Door window thickness

Hi All,

This is my first post/question to the group.

I am rebuilding a Kitfox Speedster and the threads here have already been a great resource for ideas and help. Thanks to all contributors.

The search function returns many hits on the poly-carbonate vs acrylic debate but I could not find any reference to the thickness required on the doors. I would not think it is as critical as the windscreen but the previous owner used .125 acrylic and it makes for a really heavy door. What did the kit originally come with?

Thanks for any feedback in advance.
Charles

I would say .060"lexan should be plenty thick. I think that is what came in the earlier kits. Actually I used .060" lexan for the windshields in all 4 of my Avid Flyers, but at about 100 MPH, the windscreen starts to buckle back against the tubes. Seldom if ever hit 100 MPH with most of them, so it wasn't a problem. On the Kitfox 4 I'm rebuilding, they used .090" lexan for the windshield. JImChuk

The original acrylic door was .125 but now you can get .100

I used .060 in the doors
And .090 for the wind screen
As Per my manual .
Mike

Mjke's answer is correct as far as the long wing Model IV is concerned. The speedster increased the windshield thickness to .118 (1/8") which gave it its higher top speed. The .118 was problematic because of the difficulty of getting the curve necessary around the wing root without almost instant crazing. Cold forming guidelines recommend a minimum bend radius of 12.5 inches for the 1/8" sheet - as opposed to the approximate 2" radius needed around the wing root. The typical IV - .090 will give early crazing as well. I have the .090 on my current IV, but with typical crazing at the wing root, I will go down to .060 when I do the inevitable replacement. 900 hours on my first IV with the .060 windshield with one replacement due to the typical wear and tear. As Jim mentioned the windshield will sag inward at high speeds, but not a real problem as typical flying speeds don't normally approach those speeds and Lexan is very tough - rarely if ever cracks.

Thanks all for the responses.

I do have a CD version of the build manual coming so that will be another reference point.

It seems like the .060 Lexan for the door windows would be the way to go for weight, toughness and ease of installation.

Charles

Remember that along with the positive aspects of Lexan such as weight, toughness, installation, there are a couple of very negative aspects such as no resistance to fuel spills, and much more prone to scratches. As careful as I try to be, there are times when I drip some fuel onto the doors during fuel sampling or refueling; at those times I am very glad I have acrylic door windows.

While Lexan doesn't like fuel as much as plexiglass, it doesn't just fall apart the second some gas touches it. I've had it spill on my windows from time to time with little effect. It does scratch easier than plexiglass though, no doubt about that. Probably less of a problem that way on the windows then the windscreen though. JImChuk

For me, weight is the main issue between Lexan and Plexiglass. Cost second and ease of install third. I could replace my windshield - skylight in about an hour or so with no risk of cracking. I did one plexiglass install and it was much more challenging. Since it was for a friend - much more stressful. When I do decide to change mine out, it will be simply remove the old one. Lay it on top of the new sheet of Lexan drill and trim and screw the new Lexan back on. It will fit exactly like the piece I took off