how do i remove spider cracked gelcoat in cockpit

I have a 1973 16' Neptune sailboat with severe spider cracking on the cockpit floor and other areas of the top deck. The previous owners did a terrible job painting over the spider cracked gelcoat and i need to remove the gelcoat and paint and start over. What is the best way to remove the gelcoat for a new non skid cockpit deck?

Re: how do i remove spider cracked gelcoat in cockpit

rburns6096 said:

What is the best way to remove the gelcoat for a new non skid cockpit deck?

Click to expand...

Gelcoat is a layer of polyester fiberglass resin that is developed for a higher degree of weather resistantance and cosmetics than the the underlying laminating resin. The only way to remove it is by sanding down to the structural layer.

If spider cracking is light, you can wetsand past the cracks then compound the fresh surface back to a new shine. When neglect is deep remove the gelcoat and re-coat.

Re: how do i remove spider cracked gelcoat in cockpit

Like the other poster said, the only way to fix it properly is to remove the cracked gelcoat. A boatyard would grind the gelcoat away, down to the fibreglass, then add a new layer of gelcoat. I've seen a dremel tool used to take the cracks down to the fibreglass, thus leaving much of the uncracked gelcoat untouched. Then you fill the cracks and sand smooth.

If you decide to do the same, watch out as using power tools on gelcoat or fibreglass is dangerous without protective gear.

Re: how do i remove spider cracked gelcoat in cockpit

Ok it is grinding time. The two paint layers need to be removed first. I used stripper in one small test area and it removed both layers but it took three applications and a sharp putter knife to remove most but not all the paint. Would a power washer be ok to use to remove all the paint from the deck first then grind out the spider cracking areas and repair with new gelcoat with non skid material rolled?

Second where to i purchase the correct orbital sanding disks to remove gelcoat? which ones should i purchase? Thanks for the advice. this looks like a fall project.

Re: how do i remove spider cracked gelcoat in cockpit

please see the reply i posted. Can i use a power washer to remove the two layers of paint on the gelcoat?

what grit orbital sand disks do i use to remove the gelcoat.

What material do i add to the gelcoat to make it non skid on the deck surfaces?

thanks for all you help

Re: how do i remove spider cracked gelcoat in cockpit

Don't forget what the posters are saying:
Basically Gelcoat is more like Fiberglass than it is like paint. It's not just a cosmetic covering, so to get through the gelcoat, you're probably going to have pretty big 'bowl' to repair. Once that 'bowl' gets too big, you're also affecting the structural integrity of the deck itself.
Lot's of marine stores should carry the product, and if not, ask local Marinas if there is a supplier in the area. If not, "iboats" probably carry it.

The same place that provides the gelcoat will also have the non slip additive, I'm sure.

Another option is try a fiberglass faring material to try and cover the spider cracks on the actual top. It's much easier to fix a flat surface than it is to fill a 'bowl'.

Re: how do i remove spider cracked gelcoat in cockpit

rburns6096 said:

please see the reply i posted. Can i use a power washer to remove the two layers of paint on the gelcoat?

what grit orbital sand disks do i use to remove the gelcoat.

What material do i add to the gelcoat to make it non skid on the deck surfaces?

thanks for all you help

Click to expand...

I'd say if the power washer works, it's fine to remove the paint. Geez, can't be very well attached then!

Re: how do i remove spider cracked gelcoat in cockpit

emoney said:

Basically Gelcoat is more like Fiberglass than it is like paint.

Click to expand...

Actually, it is fiberglass - polyester resin - the difference is gelcoat has color and extra UV resistive chemicals added - and no glass fabric, but it's the very same base resin.

emoney said:

Once that 'bowl' gets too big, you're also affecting the structural integrity of the deck itself.

Click to expand...

Gelcoat is typically about 0.020" thick (paint, 4 - 5 layers is around 0.010" thick total.

A Dremel with a depth collar and a pointy bit (not the one shown) works perfect for widening cracks without creating the wavy surface a grinder does.

Once the cracks are filled, then you sand the whole surface without having to deal with leveling valleys left by grinding cracked areas.

emoney said:

Another option is try a fiberglass faring material to try and cover the spider cracks on the actual top. It's much easier to fix a flat surface than it is to fill a 'bowl'.

Click to expand...

Cracks cannot be covered - paints, gelcoat, fairing compound all just bridge, but don't fill. The cracks reappear quickly - but you've already experienced this.

rburns6096 said:

Would a power washer be ok to use to remove all the paint from the deck first then grind out the spider cracking areas and repair with new gelcoat with non skid material rolled?

Click to expand...

I've never seen a power washer that would remove anything that wasn't already loose - even a steam cleaner doesn't touch attached paint.

These days non-skid comes as ground rubber you mix into gelcoat or paint or, for gelcoat, there are overlay mold sheets you place on wet gelcoat.

rburns6096 said:

Second where to i purchase the correct orbital sanding disks to remove gelcoat? which ones should i purchase? Thanks for the advice. this looks like a fall project.

Click to expand...

A specialty plastics supplier if you have one. Otherwise, go to NAPA or another auto bodyshop bulk supplier. They should even be able to advise you on the grades of disks.

Re: how do i remove spider cracked gelcoat in cockpit

To deal with a seriously cracked gel-coat on a '68 Sailmaster 26 I used a sandblaster.This removed anything loose and left a clean rough surface to fair
out. With a light touch and the right blast media all the material you don't want
goes away and the solid stuff stays. If you have a cast iron keel that needs re-
finishing sandblasting is just the thing.

Re: how do i remove spider cracked gelcoat in cockpit

I have the same thing on my '73 O'Day 20 and am planning the same project when I pull it out of the water in a few weeks.

Why can't I just do a quick sand/scuff of the area with 60 grit, roll on a few coats of resin to seal and protect, then a final top coat of color and texture?

You're saying the original gelcoat is only 0.02" thick so it seems this would be a dramatic improvement to structural integrity and finish quality without all the mess and hassle of removing the old stuff or grinding out every single spider crack - which sounds insane by the way.

Re: how do i remove spider cracked gelcoat in cockpit

In my case on the '67 Sailmaster the gel-coat was too thick to start with.
The cracks will keep coming back until they are cleared out. Otherwise you
are just pasting over a contaminated surface.

Re: how do i remove spider cracked gelcoat in cockpit

So why use gelcoat at all? Why not just add color and texture to regular fiberglass resin which seems to be much stronger and easier to work with?

Re: how do i remove spider cracked gelcoat in cockpit

jwimberly said:

So why use gelcoat at all? Why not just add color and texture to regular fiberglass resin which seems to be much stronger and easier to work with?

Click to expand...

Gelcoat is polyester resin (fiberglass resin). Add colorant and UV inhibitors and leave out the glass fibers and what you get is the top coat we see.

I think you want it to have a little more give than the structural resin underneath, otherwise a typical scrape would result in more breakage than scuffing.

jwimberly said:

Why can't I just do a quick sand/scuff of the area with 60 grit, roll on a few coats of resin to seal and protect, then a final top coat of color and texture?

Click to expand...

As ghamby pointed out, doing a marginal prep job just results in the cracks reopening. A top coat only sticks and stays stuck as good as the layer it's put on. If you don't remove the old soft, powdery oxidized gelcoat layer down to good gelcoat or all the way to the first structural layer, if need be, and you leave the open voids cracks create, six months later your new job will be flaking off and full of cracks. This goes for paint too - the prep work required is about the same - and lasting quality is a direct result of the prep you put in.

jwimberly said:

You're saying the original gelcoat is only 0.02" thick so it seems this would be a dramatic improvement to structural integrity and finish quality without all the mess and hassle of removing the old stuff or grinding out every single spider crack - which sounds insane by the way.

Click to expand...

If your boat needs a structure boost from its top coat the hull has way more problems than gelcoat or paint will ever be able to fix.

20 thousandths is thick for a cosmetic layer, thicker than paint. But, too thick without fiber reinforcement and it expands and contracts different from the underlying structural layers. This results in cracking too. So, it's a balance.

If you think it's insane, just go for it your way. You are your own guinea pig for the experiment - and your own financier.

Re: how do i remove spider cracked gelcoat in cockpit

BTW the Boat building, restoration, and hull repair forum is chock full of threads
on gel-coat repair. The examples are almost all powerboats but the same principles and methods apply.

Re: how do i remove spider cracked gelcoat in cockpit

Thanks SailDan and Ghamby for the info. The insanity comes from the fact that my "spider cracks" number in the thousands and are unnoticeable by touch. Are you saying that these cracks need to be cleared out to refinish?

Re: how do i remove spider cracked gelcoat in cockpit

If you don't want the cracks popping through the new finish, YES.
I can understand your frustration. My Sailmaster was more cracked than solid.
If the builder laid on the gel coat too thick you're screwed. I used sandblasters,
sanders,and routers to reef out the cracks and reduce the thickness of the gel
coat. You have to ask yourself if it's worth it. Post some pics of this boat.
GH