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

[targa911man]

Bell--

Great idea. Just a suggestion--maybe the smoked lexan would be better. It would hide the hardware better. Also, when I visualize the clear top, I just get the feeling when the sun's out you'd feel like an ant under a magnifying glass.

[zuerchers]

i think a 20% tint would be perfect. you can still see the "birds and the stars" while still offering sun and heat protection.

here's a cool link to see what the different tint levels look like...

http://autowindowtintings.com/tonline.cfm?action=carred#top

[steve911]

I'd be interested too...

[Kirk Hawes]

Bell,
I'm interested and, believe it or not, I don't have any "suggestions" to make. Can't wait to see pics.

[bell]

i do plan on making the first one clear for visual/inspection purposes. i'm hoping to be able to capture a glass smooth top then blacked out where the frame is, but i like the smoked look myself.
and yes you will be able to tint this with any tint you want, if my hardware resource can come through the "glass" will be able to be removed easily from the frame.

another step today..........went to the other shop about "rolling" the form. they want WAY too much money to make this feasable. so my machinist and i came up with a brilliant alternative, there will be a "frame" welded underneath of a sheet of 1/16" steel creating the desired curves. i'm going to get some steel next week and get cutting/welding, the sooner the frame is done the better, the actual frame/latches are going to be the tricky part.
i also want to really get somewhere whith this before i start adding fat fenders to my targa
i'll be posting picks once i get started

[Joeaksa]

Bell,

This does sound like a plan but I just had a thought... considering the trailer you have on your postings, wonder if it would not go faster and be a lot more interesting for all involved if we could find a barrel of lesbians to assist you?? We could even include one or two with each top!? Bet the sales would take off then...

Joe

[bell]

i just happen to know of a circle of girls that i once........oh nevermind
i think truckers would like the clear tops for looking at the ladies in passenger seats.

[Moses]

Originally posted by Joeaksa
if we could find a barrel of lesbians

I was kind of hoping for a great collection of lesbians in a Lexan barrel.

[mr914]

Cavemen! Bear skins and stone axes! Unwashed heathens... (No offence intended, I've been in plastics for awhile)

First of all Lexan is a tradename for Polycarbonate and there are many versions. What you specificly are looking for is MR Polycarbonate (Mar Resistant), it's the same type of plastic that is used in Motorcycle and Snowmobile windscreens. The particular manufacturer is GE.

Second of all. Forming of polycarb is a difficlut process. You have to have the proper heat soak from both sides. Not too hot, it will blister and too cold will cause stress cracks. Form temperature is in the 325F range.

You will need a top and bottom mold covered with a moleskin type of material and apply about 18-25psi of pressure untill the part is cooled.

As far as building the mold. Three ways...

Basic caveman -

1) cover your precious targa top with saran wrap (or if you have an old one to sacrifice, johnson paste wax)

2) cut several wood strips the length of your targa top

3) (time to cringe) Mix up a gallon of bondo or repro and cover your top inserting the wood strips to act as stiffeners.

4) Sand bondo and fill imperfections.

4a) apply sheet wax in anticipated thickness of plastic to be used.

4b) make second mold for top.

5) Cover mold with moleskin material.

6) Borrow pizza oven (home oven too small) - use infared pyrometer to determine temperature of sheet.

7) Bake untill done. When done. pull sheet out and place over lower mold

8) put upper mold on quickly.

9) have beer an wait to cool.

10) figure out how to trim and polish....

Basic Caveman - downsides - Plastic shrinks when it is heat cycled. The shrink is in the .003-.014" per inch.

The mr914 approach.

1) Digitize existing top on car. Digitize mounting base area with top removed. Anyone have a digitizing arm?

2) Take math data into CAD/CAM software.

3) Apply shrink to the mold and mirror for second mold.

4) Make wood bucks and cut on CNC

5) Take to thermoformer and form parts

6) CNC trim top to correct size.

7) glue on stiffening and associated brackets/clamps.


Been there, Done that (not with the 911)

If there are enough of us interested, I can make it happen.

The steel frame for support is a great idea or it could be cnc cut out of wood for some prototypes.

Wonder if I can get my 911 into the CNC for digitizing.....

[mr914]

Walked out to the '74 911.


Took some rough measurements. (8 datapoints)

Drew up a mold and layed a toolpath on in less than 20 minutes.

Cut time for one mold is 1:47 with a 1/2" ball nose bit on a CNC. @ 300ipm

The more datapoints, the more accurate it would be.

Facility manager by day. CNC programmer/moldmaker by night.

[bell]

i've done my method before with perfect success. i know of the different types of "lexan", and i was planning on using the polycarbonate. i've got a specific "oven" that i've used many times making custom"bulletproof"windshields for spl vehicles (audio stuff).
i think everybody will be suprised as to how this will turn out.

[Joeaksa]

Keep moving forward guys, we have made more progress in the last couple of weeks than in several years. This can be overcome and everyone in the Targa world will be beating a path to your door for a good top!

joe

[zuerchers]

i was just thinking the same thing. its funny how there hasnt been a new top in production for several years and all of a sudden we have two very interesting and promising projects going forward. very cool.

[Chuck Moreland]

Strike that. We have three - count 'em - three top makers dueling it out.

Bell, MR914, and JMPRO are all at it in parallel!

May the best product win.

And I'm not even counting Sundial.

[mr914]

Project? what project?

Just an exercise in design on my part...

Now if we colaborate on the top, I think we can make something great.

I've got no real interest in fiddling with the supports and the latches. Too many other projects, top end rebuild 911, engine rebuild 914, and the many honey-do's at the house.

I'll check tomorrow on the logistics at the work to see about cutting on the CNC and forming a few parts.

I'd still need to get the datapoints for the top.

Anyone? How thick do you want the top? Or, how heavy?


Lexan is a tradename. The proper term for the type of plastic is polycarbonate....

[Joeaksa]

Thick enough to be somewhat rigid, yet not too heavy for one person to easily remove and such. Last thing we need is extra weight and especially high up in the car.

Should look as much like stock as possible with the one exception of if the owner would want to paint it to match. I still plan on sanding my "sundial" top to paint it unless you gents come up with a better option! Hope so...

Joe

[BlueSkyJaunte]

I'll buy one of each of the three, just to support all of you guys.

One clear ("smoked")
One "stock"-looking
One to paint hellblaumetallic

I don't care who makes it as long as it's a quality product. I hope all of you succeed!

[s2per]

I'm definitely on the interested list, too. Smoked or black-out are my choices.

[Ed S]

Bell,

When you stop over this Sat. to look at my Saratoga Top, you can measure the thickness, weight, etc.

Ed

[PeterK]

I am in the market, and eventually ( nostatic led the way ) will buy either an SC or a Carrera.

My dilemma has been I have had to narrow down my search for cars to a sunroof coupe. Kind of throws out half the cars available right there. I just can't get by with the idea of a targa top as the OEM ones in my opinion are junk. Why they didn't continue a hard top version I will never know.

Anyway, IF a great aftermarket top were available it would definitely open up a whole new world for Targa owners along with Targa buyers.

So, kudos to all the tinkerers out there as I feel there will be a strong market for the product if it is designed and built right. I am also thinking that a price of $ 500 to $ 700 would be a good pricing point. Maybe even up to a $ 1,000 if it is a truly outstanding air tight / water tight unit. Another idea would be to offer opaque units in primer ( ? ) ready for paint to match owners.

All Pelican eyes are upon you gentleman and may the best succeed


p.s. Do you know offhand if the roof will fit into the trunk longwise so it could easily be stowed and then mounted? I know it won't fit as nice as the 914's but if it could just lay there on the carpeting that would also be a definite plus