demonfish

Discuss....

LA964RS

with a fully welded in cage...and a need to more than likely remove a sunroof....why not. Otherwise, why?

demonfish

well, i need to ditch the sunroof i never use, all that up top weight.

I have a rear welded in cage, but apparently, if you leave an inch of existing roof skin, you lose no rigidity.

At least thats how the company that makes them do it. I've seen it done that way too.

I must admit, part of it is the "cool" factor.

I'll go carbon bonnet in the future to, as well as lexan rear windows.

Geoffrey

The non sunroof roof skin does not weigh that much to begin with and for me personally, I would rather have a steel roof than a carbon roof. If the car flips, the steel will protect you better. In PCA club racing, if you have a non metal roof, you are required to use wrist restraints which are a pain.

demonfish

true - but you have to find a metal roof, weld it, paint it.... this is just a bond on job isnt it?

looking at around £450 ($650?)

Tom W

If I recall the numbers correctly, the sun-roof (gutted and the panel simply bolted in place) was 58 lbs. The non-sunroof replacement was about 35 lbs. The fiberglass replacement was about 15 lbs and it allowed the removal of another 5ish lbs of metal from the cowl between the hood and front window too..

One area of concern on replacement is how you weld the replacement in and how much "bondo" gets used improve the looks. If you are trying to save weight, adding more back for cosmetic reasons isn't the best way to proceed.

rroobbcc

This is good to know. I have started a 964 track car project myself and was also wondering about a CF or Plexi roof panel vs. steel. I need to go back and re-read the rules very carefully, and make a spreadsheet to ensure I don't miss something important.

aussie993gt-faux

if u want something a bit stronger than CF you could try with kevlar. if u r planning to do this yourself you can do it in much the same way as you lay up carbon fibre. One thing though is that you'll need to bake properly or vacuum bag if you want structural strength rather than aethetical looks.

I probably would not trust a thin piece of carbon fibre there....go kevlar or keep steel.

D666S

That is very Porsche! remember 935,917,etc.

David

rroobbcc

LOL! Yeah I guess my comment was a bit Norbert Singer-ish.

LA964RS

I think steel is the best way...that's what I did in my car....but more importantly one must look to why they are doing it:

1. Performance
2. Cool factor

Performance wise, you will not notice any difference if you do steel vs CF...and I mean 99.9% of the people and that's race drivers included....if the car weighted 1000lbs...then that's a different story

Cool factor....well that's a personal choice and if it makes you happy then go for it.

Unless you run a full cage, you will notice a rigidity issues w/CF vs. steel, unless you are just replacing the sunroof door....I think Geoffrey has a good handle on how much flex is in the 64 platform and what you need to do to get rid of it...and its more than a full cage.

Just keep us informed and if you go CF take a bunch of pics and post them here so we can all follow it and vicariously enjoy the process and results.

Best of luck.

Geoffrey

I think that if you simply replace the roof skin with a CF roof skin there is no rigididy issues. The strength is in the channels. Now, if you replace the roof like Tom did, then yes, you need a cage to replace the chassis channels that are cut out.

D666S

Channels means Pillars?

I'm very interested in that point. Fastest options to improve torsional rigidity? strut brace, bolted half roll cage... what else?

David

demonfish

you also have to look at steel roof availability, fitting hassle and paint.

carbon can go straight on.

What did tom do?

Geoffrey

Ok, the 964 chassis is designed with an 'A' Pillar channel that comes up to the roofline and then has a channel of boxed sheet metal (think of it as a square tube) that runs the perimiter of the roof and then blends into the 'C' pillar. The 'B' pillar attaches to this perimeter channel. This is what makes the roof strong enough for a rollover accident. Simply removing the roof skin doesn't affect this channel or the strength of the chassis to a material degree.

Tom cut his car at the base of the 'A' , 'B', and 'C' pillars and replaced the entire section with a single carbon piece which has no strength. His strength came from the rollcage that now replaced the stock perimeter channel.

The best way to strengthen the 964 chassis is to first install a welded in roll cage that is welded directly to the 'A' and 'B' pillars and along the inside of the above discussed "channel". This is how my car is done and is slighlty better than the Matter cage in the RS Clubsport and Cup cars because it has some additional mounting points and the top of the cage is fully welded, unlike the Cup/RS cage. Second is to seamweld the ENTIRE chassis like I did with my car. The RS and Cup cars have minimal seamwelding around the suspension points only. I seamwelded every single panel in the car inside and outside. From there there are some custom tubing that can be added to support the front suspension attachment points, side cross members, rear torsion tube. These are custom pieces and not something the factory did.

FWIW, I bought a non sunroof roof skin from a 1969 912 off ebay for $26 and glued it on my car with welding only in the corners and across the front. Do a search here on "Racecar Project" and you can see the steps in the process.