lexan targa top project........

bell · bell's Garage

in another thread ( New Saratoga Targa Top....Maybe.... ) i thought of a personal challenge, to make a custom lexan targa roof for my 85'. this is the first step in a process i have worked out in my head.
the first step i need to do is to get the "mold" for the curvature of the roof made before i can start on the frame/latches.
so after some thought with the machine shop behind my work we have the first step. i have a good contact and will be meeting with him towards the end of the week for the forming of the "mold" for the lexan. i've also been researching how to seal it, and to try to make it seal better than the stock folding targa roofs.
i'm doing this in a manner where i can duplicate it should it turn out as i think it may, i am hereby the guinee pig

i'll post pics with any "breakthroughs" i have.
this is my 911

Kevin Stewart · 08-20-2002, 08:49 PM

Bell you may want to find something dfifferent then lexan, we use it on the super late stock car and have to replace it every two years, it does scratch regardless of what they say, also if you do decide to move on with it use mar resistent, and yes it does scratch very easy just not as bad as standard, i do not allow any of the guys to clean the windshield accept me because a circlular cleaning will leave just that in the lexan, you must always clean it the same direction, I think somewhere like laneautomotive.com will have it but a half sheet of mar resistant (4x8) is like 125-150 dollars, Kevin

Kevin Stewart · 08-20-2002, 08:50 PM

whoops sorry a 4x4 sheet is a half sheet a 4x8 is a full sheet, Kevin

bell · bell's Garage

i have access to pretty scratch resistant stuff. i've been incorperating polished lexin in audio systems for years

i built a 1" thick windshield for an s-10 blazer a couple of years ago, this thing came out so perfect you couldn't tell it was 1" thick or that it wasn't glass, i'm going to try to find some pics of it.
also i can get different colored (darked smoked too) lexan, the way i'm designing this the lexan could be easily replaced with another panel.

Joeaksa · 08-20-2002, 09:33 PM

Bell,

Glad to see that things are moving forward.

For me personally Lexan or not is a moot point but I want the top and one made out of a sturdy material. Being able to look out of it or not is not a big deal for me. It could be Lexan and painted and I would be happy...

Pls let us know how its going and if we can help in anyway.

Joe

A Quiet Boom · A Quiet Boom's Garage

bell,

be sure to contact me if you have any concerns about bonding other parts to the lexan. I work in the adhesives industry and can certainly help you in that regard if need be.

AQB

Targa Dude · Targa Dude's Garage

Hi Bell, I too have pondered making one..One of the most important pieces of equipment you'll need is a Infared heat lamp. Infared spectrum penetrates Poloycarbonites with the best heat uniformity. and will not distort the material thinkness.
I'm looking forward to your progress. If you like to discuss some processes please let me know.

Jorge (Targa Dude)

bell · bell's Garage

the lexan will be "bolted" to the frame, not with glue. i have some pretty cool flat bolts which will look "oem" quality when complete, i'll explaine more on these later.
the lexan will be at least 1/4" thick for strength, the "oven" i used for the 1"thick windshield formed it in 8 hours, this should only take about 3-4 hours to form. i'll post pics of the oven when i get it set up after i get the mold made.
i can also get lexan so dark it looks solid, but i don't know how this will react to the forming, i may need to make a black one too to find out

clnilsen · clnilsen's Garage

Bell:

Hey, since i think you live pretty close to me, when you get to a point and if you want to try it on a different car, let me know. I'm in the portage lakes, and I have an 80 SC Targa. I'm going to be very interested in this whenever it gets done!

Thanks and good luck!

Chuck

red911 · red911's Garage

I would also be interested. Keep me posted please. I have an 83SC Targa and tried the fiberglass from Sundial. Didn't work to good. At least I returned it and got a complete refund. The latching and side seals were not very good.

Thanks,

BlueSkyJaunte · 08-21-2002, 07:27 AM

Bell,

I'm extremely interested as well. Looks like you have the lexan part well-thought-out. I'm curious how you're going to handle the seals?

I'd probably buy two: one to paint and one clear ("smoked").

John Brandt · 08-21-2002, 07:34 AM

Quote:

Originally posted by bell

i built a 1" thick windshield for an s-10 blazer a couple of years ago, this thing came out so perfect you couldn't tell it was 1" thick or that it wasn't glass

Getaway car?

zuerchers · 08-21-2002, 08:04 AM

hi bell, i think it's great that you are taking on this challenge. i have a few questions for you...

1. what is your end goal with this? after completion will you make the plans available to others or are you planning on manufacturing these? if it works well, i would prefer to pay you for a completed unit. (please, please, please)

2. (assuming you are going to produce these)... you had mentioned that the material comes in different shades. will i be able to order one in a particular shade? if they come clear, can you apply a tint similar to what they use for windows?

3. i know its early in the game, however, i have to ask if you have any idea when they might be available and what the consumer price might be.

thanks and good luck,
mike

ron69912t · 08-21-2002, 08:11 AM

Bell:
If you are talking about injection molding a 3 foot square peice of Lexan you will need an enormous injection molding machine in the many of thousands of tons size and a very expensive injection mold which could cost over $100,000.

Why not thermally form sheets of what ever thermoplastic you choose. Make a wood/plastic/fiberglass or? cavity, put the sheet of plastic over it clamped at the edges and sealed with rubber strips, heat the plastic sheet with lots of heat lamps, when it starts to sag pull a vacuum on the cavity and suck the sheet into the cavity form. Trim it and you are done.

You can do this in your garage.

An idea for what it's worth.

I would buy one but would like it to hinge in the center so it will fit inside my trunk.

Thanks,
RonD

BlueSkyJaunte · 08-21-2002, 08:26 AM

Ron,

If you read carefully, Bell has done exactly what you're suggesting--"Why not thermally form sheets"

Planter91C2 · 08-21-2002, 09:16 AM

sounds like the most expensive part will be the latches.

goat43 · 08-21-2002, 10:43 AM

I'd like to be in the loop, too, if anything gets developed. Thanks.

TimB · 08-21-2002, 10:45 AM

Bell,
I'd be highly interested in buying one just as you described your prototype. Put me on the waiting list!

Ed S · 08-21-2002, 12:10 PM

Bell,

I have an original Saratoga for my 914 if you want to review how it works. It is in perfect condition.

Ed Secrest
Strongsville, Ohio

Grew up in Northhill/Akron.

bell · bell's Garage

ed....i may be intersted in the view of your top, let me know what your weekends are like and i can easily make the trip.

no injection molding going on here

i wasn't going to get into detail as to how to form the lexan but i think i will. i'm still looking for a pic of the 1" job.
basically i create an "oven" using cynder blocks, the leave a small opening for my kerosene torpedo heater. i used a "laser" temp guage (snap-on) to watch the temps. the "mold" is a 1/2" thick formed peice of steel to the shape/comtour needed. after many hours of babysitting gravity will take over, the lexan will slowly form to the steel, when it does let it cool correctly and ta-da....after many hours of polishing it's ready for more polishing. then you polish some more.....then a little more etc....

the framework took a step today too, machinist found some stock he had which is cheap and easy to work with, i've got a small chunk for measuring.

my intentions with this are simple, get it to where i'd use it on my car. when it's done and i have the process down i know how much i can make them for. if it's something people want and are willing to pay i will definately consider producing them.

my other goal is to keep the cost under $600.00, that is the most I would want to spend on a roof, so i'm sure others feel simalarly.
my plans are to build 2 initial roofs (always learn more that way) one will come out better than the other, then that's the one i'll build. i'll have samples of the lexan (colors too) by the end of the month.