To Gel Coat or not to Gel Coat?

[mcole01]

Hi Members,

When I got my +2 it had very little original paint on it. The Lotus factory told me that it was sent to the U.S. in gel coat/primer and was painted here. A large area of the fiberglass is bare, other areas have top coat and some have gray gel coat/primer, I'm not sure which. The body shell needed some repairs and these have been completed with a final layer of veil. My question is: should I completely remove what's left of the paint and gel coat the body or simply prime it or should I gel coat and then prime?

Thanks in advance for any and all suggestions.

Mike

[snowyelan]

The gel coat was sometimes clear, without pigment. Not typical for the times. Mine appeared to have no gel coat but upon further investigation was clear gel coated.

[Andy8421]

Gelcoat as originally used by Lotus was designed to be the first layer in the mould, providing a hard and smooth surface when the mould was removed. It only sets hard if it is protected from air during the curing process or it forms a tacky surface which is difficult to work with. If you paint it on your car you will end up with a tacky mess.

You could just use polyester resin which will set hard, but I am not sure why you would want to.

For a quality job, the best approach seems to be to sheath the car all over with tissue mat and polyester resin and work up from there.

Have a look at Option One, who describe their process in detail:

https://www.option1sportscars.co.uk/restoration/

[nmauduit]

Gelcoat as originally used by Lotus was designed to be the first layer in the mould, providing a hard and smooth surface when the mould was removed. It only sets hard if it is protected from air during the curing process or it forms a tacky surface which is difficult to work with. If you paint it on your car you will end up with a tacky mess.

for a finishing gelcoat layer one usually uses some paraffn (wax) adjuvent (2-4% typ)

[Andy8421]

It may be more of a boating thing where the gelcoat is pigmented and becomes the final finish (not painted over like the Elan).

I had understood that this was usually referred to as 'flowcoat'. I believe this needs to be 'de waxed' prior to painting over. Going back to the OP's question, I can't see why you would want to do this.

[nmauduit]

It may be more of a boating thing where the gelcoat is pigmented and becomes the final finish (not painted over like the Elan).

I had understood that this was usually referred to as 'flowcoat'. I believe this needs to be 'de waxed' prior to painting over. Going back to the OP's question, I can't see why you would want to do this.

as stated above, the gelcoat was normally applied on the mould when the original Lotus part was created, hence not exposed to air. Applying gelcoat in a repair job will often differ from that operation, unless you have a mould to fix up your part at hand... Indeed there are alternative specifically designed for sealing the fiberglass prior to apply paint.

Adding pigment in a gelcoat (or mere resin) is something else.

[Gordon Sauer]

There’s a gel coat you can use that doesn’t require any covering and it dries from the catalytic action of the two chemicals. I used what’s referred to as Finish Gel Coat available from West Marine, boating stuff. I’ve seen paint jobs where fiberglass shows through and also knew that this was how it was originally done so that’s what I did. Then I used a two pack primer and then the urethane paint and a decade or more on the car and no problems ever. I don’t know if the new two pack primers will be good enough to keep any fibers from showing through and I don’t know if it’s the gel coat application that keeps micro blisters away which seems like so many cars for sale report when they’ve been repainted. Gordon

[Andy8421]

I seem to have derailed the conversation by mentioning boats. This gentleman seems to know his onions and has a good video about gelcoat and flowcoat. He mentions flowcoat is also referred to as topcoat, and I would imagine is the same as West Marine's 'Finish Gelcoat'.

https://www.youtube.com/watch?v=rY_Nf1hPado

I will admit to being no expert about fibreglass repair, but I have done quite a bit of digging prior to starting my restoration, and my understanding is:

If you paint gelcoat on the outside of you Elan it won't set properly.
If you paint flowcoat / topcoat (and possibly 'finish gelcoat') on the outside of your Elan it will set hard, but the surface won't be suitable for overpainting without significant prep - dewaxing and abrading.
If you want to avoid fibres showing through the paint, then tissue mat and polyester resin will prevent this
The top quality shops strip the paint, repair defects then sheath the entire car in tissue mat / polyester resin and use this as a base for primer and later paint stages.

Happy to be corrected.

Andy.

[reb53]

[quote="Andy8421"
If you want to avoid fibres showing through the paint, then tissue mat and polyester resin will prevent this
The top quality shops strip the paint, repair defects then sheath the entire car in tissue mat / polyester resin and use this as a base for primer and later paint stages.

Happy to be corrected.

Andy.[/quote]

I won't be correcting you Andy as that's exactly what I did to my Sprint 30 years ago.
Prior to doing that it had paint that looked like crazy paving.
Since doing it I've yet to have a single crack come back.

Ralph.

[smo17003]

Paul Mason did my car earlier this year. His process, after GRP repairs, is tissue, polyester, primer then paint. After the polyester he leaves it a minimum of two weeks before flatting and then applying the primer. His primer is a product called Durabuild.

Mike

[Andy8421]

Paul Mason did my car earlier this year. His process, after GRP repairs, is tissue, polyester, primer then paint. After the polyester he leaves it a minimum of two weeks before flatting and then applying the primer. His primer is a product called Durabuild.

Mike

Mike,

Thanks for this. The Durabuild looks to be good stuff. I had been looking for a 2 pack primer / filler that didn't use isocyanate. MEKP catalyst is nasty stuff, but doesn't seem to have the occupational health asthma issues that iso paint has.