Working with Lexan.

[breakaway500]

I am going to put a Lexan (polycarbonate) panel on the rear window/deck lid area of my car (Focus)..and after watching a few youtube "how to" videos decided to see if someone here may know how to work with it. I am using 1/4" thick (coated clear) Lexan and will mount it into the old glass window opening using 1/4" aluminum bolts/aluminum washers/Nylock nuts. I will need to bend it about 26" down from the top at approx 15-20 degree angle the full sheet width (sheet is 48.5" wide and 42ish long) Some say to use heat...others say it bends without heat. I do have access to a 10' metal flashing/siding brake but not sure if it's strong enough for 1/4" Lexan. Probably not. Maybe try a softer bend between clamped boards etc. My metal brake is only 30" wide so can't use that.
I am thinking the bolt holes in the plastic should be a bit larger than bolt diameter to allow for expansion of the panel in heat..but not sure of any exact numbers.(1/16 inch?)
Looks like Lexan can be easily cut with plywood blades and drilled with steel cutting bits...?
I think closing up the back of the car will be good for aero and keep the interior turbulence down. I'll do the rear door window areas as well. Total weigh gain (over having nothing) should be about 20lbs.

Thanks for any insightful tips or links to helpful sights etc.

[jvangelder]

years ago i helped build a camaro ice racing car and we did lexan all around. the rear hatch had a nice arch to it and we made it work without heat. as for mounting it we drilled slightly oversized holes and then used rubber washers under flanged nylocks so it had some ability to expand and contract with our 60deg shop to 10deg racedays.

i dont remember how we cut it, but i imagine it was with a fine tooth blade put on backwards similar to cutting vinal siding. drilling was with generic steel purposed jobber bits, and id reccomend you tape off where you drill so the swarf dosent discolor or fog around the holes if you care about that sort of thing

[962porsche]

I do lexan windows for cars all the time average is one job a month .
it's not to bad to work with . the heating point between melting it to get a bend and having it bend is a kind of small window for the heat range .
I used to try and nut and bolt them but I found rivets work best .
you will also find one side will take paint ever will and the other side (treated side ) will not no matter how much you sand the thing .
sand it with a red sanding pad this will give you the tooth for the black paint to stick to the border and you will not see the sanding scratches thru the lexan.
for cutting it I use a 4.5" cut off wheel on a angle grinder . then 80 grit on a DA sander will clean the edges and take off any shaggy edge from the cut off wheel .
a 4.5 80 grit flap wheel on the grinder is good for making rounded corners .
I have tried all types of saws and they don't do a very good job for cutting the lexan .
to bend as needed I use a short wave heat lamps that are used for drying paints and primers in a body shop .
the reason I use this type of lamp is it heats the lexan from the inside out NOT the out side in so there is a lot less chance to melt the lexan and you can control the heating better .
if your looking to do some thing like a 944 rear hatch or rx7 that is very rounded I 1st make a template of the glass and then cut out the lexan center it on the window opening were it needs to be then rivet the center part to hold it . I then take the heat lamp and heat one side at a time letting it get up to about 300 to 325 degrees and then I do the roll to the window opening as needed . before it cools I will install about half the rivets before it cools to much . skipping every other rivet . then I go do the same on the other side . after its all cooled back down I go back and finish installing al the rivets .
this is one reason I don't used nuts and bolts . they take to long to install and if you don't get the fasteners installed in time it will lose it's shape .

your other option is to make a mold and vacuum form it but if your only doing a one off part it's not worth the time and expense .

[jlwhorf]

Hey Mark,

I have used lexan quite a bit in my stock car days, but I only used the 1/8" or 3/16" stuff. I cut it with tin snips and drilled it with steel bits. I have always used rivits to fasten but bolts should be fine. I did use 1/4" on a spoiler I made and I can tell you it is tough stuff, You will need a heavy duty brake to bend it and I cut it with a band saw. I have never heated it but have had friends that did with good results, but it seems more prone to crack.

[breakaway500]

Thanks for all the great replies! I believe I will make cardboard templates up first so I don't make as many mistakes.

[962porsche]

make your templates .
if you try and put a bend in it with out heat it will crack also if you try and bend it to much with out heat it makes it like your looking thru a ice cube . the ice cube affect is caused by stretching the material as it's getting bent . heat keeps it all the same thickness so that doesn't happen .
I'm not thinking for the rear window of the ford you will need to heat it the lexan should make that roll just fine .
you will want to do two 1/8 X 1" strips of aluminum from the top to the bottom of the rear window opening .
put the straps on the out side of the glass evenly spaced from the out side edges .
this will do two things one stop the window from blowing out in a bad crash and 2nd stops the 1/8" from fluttering from air flow .

[dinoracer]

Mark

On the cutting, I've used a jig saw and sawzall with good results, but there is definitely a learning curve to find the right number of teeth and speed to cut to make dust not melt, and not create stress cracks. Practice on scrap to get comfortable.

[breakaway500]

Just thought I'd post up some in progress photos of my Lexan experience. I used 1/8" as it was 50% lighter (than 1/4") and still plenty tough. Cut with a jigsaw with an 18 tooth blade and the material is pretty much impossible to break. This is NOT Plexiglass.
Much more tidy body panels than what I had, and sure to be of some aero help. (Dans not getting any slower.. ... )

Rear "hatch' opening and rear side windows:

[962porsche]

Mark it looks great !
not for nothing but don't make the car any lighter if you do in the wind it will blow away !

[breakaway500]

Thanks! I actually added some weight but it's minor and I know the inside dirt storm will be much less..

I have a few Lexan scraps left and am going to try a front splitter/air dam sorta thingy...

Hoping to try it all out at Whiskey Hill this Friday..

[DanDarcy]

Looks good Mark but I think any improvement to your car should be illegal. I'm not getting any slower but I am getting older and keep forgetting where the next corner is !! It s not nice to beat an old man . See you Friday