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Thread: Windshield tips

  1. #1
    Senior Member aviator79's Avatar
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    Default Windshield tips

    I'm being a little bit ambivalent about getting my windshield installed. I'm kind of terrified of cracking it or trimming it incorrectly. The instructions for the initial fit are a little vague about how to trim around the forward carrythrough tube. does anyone have any tips, pictures, tricks, or assistance to share about how to do this successfully?

    Specifically:

    -It appears to me that I need to take some material off to clear the bottom of the carrythrough tube, but I'm not sure how far to go back on top. The manual seems to say that you should go back far enough to get the hardware in, but that's a lot of material to take off. I'm wondering if through-holes would be better.

    -Would it be a good idea when removing material under the carrythrough tube to put a nice round relief in to help prevent cracking during handling?

    -During initial fit with the vertical edges of the windshield outside the mounting angles, I'm worried that pushing the top of the windshield into position will crack it. Those that have been successful, how did you get everything into place for the intial fit?
    --Brian
    Flying - S7SS

  2. #2
    Senior Member Esser's Avatar
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    Default Re: Windshield tips

    My thoughts. The windshield is way stronger before being trimmed. Getbit pretty much installed so that you won’t have to remove it again. Then take a die grinder with an aggressive sanding drum to start trimming atbthe carey through tubes. You need to take out lots there for the spar to have enough room to pivot in.
    ------------------
    Josh Esser
    Flying SS7
    Rotax 914iS
    AirMaster Prop

    Edmonton, AB, CWL3

  3. #3
    Senior Member jmodguy's Avatar
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    Default Re: Windshield tips

    I believe the vertical edges go inside the angles. I was also wondering about not relieving the corners and just making a hole for the forward pin to go through... I don’t think I will ever fold the wings so that feature is not important to me.
    Jeff
    KF 5
    340KF

  4. #4
    Senior Member aviator79's Avatar
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    Default Re: Windshield tips

    Quote Originally Posted by Esser View Post
    My thoughts. The windshield is way stronger before being trimmed. Getbit pretty much installed so that you won’t have to remove it again. Then take a die grinder with an aggressive sanding drum to start trimming atbthe carey through tubes. You need to take out lots there for the spar to have enough room to pivot in.
    I definitely have to do some trimming prior to getting in on, as it interferes with the forward carrythough tube and can't seat in place as-is. I wouldn't mind seeing photos of the completed area around the carrythrough tube if you have any or wouldn't mind removing the root fairing and snapping a few.

    I believe the vertical edges go inside the angles
    They do, but when you first put it on, it won't fit between the angles. I believe you mark the aft edge of the angle on the windshield with the windshield on the outside of the angle, trim it, and then fit it inside. I could be mis-remembering the instructions though.
    --Brian
    Flying - S7SS

  5. #5
    Senior Member jiott's Avatar
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    Default Re: Windshield tips

    I agree, don't force the vertical edges behind the angles before you have trimed them at least somewhat close to final dimension. I have heard of several cracking incidents trying to do this too soon. Bottom line, you should never have to apply much force to flex the windshield into place.

    Also, as was asked, yest you should never leave sharp corners, but always use smooth radiused corners, and smooth and round all rough edges to eliminate stress risers.

    I had to take my windshield on and off about 5 times to get it right. Its no problem if you are careful and don't flex it in the process; 2 people make it much easier.

    The trimming around the front carrythru tube- just trim enough so the tube and spar (when folding) don't touch the acrylic and allow for thermal expansion. Large gaps are not required. I used a generous clearance hole thru the acrylic for the front spar pin. The photo below shows this, but it may not be real clear.
    Attached Images Attached Images
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  6. #6
    Senior Member aviator79's Avatar
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    Default Re: Windshield tips

    Thanks Jim, that's very helpful.
    --Brian
    Flying - S7SS

  7. #7
    Senior Member efwd's Avatar
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    Default Re: Windshield tips

    I laid the thing up and used a marker to draw where I thought the cuts would be made around the cross tube. Ended up I was wrong on the geometry. I could have removed far less. The good thing is, the root cuff panel covers it. The way I see it, there is no need for the extra glass that would remain over your front spar bolt should you think you would just like a through hole drilled in it. The root cuff panel covers the entire area anyhow. The dremel sanding drum is what I used as well. It will make short work of the process.
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

  8. #8
    Senior Member jmodguy's Avatar
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    Default Re: Windshield tips

    Huh... I couldn’t get mine outside the angles. I was afraid it would snap! It is an older part (95 vintage).
    Jeff
    KF 5
    340KF

  9. #9
    Hockeystud87's Avatar
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    Default Re: Windshield tips

    If I needed to replace my window on my model IV is the glass a special plastic or can I just grab a similar Plexiglas and find a outline to trace?

  10. #10
    Guy Buchanan's Avatar
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    Default Re: Windshield tips

    For the acrylic windshield:

    1. I would remove as much material as possible from around the forward carry-through tube. This reduces the stresses in the corner which are the nemesis of all Kitfox windshields. You can remove everything covered by the root cuff, minus whatever overlap you want. (I did about 3/8" overlap.)
    2. Make sure you polish the edges before you apply any load.
    3. Use holes to insert wing bolts.
    4. Use acrylic drills (0 rake angle) and step drills to drill holes. Never a standard drill. Polish hole interiors, if possible.
    5. Use a Dremel with diamond wheel to rough cut. Dremel with sanding wheel for female corners. Sandpaper for straight edges and male corners.
    6. You may need to remove the aft corners a bit to clear the wing when it folds.
    7. You know about the fastener clearance holes.

    For the polycarbonate (Lexan) windshield:

    1. I switched to polycarbonate when I saw how easily my acrylic window shattered on impact. The polycarbonate is much, much tougher; used on F-16's. Unfortunately it's also not as clear and scratches much easier.
    2. Polycarbonate is much easier to fabricate and install because it doesn't need to be (indeed can't be) heat formed. You just cut it and bend it as required.
    3. I did most of the same stuff above with my polycarbonate windshield.
    Guy Buchanan
    San Diego, CA
    Deceased K-IV 1200 / 912uls / 70" Warp 3cs

    gebuchanan@cox.net

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