Composite hoods

[Luke]

Yesterday Elliot and I finished off the hood mold and after waxing and some PVA, sprayed a coat of primer/gelcoat right into mold. Today I started construction of the first hood.

The fiberglass surfacing layers:

The kevlar Layers:


So far so good! Later this week I will build the bracing ribs and then layer over them. Can't wait to pull it off.

[Crazyswede]

I think I need to come down one weekend and help build a hood...for me

we need to build a fiberglass hatch for the 3 doors too.

[Luke]

I released the hood from the mold this morning. I was afraid if I waited until I put the ribs in it would become too stiff to flex out of the mold. It came out clean except for one 2"x3" area where it lifted the mold surface. Its not a huge area but it will have to be repaired on the mold. So far the hood is VERY light and I don't think the ribs will add too much.

[SaabsBreakDown]

It doesn't seem to me like the stock hood weighs entirely too much. I totally agree about a hatch mold though. A fiberglass hatch + lexan window would be a huge savings.

How much weight do you expect to save? Do you still use real glass for everything? besides the windshield.

My sister just purchased the only 9000 hood mold made and also the only carbon fiber 9000 hood in existance.

For her, its more for looks though.. she still has an interior in it.

[Crazyswede]

A stock saab hood probably weighs about 65 lbs +/- while a good fiberglass hood might be around 10 or 15. A hatch with glass is probably around 100, I'd expect a hatch with lexan to be in the 10 to 20 lb range. Combine the 2 and thats a huge weight savings. thats like adding a big chunk of hp to your engine.

[Luke]

I weighed a stock hood today: 55 lb
The composite hood without ribs: 10 lbs

The stock metal trunk: 26 lbs
The fiberglass trunk: 7 lbs

So thats a total weight reduction of 64 lbs.

I am also running a lexan rear window and side windows. The side windows don't weigh much but the back glass has some heft.

There are a lot of things required in rally cars that add weight, such as roll cage, skid plate, spares, safety equipment etc. Thats why we make every effort to shave a little here and there to get the weight back down. If you do a lot of little things pretty soon you just knocked 150 lbs off the car.

[Crazyswede]

I forget what the correlation is between cost per hp and cost per pound and the benefit of each......but the general idea is that adding hp tends to cost a lot more then reducing weight...and for each lb reduced is like adding X HP.

ie a 3000 lb car with 100 hp will be that much slower of a car then the equivalent car weighing 2500 lbs. Or look at motorcycles....my KTm 950 has about 90HP and full of fuel weighs about 500 lbs....Its damn fast....on or off road. If we say that weight and HP are linear then the equivalent car to my bike would say weigh 2500 lbs and have 450hp.

[SaabsBreakDown]

I've installed both 99 and 900 hoods without an assistant. I had no idea they weighed that much.

I don't know about you guys, but around my house horsepower is free

Something tells me luke's hp is pretty cheap too..

[max]

I've installed both 99 and 900 hoods without an assistant. I had no idea they weighed that much.

I don't know about you guys, but around my house horsepower is free

Something tells me luke's hp is pretty cheap too..

We're still convinvced Luke has only spent about $500 on cars, total, in his entire life. We think he might be developing a new engine that will run on his mom's organic vegetables so he can save on fuel costs.

[Saab99_16vT]

what luke didn't show you about the hood, is inplace of the carbon fiber, he used solar cells which will help power the car buy using the altenator to as a motor to help turn the engine some. should give the car a 5 hp gain, plus the decrease in weight should help too.

[SaabsBreakDown]

I was at about the 500 for all my cars until I bought a car for 800 on saturday. Spring green 76 99 3 door. Set me back almost a month on the rally car project..

[Luke]

The hood is finally complete. All it needs now is a little final prep and paint. I made the ribs out of sandable polyurethane foam which shapes nicely and then covered it with kevlar. The final hood tips the scales at a wopping 12lbs and is quite stiff!

[max]

That is pretty freaking sweet looking. I can't wait to see it on the car.

[Rallyho]

Luke-
When are you going to make one for a 900?!

What can you tell us about the project?
How did you build the mold?
What kind/weight/weave Kevlar did you use?
Where did you get it?
Did it "shrink" and how does it fit?

If anything the 900 hood feels even heavier to me...it's a monster.

The hatch I <think> can be lightened in a big way by carving out the inner supports and putting some lexan in.

[Crazyswede]

luke bought the mold...or traded himself for it and repaired it. There is someone who sells carbon fibre hoods on saabnet. Last I checked I think the same guy was trying to sell his molds.