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Thread: Cracked windshield

  1. #21
    Senior Member SkyPirate's Avatar
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    Default Re: Cracked windshield

    Hi Marc,.. yes you can make one from lexan,..without a pattern it takes a little more time,..but can be done . get some measurements off your present wndshield so you'll know what size piece of lexan to get,..you do have some choices on grade of lexan,..I'm using M-5 bronze on my doors and turtle deck,..and clear on the front. (M-10 requires heating to form)

    1/8" clear lexan,..leave the protective skin on the lexan until you have finished cutting the new windshield.

    your going to have to have the wings folded back to start with when sizing the new screen. once the old windscreen is removed,duplicate the bottom arc on the old screen to the new lexan where it meets the cowl,.cut that piece but add an inch or so it can be trimmed later if need be.take the new lexan and place it in an arc where it meets your top leading edge of instrument panel and cowl, use some squeeze clamps at the door posts to hold it ..put the top nose cowl section on and put a rolled towel on top of instrument panel pushing the lexan out to meet the top section of your cowl,. now pull the lexan to the top of the door post / front wing attach point and clamp it there too,,swing your wing towards the lexan and trace the leading edge where the wing meets the lexan,..do both sides,.. and trace a line down each door post on the inside of the door opening.
    remove the lexan,..you'll need a drill ..a hole saw I'm thinking its a 2.5 Inch hole saw,..and some good tin shears,..the straight edges you can cut with the tin shears..the section where the wing meets the lexan you'll need to use the hole saw,..once you've cut to this point ..put the windscreen back on the plane in the same manner,..and this time swing your wings to flight position and put the pins in,..you might have to manipulate the lexan a little ,,and or trim a little but once it fits well around your leading edges and you have the towel back in pushing the lexan out to the cowl ..,..you can fold the top part of the lexan down on top of the wing,..grab a bag of dog food or something to hold it down on top of the wing..do not cut this section yet.
    Now once all of the front section looks good you can start your drilling,..start at the top just under each wing and work your way down.and then cut the top to fit,..in place or mark it remove it again and cut it ..once the cutting is done remove the protactive covering from the inside edges and where your attaching the wind screen,..
    the top ,..ensure that your lexan is flat where it meets attach points,..once you know that it is,..start at the leading edge and work to the rear on each side about 3 inches from leading edge ..then go across the back where it meets the turtle deck,..then come back and finish from where you stopped at the 3 inch mark on each side of the top,,

    sand all the sharp edges with fine sand paper peel the rest of the protective skin off ..and try her out

    hope this helps

    Chase

  2. #22
    Senior Member
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    Default Re: Cracked windshield

    I'll give y'all the final scoop on my cracked LP acrylic windshield. If you remember, mine cracked at the front spar attach point while setting it into place. I ordered a repair product and repaired it. I started back to work installing it and had it in place with all holes drilled and just minor trimming left to do. I had my buddy with me to help handle and we used extreme care to be extra gentle to do some final trimming on the bandsaw. We never made it to the bandsaw before it cracked again in a new spot, but also around the same wing attach point, under its own weight. I don't know how we could have handled it any more carefully. I don't know if I just got a lemon or if all are that fragile. The paperwork clearly states that there is no guarentee against cracking so I'm out if $500+ with nothing to show for it. I tried calling LP and left a message be they never returned my call. So I ended where I started with a sheet of Lexan. It's easy to work with and reasonably priced. Maybe I'm just too heavy handed for acrylic bit I don't know of anything I could have done differently. James Thomas

  3. #23
    Senior Member SkyPirate's Avatar
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    Default Re: Cracked windshield

    something I'm going to try,..on the top,.I'm going to put a piece of bronze M-5 right over my head under the clear lexan windshield,..basically layered one on top of the other so I end up with a little sun screen on top that will match my turtle deck and door's,..I'm hoping for no chafing between the layers ..might have to run a bead of adhesive to keep the dust out where the M-5 ends at the top of forward view area.

    Chase

  4. #24
    Senior Member HighWing's Avatar
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    Default Re: Cracked windshield

    For what it's worth. I just checked my original 1993 Model IV windshield it is .060" I still have it to cut up and use on projects. The speedster came with the .093" and that is why the VNE was higher than the standard IV. I replaced it once in 9 years and 900 hours. I plan on using it again this time as well. It did sag a bit when in those steep fast descents, but I could cruise at 115 mph before repitching for climb and I had no problems with it. One issue with the .093 is that the crazing at the forward carry through was a bit more of an issue - guys complained a lot about it. I personally know of two instances where a Polycarbonate windshild actually split from to to bottom. Both were field repaired with tape while on fairly long cross country trips. I believe one was drilled and sewn together with safety wire as well. That one happened on the group Alaska trip some of you might remember.

    My suggestion is to stay away from anything thicker than the .093" unless you can figure out how to aviod the tight bend at the wing. If you check the specs on Polycarbonate, the recommended minimum bend radius is thickness dependent and even the .060" is over stressed in our typical application - it is something like three inches, as I recall. It crazes as well. Regarding the abrasion resistent varieties available. These are designed for glazing applications in flat panels. The minimum bending radius is in feet as the abrasion resistant feature is a coating and it will crack it stretched around a bend.

    If you plan on heating around the bends, keep in mind that Polycarbonate is hydrophilic - it absorbes moisture. When it is heat formed in production runs, it is heated at 250 degrees for a set time depending on thickness to avaporate absorbed water and heat formed soon thereafter to avoid the reintroduction of water. I have tried vacuum forming without drying and it look like a transparent sponge. The 250 degree drying cycle doesn't cause problems, so my susggestion is that would be the max temp.

    The ultlimate benefit, in my opinion, is that not only being relatively enexpensive, that once fitted, you have a perfect pattern for the next one and it is lightweight for those that want to eventually get off the ground.

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