Aero LP Windshield and bubble doors

[DanB]

Well, last weekend was my first attempt at installing the acrylic windshield on the Model IV...it didn't go well to say the least. I didn't even get a hole drilled and it cracked at the top of the pilots side (inside the hole) about 3/4" in. It was stop-drilled at that point and I decided I didn't want to mess with it any more. I went and got some polycarb and that went on very well.
I decided to try my hand at the bubble doors...nope. This stuff is a real PITA. My opinion is a person shouldn't have to tip-toe around a plane trying to get it built.

[n85ae]

Try a step drill, it will drill easily without the the cracking.

Jeff

[n85ae]

Odd coincidence I actually have an undrilled co-pilot side bubble door in
my hangar for a Model 5

Jeff

[jdmcbean]

When drilling acrylic you MUST use an acrylic drill bit. Using a standard drill bit will almost always chip and crack acrylic.

Step drills can work well but be careful.

[RobS]

Boat builders experience similar problems. A nice description of the issue and methods to minimize the risks when drilling acrylics can be found here.

http://bertram31.com/proj/tips/drill_acrylic.htm

[n85ae]

I own both step drills, and the bits sold by LP Aero, and have reground some
of my own. You mileage may vary, but for me I've had no cracking with step
drills, but have cracked acrylic with the LP Bits, and my own reground bits.

Regards,
Jeff

[jrthomas]

I would advise anyone thinking about using an LP acrylic windshield to think long and hard before spendingthe money. I should have just thrown my $500+ is the garbage. That's where my windshield ended up. Mine cracked around the front spar on the pilots side when I set it in place. I was only positioning it in place. I repaired it and figured the cuff would cover the crack so I went ahead, planning to use it anyway. I used extreme caution from then on, drilled all my holes with no problem. I got my buddy, who is an experienced builder, to help me set it off to do some final trimming.Under its own weight it cracked again in our hands,this time on the passenger side at the front wing spar. I had no problem drilling the holes but my belief is that there was a manufacturing problem that caused my windshield to be overly brittle at the point where they cracked. I called LP but was never able to get a live person. I left a message explaining my problem and asked that they return my call but I never got a call back. On the positive side, I used the LP bubble doors and I never had any problem. I used the bits they included, drilled very slowly and had no problems. I did my trimming with a Dremel and used a belt sander for the fine fitting and everything turned out real nice. I believe my windshield was defective maybe due to the curing process where it was shaped and moulded around the front spars. I did some "torture testing" with some scrap pieces of the same windshield and it would handle some pretty bad abuse, everywhere except at that same spot at the spars. I'm not trying to trash LP. I love the doors. This is just what happened to me and if it helps some of y'all avoid the same bad experience as me, that's a good thing. James Thomas

[DesertFox4]

jrthomas- I was helping Dan when the LP windshield broke. Same deal as yours. I was positioning it into place against its own weight and it popped at the front pilots side carry through, like yours. I mentioned to Dan to expect the chance that even in our 100 degree temps. the acrylic may break. I've heard some stories of the same outcome. BTW, no holes had yet been drilled.
Dan picked up a 4x8 sheet of .093 "Lexan" from one of our local TeamKitfox members , thanks DesertFox1. We used my old windshield as a template and I think we had a new windshield ready to install in less than two hours of cutting and sanding. Saved weight also. Just didn't save any money or time. You win some, and .....some you don't.

[DanB]

James,
As you described in detail how your windshield broke...so it went with mine. It broke as we were positioning the thing. And it broke on the pilots side towards the front. I also think the cuff will cover it, but I didn't want to mess anymore with it. I also had two quite experienced Kitfoxers helping with it, but it broke just the same. I wouldn't say it was defective, I believe it is just the nature of the beast. I know I will be quite happy with my polycarb windshield and doors as I won't need to baby them.

Ha...noticed Steve posted just b-4 I did. Sometimes things just don't go the way you plan them, but like Steve said, we were ready for anything to happen. There have been too many battle scars emerge from the ranks to think we were entering anything less than a war zone. It was certainly no ones fault...the stuff just went. My hat is off to both Steve and Murle Williams for the countless hours they have invested in helping me finish up my project. Thanks guys!

[jrthomas]

It seems to me that there's a problem around the carry through tube since we both had cracks there. I went back to the Lexan like you did and I'm very pleased with the way my windshield turned out. Lexan is some amazing stuff. When I did my torture test on some scraps of acrlyic from the windshield, I pushed the limits just to see how much it would take to really mess up. It would bend a good amount before breaking, a lot more bending than would ever take place in a normal windshield installation. I believe the carry thru tube area is a weak spot. Since I also have LP acrlyic bubble doors I did some practice drilling holes in the scrap stuff. I believe the key is to use the bits supplied by LP and use light pressure, especially if you're drilling near the edges. If I leaned on the drill too much drilling near the edge, it would crack. The doors turned out great. I'd highly recommend them but go slow. I tied up way too many hours installing mine just being overly cautious. James Thomas