Is it gelcoat, or is it paint? Signs of old repair?

[Ryban]

I've been sanding my topsides in prep for new paint. Some areas were flaking from excess mechanical abrasion, and those areas I've sanded the chalky white paint completely away... at least I think it's paint. I know there's gel coat on the boat, I just don't know where the paint ends and the gelcoat begins.

https://photos.app.goo.gl/xagWtT5C8tjdPncH3 (photos)

There are some places that show a yellow or even orange color beneath the paint. But most places just appear off-white or beige.

A few asides:

1. I wasn't sure if I should sand out the scratches completely, or fill them with a filling compound and then fair the surface?

2. There is a grey patch near the water line, shown in a few of the photos, where it looks like a repair was done. Possible puncture?

[ramblinrod]

Originally Posted by Ryban

I've been sanding my topsides in prep for new paint. Some areas were flaking from excess mechanical abrasion, and those areas I've sanded the chalky white paint completely away... at least I think it's paint. I know there's gel coat on the boat, I just don't know where the paint ends and the gelcoat begins.

https://photos.app.goo.gl/xagWtT5C8tjdPncH3 (photos)

There are some places that show a yellow or even orange color beneath the paint. But most places just appear off-white or beige.

A few asides:

1. I wasn't sure if I should sand out the scratches completely, or fill them with a filling compound and then fair the surface?

2. There is a grey patch near the water line, shown in a few of the photos, where it looks like a repair was done. Possible puncture?

Applying marine finishes is about 25% of my business.

That sure looks like paint to me.

It would appear that there was some boat damage (unknown cause), and rather than repair with gelcoat, the repairs were filled, faired, and the whole boat painted.

To determine best course of action, the existing paint should be analysed by someone who really knows their stuff. An adhesion test should be performed in several places, to verify the original paint prep and application was completed properly. Then and only then, should the original paint be left on.

If OK, then any FRP repairs should be performed where abrasion or impact damage goes through the paint and gelcoat.

Then all damage to only the gelcoat and paint layers can be filled with high build primer and sanded fair.

Now you need to perform an adhesion test for a test spot between the old paint and new.

If the new paint of choice will adhere properly to the old paint, then you can just sand, remove dust, and paint.

If the new paint does not adhere well to the old, you will need to prime before painting.

[thomm225]

It should be quite easy to tell the gelcoat from the paint.

I sanded my boat down to gelcoat.

The paint was white as was the boat when I started, and when I was through sanding, the boat was almost totally beige because of the 40 year old beige gelcoat

Here is how it looked when I first started to sand off the old paint...............

[Ryban]

Tremendously helpful replies, thank you both!

I ended up sanding about 1/3 of the boat to gel coat, places where there was more wear, and filled and faired scratches in the other places with gelcoat.

[ramblinrod]

Originally Posted by Ryban

Tremendously helpful replies, thank you both!

I ended up sanding about 1/3 of the boat to gel coat, places where there was more wear, and filled and faired scratches in the other places with gelcoat.

Hmmm, be careful not to apply gelcoat to painted surfaces.

Very bad things can happen.

[icemate]

When I first purchased my sailboat their were signs of damage to the hull. I bit the bullet and sanded the entire hull to the gel coat and then could identify the damaged areas from previous owner. Assured the repairs were fine i contacted West Systems (Gougon Brothers) and asked what they recommended. I bought West Barrier Coat and in one day applied 2 to 3 coats to the hull. This was all below the water line. I then use bottom paint RED to be the first two coats. Once dried, I applied another coat of BLUE for my last coat. This enabled me to know when I needed to repaint again. I always uses a different color to make it easier tell when it was due. My boat was 25b years old when I sold her in Australia and it did not have any signs of blistering where I did this work. Half the joy of owning your boat is the knowledge that you did the best job possible and can then cruise with one less thing to worry about. Sail, Sail, Enjoy and be safe.

[donradcliffe]

Rod's advice is spot on--you need to be using 2 part epoxy for the filler, and a 2 part epoxy primer over any exposed gelcoat.

[Ryban]

It's sort of too late, but can someone elaborate on "be careful with gelcoat on painted surfaces"? The gelcoat is going onto gelcoat itself, but is being fair even to the surrounding paint.

Reading the AwlGrip application guide, they don't mention the need for an epoxy primer on properly prepared (cleaned and sanded) gelcoat surfaces and compatible paints. A gallon of AwlGrip primer and associated converter will cost me $500, and seems unnecessary under the conditions. Were you referring to if I had used a different paint, like Interlux Perfeciton?