![]() |
|
|
|
Bill is Dead.
Join Date: Jul 2005
Location: Alaska.
Posts: 9,633
|
DIY acrylic windows?
I was thinking about going to the local DIY hardware store and picking up a sheet of acrylic to replace the large, heavy rear window in my wifes RX7.
First, let me ask if this is a bad idea. Second, can it be done? The factory glass has a bit of curvature laterally as it slopes off the side of the car, but longitudinally it is not curved. I thought I would attempt to use spring clamps to hold the acrylic to the glass, then heat with a heat gun to get the curvature.
__________________
-.-. .- ... .... ..-. .-.. -.-- . .-. The souls of the righteous are in the hand of God, and no torment will ever touch them. |
||
![]() |
|
Cars & Coffee Killer
Join Date: Sep 2004
Location: State of Failure
Posts: 32,246
|
Are you tracking this car?
Over time, you will end up with a foggy yellow scratched semi-transparent rear window. If you are tracking it, the weight reduction is worthwhile. If you are not, I'd take the rear visibility any day.
__________________
Some Porsches long ago...then a wankle... 5 liters of VVT fury now -Chris "There is freedom in risk, just as there is oppression in security." |
||
![]() |
|
MAGA
Join Date: May 2004
Posts: 10,776
|
Cash, my memory is failing me, how much curvature? Obviously a slight gradual bend does not even need to be heated, but I am assuming you are talking about a substantial turn down at each side.
I have blown acrylic airplane bubble canopies using a homebuilt "oven" to heat the sheet then used air pressure to blow bubble. Based on this experience, I am guessing that if you are real careful, you might be able to pull this off provided the bend it not too small of a radius and you figure out a way to gradually apply heat in the proper places. Since you are involved in aviation maybe you can cob up a Red Dragon style propane heater to blast some heat in the bend area as you slowly apply bending pressure? Industrial small heat gun may prove difficult to direct the right amount of heat over enough of the bend area and you may get uneven bending. Whatever you do, IMO avoid Lexan (polycarbonate) as it scratches way easier than plexiglass (acrylic). Good luck!
__________________
German autos: '79 911 SC, '87 951, '03 330i, '08 Cayenne, '13 Cayenne 0% Liberal Men do not quit playing because they get old.... They get old because they quit playing. |
||
![]() |
|
Bill is Dead.
Join Date: Jul 2005
Location: Alaska.
Posts: 9,633
|
Tim, the curvature is gentle. You can see it in the main rear window in this pic I googled. Between the hinge points the glass in only very slightly curved. What I want is to heat-form the areas from the hinge to the edge so that the plastic window will sit more-or-less properly on the back of the car.
I've seen it done with aircraft related work in the past, but was not sure if it was the same material at Lowes / Home Depot. And I was thinking the same thing about heating the large area all at once... I have a 50k btu shop heater I was going to direct at the project. ![]()
__________________
-.-. .- ... .... ..-. .-.. -.-- . .-. The souls of the righteous are in the hand of God, and no torment will ever touch them. |
||
![]() |
|
Banned
Join Date: Jan 2005
Location: cutler bay
Posts: 15,141
|
to hot and it bubbles
way tooo hot and it burns too cold it breaks |
||
![]() |
|
MAGA
Join Date: May 2004
Posts: 10,776
|
The only difficult part, will be getting the temp right, too much and it will outgas bubbles and not enough and it wont lay down/bend evenly over your glass "form". You will need to hold it down while it cools so that it "cures" in place. Try a small scrap pc to get your technique down before buying and potentially scrapping a big sheet. I blew a bunch of 1/4 scale mock ups before I attempted blowing full canopies out of $100 sheets of acrylic. As far as I know acrylic is acrylic although one can find better more expensive grades and brands from various plastic suppliers, but I think the hardware grade stuff will be fine for what you are doing.
__________________
German autos: '79 911 SC, '87 951, '03 330i, '08 Cayenne, '13 Cayenne 0% Liberal Men do not quit playing because they get old.... They get old because they quit playing. |
||
![]() |
|
![]() |
Bill is Dead.
Join Date: Jul 2005
Location: Alaska.
Posts: 9,633
|
Any idea what the ideal temp is?
I have a large oven that I cure FG radomes in... maybe I could slide this project into there if the oven is wide enough. That would give it good all-over soaked heat rather than a directed blast of heat.
__________________
-.-. .- ... .... ..-. .-.. -.-- . .-. The souls of the righteous are in the hand of God, and no torment will ever touch them. |
||
![]() |
|
MAGA
Join Date: May 2004
Posts: 10,776
|
Quote:
__________________
German autos: '79 911 SC, '87 951, '03 330i, '08 Cayenne, '13 Cayenne 0% Liberal Men do not quit playing because they get old.... They get old because they quit playing. |
||
![]() |
|
MAGA
Join Date: May 2004
Posts: 10,776
|
I think the easiest way to figure this out will be to try some small test samples to determine best temps and clamping procedures.
__________________
German autos: '79 911 SC, '87 951, '03 330i, '08 Cayenne, '13 Cayenne 0% Liberal Men do not quit playing because they get old.... They get old because they quit playing. |
||
![]() |
|
MAGA
Join Date: May 2004
Posts: 10,776
|
Here is a pic of the finished canopy I blew for my DR-107 project. If you look closely, you will see the white steel cabinet in the background (with a prop sitting on top of it) that I had set on it side on sawhorses and lined with insulation to make my temporary oven. I wired up two cooking oven heating elements I got from the local appliance repair shop. My temps were uneven so I made so aluminum shields to sit above the heater elements to diffuse the heat and then I ended tearing apart a window box fan and installed the blade inside the oven on a cobbed up extension rod to further "stir" the heat. The 1/4" acrylic was sandwiched between a sheet of 1/2" plywood and a plywood ring, then the whole thing was set on top of the oven opening. On the final blow, I just peered inside an inspection hole and watched for the sag to start. Once it sagged a couple inches, a helper and I quickly lifted it off and did the blow.
Places that do this for a living, often have large vertical even heat type custom built ovens that have sliding rails with clamp bars that they can clamp the upper edge of a sheet to,then slide it in to heat it while hanging vertically.
__________________
German autos: '79 911 SC, '87 951, '03 330i, '08 Cayenne, '13 Cayenne 0% Liberal Men do not quit playing because they get old.... They get old because they quit playing. |
||
![]() |
|
MAGA
Join Date: May 2004
Posts: 10,776
|
Oops, fogot the pic
![]() ![]() 1/4 scale mock up I used initially to figure out the process and to finalize the proper retaining ring shape to generate the proper shape I was after. You can make out a pc of black inner tube also that I would blow while holding over my 1/4 scale plans to check shape against. ![]() Oh yeah, I did not need to touch the plastic anywhere in the part I used, but I read somewhere that felt is good to use if you need to apply pressure directly to the plastic while forming to help avoid imprints in the hot plastic.
__________________
German autos: '79 911 SC, '87 951, '03 330i, '08 Cayenne, '13 Cayenne 0% Liberal Men do not quit playing because they get old.... They get old because they quit playing. |
||
![]() |
|