Need help mixing gel coat

I am going to be making some small repairs which will require my working with about a table spoon spoon of gel coat at a time, How much hardner ( Drops ) will I need to mix with a table spoon of gel coat to get a proper cure. I purchased the gel coat which is matched to my color hull from Ranger boats and purchased MEK ( catalyst ) from O'Riley. Also I understand, after an area has been repaired that it should be covered with clingwrap or a material such as a plastic bag in order fo gel coat to cure properly. Thanks in advance for your help.

hereto

Re: Need help mixing gel coat

you only cover the gellcoat with plastic to smooth it out the gellcoat will not stick to the plastic.this ensures a smooth finish once cured

Re: Need help mixing gel coat

A drop(1) will probably do a tablespoon of resin. GH

Re: Need help mixing gel coat

Actually you cover the gel coat to help it cure, then sanding the gel coat down starting with 150, 220, 400 wet and 600 wet. Then use a rubbing compound to remove the rest of the scratches.

Good example video here.

Re: Need help mixing gel coat

I want to say poly resin needs 10 drops of MEKP per 1 oz. and gelcoat needs twice as much catalyist. 1 TBS = 1/2 oz. therefore by my calculations you'll need 10 drops.

As mentioned above, the plastic is to help with the cure. Poly products need to be sealed from air to fully cure.

Re: Need help mixing gel coat

_7_ said:

then sanding the gel coat down starting with 150, 220, 400 wet and 600 wet. Then use a rubbing compound to remove the rest of the scratches.

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with a table spoon of gelcoat....the 150 grit will wipe it away with a few swipes.....if the wet sanding scratches the gell coat ....you will never get rid of the scratches.....sand it dry from 400 all the way to 1500 and you wont se the repair at all.

bigredinohio said:

I want to say poly resin needs 10 drops of MEKP per 1 oz. and gelcoat needs twice as much catalyist. 1 TBS = 1/2 oz. therefore by my calculations you'll need 10 drops.

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big red....that is a huge amount for a table spoon of gellcoat.....
the cat rate is between 1.7 to 2.5% @78 deg.

an under or over cat will cause cracking and besides pooling is the primary cause of gellcoat failure.

Re: Need help mixing gel coat

oops! said:

big red....that is a huge amount for a table spoon of gellcoat.....
the cat rate is between 1.7 to 2.5% @78 deg.

an under or over cat will cause cracking and besides pooling is the primary cause of gellcoat failure.

Click to expand...

I'm a little confused. I'm basing my information from what US Composites recommends and sends with their poly products. I merely did the math to convert tablespoons to ounces. What does 1 tablespoon convert to in ounces? If 1 tablespoon equals 1/2 ounce, then isn't what I suggested previously - 10 drops for 1 tablespoon of gelcoat then 2% since poly resin is mixed at 1%?

This is US Composites information.

Polyester resin is catalyzed with MEKP (methyl ethyl ketone peroxide). The ratio is approximately one ounce of hardener per gallon of resin. Ues the following ratios for smaller amounts.

Amont of resin - Hardener required
1 ounce - 10 drops
1 pint (16oz) - 1/8 ounce
1 quart (32oz) - 1/4 ounce
1/2 gallon (64oz) - 1/2 ounce
1 gallon - 1 ounce

(Double the hardener amounts given when using gelcoat)

it goes on into surfacing agent...

Re: Need help mixing gel coat

im sure jody will see this and drop in for a visit.

Re: Need help mixing gel coat

i definately am no subject matter expert but from my trials and errors this past week ( more errors than trials). my can of poly gel states the following:

16 drop per OZ in temps 71-90 deg
12 drop per OZ for temps 90 or higher.
so if your tablespoon does equal to 1/2 oz, then i'd go with 4-5 drops. Since you are using so little it wouldn't be too costly to do some trials before applying to boat.

In my situation i was using 10 drops per oz (12-14 oz at a time) and still had the pot cook off half way through application. very costly miscalculation. So will be using 8 to see how that works for me. i don't mind waiting a little longer for it to set, so long as i get same end result.

Re: Need help mixing gel coat

This thread is over a year old. Closed.