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Old 05-31-2013, 11:01 AM   #1
ntomic

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Default One off carbon fiber hood question?

Hello,

I have been experimenting with carbon fiber for the last year. My next project is to make a 100% carbon fiber hood for my Honda Civic hatch for road racing. All the write-ups ive seen include making a mold using tooling gelcoat with fiberglass to add stuctural support for the mold. Is it possible to make a mold of the top of my hood without tooling gel coat? My idea was to use a couple layers of s-glass and epoxy resin in a vacuum bagging setup to replace the tooling gel coat. Then, I would top that with several layers of chopped fiberglass. I would do the underside of the hood the same way. Is this a feasible idea or should I just do the traditional method with tooling gel coat? I only plan on using this mold once or twice. Thanks for the inputs.
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Old 06-01-2013, 09:30 AM   #2
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tooling (polyester) gelcoat will make sure that the surface of the mold will be perfectly smooth so in my opinion you should better use it, after-all it's not an expensive or hard to work material
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Old 06-04-2013, 03:43 PM   #3
mugget

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I asked about this at my local composite supplier last week. My project is a bit different, lots of small pieces, nothing as large as a hood. But if you're just doing one off then regular good quality gel coat will be fine. Tooling gel coat is really designed for production where you'll be making hundreds of parts. Not sure about prices where you are, but it's much more expensive here and the local supplier only sells it in 25kg.

You can still get a smooth surface with regular gel coat. The purpose of tooling coat is to give extreme hardness & scratch resistance (for many repeated uses) as well as being highly polishable and dimensionally stable (it won't flex and move as much as plain gel coat).

If it was me - I would use good quality gel coat and CSM for the mould. I don't see a need for epoxy resin or woven glass. The glass could make the mould lighter for the same strength if you think that weight will be an issue, but epoxy resin would just be unneeded cost for me. I would definitley use a gel coat though. I've been using woven glass to make quick splash moulds, but that is not durable at all. (I did it because I was modifying parts, and they'll be painted & polished before I make the final part).

Anyway, just make sure your hood is polished to a high gloss, you'll get the same finish on your mould. I guess you are going to paint your finished hood with 2k clear to provide UV protection? If that's the case I would say that the highly polishable properties of tooling gel coat would provide no advantage..

The other things to consider would be adding some core material in strips across the part to add strength and stop the part from twisting.

And a note about the underside of the hood... that is really unnecessary for a composite part - it will be much lighter than the steel hood, so it doesn't need that extra support. It will hold it's own weight just fine! Unless you just want to do it for looks, but that's all it will be for. A lot of extra work and added weight.

Hope that helps.
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Old 06-05-2013, 11:37 PM   #4
hojo

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if you are only doing a one off, it would be easiest to just use the hood as the mould. will require a little extra final finishing but lot less than making a mould then a part
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