What is a good method for cleaning the hulls prior to doing gelcoat repair/spraying?

Of course I'm going to wash them 1st but the dirt and water stains can be stuborn.

Sandpaper....seriously - about a 180 grit. The fresh layer of gelcoat needs a surface to grip onto.

Also wipe down thoroughly with a dewaxer BEFORE sanding so you don't rub wax deep into the surface.

Use acetone first. If theres any wax or other stuff it won't get sanded INTO the gel coat. use plenty of acetone.
Acetone,sand,acetone again, then I used a slightly damp ''white'' clean rag~rinse with water & do it again, and if ya want use acetone again, go ahead it won't hurt.
If ya have serious trouble with stains, use ''ON/OFF ACID''~~ be sure to wear a good heavy rubber glove. It will burn ya, turn grass brown, smoke, and make ya Gagg!!! Thats what I did before I painted my cats... 3 of them and they look great.........I did use a 80 & 100 grit- 3 coats of paint, no grit marks.. It won't hurt to try 180 grit, see what it looks like !!!! GOOD LUCK!!

If they are white hulls you can use some Oxalic Acid. Heavily dilute with water and use gloves. Wood Bleach is Oxalic Acid.

chemical warfare? <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Start with rubbing compound. Maybe you need not to paint or gelcoat anymore, because the surface is again shiny.
If you don't get rid of the dirt, sandpaper removes nearly everything, but you have to polish or paint after.
In case of tar, pitch, crude oil... chemical warfare.

Cheers,

Klaus

If they've been waxed recently I would clean them first with FSR (Oxalic acid) or snobol( hydrochloric acid). Snobol cheaper. If it's been a year then I wouldn't worry about removing it other than washing the hulls with Dawn. I wouldn't use acetone. Old Gelcoat is pourus and the acetone will only wash the wax deeper into the surface.

I would sand with 80 grit. Sprayed gelcoat covers 80 grit sanding scratches so what's the point of using finer grits?? Why work harder than you have to.

Someone posted this a while back. Do some reading and pratice on something smaller before tackling the boat. gelcoating

Check this site out. fiberglass coatings

You can call and ask questions. I know they have how to manuals there that I believe are free.

I was going to provide a link to my website - Bottom Job Part 1 ... but apparently it has pooped again.

EDIT;my host is finally upgrading Team Seacats to a new server - should hopefully see some additional performance improvements....back up soon.

With respect to the hull below the waterline. The people who owned the boat before me docked it so they painted the bottom with an anti-fouling paint that is faded and has a rough texture. Since I trailer in and out I was going to sand it off and refinish and wax the bottom. Someone told me that the boat will actually go faster with a slightly rough surface below the waterline. Is this true?

Someone told me that the boat will actually go faster with a slightly rough surface below the waterline. Is this true?


yes, sorta, not really. first slightly rough is the difference between glossy and and 400/600 grit wet dry. the theory is if the water sheens on the (sanded) surface vs beads on the (glossy) surface. The sheened surface will have slightly less surface tension. the difference is extremly small. not really measurable.

IMHO not worth it. and the surface will be hard to keep clean.

It won't go faster with the bottom paint you describe above. You'll be fine if you just remove the bottom paint,Etc. The bottom paint can be some nasty stuff to breath so protect your lungs from the dust.

Be cautious sanding anti fouling paint. Pestacides in the paint can be very harmful to you and your pants. I recomend using a stripper vs sanding. No dust that way.

EDIT:Pestacides in the paint can be very harmful to you and your PETS. Your pants will be okay either way. <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Try this before spending a lot of money. My H-17 had set outside for about 3 years or more of none use and had that green mold all over it. I got a $1 can of Bon Ami at local grocery store and a stiff bristle toilet brush. Made the boat look like it was brand new. Paste of it even got out rust stains!!

Try it, all you will loose it $1 plus tax.

Doug

My source suggested that "Orange Peel" was the desired texture because it caused bubbles to form under the hull and the bubbles were less "sticky" than water.

What about yellow hulls? After removing the old stripes revealing the original color, the exposed gel has darkened. Somewhat surprising to me, guessed would be lighter/faded from oxidation. Cleaning them before sanding and/or rubbing compound, any bleach type product is a bad idea, right? Use a wax remover only?

If you are adding gelcoat, remove gelcoat, that crap is heavy...... Sometimes the upper layers get contaminated, remove them with 320 grit.

barkeepers friend works great!!!

non abrasive to fiberglass