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3 piece windshield

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Posted

I am installing a 3 piece windshield in my Bandit. This will be the 3rd time I have had to replace it. I'm hoping this will take some stress out of the curved area of the Lexan and it should be some what easier and cheaper to do.

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Posted (edited)

I am installing a 3 piece windshield in my Bandit. This will be the 3rd time I have had to replace it. I'm hoping this will take some stress out of the curved area of the Lexan and it should be some what easier and cheaper to do.

What thickness are you using? I thought at one time in Anchorage when we were overrun with geese, that I might put welded fence wire in front of my WS, or just behind it !

I believe with some modification to the cowl, that we could make 3 flat pieces of windshield like I have seen on some other planes. might look a little different, but could work.

ED in MO

P.S. Where is yours cracking?

Edited by Ed In Missouri

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Posted

What thickness are you using? I thought at one time in Anchorage when we were overrun with geese, that I might put welded fence wire in front of my WS, or just behind it !

I believe with some modification to the cowl, that we could make 3 flat pieces of windshield like I have seen on some other planes. might look a little different, but could work.

ED in MO

P.S. Where is yours cracking?

.063 I think or close to it. It cracks on those two triangle pieces I am cutting out and replacing.

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Posted (edited)

.063 I think or close to it. It cracks on those two triangle pieces I am cutting out and replacing.

I thought the standard was .093 - there was one, the Speedster, I think, that came out with .118 thickness, and they issued a service bulletin to replace it with .093 because of cracking.

Does it crack on the bolt holes, or where? The holes should be at least 1/16 or 1/8 inch oversize of the bolts, and I use rubber washers topped with steel washers under the heads. Dont know why you couldnt make the holes bigger and use rubber grommets if you can find them the right size.

Good Luck,

ED in MO

Edited by Ed In Missouri

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Posted

Mark,

hmm.. looks interesting, but I am not too sure I would want that line of bolts or rivets on the windshield. The way it flexes and bends as you approach the higher speeds and wind gusts, I am not too sure how long it is going to last before it turns loose on you. I hope it works out and if so, you may start a new fad on the windshields! That is the beauty of the experimental world, we are free to figure out what works and what doesn't. Somethimes thinking out of the box is what it takes to fix a known problem!

:BC:

Ed,

They crack at the corners at the wing root. The tight curve there makes them all crack over time. Some get lucky and get a few years, others a few months. I need to replace mine when I get home if I have time, if not, this will be the last trip to the lodge with it until I get it replaced. I have never had any issues with it cracking around the bolt holes on the windshield... the doors, well that is a different story. I change the doors out once or twice a year. I have drilled over size, chamfer the holes, be bur everything, used screws and rubber washers instead of rivets etc. I ahve tried damn near everything and I cant get them to stop cracking.

:BC:

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Posted

Mark,

hmm.. looks interesting, but I am not too sure I would want that line of bolts or rivets on the windshield. The way it flexes and bends as you approach the higher speeds and wind gusts, I am not too sure how long it is going to last before it turns loose on you. I hope it works out and if so, you may start a new fad on the windshields! That is the beauty of the experimental world, we are free to figure out what works and what doesn't. Somethimes thinking out of the box is what it takes to fix a known problem!

:BC:/>

Ed,

They crack at the corners at the wing root. The tight curve there makes them all crack over time. Some get lucky and get a few years, others a few months. I need to replace mine when I get home if I have time, if not, this will be the last trip to the lodge with it until I get it replaced. I have never had any issues with it cracking around the bolt holes on the windshield... the doors, well that is a different story. I change the doors out once or twice a year. I have drilled over size, chamfer the holes, be bur everything, used screws and rubber washers instead of rivets etc. I ahve tried damn near everything and I cant get them to stop cracking.

:BC:/>

I've not had one crack at the wing root yet - But have given some thought about that bend, and will be considering trying to take out that bend, or some of it, when I install the next one - Of course, mine is seperate from the skylight, so there may be a solution to this. Will post photos if I make a major change, but that will be a long time off. Maybe you should just attach the door glass with zippers or velcro? Kidding....

Would heavier glass help in the doors?

ED in MO

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Posted

I've not had one crack at the wing root yet - But have given some thought about that bend, and will be considering trying to take out that bend, or some of it, when I install the next one - Of course, mine is seperate from the skylight, so there may be a solution to this. Will post photos if I make a major change, but that will be a long time off. Maybe you should just attach the door glass with zippers or velcro? Kidding....

Would heavier glass help in the doors?

ED in MO

I tried heavier on the doors and they crack even worse. the .063 seems to last longer than the .092. That just may be something I have to live with to have full lexan doors and flying at -30 :lol:

:BC:

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Posted

I tried heavier on the doors and they crack even worse. the .063 seems to last longer than the .092. That just may be something I have to live with to have full lexan doors and flying at -30 :lol:/>

:BC:/>

Yes, I know how -30 or -80 is. Only thing I have to worry about here is melting off in hot summers!

Well, got to swallow that one - in about 1959 I was driving a truck in Southern Missouri, and got up at a Motel and thought my truck grunted a little more than usual - walked across road to have breakfast while truck warmed up, and the waitress said it was 30 below in West Plains, MO that morning, and 30 above in Alaska - Right then I knew I had to go to Alaska someday - Took me 30 more years, but I made it! :lol:

ED

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Posted (edited)

I tried heavier on the doors and they crack even worse. the .063 seems to last longer than the .092. That just may be something I have to live with to have full lexan doors and flying at -30 :lol:/>/>

:BC:/>/>

I have wondered about using a U-channel or angle aluminum and siliconing the doors in, like they do with the triangle windows in back - my doors should be under positive pressure, so got to make sure they dont cave in on me. I was thinking about .125 Lexan for that.

ED in MO

Edited by Ed In Missouri

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Posted (edited)

Mark,

hmm.. looks interesting, but I am not too sure I would want that line of bolts or rivets on the windshield. The way it flexes and bends as you approach the higher speeds and wind gusts, I am not too sure how long it is going to last before it turns loose on you. I hope it works out and if so, you may start a new fad on the windshields! That is the beauty of the experimental world, we are free to figure out what works and what doesn't. Somethimes thinking out of the box is what it takes to fix a known problem!

:BC:/>/>

Ed,

They crack at the corners at the wing root. The tight curve there makes them all crack over time. Some get lucky and get a few years, others a few months. I need to replace mine when I get home if I have time, if not, this will be the last trip to the lodge with it until I get it replaced. I have never had any issues with it cracking around the bolt holes on the windshield... the doors, well that is a different story. I change the doors out once or twice a year. I have drilled over size, chamfer the holes, be bur everything, used screws and rubber washers instead of rivets etc. I ahve tried damn near everything and I cant get them to stop cracking.

:BC:/>/>

Yup, That is what I have been through with my windshield Leni. Nothing seems to work for long. My sunroof is seperate from the front. This made it much nicer to change it out. My curve was cracked so bad that I could stick two fingers through the cracks and pieces that were missing. I am going to fly this weekend if it clears up. I will let you know how it go's and take a picture of the finished windshield. In my Bandit I don't aproach any high speed's, so I'm hoping it will hold together. If not I will have a open cockpit airplane. The only thing I am concerned about is that I only used a 3/4" alminum strip to rivet the seam together, so the rivet holes are real close to the edge of the Lexan. Time will tell.

Edited by Bandit

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Posted

Yup, That is what I have been through with my windshield Leni. Nothing seems to work for long. My sunroof is seperate from the front. This made it much nicer to change it out. My curve was cracked so bad that I could stick two fingers through the cracks and pieces that were missing. I am going to fly this weekend if it clears up. I will let you know how it go's and take a picture of the finished windshield. In my Bandit I don't aproach any high speed's, so I'm hoping it will hold together. If not I will have a open cockpit airplane. The only thing I am concerned about is that I only used a 3/4" alminum strip to rivet the seam together, so the rivet holes are real close to the edge of the Lexan. Time will tell.

I was wondering if you could have just used a heat gun to take the strain off of the curves?

ED in MO

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Posted

I was wondering if you could have just used a heat gun to take the strain off of the curves?

ED in MO

Heat gun has been tried by MANY with varying degrees of success..

:BC:

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Posted

Heat worked for me, but the procedure involved more than just a heat gun. I replaced my Model III windshield/skylight (.060) and did some research at the time. GE, the manufacturer of Lexan brand polycarbonate says controlled and uniform heating of the entire polycarbonate sheet is a critical factor for hot bending, as slow heating rates will balance out hot spots and allow the sheet edges to reach the required forming temperature. After attaching to the butt ribs, on a suggestion from a fellow Avid builder, I hooked a 1000w halogen work light to the headrack inside as a heat lamp and my twin halogen stand positioned outside so as to shine not only on the bend area but to warm the entire sheet for a period before getting started. So I think this approach has merit and, like super smooth edges, may help reduce future crazing. Time will tell but I figure it can't hurt. I also used a heat gun on low setting for extra stress relief while forming the acute, compound curve in the pre-warmed sheet. Blasting the acute curves only with high heat certainly makes the bending process easier but, unless you heat the entire sheet (or as much as possible around the target work area), you have not done everything you can do to help reduce crazing.

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Posted

Heat worked for me, but the procedure involved more than just a heat gun. I replaced my Model III windshield/skylight (.060) and did some research at the time. GE, the manufacturer of Lexan brand polycarbonate says controlled and uniform heating of the entire polycarbonate sheet is a critical factor for hot bending, as slow heating rates will balance out hot spots and allow the sheet edges to reach the required forming temperature. After attaching to the butt ribs, on a suggestion from a fellow Avid builder, I hooked a 1000w halogen work light to the headrack inside as a heat lamp and my twin halogen stand positioned outside so as to shine not only on the bend area but to warm the entire sheet for a period before getting started. So I think this approach has merit and, like super smooth edges, may help reduce future crazing. Time will tell but I figure it can't hurt. I also used a heat gun on low setting for extra stress relief while forming the acute, compound curve in the pre-warmed sheet. Blasting the acute curves only with high heat certainly makes the bending process easier but, unless you heat the entire sheet (or as much as possible around the target work area), you have not done everything you can do to help reduce crazing.

Doug,

How long did you leave the lamps on the Lexan? Did you check the temperature of the Lexan? Was it allowed to cool slowly, just normal room temp or what?

Thanks,

ED in MO

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I used a heat gun and an infrared thermometer during my install. I tried to heat roughly a 16x16 area and it seemed to work OK. It may have worked better if there was something to insulate on the back side but once I was able to get the curved area to 300 It was definately relieving some stress. I have the window out now because I'm still building but it's holding a somewhat curved shape on its own.

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I've tried a lot of different things on my racecar to stop the cracking around the screw holes on my side windows.The thing that has worked best was oversize the hole in the lexan and the tabs that they attach to. Use a screw with lock nuts and just barely snug them down.Polycarbonate has to be able to move with expansion.Not sure if this would work for Leni at 30 below but it stopped all my cracking and crazing around the screw holes.Dont use Loctite on the screws,it will cause Lexan to craze and crack.Drill with dishsoap and drill slow,then clean the sharp edges off with a file or tapered mill.Randy

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Posted (edited)

I used a heat gun and an infrared thermometer during my install. I tried to heat roughly a 16x16 area and it seemed to work OK. It may have worked better if there was something to insulate on the back side but once I was able to get the curved area to 300 It was definately relieving some stress. I have the window out now because I'm still building but it's holding a somewhat curved shape on its own.

Believe 275F is what the 43-13 says for forming Plexiglas - think Lexan is 285 - but better check those figures.

Sounds like you were just under "melting" - glad it worked. I bent some boat windsheilds 90 degrees once with a heat gun, and got a few little bubbles in the bend, but it never cracked - and that was in Alaska, and the bottom was attached with screws and rubber and steel washers, and the unframed top was often a handhold used by others while I held my breath and watched for it to break and put them in the water - but that never happened in 5 years. 1/8 inch Lexan. What thickness did you use?

ED in MO

Edited by Ed In Missouri

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Believe 275F is what the 43-13 says for forming Plexiglas - think Lexan is 285 - but better check those figures.

Sounds like you were just under "melting" - glad it worked. I bent some boat windsheilds 90 degrees once with a heat gun, and got a few little bubbles in the bend, but it never cracked - and that was in Alaska, and the bottom was attached with screws and rubber and steel washers, and the unframed top was often a handhold used by others while I held my breath and watched for it to break and put them in the water - but that never happened in 5 years. 1/8 inch Lexan. What thickness did you use?

ED in MO

I used .093 Makrolon poly

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Posted

I used the molded plexiglass windshield from LP Aeroplastics. I plan on the same for the project plane, also the bubble windows for the doors.

No crazing, no worries of the lexan.

For the record, the same window fits the Avid as the Kitfox IV. And they make bubble windows for the Avids, too.

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Not saying this will happen to you, but when I got my Kitfox 4 kit, it had a windshield from LP Aeroplastics in a big box. When it came time to mount the windshield, as I was positioning it on the butt ribs, it cracked. I had it sitting in place, and lifted one corner about 3/4" to move it, and I heard this little plink sound... It broke right at the top of the cutout for the wing spar. Sure glad I wasn't the one who paid $400 for it. I've changed about 5 windshields on Avids, and never used heat on them. Never had problems with them cracking either. I'll take that back, I did break 2 of them, but they were trying to hold the rest of the plane up and they couldn't pass muster on that!. Oh well, that's my story and I'm sticking to it! Take care, Jim Chuk

I used the molded plexiglass windshield from LP Aeroplastics. I plan on the same for the project plane, also the bubble windows for the doors.

No crazing, no worries of the lexan.

For the record, the same window fits the Avid as the Kitfox IV. And they make bubble windows for the Avids, too.

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Posted

Not saying this will happen to you, but when I got my Kitfox 4 kit, it had a windshield from LP Aeroplastics in a big box. When it came time to mount the windshield, as I was positioning it on the butt ribs, it cracked. I had it sitting in place, and lifted one corner about 3/4" to move it, and I heard this little plink sound... It broke right at the top of the cutout for the wing spar. Sure glad I wasn't the one who paid $400 for it. I've changed about 5 windshields on Avids, and never used heat on them. Never had problems with them cracking either. I'll take that back, I did break 2 of them, but they were trying to hold the rest of the plane up and they couldn't pass muster on that!. Oh well, that's my story and I'm sticking to it! Take care, Jim Chuk

There are repair procedures and sometimes that is cheaper / easier than replacing the whold thing.

ED in MO

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Posted (edited)

I was wondering if you could have just used a heat gun to take the strain off of the curves?

ED in MO

Tried that doesn't work.

Edited by Bandit

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Posted (edited)

There are repair procedures and sometimes that is cheaper / easier than replacing the whold thing.

ED in MO

No repairing this problem. I'll post pictures of how bad it cracks if left long enough.

Edited by Bandit

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Posted

No repairing this problem. I post pictures of how bad it cracks if left long enough.

I sort of figured that for yours, since you said you could put 2 fingers in the crack. I was mostly referring to just a little crack with no missing pieces, but sometimes we have to do major things to keep the bugs out until we remove and replace. I've seen them with so much duct tape you needed radar!

ED in MO

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Posted

If you were referring to stop drilling to keep the crack from going further, I wasn't about to take any chances with that windshield. It broke so easy that I didn't want to give it a chance to shatter and come flying into my face at 100 MPH. I had a sheet of 4'X4'X .090 Lexan that came with the kit and built the windshield out of that. I've heard of others that have had the plexiglass windshields break on them also. I know the Lexan scratches easier, but I'm sticking with that. I just bought a 4'X8' X.090 Lexan from a local commercial window builder/installer for $75, and that will make 2 windshields for me. Actually I got a break on the price cause my son who is a construction superintendent works quite often with this guy and they help each other out when they can. Take care, Jim Chuk

I sort of figured that for yours, since you said you could put 2 fingers in the crack. I was mostly referring to just a little crack with no missing pieces, but sometimes we have to do major things to keep the bugs out until we remove and replace. I've seen them with so much duct tape you needed radar!

ED in MO

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