h2pmr

http://www.928.org.uk/locator/list/632.htm

am no good at posting pics so hope a link is ok

Phil

danglerb

Dan, what are the pieces being held in the yellow gloves?

The picture with the blue tint plastic covering the interior, was that complete torn down or did the yellow glove pieces replace something?

I'm also wondering about what appears to be a gap between the roof and where the interior panel mounts?

Thanks to both for the picts.

puyi

Considering body panel and resistance, consider that :
The steel pannel should weight 6
The aluminium panel should weight 3,5
The GF panel should weight 3
The CF panel should weight 1

All that stuffs as the same fontionnality, body panel, the same resistance.

Puyi

S4ordie

Hi Mike - IIRC the two pieces Ron Ruff is holding make up the rear cross support for the roof. One piece is is the main cross bar the second is the peice that containts the rear hatch attachment points. The original attachment piece got a little tweaked when removing the hatch. Decided to go ahead and replace it as the cost was nominal. The pic with the blue tin plastic was just before the rear cross brace was welded on. Ron was just test fitting when the pic was taken. If you look close it is not quite perfect when the shutter clicked.

Interesting. 6 (lbs or kilos?) is pretty light as I suspected for the steel roof panel. 1 (lbs or kilo?) for the CF is pretty incredible. I have had parts of my boat replaced with CF but I never saw a 6 to 1 reduction in weight. more like 3 to 1.

slate blue

I plan to replace the entire roof section with CF, should save a lot since I have a sunroof, I would guess around 40 pounds. There are glues around that are designed for steel to CF, you need to prepare the steel and or alloy surfaces very well due to corrosion and this corrosion will eventually break the bond. I can't remember the glue I found but it is used by the OEMs for this exact purpose.

One problem with CF is the lacquer coat, when it is damaged the raw CF look is cosmetically finished, I was reading today there is a CF approach that doesn't use the lacquer and still has a high gloss, the other way would be to just paint it body colour as there is paints around that are designed to go over composite panels. The glues were not that expensive either, highly rated in terms of strength and just enough elasticity.

What people may not realize is that the CF panel needs to have a reasonable thickness for strength, maybe 10 layers or so depending on how heavy the material being used is. I think (guess) the CF panel would have to weigh 2 to 3 kgs to have enough strength for an accident.

While less layers will be quite strong statically, it is in a roll over that it will fail and be potentially dangerous. If it is fitted on a street car like mine, I will probably have to get an engineers cert. as it is a big structural change. I don't think making a mold will be that hard especially if you had a brand new part to come off like in the previous pics!

Greg

S4ordie

One thing I have found is that the weave of CF often is visible in the paint unless you slather it with a fair amount of filler. Like Greg Gray says it takes quite a few layers of CF to make it structurally strong. I still supposition that once you get that newly fabricated CF roof panel mounted, sealed, covered with body filler and primer so it will look perfectly shiny without the weave showing through, you probably have not saved yourself much weight at all and IMO makes the car less structurally safe.

The sunroof delete panel is inexpensive and is a better financial, asthetic and safety option. If you are that keen on dropping a couple of kilos of weight from your car, then skip one meal a day for 3 weeks.

Of course my comments, especially relative to cost, can and maybe should be, totally disregarded. I am spending money faster than the U.S. government on my car for many asthetic purposes

123quattro

I'd love to have a naked carbon roof on my car since it's currently got a sunroof and is a black car. Any idea on prices guys?

FlyingDog

I have been talking to a friend who races a Vette about doing this. We were originally talking about making ducted hoods and 1-piece front ends, then the discussion moved to roofs. I think he said a CF World Challenge roof for a C5 weighs 6lb, fiberglass weighs 9lb, and the factory stuff is 20-something. We're guessing based on numbers I've heard in the past that a replacement panel on a 928 would save 25+lb vs a steel sunroof depending on material and assembly process.

We are talking about doing this on race cars with full cages, not street cars. It should be rigid and well attached, but it does not need the absolute crush/intrusion safety level of a street car without a cage or safety gear-wearing driver.

S4ordie

Even in a race configuration there is still probably not much weight savings between replacing the sunroof panel with the sunroof delete panel vs the CF panel. I paid about $400 for the OEM roof panel from Porsche. Not sure what it would cost for a CF panel.

FlyingDog

25+lbs 4ft off the ground is a huge savings.

S4ordie

No, Perhaps I am not being clear. The weight savings comparison is not between the existing roof with the sunroof which is 25lbs (possibly more) but between the steel sunroof delete panel which is 6 lbs and the CF panel which is 4 lbs. You are going to cut off the sunroof panel anyways and replace it with either the sunroof delete panel or the CF panel. The delta is 2lbs or less and probably a whole lot of money more.

The roof is a small area so the the wieght delta between the stell replacement panel and CF is minor. The delta on something like the hatch and the hood/bonnet would be considerable due to the larger areas.

mark kibort

im confused, why is that yellow piece having to be removed? it looks like the entire stock roof is glued on. I cant see where the spot welds are except toward the rear on the rain gutters area. can that rear yellow piece remain when you remove the roof, then just replace the non sunroof portion around it, or is it a different piece that needs to be welded when doing the conversion?

chassis research

it depends on if you wanted a paintable or a clear panel that shows the weave. I am being quoted 200-300.00. I am not sure who is doing the carbon finer work for some of these guys but everything coming out of this shop is smooth and shiny. these guys build NHRA funnycar bodies. They are quite strong as they need to be rigid at speeds close to 300mph. the carbon panels are usually 25% of the weight of steel.

FlyingDog

prepreg or wet carbon? all carbon or carbon/kevlar/glass? autoclaved or vacuum bagged or atmosphere cured?

S4ordie

Hi Mark - that yellow/tan piece was replaced because the hatch attachement points got tweaked during the removal. From what I have been told by the bosy guy the panel is spot welded on.