Question about 91+ Fiberglass hoods....?

[FAST4DR]

I have seen different messages in the past about the fiberglass hoods being metal on the bottom and fiberglass on top. I never really payed attention to mine except for tonight. I was trying to get the hood light to work and I started studying the hood. Mine is plastic all over. I cannot find a stitch of metal except where the hood latch goes and a little piece pop riveted on where the light connects. Other than that it is all plastic/fiberglass. I am pretty sure the whole underside is molded plastic and the hood skin feels like plastic too. I cannot see under the hood blanket and I didn't pull it down so I don't know what is under there.

Anybody else have any comments on this?

 

[sdpatt]

There is no other metal except the hinges themselves. The hood light uses a two-conductor wire so there is no need for a ground strap.

 

[Shoman594]

Yes it is said that the hood is plastic not fiberglass. There have been storys of the hood "delaminating" and breaking right off the hinges!!!! have not heard of any in a while though

 

[sdpatt]

Plastic would not have sufficient strength to perform as a flat panel hood. The non-metal SHO hood has a fiber matted structure bonded by resin. We usually call that fiberglass.

Scott

 

[shojuan]

Well composite materials feel like plastic because the epoxy or polyester resins are plastics. Here's a quick primer on composites: You have your fabric and your resin. Fabric can be fiberglass, kevlar, or carbon fiber. Resin can be polyester or epoxy. Kevlar is for abrasion resistance, carbon fiber for lowest weight and highest strenth, and fiberglass to save money. Generally you use fiberglass unless you really *need* the weight savings, abrasion resistance, or weight savings since it's a lot less expensive.
Resin choice is mostly a cost issue. Epoxy is more expensive, but the strength gain is generally worth it.

Here's an example of what the cloth does to the resin. Let's say you have an epoxy with a compressive strength of 6000psi (a *very* strong resin indeed!). Fiberglass cloth by itself is extremely fragile but when you mix the too to compressive strength can be 58,000 psi or so. At 6 times the cost carbon fiber-epoxy will have a compressive strength of 72,000 psi. So unless you really need the extra strength (it's somewhat lighter too) you use fiberglass.

You can also layer the materials to combine the benefits of the different material. If you're on a budget but need a stiff piece with abrasion resistance you can start with mostly fiberglass with a few layers of carbon fiber for stiffness and a kevlar outer layer for abrasion resistance.

Rick