im picking up a cf hardtop today so i need this!

 

You're making up numbers. 8 hours? Hardly. More like 2-3. If you're worried about ruining the sheet, then simply cut it oversize and trim it down. That's how I do it. Of course, if you're only allowed to use kindergarten scissors then it's possible this is a bit too advanced a project.

If there's this much demand for a pre-cut sheet, I'll see about making them available. Drilling holes and shaping the sheet will likely be left as an exercise to the installer, as you'll have to drill holes in your hardtop to install it anyhow.

The engine has survived the week-long Targa Newfoundland, more than a dozen track days for development and a number of dyno runs just fine. Next, it's going to Laguna Seca for a two-day track event. It has a nice wide torque spread so I don't have to spin it to 8500 all the time, but it's good to know I can. Thanks for asking!

 

that would be cool keith BUT wouldn't a pre-cut sheet be shaped already? otherwise we're back to square one again and just getting a piece of lexan. that needs to be cut and shaped.

Or are you gonna cut them slightly larger than the window and have us trim it down to proper size.

 

By shaping, I meant putting in the bends. You can do it with a heat gun, or you can let the rivets hold it in place. It's a lot easier to make and ship flat sheets.

If we're going to sell something, it'll be the correct size and will not require trimming. I'll have to see if I have a hardtop that hasn't been modified that I can use for testing first. I think the two Lexan tops here have some sections cut off.

 

Very anxious to see where this goes. I'm a couple of months out from needing a window.

I was actually just thinking the other day "Why doesn't FM sell lexan windows?" lol

 

Axis Power Racing sells their Lexan (I think, whatever window they put in their CF tops) for $300. It's flat and cut to shape. If FM can beat that, say $200-225 shipped, I'll buy it TODAY!

 

I would pay $200 in a heart beat. I figured it would cost me around $100 to make my own out of that scratch resistant stuff. If you do make one, please use that. I think its something like MR10?

 

so after calling around to local places today, no one in hte central NJ area wants to make them, their excuse is that to cut one to size would be ~500$, which is complete bullshit. I just went to Lowes and bought a giant piece for 75$.

Now if keith can come out with the precut ones within my 30day return policy i'll gladly buy theirs and return mine.

 

I do not set deadlines on product development. If we bring this to market - and it should be possible to do it within the quoted prices - it'll be available when it's available. So no promises on the 30-day window.

 

Its even worse, around here they only let me use calipers, I guess on one end they are sharp right?

If the parts are able to curve, there is no reason they could not be shaped first and shipped flat. So long as you don't shunt excessively crosslinking in the heat up cycle there will be no more brittleness then when you started.

I'm not understanding why you can't make the parts to work with a stock style install. Get the right thickness, and a little reinforcement on the edges, and boom, call an installer and have him seal it. There is a definite reason engineers decided to install a window without rivets. Crack propagation, efficiency, seal, and all of those apply to polycarb as well as glass.

 

I'm sure you could build a replica of the stock glass. By the time you've done that, with the appropriate curve and paid someone to have it installed "stock style", you've gained nothing. I suspect the extra thickness of the polycarbonate will negate any weight advantage. 1/8" polycarbonate weighs almost exactly half of the weight of the 11 lb glass window. I'll check the thickness of stock glass at work if I can find the loose hardtop window. Meanwhile, the cost of having it installed on top of the higher production and shipping cost will eat up any savings over glass. So now you have a rear window that costs the same, weighs much the same and happens to be more scratch-prone than glass. I'm not seeing the advantage. As I mentioned, I'll confirm this if I can dig up the spare glass to see what fasteners are bonded to it, I seem to recall some studs glued on to the lower edge.

Bend it, then trying to force it to stay flat in shipping? It'll have to be shipped between two sheets of plywood screwed together to keep it from ripping through the packaging, and if it's more than 1/8" thick I don't think that's going to be possible. The hardtop glass has a fair bend to it. The windshield is much more gradual.

Polycarbonate is far more resistant to crack propagation than glass, and I've not seen any sign of problems in the various cars I've done. Seal - the top on my Targa car has seen some good rain, and hasn't leaked a drop. I used some exotic silicone sealant from Home Depot there. Efficiency...umm...I'm not sure exactly what that means. Do you mean aerodynamic efficiency?

I view this as a race modification. Lexan windows aren't even road legal in some states. If riveting it in means a lighter window, an easier installation and a lower overall cost, I call that good. I'm basing this on having actually done it a number of times, with cars that have seen the stresses of track use.

 

Ah, your too much of a pessimist. You can easily get around all the problems mentioned with a little ingenuity, and use a minimum thickness polycarb sheet while your at it. (.09375? .0625? let the HT do the structural work)

This also reduces shipping "forces" where flattening with cardboard would be reasonable.

Efficiency in the installation process, it costs a lot to design a machine to 3d interpolate over the top of a piece of glass and rivet it into place from the factory. It also takes a surprising long time for one person to rivet this into place in the drive way. Too much effort, holes, and then on top of that its not as sound as the other way.

A race modification or a cost effective replacement is a delicate balance. One implies expensive one implies cheap, in this case its both. Killer part. I view that 175-250 range shipped as reasonable for a pre-shaped water jet cut piece.

 

Oh jesus you guys go way over board and worry too much. I consider cutting and mounting a lexan window a fairly good skill to have, why let someone else do all the work. Buy a piece of lexan and go at it, you can do it!

I tore off my old pastic window today, it was pretty bad. the bottom edge has curled up exposing the bottom half of the hard top lip, and when I flattened the corners out to trace out the pattern on my lexan sheet, it cracked about every two inches. To give you a reference, it has been on there for at least the 7 years that I've owned the car, and opaque for about the last year. This is out of 1/16" plastic of unknown quality/brand. For this reason I suggest not using anything much thinner than 1/8".

I have a bunch of photos I could post, but they're all of the tear down, which would not be what you're doing. Are there any specific photos you guys want now that I have a hard top without a window, and any photos you want as I cut/mount the window?

Now some questions for Keith: I was considering using an electric sawzall to cut out my rough shape, probably with a metal blade since its more fine. Would this be advisable? I'm worried about it being too violent and tearing up the edge, and the feet/guide scratching up the edge as I follow my traced line. Also once I've cut out the rough shape, I'm worried it won't be precise enough to trim any excess off as needed, is there any warrant to my worries? I have available to me many wood and metal manual saws, and an angle grinder with various metal cutting wheels. But if you suggest only a band saw, jig saw or reciprocating saw, I'll gladly go see what I can pick up to use, I don't wanna screw up my sheet of lexan, but I'll gladly pick up another tool

Anyways, good luck with the pre-cut stuff guys, and thanks in advance Keith for your answers, you and your photos have been a huge help!

 

Use a regular jig saw with a metal blade. It cuts the lexan like butter and will give you WAY more control than a sawzall. Just buy the $30 cheapo at lowes. Its what I have, works perfectly.

I think Keith and Travis are making it too difficult as well. I personally think the cutting and riveting are cake (I've done it on mine already). All I think is really needed is a paper/cardboard template that one can buy to trace onto their polycarbonate of choice. The most likely candidates to do this whole job are those picking up hardtops without existing rear windows. I've done the whole trim here and there to get it to fit, it doesn't end up too pretty and the fit isnt the best. If I had a template it would have fit perfectly.

 

I'm not making it difficult, I'm simply answering questions that are designed to be difficult. It's easy. I started off saying this, but it's become clear that not everyone wants the DIY route.

It wouldn't surprise me at all. Why not? Because I've done it. It doesn't take long. You're drilling polycarbonate and fiberglass, then popping in a rivet with a backing washer. There's no need to pre-bend the polycarbonate at all unless you're simply trying to make life difficult. Drilling a windshield frame made of high-strength steel, that takes a while and is no fun at all.

Now, back to some good questions.
I'd stay away from a sawzall. Great for cutting frame rails, not so good for shapes with bends. Polycarbonate is really easy stuff to cut, but it will melt so rotary tools can get messy. The jigsaw is pretty much perfect. I've used bandsaws as well. If you have an air compressor, then a little air saw does a great job. Once you've got one, you'll find how useful they are for doing light fabrication work like heatshields as well. Here are a couple of cheap options:
electric: Harbor Freight Tools - Quality Tools at the Lowest Prices
air: Harbor Freight Tools - Quality Tools at the Lowest Prices

The nice thing is that you can practice on the edges of your sheet to get an idea. By the way, it's really easy to trace and cut out a triangular vent window or two, and those slide right into the stock location without any difficult installation or bonding. Good way to lose a bit of weight and you can rivet in a NACA duct for a real race touch - see below. The clear vents are from Pegasus Racing and I think they're about $25. Use the top from a spray bottle to plug them, I've run this on a road car.

 

I need to get off my *** and make those vent windows Ive always wanted to also

 

ok so a question now about weatherproofing and silicone. would it make more sense to silicone underneath the lexan then put rivets through it, and then again around the lip? adding an extra laying of protection?

 

Thats just it Keith, they are trying to make it difficult.

I'm glad you said what you said about the cheapo jigsaw, cause that's exactly what I did today, bought a $30 black and decker from home depot, I'm about to go out and start cutting, I'm excited to get this done, I haven't had a clear rear window in ages!

I'm definitely going to put in the triangle windows with NACA ducts, at least on the driver side, I've wanted some air in my helmeted face ever since I had to put the heater on full blast to keep from over heating at the track.

Disturbed, I think one bead of silicone under the lexan would be fine. The PO had a 1/2" bead of what seemed to be roofing tar (seriously, it was disgusting) under my old plastic window and it sealed fine. A small bead of silicone would do great.

 

I think people were talking about a molded window so that it could be installed without rivets (like stock), for a stock look. At this point I would be thrilled just to have a pre-cut flat sheet that I can bolt in. I agree, molded sheets would most likely bring the costs up high enough to negate the 5lb wieght savings of a Lexan window.

 

Well, after cutting out my window last night, I have to admit that a precut sheet would be a pretty sweet deal. Although I was working from a really crappy template. With a supposedly 'perfect' template, I would have no problems making a fairly accurate window, my new $30 jigsaw worked great.