Diy Lightweight Fibreglass Bonnet

[Coxie]

hey guys, just thought i'd fill you all in on my little project at the moment...

One of my mates has a fibreglass bonnet on his r32 and the thing weighs easily less than half the weight of the original steel bonnet and looks cool too so I thought i've give making a custom fibreglass bonnet a go.

I've almost finished the first layer of fibreglass but ran out of matting so it's on hold at the moment... I coated the bonnet in tinfoil and laid the fibreglass over the bonnet, I'm hoping I can get away with this top layer and then a coat of resin to smooth things out abit and then put another layer on the underside and also some fibreglass bracing to make it more sturdy, hopefully this method will give me a shape similar to the original. I also added a bulge just for the hell of it & to try make it look a bit different to all the other r33's out there, might cut in a vent behind the bulge at some stage too.

Hardest part will be getting the finished surface smooth, hopefully not too much sanding/filling is needed.

Here are a couple of pics, anyone else attempted this sorta thing before? got any pointers or info that might be handy?

[Dan_J]

good idea and nice effort

shud be slightly distorted as your making a copy straight off the part and instead making a mold with is also pricey, so you mite have some more sanding then usual to get just right

how much did the fibre glass and resin set u bak

keep us posted

[jeffworld2]

its fun stuff isnt it! looks good mate and will work, make sure you at leat copy the factory bracing though it will be very flexible

ideally., you should have waxed the original bonnet to the shi#$ and then done this layer, then put some wood pieces in to strengthen it and then another layer or more.

because it was all waxed up, you can hopefully easily remove it from the stock bonnet and put it upside down on the grass.. you will now have a nearly perfect smooth mould. wax the mould and put a few layers in and viola!! should be nearly as smooth as the original straight off the bat

[funkymonkey]

you could unpick the welds holding the steel ribbing to the sheet metal, then use the ribbing with the fibreglass skin you just made, and add another layer of resin to hold the two together from the underside?

I'd have to agree, probably a better idea to make a basic mould first and then go from there building up vents etc. But as long as you keep it to a couple of layers thick you should be fine though. The difference will be negligible.

[Coxie]

Thanks for your input guys.

I had to source some bulk resin as buying it from hardware/auto stores really hurts your pocket, charging upwards of $30 for 500ml, ended up paying $55 for 5L of resin & catalyst to match, and the matting is around the $10 mark for 1 square metre, so it's not costing a hell of alot really. Making a moult would of givin me a better copy but i'm hoping since i'm only doing one layer ontop of the bonnet and the rest on the underside that I should get a result thats pretty close to the original, havent had much experience at all with this stuff so i'm just learning. Using the steel bracing would probably give good results but also add weight so I might just stick with fibreglass bracing. Will keep you posted

[jeffworld2]

making the mould means when you pull it out, gravity has done all the smoothing for you

it means less bog, less sanding, and therefore less weight.

you are right though, as long as you get the side edges right your top layer idea will work fine!

[SABBAi]

Great effort mate. Looks good.

20 points for doing it yourself.

[mad082]

making a mold is the best way. my brother in law has made a few fibreglass bonnets before (and canoes, and pedal cars, and side skirts) and he makes a mold. when making the mold you need to make it as smooth as possible on the lower side. then once it is done and you want to make a copy you just spray in some gel coat then once that has dried you put in the layers of fibreglass behind it, let it set and pop it out. then if your mold was good you shouldn't need to do any sanding of the gel coat and can just paint it. my father in law works at a place that makes fibreglass guards and side steps for the old F trucks and that is also how they do it.

oh and just out of curiosity, aren't fibreglass and carbon fibre bonnets illegal? i always thought they were.

[Coxie]

sorry I havent replied in a few days, was away all weeknd so I havent made much progress on the bonnet, also waiting on some more matting. just been shaping the bulge a bit getting the edges square and flat, contemplating wether to cut holes on the backside slope of the bulge and mesh for vents, but unsure what it will look like.

And no over here in NZ carbon fibre/fibreglass bonnets arent illegal, although I think you are supposed to get your car certified with it on to make it road legal.

[Coxie]

I am discovering that making a mould would have been a better alternative... The rest of the matting should turn up tomorrow, have been using filler and sanding the bonnet smooth. It is turning out ok, but might end up being slightly wavey and not completely flat, not sure how bad it will be once finished though. Here some more pics...

[mad082]

yeah i would say that the mold would've saved you a lot of work because the first thing you do when making the copy once the mold is done is spray in gel coat. that automatically gives you a smooth finish (unless your old bonnet has lots of stone chips).

[Coxie]

Only problem is making a mould for such a large object uses alot of material. Ohwell I'm learning as i'm going. Glassed the front of the bonnet today, the rest of it is pretty smooth now, have to sort out what to do with the bracing underneath next.

[mad082]

yeah that's the only downside to making a mould.

[Fry_33]

Good work so far man. There's a fair bit of work involved there. I don't know if it helps at all but when smoothing out some fibreglass recently I tried something slightly different. I'd read that to make the bog/filler a little easier to work with you can mix it with the fibreglass resin to thin it down. You just get the quantity of base filler you want and then add some polyester resin and stir them together. Add more etc until it's about the consistency you want. You can then add the resin hardner and go for it. I added a little of the filler hardner and then about the right amount of resin hardner. Some say that you don't even need the filler hardner in there. You can even make it thin enough to brush it on. It may not help you for this project but I thought it was worth sharing as I found it to be quite good for some things.

Good luck with the rest of it.

[Coxie]

Sorry about the slow posts guys, heres an update for any of you that are interested...

Am getting abit of progress done here and there, pretty much finished the top surface and have started on strengthening the underside and making a skeleton. I'm trying to keep the ribbing low profile and hopefully gain abit of bonnet clearance over the engine as my bonnet is currently raised slightly on washers & has a small bit of the factory bracing ground away to make clearance for intercooler piping, and considering doing an RB30 swap in the future so having a bit more clearance wont hurt in that situation either.

Thanks for the tip Fry_33, tried this with the filler and it does work quite well, makes it easier for smoothing large surfaces, will definately use this trick again in the future.

As it is now it weighs around about the 5kg mark, and I think the stock bonnet is up around the 20kg mark from memory? correct me if i'm wrong. Will weigh again once all the underside is glassed and that should give me an idea of the finish weight, may end up having to glass more on the underside depending how strong it turns out.

A couple more pics...

[Coxie]

Can you guys let me know if anyones actually still following this thread so I know whether to keep posting or not. Maybe I should of put it in the cosmetic/styling mods instead of fabrication...

[thrtytwo]

yeh mate, a good read, keep posting

[jeffworld2]

yes definitely keep posting

If doing it for clearance, be aware the bit that fouls is usually the front edge of the timing case cover, about where your vent thing is. put as much bracing as you can while leaving it thin or unbraced at that point.

interested in a pic of my CF bonnet underneat? sort of shows what im trying to say

all in all the more bog you do the smoother it will be... my cf bonnet is rough but i wont fill it because then it will be heavier lol.

I'm impressed so fdar and looking to see the end result. good job

[Coxie]

Yeah a pic of your bonnet would be cool, just too see what others have done for bracing, hopefully the bulge in my bonnet will act as bracing so I will not need to brace that area as much, could work to my advantage. When you say your bonnet is rough and could do with some filling, is it a bonnet you made yourself? or just some defects on an aftermarket bonnet?

The part i've braced so far appears to be pretty strong, so may not need another layer of glass which is good. Hopefully today will be nice and sunny so I can get the rest braced and give it a good chance to cure, no chance of it curing once the sun goes down here in NZ at the moment lol.

[Coxie]

Finished glassing the rest of the bracing onto the bonnet, waiting for it to set now, hopefully it turns out alright, sunniest day we've had here for awhile so it should get a good chance to cure.. Heres another pic...