into the angle iron and ream:
    image2.jpg

    Et Voil*. The properly angled holes mounted to the wing. This provides the proper spacing to size the root ribs properly:

    IMG_7630.jpgTo maintain the washout twist when gluing in the tanks, with the wing set on 2 saw horses, place a 1/2” block under the rear spar at the 159” point, close to rib #9.
    Building N137DF
    STi, Rotax 915is, Airmaster

  7. #47

    Join Date
    May 2020
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    Boise, ID
    Posts
    98

    Default Re: One Lucky Fox

    Here are some pictures of how I installed landing light brackets in the STi wing tips. I did not cut out the entire internal 'glass tubing, just enough enough for the AeroLED lights to fit into the space:

    IMG_8070.jpg

    The fiberglass is too thin to hold a screw, so I bought some 1/8" aluminum and bent it to match the airfoil on the backside of the light brackets and hysol'd them into place. I'll drill through this and tap the holes for #6 stainless flat head screws.
    IMG_8069.jpg

    IMG_8068.jpg

    Nice flush fit. The plexi lens fights exactly even with the airfoil.
    IMG_8091.jpg
    Building N137DF
    STi, Rotax 915is, Airmaster

  8. #48

    Join Date
    May 2020
    Location
    Boise, ID
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    98

    Default Re: One Lucky Fox

    In section D, Flight Control Rigging, page 33, it says to use a 2 13/16 block placed against the bottom of the front spar. I'm sure this is for the normal airfoil, not the STi wing. What size should that block be for the STi?
    Building N137DF
    STi, Rotax 915is, Airmaster

  9. #49
    Senior Member Kitfox Pilot's Avatar
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    Aug 2019
    Location
    Spring Garden Illinois
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    859

    Default Re: One Lucky Fox

    I will have to check but I'm pretty sure I used a 2 13/16 block on mine.
    Harlan and Susan Payne
    Sold Piper Archer
    Flying FarmFox STI Kitfox N61HP
    Rotax 915is, Airmaster prop
    https://www.youtube.com/channel/UC5A...oCVUP15G0uB-Yw

  10. #50

    Join Date
    May 2020
    Location
    Boise, ID
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    98

    Default Re: One Lucky Fox

    Hm. Thanks Harlan. My *minor* concern is that in cruise flight, no flaps, the flaperon will have a slight *negative* AoI due to the additional 1/4” or so of thickness on the LE of the STi airfoil at the front spar location. High performance gliders use negative flaps at high speeds, but this ain’t no laminar flow airfoil. 😉

    I’ll ask John and Brandon on Monday, too.
    Building N137DF
    STi, Rotax 915is, Airmaster

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