got a problem with gellcoat.

[oops!]

i am rebuilding a jet ski for a guy that was wrecked in a storm......it was a total write off.

i am finished the repair and about to gellcoat.

yesterday ...in cooler temps...(60 deg).
i sprayed some gellcoat on the jet flea using a prevail aresol sprayer....i thinned the gellcoat with acetone at a 15% ratio....activated it at 1.7% and 10 % wax.

the gellcoat was purchased form a place in ontario that was able to match the color.


the problem is that the stuff did not cure !....after 2hrs...i put the heat lamp to it......after another 2 hours i put a heat gun on it.....the combination of the two gave me a hard skin.....but it was still soft underneath.
i have never had gellcoat do this on me.....

any ideas on how to get this stuff to cure?

rvr...if you see this....what ingredient could be missing from the gellcoat....styrene???

 

[sasto]

Re: got a problem with gellcoat.

I noticed alot of guys using acetone as a thinner. I don't know... but we always used styrene and/or MEK (not to be confused with MEKP)... 10% paraffin wax seems like alot... You the man, let us know.

 

[erikgreen]

Re: got a problem with gellcoat.

10 percent seems kinda high to me, too, but that might work depending on other factors like the gelcoat formulation.

Personally I'd have skipped the wax and just oversprayed PVA or something, but that's me.

How long did you mix the gelcoat for? I usually try to stir it with a power tool for 15 seconds or by hand for 1 minute to ensure the catalyst is everywhere...

Erik

 

[oops!]

Re: got a problem with gellcoat.

15% of acetone is very high.....you should never go over 10.....but i needed it to get thru the arasol sprayer i was using.

the wax at 10 percent was because the *&%*@)*! sold me unwaxed pigmented gellcoat and marked on the can it was waxed !

why anybody would sell unwaxed pigmented resin (specifically sold for a jet ski) i have no idea

 

[sasto]

Re: got a problem with gellcoat.

We would determine if wax was the problem or the "kicking" process was the culprit...If the surface is tacky, then as you know, a catalist or styrene problem... A setback ..If the surface is waxy then we would use naptha to remove the uncured gelcoat. Liquid laundry detergent worked well too. May not be a sanding your project yet..

 

[oops!]

Re: got a problem with gellcoat.

i just heading back over there now.....gotta check with the manufacturers ....they might be suggesting a different cat rate

 

[erikgreen]

Re: got a problem with gellcoat.

why anybody would sell unwaxed pigmented resin (specifically sold for a jet ski) i have no idea

Well, I'd personally use it for multiple coats, where only the last one was waxed. Or, if I used an overspray of PVA I wouldn't need the wax mixed in.

Especially if I was going to use a preval sprayer or similar to spray the stuff... the wax adds a ton of thickness, so not adding it would help me spray.

Different people do things differently, though.

Erik

 

[Yacht Dr.]

Re: got a problem with gellcoat.

Hello Oops..

Are you dealing with MiniCraft Gel ?

In any case.. Alot of the newer gel mixes you get are LVOC..meaning 2% cat ratio..

For spot spray repairs I would allways suggest a Patch Aid agent ( Cook sells some good stuff ).

What ski are you working on ? ( Again..alot of those skis are Imron..Like Yamaha etc on the hull ).

Acetone shouldnt matter on reduction for most spot applications.. Colors do tend to wash though..

YD.

 

[saildan]

Re: got a problem with gellcoat.

Fibre Galst says this in their data sheets:

Slow Gel Coat Cure
Any temperature below 70 degrees F will retard the gel time... Do not apply when temperatures are below 60˚F.

An under-catalyzed gel coat will also result in a slow cure but this is not a recommended technique for deliberately lengthening gel time.

High moisture and humidity will lengthen the gel time.

Acetone
It is not recommended for thinning resins or gel coats as this can lead to added pinholes and premature yellowing. We recommend #70 Styrene for thinning Polyester Resins [gelcoat is a polyester resin].

http://www.fibreglast.com/product/LC_009​

A can of US Composite gelcoat I have says this on the label.

Do not thin gelcoat with acetone, MEK or lacquer thinner. Thinning with these materials can lead to an un-curable application that will aligator on the next shoot, destroying all the time and materials for both shoots

What do the instructions for your brand tell you is acceptable?

 

[oops!]

Re: got a problem with gellcoat.

How long did you mix the gelcoat for? I usually try to stir it with a power tool for 15 seconds or by hand for 1 minute to ensure the catalyst is everywhere...

Erik

lol....i didnt see your first post we were typing at the same time....

with all gell or resins i am anal about mix times....i shook the main can violently for 10 mins and stirred it in the mix for 5.....(i was only mixing a small batch...so i didnt use the eggbeater on the drill thingy).

Well, I'd personally use it for multiple coats, where only the last one was waxed. Or, if I used an overspray of PVA I wouldn't need the wax mixed in.

Especially if I was going to use a preval sprayer or similar to spray the stuff... the wax adds a ton of thickness, so not adding it would help me spray.

Different people do things differently, though.

Erik

yeah...i know bud......im just mad that they sold me unwaxed when the can said waxed

Hello Oops..

Are you dealing with MiniCraft Gel ?

In any case.. Alot of the newer gel mixes you get are LVOC..meaning 2% cat ratio..

For spot spray repairs I would allways suggest a Patch Aid agent ( Cook sells some good stuff ).

What ski are you working on ? ( Again..alot of those skis are Imron..Like Yamaha etc on the hull ).

Acetone shouldnt matter on reduction for most spot applications.. Colors do tend to wash though..

YD.

yd....i really wish i had some patch aid.....i going to have to grab some.....

its a sea doo.......bombardier.......so the sales agent is gellcoat international out of quebec i think....

the damage was done to the upper cap....so that is still a polyester based/gellcoated area......they are using ve resins on the hull.

get this......a liter....(like a quart i think) cost 99 dollars to get here.....and i still think its the wrong color....kind of orangy when im looking for red.

they are calling for 2% cat ratio. even though its cooler here at around 60 deg. (currently low humidity) I am heating the substraight with the quartz work lights.


ok.....up date.....

went to see the jet flea.......the stuff was still WET in areas.....i took acetone......and WIPED IT OFF !

I decided to test the product.....mixed a batch with 5% wax....10% acetone......and 3.5% mekp......it took 2 hrs to cure to hard !

i really do not like to go over the 2.5 max ratio because the gellcoat will tend to craze over time.

i also went to 2 different suppliers today.....and started asking questions......i got lucky and a district manager was in the area that day.....i told him the problem......he did not know......but he said..."i know who does"......he consulted his personal phone book and dialed.......he put the cell phone down in front of me on speaker mode......lol.....he was calling ondarvr !.....(left a message)

any how......i told the owner the about the cat rate....he wanted me to spray it any how......i really dont want to have to warranty the thing.....so i told him i would spot test at 3.5% cure. and we will call the manufacture tomorrow.....im sure somehow this is a bad batch.

i sprayed an area with the same prevale sprayer....(i was not going to spend an hour cleaning a pressure pot for a 20 second spray job)
even at 3.5% and a heated substraight....it took 2 hours to cure.

im going to look at it tomorrow. and see if its sand-able or if it just wipes off....talk to the manufacturer and see from there.

i really love gellcoat....its a great product....but this batch is really ticking me off....it has cost me 3 days now !

thanks guys
ward

 

[Yacht Dr.]

Re: got a problem with gellcoat.

Hello Oops..

Be careful about then reds .. They are Very transparent.. ( Viper Red etc ).

I Allways finish my repair With a gel paste made from the color of the finished gel. That way if I start to get thin you wont be able to see through it.

If you dont do this then I suggest dishing out your repair area so you have room to build up with your gelcoat without making a bump on the surface..

YD.

 

[ondarvr]

Re: got a problem with gellcoat.

If the company custom tinted it for you, that may be the issue.

A tinting company buys white tint base and neutral tint base, you can make about 90% of the colors with these two bases without any problems. But some colors require a huge amount of pigment, some reds and yellows are two that do.

The resin used in the liquid pigments is a non reactive product (it doesn't cure), its done that way for extended shelf life, so when large quantities are added to a base it will slow the cure and change the viscosity.

Tint companies don't typically test the gel coat for gel times after its been color matched, they put in the pigments, check the color, then ship it, this works 99% of the time, but there can be issues.

Acetone will inhibit the cure even further, then when its sprayed in a thin film there just isn't enough of a chemical reaction to generate the energy and heat needed for it to become hard. The wax will also trap some of the acetone in the film and not let it evaporate out in the same way it would without the wax, so it stays there and inhibits the cure even more.

Companies that make gel coat tint it to the correct color, then do the QC work to verify the gel time and other aspects are in spec.

Patchaid has ingredients that will speed the cure for faster and better results.

 

[Yacht Dr.]

Re: got a problem with gellcoat.

EDIT: Take this discussion offline. Maybe while you're retyping it, you can figure out how to do it in a less confrontational manner.

 

[oops!]

Re: got a problem with gellcoat.

If the company custom tinted it for you, that may be the issue.

A tinting company buys white tint base and neutral tint base, you can make about 90% of the colors with these two bases without any problems. But some colors require a huge amount of pigment, some reds and yellows are two that do.

The resin used in the liquid pigments is a non reactive product (it doesn't cure), its done that way for extended shelf life, so when large quantities are added to a base it will slow the cure and change the viscosity.

Tint companies don't typically test the gel coat for gel times after its been color matched, they put in the pigments, check the color, then ship it, this works 99% of the time, but there can be issues.

Acetone will inhibit the cure even further, then when its sprayed in a thin film there just isn't enough of a chemical reaction to generate the energy and heat needed for it to become hard. The wax will also trap some of the acetone in the film and not let it evaporate out in the same way it would without the wax, so it stays there and inhibits the cure even more.

Companies that make gel coat tint it to the correct color, then do the QC work to verify the gel time and other aspects are in spec.

Patchaid has ingredients that will speed the cure for faster and better results.

this is making perfect sense to me. if i cant find patch aid in the area....what else can i use to help ativate. can i add styerene? im worried about messing with the content as to put it out of manufactures specs.

 

[oops!]

Re: got a problem with gellcoat.

I Allways finish my repair With a gel paste made from the color of the finished gel. That way if I start to get thin you wont be able to see through it.

If you dont do this then I suggest dishing out your repair area so you have room to build up with your gelcoat without making a bump on the surface..

YD.

i just saw this last paragraph now.....lol ...this whole boat was whacked...so dishing out is out...the nose repair area is the whole nose. (yeppers...all the curves and contours needed to be rebuilt)
both side gunwhales?....were totally trashed....one was actually gone and needed to be rebuilt. the seat section was badly scarred......this thing is a hair short of a full shoot, and i actually discussed with the owner a full shoot, but he decided against it.

and thanks for the heads up on the transparency ! i know that just saved me a lot of grief


ok....up date........

ondarvr is correct with the lack of "cure" in the pigments..
that is why the straight tinted gellcoat (no wax or acetone)..... only partially cured at 3.5% mekp (in some castings i made)

when i added the acetone and wax..i compounded the problem...i washed the stuff out so bad that it could not cure ....so...what to do?
because of the short shelf life, there is no patch aid in the area.

i showed the castings of the bad gellcoat to brad at IPS....( i was hoping he had some styrene DMA and other promoters...so we could make up a make shift batch of "hot juice")
he did not have any but suggested that i just add neutral gellcoat to rebuild the base of promoters and activators!

again...a very simple solution to a complex problem.

i went back and mixed a 60 (bad) to 40 (neutral) and activated at 2 % and away it went !
very little color wash....due to the age of the jet ski i need to add a speck of white to match the color any how....

im shooting the whole thing tomorrow.
so finally i will be done with the jet ski from hell....lol.

thanks for all the help on this guys.....i really appreceate it

cheers
ward

 

[Yacht Dr.]

Re: got a problem with gellcoat.

Just make sure you Flush your gun after every kicked off batch.

And the last coat should be From one batch.

Keep some acetone in a cup handy Just in case it starts to kick while your spraying ( if it starts to slow down during spray then Stop and Flush ! ).

YD.

PS. can mods actually see what Im typing before I post ? .. that would be funny lol .