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Lightweight Hatch
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Joes924Racer  



Joined: 03 Nov 2002
Posts: 11964
Location: Oregon, Denver Colorado native!

PostPosted: Sat Dec 14, 2002 1:46 pm    Post subject: Lightweight Hatch Reply with quote

So im full of envy for the porsche guy who has a lightweight hatch...
Has anyone made one here in the states from the ideas we thru
around last time..
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924RACR  



Joined: 29 Jul 2001
Posts: 8346
Location: Royal Oak, MI, USA

PostPosted: Sat Dec 14, 2002 2:09 pm    Post subject: Reply with quote

GT Racing sells the lexan replacement for the glass, costs about $600USD, saves about 67lbs.
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jpab924  



Joined: 03 Nov 2002
Posts: 1538
Location: Crown pt. IN. 50 miles southeast of Chicago Ill.

PostPosted: Sat Dec 14, 2002 5:42 pm    Post subject: Reply with quote

So you got one on your car yet Vaughan?
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924RACR  



Joined: 29 Jul 2001
Posts: 8346
Location: Royal Oak, MI, USA

PostPosted: Sun Dec 15, 2002 12:09 am    Post subject: Reply with quote

No; I still have to pick up the donor hatch (maybe this weekend if I can get to it) and order the lexan. Have to wait for a fat paycheck opportunity to buy. It's a low priority, as I don't need it until I run 944Cup again, and that schedule's not out yet.
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gwsg  



Joined: 03 Nov 2002
Posts: 160
Location: Melbourne Australia

PostPosted: Mon Dec 16, 2002 6:40 pm    Post subject: Reply with quote

924RACR wrote:
GT Racing sells the lexan replacement for the glass, costs about $600USD, saves about 67lbs.


I have never actually ordered bent Lexan but I deal with quite a bit of flat polycarbonate and acrylic and I have had glass custom bent. This price seems very high and I think it would be worth phoning a couple of plastics engineering firms and enquiring about the cost of custom bending using an existing glass hatch for the mould. Also, although not as strong, Perspex has better scratch resistance, better UV resistance and is cheaper than Lexan. Just a thought that may save dollars. Worth a try if you can find an enthusiastic plastics engineer and there are plenty in the Yellow Pages.
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924RACR  



Joined: 29 Jul 2001
Posts: 8346
Location: Royal Oak, MI, USA

PostPosted: Tue Dec 17, 2002 2:42 am    Post subject: Reply with quote

Of course it's high - they've cornered the market.

We need to get Jeff @ 944Racing to get to work on some of these...
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CBass  



Joined: 03 Nov 2002
Posts: 2807
Location: Vancouver, Canada

PostPosted: Tue Dec 17, 2002 7:16 am    Post subject: Reply with quote

This would be a great way to reduce weight. Perhaps they could offer a combo of a lightweight hood, and hatch. On a side note, a friend of a friend works at the local plastics store here, and my friend can get whatever he wants at cost.

I've worked with acryllic tube before, and it's pretty easy if you have a heat gun. All the would really be needed is to remove the glass from the frame, bend the polycarbonate over it. I'm not quite sure what thickness to use however...

The greatest thing about these plastics is, they are very forgiving and easy to work with. The downside is you end up with burnt hands often as not
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Lizard  



Joined: 03 Nov 2002
Posts: 9364
Location: Abbotsford BC. Canada

PostPosted: Tue Dec 17, 2002 7:19 am    Post subject: Reply with quote

hey it is worth a shot, hey cbass new job for you create us all light weight hatches
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Peter_in_AU  



Joined: 29 Jul 2001
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Location: Sydney, Australia

PostPosted: Tue Dec 17, 2002 8:33 am    Post subject: Reply with quote

as we discussed last time the problem with just laying a sheet of polycarbonate over the hatch glass and hitting it with the heat gun is that the polycarbonate won't fit the frame - think about it, it'll be too big.

What you need to do is make a mould from the glass (either inside or outside surface) then use the mould to shape the polycarbonate. Fibreglass would probably be OK for the mould as the service temp of fibreglass is greater than the mould temp of polycarbonate. You could just make a paper pattern from the glass to mark the polycarbonate for cutting.

It would be a great project and reasonably easy to do especially creating the mould from the glass. I'd do it if I had a spare hatch to play with (anyone in Sydney got one I can borrow for a week or two?). You could do the side glass the same way and that would be even easier.
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gwsg  



Joined: 03 Nov 2002
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Location: Melbourne Australia

PostPosted: Tue Dec 17, 2002 8:53 am    Post subject: Reply with quote

Peter_in_AU wrote:
as we discussed last time the problem with just laying a sheet of polycarbonate over the hatch glass and hitting it with the heat gun is that the polycarbonate won't fit the frame - think about it, it'll be too big.


You would not bend the plastic over the outside, you would slump it into the inside. The plastic screen would be made oversize and trimmed back to fit. Either Lexan or Perspex would be forgiving enough to accomodate minor shape difference. I also dont know the thickness of the rear hatch glass but using thinner plastic would also help fitting and the plastic would be strengthened by the curve. Many modern windscreens are now only 3mm thick because manufactureres have realised the increased strength of curved glass but I bet the Porsche glass would be 5-6mm thick.
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Peter_in_AU  



Joined: 29 Jul 2001
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Location: Sydney, Australia

PostPosted: Tue Dec 17, 2002 9:58 am    Post subject: Reply with quote

yeah, might be close enough. Only way to find out is build one and see.
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gwsg  



Joined: 03 Nov 2002
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Location: Melbourne Australia

PostPosted: Tue Dec 17, 2002 5:28 pm    Post subject: Reply with quote

Been thinking about those 67lbs. If this is correct the glass would be closer to 8mm thick! Anybody got one that they can measure the thickness of.

I'm sure if you put your mind to it you could whip one up in your lunch hour Joe.
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Peter_in_AU  



Joined: 29 Jul 2001
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PostPosted: Tue Dec 17, 2002 6:59 pm    Post subject: Reply with quote

8mm? Which glass are you talking about?

Wrap your fingers around the rear hatch glass, it's 3mm tops.
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1982 924 (As featured on Wikipedia)

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924RACR  



Joined: 29 Jul 2001
Posts: 8346
Location: Royal Oak, MI, USA

PostPosted: Wed Dec 18, 2002 12:29 am    Post subject: Reply with quote

I have a loose piece of glass but have no scale, so I won't be weighing it... unless my neighbor has a scale I can borrow. Will have to check. It's seperate of the frame. Yes, it is about 3mm thick. It also weighs somewhere from 60-80lbs. The frame weighs next-to-nothing. This should give us a really good idea of the potential weight savings. I'd think the completed unit couldn't weigh more than about 20lbs.

Bobby responded, he's been talking about it with Jeff, and they'd like to do it but it's much lower on the priority list. Maybe I should get off my butt and make my own. I agree, there should be some degree of tolerance using plastic and not putting struts on it - just prop it up when necessary. However he did express some concern about what to build a mold out of, due to the heat.
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Zuffen  



Joined: 31 Jul 2001
Posts: 1424
Location: Owasso, Oklahoma 74055

PostPosted: Wed Dec 18, 2002 2:12 am    Post subject: Reply with quote

I'm leaning more to 4mm thick.

If I can get my scale back to the house I'll weigh a hatch frame, glass and let everyone know the results. I'm going to have to find a fishing scale to do the hatch frame as it weighs like 5 lbs.

What we need is some research to find what is spec for most sanctioning bodies. If we go thinner we will have to NASCAR strap the piece in.

What do you guys think of this idea.

Use the outside of the old glass as a mold, but to allow for the extra width I'll diamond cut the glass in half and remove a small amount to make up for the exta mold width if it were whole. Then butt the two halves together and fix so it won't move. This should be a perfect mold and fit the width of the hatch frame (the curved section from one side to the other). Thenall that will need to be done is trim the outside edge to pattern and about 1/4 inch in for an exact fit.

I've got plans to build an oven to do the actual bend. Less stress on the piece if the entire unit is heated and fluid so the material forms too the mold versus heating and forcing in sections.
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