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Making a Lexan Hardtop Window

36K views 42 replies 35 participants last post by  dweedlebug 
#1 ·
I just thought I would share this little project in case anyone was interested.
A little background first. The project car I did the install on was a POS I picked up last year and have been slowly fixing up. No major projects yet, just more or less clean up and sort out. My purpose when I bought it was to tear out everything non-essential and reduce weight as much as possible. I had done pretty well getting down to just over 2000 lbs. I had ditched the soft-top for a hard top I bought from another CR member. I had shipped the hardtop up from SoCal and the hardtop suffered major damage in shipping, cracked the shell and broke the window. At the time I decided to keep with the low-weight theme and fixed the fiberglass and ran without a rear window (I had no side windows anyway).
Fast forward to this October. On the way to work I wrecked my 4-Runner, I made the decision that I didn't want to buy a new vehicle so I decided to throw doors and a rear window into the Miata and drive it. Well doors weren't bad but dear god is the glass for a hardtop expensive. I decided to make a rear-windshield from Lexan, I figured it would be cheaper and lighter and would fit with my "Minimalist Roadster" theme. I chose 1/16" Lexan which came to $80 (would have been cheaper but I had them cut the windshield pattern from a template I supplied). I then used a heat-gun to form the Lexan to the frame. The straight center portions of the windshield were fixed with brushed aluminum runners and the curved side portions with bolts and washers (all hardware in stainless). I used a flexible clear silicon sealer to seal it all up but I plan to take it all apart this summer and do more finish work (and perhaps a total vehicle repaint). At that time I'll weigh it to see just how much I saved.
Here are a few pictures from the project.







 
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#27 ·
Use Plexux and a microfiber cloth to clean. Eagle 1 metal polish will pull.scratches out, as will the finer McGuire's polishing creams (in the tan bottles). Honda spray cleaner is also a good daily use cleaner like the Plexus, but IMO not as good as Plexus (but almost as good and cheaper).
 
#6 ·
wow thats awesome man. do you still have the template?
Leatherface24-Yes, i kept it just in case. My only mistake is that I didn't account for losing a little length as the flat Lexan was bent. This caused the edges to shorten a little, and you can see in the last picture that the Lexan doesn't extend fully to the edge where the original weatherstripping would be. If I make a new one, I'lll make it a little long. And if anyone wants a copy of the template I could arrange to trace it on paper and ship a copy.

cool little project. and 80$ for the lexan doesnt seem too bad. I wonder how much total weight you saved. Is there any wind noise?
PcolasNA-The original windshield was HEAVY, I'm guessing around 10lbs (just a wild-ass guess though). And I didn't drive it today so I haven't really had a chance to evaluate wind-noise. Later I'll update the thread with weight and wind noise info.
 
#11 ·
What size rivets did you use? Or are those bolts?
Slutz4-They are actually small stainless steel hex-head cap bolts. Those cost almost as much as the Lexan. Could easily be riveted in or attached with cheaper hardware. Also, I didn't mention in the original post but once I formed the windshield I was halfwat tempted to order new molding and simply install it as a replacement for the glass. I think if it were formed oversize (possibly heating and molding it against the original glass) it could then be trimmed and fit into th original molding. My molding was shot so I didn't go this route.
 
#12 ·
WOW! considering that you can buy an aftermarket hardtop without the glass for $500, this could make a really affordable alternative to a used one.
 
#22 ·
I was wondering about the template. I have a hardtop but the glass was busted in it. Could I just make the template from the strip from the edge of the glass? I am thinking about trying just wondered if anyone else had. If not then I will be trying this soon. Hope it all works out as my past dealings with lexan and similar materials have had mixed results.
 
#23 ·
I just did this for my son's car. My car still has glass, and there's an appreciable weight savings (which should also translate into the top wiggling around less, thus making less noise as there's less mass up there).

There's no need to form the Lexan; as you bolt it down, it will form very easily and you won't run any risk of warping the product and causing optical defects.

We used some flat weatherstripping from ACE hardware that worked superbly. Then we bolted the window down and went over the bolts and covered up the area where you could see through the window to the internal structure of the top (like the OEM hardtop does) using Plasti-Dip which also covered the hardware. This is what we were left with:







I also have a template, but it isn't quite perfect. We used some carpet protector plastic so it'd stick to my OEM rear window. It is close but required some trimming as they fit differently and sit further into the top than the glass ones do. This left us to have to trim a bit. However, now that we have the basic window, we're able to work up a template that is very well dimensioned. As with the OP, if anyone wants a copy, I'll send one if you cover shipping. If you want a window, we can do that too for a price.
 
#25 ·
That's what we used. I was concerned that it would be too thin but it worked out to be ideal for this application due to the complex, tight curves. They were out of Acrylic and the cost delta was a consideration, especially as this was our prototype.
 
#26 ·
nice work!
 
#28 ·
I didn't make my Lexan window but I did install it so I thought my post might be relevant?

My Lexan window came with my Chaser Hard top. It DOES suffer from the shortening effect of curving and installation is completely up to the user. It comes with aftermarket seals, but I used supplemental seals. There are gaps large enough to bother me at both sides of the window... but it does not leak. The seal is fine after I dinked around with it a bit.

I first put down a black silicone weatherstrip from Home Depot - tear drop shaped.

I marked the location of all the holes I wanted to drill on the lexan by using a tape measure to space them. I then fit the lexan to the frame using masking tape - I found a couple of the rivet holes were too close to the edge of the hard top frame, so I had to make some adjustments in hole placement. Drilled holes and used rivets that I coated in silicone glue before punching them in.





My ultimate intention was to use the old window as a template for a new piece of Lexan when it is time to replace with adjustments for length (width?). I would also include painting the black border with my next install as it hides the hard top frame edge from view. Would make it a bit more tidy.

I will say this for those who are considering Lexan - they are "high maintenance" if you want to keep them clear. They scratch with anything less than the most clean plush microfiber towels. Just touch it with terrycloth and it'll look like sandpaper was raked across the window. Even with microfiber the window will still show swirls in sunlight. I have had limited success with Meguire's Plastic-X for polishing - it works as well as the user and it is just as easy to induce more swirling while trying to polish out swirling. I keep a minimalist approach - I touch the Lexan as rarely as possible.
 
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