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[Mezevenf]

Hey guys,

Just getting my boot and bonnet done up... and the glass guy gave me the option of either CF or fibreglass, and he mention the CF would be like 300 grams lighter than fibreglass..

For a boot/bonnet, why would one use CF over normal fibreglass? Is strength really an issue if its braced underneath?

Looking for answers from those who know whats what

[Micke]

For a boot/bonnet, why would one use CF over normal fibreglass?

Quite obvious. 2 reasons actually.

1) You're a REAL pro and want the last g whatever the cost

2) Bragging in the bar CF sounds 18 dB better than plastic. And when you don't protect it from UV with paint or similar you're a cool cruiser......


In parts which require structural strength (like a working wing, CF is an option)

[Mezevenf]

So my thoughts are true! It's only really for the ricer appeal!

Thanks for clarifying Nice post

[rz]

carbon fiber is less strong than kevlar!i used all parts in kevlar.because when you hit something small with cf it tends to explode into thousand pieces.( i was told by the cf man)

[Mats]

Yes and no. CF is stronger then Kevlar but it is very brittle. So if you hit it with a sharp object it will go right through it and it can snap like a dry treebranch (think americas cup boats ) Kevlar turns into fabric if you hit it, much safer indeed. There are combination cloths to be found. not really good at anything.

The CF will also behave more or less exactly lite steel if cured in a vacuum bag in an autoclave, it will be superstiff and very hard. Not many people have an autoclave and all the *BLING* hoods you see are probably done without it, or they are done in colored fibreglass...

Go with the fibreglass, once you paint it you will never know the difference.

[Mezevenf]

Thanks Mats,

He said that he could not use an autoclave, and that heat may also be an issue if it is not cooked. Something about the resin they used.

[zambon]

Fiberglass is very good.
I, however, made a hood out of carbon fiber, kevlar, and kevlar honeycomb. I used a vacuum bag but no autoclave. My hood weighs about 5.75 lbs before paint. My hood is stiff and wont be flopping around in the wind.
I am not any type of professional, so my results might not be near the limits of what an expert could do with the same materials.
I will be curious to hear about how stiff and light your professionally made glass hood ends up being.

Oh, and about UV protection... West System makes a UV resistant epoxy.

[Mats]

Your hood is stiff because you built it right. Sandwich is the only way if you want a stiff and light hood. Usually people only do a single laminate and to get it somewhat unfloppy they make that laminate thick.

I have a piece of sandwich laminate I did for my boat in my garage, kevlar-kevlar with divinycell in between, that is, single layer of kevlar on each side. it is super stiff, it just does not bend and it is as light as a piece of cardboard. I made it to use it as a hatch but it warped, now I just use it as a demonstration for people that doesn't feel that they wanna spend the extra hour to make their hood using sandwich technique. Usually they change their mind pretty quick.