Gelcoat wrinkled/lifted Question

Hello guys

I thought I had a pretty good handle on the use and application of Gelcoat
but ran into a situation.

I built integral fuel tanks for my boat with Vinylester resin and sealed the interior of the tanks with Gelcoat.

I rolled on a coat of unwaxed Gelcoat catalyzed at 2% let kick for 2 hours at 70 degrees F then rolled another coat with wax and had the second coat wrinkle and lift badly in some areas.

I ended up scraping most of it off but what a nightmare

My question is two fold was my recoat time too soon and how concerned should I be about wax contamination from the parts I didn't scrape off. Can I acetone wipe and sand and be ok.

what is the recommended recoating time to roll multiple coats with a finishing flow coat.

Thanks Guys

 

Maybe styrene "vapors" entrapped/dammed in the tank, usual practice is to blow a fan across the top to shift some fresh air in. Worth a try... is it worse deeper into the tank? 70F is about 21C nearly ideal, one test is the "squeak" of an extended middle(rude) finger across the gel.... not to scientific but dont go again b4 it squeaks!
Jeff.

 

Thanks for the reply

there is a lip where the lid goes on and the wrinkles were on the vertical walls and under the lip. I was wondering about vapor entrapment.

How concerned should I be about wax contamination where I was unable to scrape off the effected gelcoat

 

Just thinking out loud,.... for the vapor issue I'd expect it worse deepest in the hole unless there's a variation of your thickness & the bottom thick & kicked nice & the sides thin & affected. There's nothing wrong with giving it a good scuff up before going again. What fuel is going in the tanks?
Jeff.

 

The thickness was pretty even I think the bottom flat was a little heavier but the sides were pretty thick.

In some places it wrinkled just under the out turned lip and others most of vertical wall, but honestly I seemed to notice the wrinkling start at the top not the bottom

The tanks are for Diesel fuel

Thanks

 

The usual causes of triping (wrinkling) are under cure from under catalysing or too thin a layer or insufficient cure time.
Your catalyst level is ideal, my guess would be from under cure, as mentioned ventilation of the styrene is critical, given where it occurred I would suspect the gelcoat was too thin there and I would double the cure time at least before re-coating. With the first application being unwaxed 24hrs is no problem.

 

Also; it is imperative that the second coat goes off quickly to minimise the styrene attack, keep the catalyst level up and use heaps of ventilation.
Good luck.

 

In retrospect I think it was due to under cure, because it started to wrinkle soon after the second application went on

After a day of scraping and sanding I recoated the tanks this time with good ventilation and adequate cure time.

All worked out well

Thanks guys

 

Using Flowcoat in Diesel Tank

Hi.
Looking for some advice. I have built a polyester fibreglass tank for holding diesel. I am planning on coating the interior with flowcoat. As flowcoat has a wax additive to enable tack free cure, could this contaminate the diesel.

Any thoughts?
Regards.

 

Your flowcoat has paraffin wax in it. Paraffin can be found in most diesel fuel up to 20% of volume. So you do not need to worry.

 

Thanks for the reassurance.

 

I guess in the UK, paraffin refers to the liquid, kerosene. I don't know if the paraffin wax in gelcoat is the same thing.