Lexan vs Acrylic/Plexiglass - help

[Osprey220]

Hi All,

Getting ready to replace the windshield and doors - and trying to decide between Lexan vs Acrylic/Plexiglass.

I've been reading through the archives here and at Avidfox - and there are good arguments for both.

Seems like most posts have been on use of Lexan, but a few mention Lexan's sensitivity to gas, UV, and crazing around bends and so strongly recommend acrylic.

The price here is almost the same 4'x8'x1/16th" sheet of Lexan ~$62 and $75 for Plexi - so pretty much a wash there.

Downsides on acrylic I've read are propensity to crack when drilled or bent, easier to scratch but much easier to buff.

The plane sits outside with a cover.

So any suggestions? Which way should I go? Do I heat at the plastic for the forward spar bend?

Cheers,

Owen

[jiott]

Acrylic is much LESS easy to scratch. Also I believe it is more optically transparent. You do have to be much more careful when drilling, bending and handling.

[HighWing]

A question. Are you taliking about replacing the Lexan with similar sheets of Plexiglas? I don't think that has ever been done. Most discussions on Plexiglas has been regarding the factory heat formed windshields and bubble doors. I suspect with the two piece doors that Plexiglas could be used because of the gentle curves, but for the windshield with the small radius curves at the wing roots careful heating would be necessary there. Not totally sure that it has never been tried, but no memory of it over the years.

[Guy Buchanan]

I started with the acrylic windshield. When it cracked I switched to Lexan. I'd blown an acrylic bubble door some years earlier and had seen how an impact could turn it into flying shards. (I also "tested" my cracked acrylic windshield. It also turned into shards when hit, and not very hard.) I didn't want that in front of my face. Yes, it's more opaque. Yes it scratches much easier. However it was much easier to fabricate and install, and will supposedly handle a bird/drone strike. (Look at the F-16 bird strike videos. Very impressive. Yes, all military canopies are polycarbonate.)

[Osprey220]

A question. Are you taliking about replacing the Lexan with similar sheets of Plexiglas? I don't think that has ever been done...

Yes - naively I thought the lexan and acrylic almost interchangeable.

So flat sheet 1/16 would not stand up to the bending for a windshield?

Owen

[jiott]

For a windshield the thickness is more important for strength than for bending. To be able to resist say 140 mph Vne a minimum thickness (probably different for Lexan vs. acrylic) is critical to avoid flexing inward in the slipstream.

[Osprey220]

Plane I'm working with is a 582 model II that cruises at ~65 and Vne is 100 or 95. The 1/16 is supposed to be sufficient for this plane.

Supposedly the 1/8th or .93 is needed for the later models with 912's.

[kmach]

My Outback, 5, has an acrylic LP Aero clear windshield that ends above the front carry through spar. The skylight is smoked lexan. The joint above the front carry through spar tube has two strips of aluminum, one top and one bottom , machine screws and rivnuts for hardware. I like the smoked lexan skylight and the joint is barely visible. This is built to the build manual of the time. Maybe an option.

I had talked with John McBean awhile back, inquiring of the possibility of using lexan to make a new clear windshield for a model 5 . He said it would only work with the thinner lexan and then it would flex in at speed, so not a real option.

lots of guys with model 4's have made new windshields with Lexan . I saw lots of advice on Facebook saying you could make one, some didn't say for what model, some have 4's .

[desertfox1]

Lexan was shipped with the early model 5 Vixen kits. I replaced mine after about 4 years but had
a little problem in sourcing a 60" wide sheet. Had to stay with clear.

Phil