How much does a CF hood actually save you in weight? Are they more show than function? I saw a CF trunk for the coupe somewhere, I always thought it'd look really cool to have a hood and trunk in CF, anyone go that route?

The weight reduction is slight, as the stock hood is already pretty light. Its usually mostly for looks, and for breathing, thats if the hood has vents. I have yet to see a CF trunk on a G, but im sure it wont look too bad. Only downfall, REAL HIGH quality CF is hard to find these days, as cheap CF will start fading and changing colors.

how can you tell the quality of the CF that you're buying?

Look at it this way, I have a knife that has Carbon Fiber handles and with Titanium liner (to control the locking mechanism of the blade). We are talking about just a simple little knife that is 5 inches closed. The cost? about $200 dollars. It uses space age CF. So, if you want to see high quality CF, go into any knife store and take a look at an expensive knife. These knives are meant to be used day-in, day-out and has to stand up to extreme use so it won't break (for safety reasons).

So, high quality CF hardly flexes, has a nice even criss-cross pattern (weave) that is evenly spaced apart, and when you look at the weave at different angles, you see one weave going one way, and if you turn you head you can see the other weave pattern crossing the original weave. Hard to describe but go into a knife store, you'll see what I mean. BTW, my knife has been though a lot and I even dropped it accidently from a 3 story building onto concrete. There were hardly any marks on the CF. Oh, and the CF is just a bit thicker than a Nickle. I would think that a hood has to be at least twice this thickness?

Here's an interesting article on the knife and some stuff on CF. Enjoy!

http://www.compositesworld.com/hpc/i.../January/705/3

Forum member had a CF trunk on black, looked out of place IMO.

I checked one out today, and the CF felt quite a bit lighter than the aluminum.
Don't know the weight diff, but it was noticeably lighter.

C.

I really wonder if the majority of the carbon fiber items sold for the aftermarket are actually CF? I mean, I've seen $600 CF hoods and they flex like crazy. They wobble and they get out of shape when they catch some air at high speeds.

I had a roommate who's a Mechanical Engineer and in his class, they studied CF and he brought home a flat piece of 3"x3"x1/16" curied CF and that thing was STIFF!!! We even tried throwing it against the doors and wall to see if we could chip it and it would actually penetrate them. No chipping what so ever.

So are these so called carbon fiber hoods really carbon fiber? Or are they just fiberglass made to look like cf?

CF is very light compared to aluminum, and there is some engineering required to know how thick to make it (# of layers) and which directions the weaves should go to cope with its load environment. I don't think a lot of these aftermarket companies do this type of engineering. It is also difficult to manufacture CF products as it is mostly done by hand and thus will have varying tolerances on dimensions.

CF is very stiff and has a very low (~0) CTE (coefficient of thermal expansion). It is difficult to bend and can break.

There is a lot of fake carbon fiber products out there. They can paint a plastic part to give the illusion of a weave.

That's exactly what I'm saying too When I squeeze my pocket knife at the two weakest point (in the middle where there are no reinforcements), I can't hardly make the thing bend, and I put alot of pressure too.
Yes, real carbon fiber takes a lot of effort to do it correctly without it being just carbon-fiber-look-alike. Also, the polymers that sandwiches the carbon is also very important. Just the polymers alone can be stiff enough to make a hood but can be hard to control in terms of flex, contractions, etc. That's why there is CF in their to control it. The right amount of CF to Polymers is important.

The wieght difference isn't enough to funk your car up like that

One guy has a CF hood on black, and pulled it off nicely

Bottom line is that, with a stock aluminum hood, the weight reduction by going to a CF (always with alot of fiberglass too) hood isn't going to be that significant...