Cosnada

iTrader: (2)

Right, I wish to make GRP panels for my car as weight saving is my next step with it and I fancy having a go. I will start with the boot lid and then do the bonnet. I will use the respective panels as a plug, make a mould from them and then make panels from the mould.

The panels I have are not perfect by any means as I am dealing with 30 year ols stuff here. Now, I am not obviously into the concourse scene but I don't really wish to replicate all the surface defects either. What is the best way to restore the paint back to a 'mouldable' condition?

1. T cut / cutting paste.

2. Wet 'n' dry various grades and eventually polish.

3. prep and repaint.

4. Brush paint with something like yacht varnish then rub down.

Don't forget that the original panel does not have to look good - it just needs a decent finish to mould from. The surface I have has scratches. Some are quite deep but dont go through the paint. If you can imagine 30 years of debris going through a car wash type of finish. It was very oxidised but a T cut has brought back a shine but has now exposed a surface that is very aged.

Your thoughts and ideas on how to get the best result please

stevieturbo

Even doing this yourself....it's going to cost an awful lot, for a very minimal weight saving.

There are videos on youtube about doing the work for either GRP or carbon. As long as the surface is smooth, the release agent should take care of everything else. Although prepping to smooth may mean rubbing the panel down and damaging the paint if it's bad.
Or they get thin sticky film to cover holes that I guess could be used to cover rough or pitted finishes to leave a smooth mould.

Ive toyed with the idea of carbon panels myself, just struggling to justify the amount of cost and work. The majority of the expense seems to be with the moulds themselves. And for some panels like a bonnet or doors, you'll need an inner and outer mould, so 2x the work and materials.

I had a single skin kevlar bonnet made for mine a few years back ( stronger kevlar allowed a single skin, so single mould needed. GRP would have needed inner/outer moulds, so while the base material was cheaper, the cost of two moulds made it far more expensive. )

I saved about 11-12kgs at most. Really not worth it.

Cosnada

iTrader: (2)

Hi Steve - its for fun too and I get what you are saying for cost.

I will be just wet laying GRP. I did look at CF and infusion bagging etc but way too expensive for both materials and equipment for a 'one off'.

I have just spent £150 on the materials and this will do both the mould and the actual panel. I will not be making a mould of the underside as yet. I will go 250gsm the 2 x 450gsm with strengtheners in the right places. The boot that I am doing first is held on with pins and springs and has no hinges. A skin for this is fine and will get good height from packing out the pins. If I am not happy I will mould the under web and then bond the two together.

The bonnet may be a different story though. I will probably have to double that up for strength as it is such a big area.

The boot lid I have for the plug weighs 14.5 kg. I am sure I can at least halve that. I hate to think what a bonnet weighs - they are a beast.

The doors are currently steel but all that remains is the top frame, outer skin and a little of the door outer perimeter carcas with 3mm poly windows. I may GRP the rears as just a skin, don't know yet.

If I bought a Smith & Deakin bonnet I would not be too far away weight wise from a steel one but they are not into the weight saving that I am. Good bonnets are very difficult to find and command good money as are rare. I will put my money into making a good GRP one and save weight too - it keeps me pottering in the garage too.

I have only had experience of a MK2 Escort GRP bonnet and was quite impressed at the strength and rigidity and the weight of it.

Why do we do theses things? Because we want to

stevieturbo

My bonnet was circa 22-23kgs, think it ended up at 11-12 kgs. That was about 7-8mm thick Kevlar.

Even a single skin of kevlar was quite floppy though, and I bonded some 20x20x3mm thick aluminium angle bar on the underside to give it some strength
Or maybe it was 25x25...either way, you get the idea.

So bonding some of that in the manufacture process might be better or easier than trying to make an inner skin from GRP

Cosnada

iTrader: (2)

What I am after though is some advice on the current finish of the panel I am going to copy. It is poor and I am thinking that 1200 grit / 1500 grit then 2000 grit wet and dry followed by a polish will do. The part I'm moulding from does not have to look good but the surface must be nice and smooth. It wont matter if there is no paint on it lol

Whats the best way to prep for moulding? I dont want to take on filling and so sanding would be my preferred method.

stevieturbo

That I havent a clue ! But there are tutorials on youtube covering most stuff.

Cosnada

iTrader: (2)

I am happy about the GRP process.............

Any paint guys wanna give advice on the shit paint to make it good (not visibly e.g. for a show car) to make a mould from?

Whats the best method for sorting old and oxidised paint please? I want a real nice clean smooth surface I can use.

Alg1k

iTrader: (2)

You need to use 2 pack paint as the gel coat will wrinkle the old cellulose paint and ruin the mold
This u wont know until you remove the finnished mold from the panel,
I have made some doors ,
the panels were perfect just coverd in cellulose so i just removed the paint to bare metal and molded from that ,
I then polished the gel coat on the mold surface,

Cosnada

iTrader: (2)

I am dealing with a factory paint finish and so will be celly as its 30 years old. I am not bothered if I cut back to steel but I want to get a nice surface.

Not heard of paint wrinkling before but I am guessing that the heat generated could peel paint potentially in the exo' stage. I will build up the mould over a few days to prevent warp and shrink etc.

Jay,

iTrader: (4)

or you could use a reface 2k primer wet and dry it up 1500 the wax at least 6-10 times leaving at least a hour between each coat then when you finished the mold polish it wit a machine polisher with g3 and plenty of water

Jay,

iTrader: (4)

no the paint reacts with the gel 2k is the best cover