TOPIC: sanding/stripping gelcoat question

I started sanding the gelcoat on my '61 Hydrodyne. I began by using 40 grit orbital sander. It is slow, but will remove the black tint. Then I tried 80 grit belt sander and it rapidly took off the tint and quickly made it pass through the first layer of cloth down to the roving. I figure I should just keep using the orbital. However, does anyone think the spider cracks go down through the resin to the roving? After sanding, where some of the resin looks and feels smooth, there still seems to appear "lines". Should I just get down to the cloth and then rebuid with resin regardless of the look of the existing resin? Also, here are some pictures of my recore (almost finished)

Unless the fiberglass structure has be hit very hard (like bashing a dock ) the cracks likely are limited to the grlcoat. It looks like you are doing a lot of damage to the hull. The sanding is going to take a horrible amount of time to fill and fair. Not every spec of gelcoat needs to be removed. The best time to stop is when the gelcoat is approaching transparent - you don't want to get into the hull glass unless it is damaged. Once the top coat of paint is laid - all the imperfections - hifh & low areas - gouges - etc.... become glaringly obvious. Consider having the hull sandblasted or doing it yourself. Wear protective equipment no matter what. An inline "longboard sander will do the least amount of damage. This is a big job on any boat, but your work will pay off if you are careful in these stages of repair..

I would not go through the fiberglass mat. Where I had cracks I grind out with a dremel drill with a carbide tip just through the gel coat and verily into the mat and then fill with Dynaglass - its a marine grade bondo with fiberglass strands in it. Then I fill, sand and fill again and sand smooth. Like Bruce said you will have a hard time filling and faring to get it mirror finish . Especially on the outside where it will be seen. I use the fiberglass filler for faring. When you grind through the mat you also lose structural strength. That's what I do I'm sure there are other opinions.

This is really cool info. I have a 1954 Jones Way fiberglass 5X7 trailer in need of gel-coat.

Thanks for the input. I only began, so mot too much damage has been done to the gelcoat. I will try removing the tint only and leaving the transparent gelcoat on. I'm hoping there won't be too many cracks that go down to the cloth. Again, all the cracking is from baking in the sun for years...no structural damage. The boat is 17ft., so I'm sure it will take quite a bit of time to get it done without sandblasting...Wondering if soda blasting would remove just the black tint and leave the transparent gelcoat...any thoughts?

If you are going to color match your existing Gel coat you can get liquid gel coat that they color match just like house paint. You have to find a supplier in your area and take a color sample to the store and they match the gel coat. It is expensive but a little goes along way- can cost about $50 - 60 a Qt. then you grind out the cracks or sand the area you want to spray . Store that sells the gel coat can give you all the info you need.You can mix the gel coat with the fumed silica till its like a thick paste to fill any cracks that you need to fill before you spray the final coat. Its not that hard after you spray you have to polish and buff - that's the hardest part

I did a lot of reading on sodablasting, and it seems this is used in the marine industry to remove paint from gelcoat. However, I read that it could damage gelcoat if used to aggresively. So I am wondering if it might be a good idea to try it out with less pressure and see if it will at least remove the tinted part of the gel coat. Any thoughts out there? Or should I just go ahead and sandblast it? Or mabey I should continue to sand it very slowly. AHHH!

What is it you are doing ? Are you trying to save the original Gel coat ? or are you going to paint it? If you sandblast it you are going to have to paint it or if you spray it with new gel coat it's very expensive and you have to know what you are doing for it to come out right. I can't figure out what you are working on. If it's the bilge and the inside of the gunnels than just rough it up and paint it with a brush . If you sandblast the boat you have alot of finish work to do. With sandblasting you open up hundreds of little pin holes in the glass that you have to fill or they show up when you paint If you are going to paint all you have to do is sand down the old paint till it's smooth( You don't have to remove all the paint ) prime it with a high build primer and then sand it again and fill any imperfections and sand again then paint spray or roll and tip. I had the convertible top on a Skagit sandblasted and swore I'd never do it again - It caused way more work than I had ever expected.

Went,

There was some discussion at the end of this thread about blasting to remove gel coat. I've got to have it done on my Glastron. Will save a ton of time, work and potential breathing in of a lot of crap. fiberglassics.com/glassic-forums/2-main-forum/53220-hardtop-progressdust-collection-question.html

Sandblast away - I've just never had a boat that I needed to remove all the gel coat ? Can't imagine why you would have to remove all the gel coat. One time I had a project that I thought I would save time by blasting because of all the curves and indention's and ended up with hours of filling small almost invisible air bubbles thought I had them all filled and when I primered it looked like little craters. No dust when you wet sand. There's alot of different ways to skin a cat .

I bought the sodablast media today. Will begin tomorrow on the blasting. Unfortunately, most of the deck needs blasted. The cracks in the gelcoat do go down to the cloth. Yeah, I know there is the potential for a lot of filling fairing and sanding, but it has to be done. I'll send pictures throughout.