DIY Forming Lexan Canopies

[island911]

Okay, seriously . . .use one of the ABS/PC blends. It will be much easier to work with . . .and I doubt you'll need to worry much about those 150MPH bird-strikes . . .no matter how toit your Vespa is.

[bell]

you could get away with using a quality heat gun (with temp settings) and with controlled heat you could bend it however you want as long as they aren't extreme bends.
cut a piece of poster board to the shape you want and position it how you want it on the vespa (you'll probably need an assistant) then use a marker to make a line over the bends......then transfer the shape to the clear stuff....then heat/bend......
wear gloves and buy enough lexan/whatever for the second one, the first one will be a prototype......the second will be golden

[Tim Hancock]

I built my airplane canopy out of acrylic (plexiglass). It started out as 1/4" thick and after blowing, about 1/8" average.

In simple terms:

I built a large temporary oven using 2 old used oven heating elements for heat. My oven had an open top. My plywood/plastic sandwich went on top. Once the plastic started to sag a few inches, I quickly removed this sandwich and set on pre-staged sawhorses, then began blowing air into the backside of the plywood thru a Jerry rig needle valve setup. When the bubble reached my floor mounted depth ruler, I closed up the valve and waited for the plastic to cool enough to remove the air pressure.

The overall shape is determined by the plywood retaining ring that sandwiches the plastic against the plywood back. I built a quarter scale mockup using a piece of truck inner tube which I blew up while holding up to a quarter scale dwg of my canopy frame.

I next blew a quarter scale prototype just to prove my idea would work. Typically you have to blow an odd shape then cut out the portion you need. The plastic behaves just like a balloon when heated evenly.

The advantage of free blowing i that you do not get any marking
that happens when using molds (but the shapes possible are limited). For canopies and windshields you need good optics which are difficult to achieve with molds especially at the DIY level.

The toughest part of this is evenly heating the plastic so you get a uniform blow.

Here are some pics:

[kach22i]

I booked marked this (see below) from my glider research, dreaming of modifying my hovercraft.

http://www.wingsandwheels.com/page37.htm

Hope it helps a little, interesting topic.

[Wrecked944]

This is one seriously cool topic. But I'm a little worried. Does thermoforming lexan and acrylic produce any scary toxic fumes or is it something a DIY'er can do indoors without fear?

[Tim Hancock]

I did mine in my shop, I am still breathing. The acrylic only gets heated to around 200 degrees (I cant remember exact #s). If you get it too hot it will get bubbles in it from outgassing which I guess could be bad to breath (your part would be junk).