Gel coating a fiberglass roadster tank

I am sure someone has done this. Is spraying a color gel coat very difficult? What spray gun is used and are there any on line tutorials available.
How smooth does the finish on the tank have to be to begin? What is the prep needed to the tank?
Worth trying or should I just take the tank to my painter. I would like to do it myself if possible.
This is an original 68 fastback tank and tailpiece.

MF

Be watching this thread with interest, since have a few fiberglass pieces that are looking a bit scrappy and have had a hard life - patches of gelcoat missing, cracks in the gelcoat, chips of missing gelcoat.

I understood that the gelcoat was sprayed (or brushed ?) into the inside of a negative mold, which was polished so that the finished article when removed from the mold would reflect this level of finish. But we will see ... ??

You could probably spray gelcoat on a horizontal surface. It would be nearly impossible to spray onto a vertical surface without runs and sags.

Just use a good epoxy primer- that's what it's made for. Jim

comnoz said:

Just use a good epoxy primer- that's what it's made for.

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And if you want to restore the glass, without any paint involved ??

I see those repair 'pens' for repairing cracks in the gelcoat, in various colors.
Anyone tried them ?

Why not just do a good prep on the old surface and use a good urethane paint and plenty of hardener? That's what the painter did on my f/glass tank and if someone said it was gelcoat I'd certainly believe it.

What is a good prep on the old surface when the gelcoat has cracked ?

Totally in the dark on this stuff.
And don't want to do something that is un-doable, as this stuff often seems to be...

The early F/G panels and tanks were prone to cracking and crazing as I can attest to. I tried bondo on one of the panels, and that worked ok on one side but not the other. Then I tried epoxy glue on the one that didn't work and so far it's holding up but the glue is hard to meld into the panel, it takes a lot of primer and sanding. I have a spot on my tank that's crazing, and there have been a few place that have bondo on them that are ok, so I'm not sure what is good. Maybe epoxy glue? Trouble is I think the F/G troubles come from inside, so there may not be much you can do about it. I covered mine in enamel paint and lots of clear coat. So far the panels are holding up pretty good after 2 years, but not sure about the tank, it may have to be redone, but I messed it up with dings etc.

Dave
69S

If you want to try to repair the gel coat, check out this video.
http://www.youtube.com/watch?v=Cmtt-tqFBl8
If you have a solid color tank, then try this kit.
http://www.massmarine.com/massmarin...it-75-108000?gclid=CID6yKyj_bMCFSpnOgodllwAjA
More than likely you have a Fireflake color, so you would need to find some large flakes and a translucent color. Way too much work!
It's a lot simpler to fill the cracks and chips with polyester resin (catalyzed) and prime with a hi-build primer and paint with a good acrylic-urethane enamel and clear. A good custom painter can mix the color with the flake and get pretty close to the original gelcoat.

It is possible to spray gelcoat. Some boatyards respray fiberglass boat hulls, instead of painting them. It is tricky, as the gelcoat is not self leveling like paint. The gelcoat is thinnned before spraying, and additives are used to get the best finish possible, which typically is no great shakes. Basically you lay on a series of coats with as smooth a finish as you can get, then sand it using finer and finer grits until you end up with a polished surface. Hopefully this happens before you sand through the sprayed thickness and have to start over again. On a boat, there is an adavantage to a gelcoat finish, as it is thicker than paint, can take more of a beating, and can be repaired in a piecemeal manner. I am not sure what the benefit is of a gelcoat finish on a motorcycle tank.
Stephen Hill

Stephen Hill said:

It is possible to spray gelcoat. Some boatyards respray fiberglass boat hulls, instead of painting them. It is tricky, as the gelcoat is not self leveling like paint. The gelcoat is thinnned before spraying, and additives are used to get the best finish possible, which typically is no great shakes. Basically you lay on a series of coats with as smooth a finish as you can get, then sand it using finer and finer grits until you end up with a polished surface. Hopefully this happens before you sand through the sprayed thickness and have to start over again. On a boat, there is an adavantage to a gelcoat finish, as it is thicker than paint, can take more of a beating, and can be repaired in a piecemeal manner. I am not sure what the benefit is of a gelcoat finish on a motorcycle tank.
Stephen Hill

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On the flip side there are also powertools specificly made to remove gelcoat then the boat would faired with an epoxy system and painted with Awlgrip or similar.

Gel coats are a fast cheap production method for providing a reasonably durable finish on composite parts

Cheesy said:

Gel coats are a fast cheap production method for providing a reasonably durable finish on composite parts

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And are sprayed or brushed into the surface of pre-prepared (and polished) molds, and the fiberglass matting and resin laid onto it - result is a nice shiny polished gelcoat surface on fiberglass parts, no (or little) polishing necessary = great for mass production.

Might try getting some suitably colored gelcoat, and flowing it into the cracks and see if it can be done neatly - and strong enough to stay there. Hopefully without too much polishing or grinding to tidy it up...

A similar discussion on this forum post

http://www.boatdesign.net/forums/sailbo ... 45528.html

Stephen Hill said:

It is possible to spray gelcoat. Some boatyards respray fiberglass boat hulls, instead of painting them. It is tricky, as the gelcoat is not self leveling like paint. The gelcoat is thinnned before spraying, and additives are used to get the best finish possible, which typically is no great shakes. Basically you lay on a series of coats with as smooth a finish as you can get, then sand it using finer and finer grits until you end up with a polished surface. Hopefully this happens before you sand through the sprayed thickness and have to start over again. On a boat, there is an adavantage to a gelcoat finish, as it is thicker than paint, can take more of a beating, and can be repaired in a piecemeal manner. I am not sure what the benefit is of a gelcoat finish on a motorcycle tank.
Stephen Hill

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AFIK polyester gelcoat is hardening under exclusion of air.
Fritz

Hi all/Stephen
As a shipwright/boatbuilder by trade and a Norton Owner I have to chime in here.
Yes you could spray the gelcoat I have seen it done a few times over the years but it is rarely done these days,but unless you know what you are doing you will end up with a big mess.I have seen it spayed onto the topside of a yacht after a collision repair,the guy did great job with colour matching and wet rubbing back/polishing.

But of why of why do you want to put more gelcoat on ??????

It should only be about 25thou thick in a mould anymore than that and it becomes too brittle and could crack.
Gelcoat when bought does not have wax in it so the surface against the mould dries and inside remains sticky for the lay up of glass. to spray gelcoat you must use spraying gelcoat rather than brushing gelcoat with correct amount of wax added.
The thought of wet rubbing/sanding back gelcoat on tank does not sound like much fun as it is a very hard surface and how do you intend to give a nice and fair finish?

My best advice is to reapir any damage with epoxy filler then have it sprayed in 2 pack paint,put the body work back on , go for ride and forget about spraying gelcoat,life is too short.
Brett

"My best advice is to reapir any damage with epoxy filler then have it sprayed in 2 pack paint,put the body work back on , go for ride and forget about spraying gelcoat,life is too short."

Totally concur - that's exactly what I did on my original '71 before selling it in '78 - prepped the tank as per normal body work and shot it with Imron. Looked better than it did when the bike was new!

I held back on replying to this one as I've no experience whatsoever with gelcoat, and wanted to know myself!

I'd back up the guys who advise a standard repair - the big issue with crazing is to get new paint to flow over and in to it rather than away from it. 2-pack etch primer is pretty good for this, and if the 'glass is 'properly' cracked I run superglue (cyano-acrylate) into it and it has worked every time so far for me - it really bonds well with the matting - even when it's been contaminated with road grime, much better than a traditional patch repair with polyester resin.
Polyester filler (Bondo to youse overseas guys) works just fine for me on fibreglass dings and gouges, and adheres well.

2-part paints are inherently more flexible than the old cellulose base, and should be more resilient to crazing. it self-levels better than anything, too - a huge advantage in my book.

I'm still not convinced Norton put the flakes in the gelcoat, and a '69 'S' tank I'm doing at the moment has reinforced this view - I put the first base coat on, and I thought I'd got a couple of sags :evil: , but when I flatted them back they were definitely 'factory-fitted', as I rubbed straight through to the old flakes - for once it wasn't my carelessness! :wink:

Been looking into this too.

The local fiberglass guys advise there is gelcoat and there is flowcoat - apparently the flowcoat has more styrene in it. (?) This means it can be more easily applied over old gelcoat, and give an acceptable finish.

Of course, there is a trick or 2 to this, to get it to adhere, and cover evenly.
And it still doesn't deal well with cracks in the gelcoat, which need to be dealt with first...

Boat guys have all the answers here. ?

P.S. Norton folks are adamant the flakes were in the gelcoat. Doesn't make sense to do all that work and then have to paint it after, as well... ??

It's been 40 years since I made fiberglass motorcycle tanks but I'll try to remember how I did it. By helping a buddy who worked at a fiberglass manufacturing plant I was given permission to make tanks there at night plus I got the guidance of my skilled buddy who knew a lot about fiberglass. Basically the gelcoat serves the purpose of providing a smooth finish to the product AND more importantly it keeps the glass cloth away from the outer surface so it never gets exposed on the finished product outer surface. Fiberglass cloth, spun or woven is impossible to get a good finish on and fiberglass resin itself is too brittle for an ideal surface finish.

Step One:
All the glass cloth pieces were pre-cut and test fitted into position 1st and then laid out around the mould so you could quickly saturate them with fiberglass resin and place them in position in the mould.
Step Two:
As I recall we painted the gelcoat on with a thick 4" wide brush. On average the gelcoat was about 1/4" thick.
Step Three:
Mix the fiberglass resin with the hardener. Once the hardener is mixed in you're in a race against time.
Step Four:
Saturate the precut sections of glass cloth with the mixed resin so it was soaked completely with NO DRY bits anywhere which could form air pockets. Place the saturated pieces in position in the mould taking care not to displace the gelcoat so the glass cloth didn't touch the surface of the mould anywhere. The saturated cloth is quite mandible and can be shaped with a paint brush to the contour of the mould. Once you had the 1st complete layer of saturated cloth done you would apply a coat of straight resin followed by saturated spun glass cloth (for strength of the finished tank). You had to work fast because the resin would harden in about 10 minutes. It would start to get quite hot and then glob up and you knew your time was up. You could mix new resin with hardener if you hadn't completed placing all your cloth yet.

Foe repairs I would use some of the other posted recommendations and just rough up the surface and clean with acetone 1st. No need to use gelcoat again as it plays a unique roll and I'm not sure how good it is for patching. Older tanks would be faded so colour matching would be difficult.

I don't know for sure but I would think the metallic particles were indeed mixed into the gelcoat on the original tanks.

Putting flakes in the gelcoat would be the most efficient way of doing it, and I guess that the original use for bass boats is exactly how it was done.
For Norton tanks, putting flakes in the gelcoat would still require a coat of clear to be applied either before of after, otherwise flakes would be exposed to the elements and would silver instantly.

All I can go on is what I've seen myself: A NOS sidepanel with a rather orange-peely finish...



It could be that this reflects the state of the mould, but I think it hiighly unlikely; and the sags in the flake of the tank I'm doing now - unfortunately I've already flatted and re-coated that one, so no photos.

It's possible that they were clearcoated after removal from the moulds - this would explain the finish I've seen, and also the thin-ness of the clear layer, which is easily rubbed through with 360 grit - this turns the flakes silver...



Given how quickly the layer under the flake comes through, I'm still comfortable with my view that they were sprayed, as it's likely that it's the cheapest way to achieve colour saturation.

Furthermore, how else could they have sanded off the mould-line which would have to run down the centre of the tank?

Whichever way they were done originally, the only way to repair is to spray the whole shooting match with flakes in lacquer, and the high-solids 2-pack clear I use is very flexible while still being tough.
I can't comment on how craze-resistant it will be over time yet, but I expect it to be far superior to the original, more brittle finish.

It would be good if some more owners of fiberglass parts in fireflake colors could add to this ? Several sales of those 2 tone red and silver tanks and tailpieces have mentioned the flakes are in the gelcoat - but as a previous thread on fireflakes mentioned, modern spray-on epoxy products could well appear to be like this.

Have seen some JPN replica faring bits, and the colors are painted on.
In some cases by a PO with a brush, it seems...