Tips on how to use GelCoat paste

[Tafflad]

After advice here I have obtained (at almost $150) a Spectrum GelCoat Patch Paste pack for my boat.

I have a couple of scratches (trailering I assume by previous owner) ... not deep and about 12" long at most
Never used Gelcoat paste - welcome any advice.
I have watched the video here :
The West Advisor: Gelcoat Repairs

I will get the fine line masking tape .. can see the reasoning on that, and other tips & hints ?

2 Q's

Q ... on the pack it says use 1oz at a time (50% of pack) as I want to use on a few minor jobs, and due to cost to import it, I don't want to waste it, is there really a problem with mixing less, say 1/2 oz ?
(in the video they just use a tspn full) found one mention on this forum of using 2% catalyst ... is that by weight or volume ?


Q ... Also when they say mix 1oz, do they mean 1 oz by weight or 1 fluid oz ?

 

[ondarvr]

Re: Tips on how to use GelCoat paste

By weight or volume doesn't make a huge difference, it will be close enough.

The problem with mixing small amounts is it's very hard to measure the gel coat and catalyst correctly with normal methods, and the chance of being off by a greater amount is increased as the volume is reduced.

I didn't watch the video, so I don't know how they used the tape, but frequently no tape is used when using paste.

 

[Tafflad]

Re: Tips on how to use GelCoat paste

In the video - he uses a parallel run of tapes, and applies Gelcoat paste with a syringe, and then pulls a spreader over it ... so ending up with Gelcoat fill the thickness of tape proud of the hull.

If you don't use the tape, and just fill in and pull a spreader over it .... does it 'underfill'
Slightly proud is preferred to sand back ..

 

[ondarvr]

Re: Tips on how to use GelCoat paste

That is one method and it works OK. What frequently happens is air will be trapped in the paste and as soon you start sanding you'll find an air bubble, which means you need to do more work. So sometimes you may need to do a spot a second time and frequently doing it twice makes for a longer lasting repair.

If the void or scratch you're filling is on the large side you may get a a good deal of shrink as it cures, this can cause it to pull away from the edges over time and possibly pop out. By doing a thinner first layer and then a second layer you will end up with less shrink, it also gives a second shot at any air. Many times the final coat is sprayed and covers a slightly larger circle which can help it blend in better.

 

[Yacht Dr.]

Re: Tips on how to use GelCoat paste

After advice here I have obtained (at almost $150) a Spectrum GelCoat Patch Paste pack for my boat.

I have a couple of scratches (trailering I assume by previous owner) ... not deep and about 12" long at most
Never used Gelcoat paste - welcome any advice.
I have watched the video here :
The West Advisor: Gelcoat Repairs

I will get the fine line masking tape .. can see the reasoning on that, and other tips & hints ?

2 Q's

Q ... on the pack it says use 1oz at a time (50% of pack) as I want to use on a few minor jobs, and due to cost to import it, I don't want to waste it, is there really a problem with mixing less, say 1/2 oz ?
(in the video they just use a tspn full) found one mention on this forum of using 2% catalyst ... is that by weight or volume ?


Q ... Also when they say mix 1oz, do they mean 1 oz by weight or 1 fluid oz ?

YD its hard to mini mix one oz. ..

 

[Tafflad]

Re: Tips on how to use GelCoat paste

The issue for me is that if I mix up 50% of pot, and it needs a 2nd coat ...then its all gone.
Hoping to keep some for other small jobs.
Cost & time to get the stuff is considerable.

 

[Tail_Gunner]

Re: Tips on how to use GelCoat paste

Ive just started some repairs using tap plastic gel and mek....a 15 dollar spray gun from harbor freight..45 large altougher. it is without a doubt the simplest repair i have ever done. I just mix up 3 ounces of gel and spray my mapped out area's..(pre plan what im going to do)..In 10 minutes i have coated 5 trouble area's. Tonight i am going on a hunt for every litte nick i can find..sparying gel with this type of gun is childs play. Google harbor freight HVLP gravity gun.

 

[Tafflad]

Re: Tips on how to use GelCoat paste

Spray is not an option for me sorry.
That is why I bought paste patch kit.

 

[Yacht Dr.]

Re: Tips on how to use GelCoat paste

I guess you could try an eyedropper for 1/2 oz. About 7-8 drops I would say.

Do not mix it on cardboard.

I believe its by volume and not weight.

YD.

 

[ondarvr]

Re: Tips on how to use GelCoat paste

More detail on measuring.

When we do it in the lab it's done by weight on very accurate gram scales in 100 gram amounts. (100 grams = 3.5274 oz)
Depending on the product and customer the actual catalyst % may vary, but our standard spec is 1.8 %. (1.8 grams of catalyst per 100 grams of gel coat) (1.8 grams = .0634 oz). The product we send to Spectrum is QC'd this way.

If you go by volume the % changes slightly because gel coat weighs more per gram than catalyst, so the % will be slightly less.

While there is a difference, it isn't enough to typically create a problem, so in the field most measurements are done by volume. Some customers that QC incoming product will use a gram scale to more closely reproduce the results we get when the product was tested in production.

We do it in a 100 gram mass because doing it in smaller amounts is a little more difficult and may not yield as reliable and repeatable of a result, with the smaller volumes the error factor can be greater. For patching purposes 50 grams can work OK, but you need to measure more accurately. As you mix less gel coat at a time it is more difficult to get the mix ratio correct, so your results may vary.

Being paste you can’t just pour it into a container and go by volume, although you can use a small measuring spoon. Typical eating utensils can vary in size a great deal, so it’s better to steal your wife’s good baking set. You can get small calibrated syringes to measure catalyst at the local pharmacy, get the smallest one possible so the calibration will be more accurate. Use the metric system whenever possible, it will make it much easier.

Like YD said, don’t use cardboard or wood to mix on or with, they will absorb catalyst and the ratio will be off, use plastic. Mix it very well.

This should allow you to mix very small amounts a little better.

 

[Tafflad]

Re: Tips on how to use GelCoat paste

Thnx appreciated.

 

[secondchance22107]

Re: Tips on how to use GelCoat paste

I use children's medicine syringe for mixing works great

 

[Tafflad]

Re: Tips on how to use GelCoat paste

Can you suck up paste with a syringe? ...thought it would be too thick.

 

[ondarvr]

Re: Tips on how to use GelCoat paste

Can you suck up paste with a syringe? ...thought it would be too thick.

Possibly, but it depends on the consistency of the paste and the syringe.

 

[Yacht Dr.]

Re: Tips on how to use GelCoat paste

Can you suck up paste with a syringe? ...thought it would be too thick.

Ive tried that .. No you cant ( I am assuming you mean your patch paste ). You can pack the syringe with paste .. but why bother at that point. Just tape off your scratches with about 4 layers of tape and use a razor blade to fill. Then unmask, let harden and block sand your patch out starting with 320 ( possibly 220 at first to get the meat off if it didnt shrink that much ).

Yes you could spray with a Preval Sprayer. You dont need any special equip. to do this kind of application.

YD.

PS. @ $150.00 you should have gotten a quart of custom gel from spectrum.

 

[Tafflad]

Re: Tips on how to use GelCoat paste

Ive tried that .. No you cant ( I am assuming you mean your patch paste ). You can pack the syringe with paste .. but why bother at that point. Just tape off your scratches with about 4 layers of tape and use a razor blade to fill. Then unmask, let harden and block sand your patch out starting with 320 ( possibly 220 at first to get the meat off if it didnt shrink that much ).

Yes you could spray with a Preval Sprayer. You dont need any special equip. to do this kind of application.

YD.

PS. @ $150.00 you should have gotten a quart of custom gel from spectrum.

OK .. I have never done this type of repair before ... in the video I found:

The West Advisor: Gelcoat Repairs

They just use 1 layer of tape .... does it need more layers ... and I can understand I want to avoid an underfill if it shrinks back.
I don't have a preval sprayer, and how would that work with paste ?

On the comment on price the Patch kit was only $38 ... the cost to ship to UK and import duty brought it up to $150 .... it is classed as hazardous material for shipping.

 

[Woodonglass]

Re: Tips on how to use GelCoat paste

OMG!!! I would SERIOUSLY be looking for a European supplier for Gelcoat!!!!

 

[emilsr]

Re: Tips on how to use GelCoat paste

RE taping the repair....

If the tape job has sharp corners you're more likely to see it after the repair. You'll have the best luck taping off a roughly round (or oval) shape around the area to be repaired.....will be more likely to be "invisible" after you're done.

I don't know why it's this way; was some advice I got a long time ago that turned out to be worthwhile.

 

[Tafflad]

Re: Tips on how to use GelCoat paste

OMG!!! I would SERIOUSLY be looking for a European supplier for Gelcoat!!!!

getting Gelcoat is easy .. getting manufactures colour matched is not ... it's a US boat.

 

[Woodonglass]

Re: Tips on how to use GelCoat paste

If it's more than a year old the MFG color match will prolly not match exactly. Gel fades pretty quickly. Mixing an matching your own will be the only way to get it perfect and even then it's a "Lost Art" on doing it. Yacht Dr. is one of our member experts at doing it and he can tell you that it's not easy to do. For the money you spent, I think I would have tried to mix my own and lived with the results. That's just cuz I'm a C.O B!!!!!