Brutal sanding job!

Hey all, new here so please be gentle.

Just bought a 1999 34' cutter rigged sailboat...big project. The first thing on the long list of 'to do' items is to fix the horrendous 'sanding' job, prior to my purchase...brutal. Looks like someone used a grinder to take off the bottom paint and in doing so left gouges clear into the fiberglass in several areas throughout the entire hull below the waterline.

I want to fix this right the first time so my idea was to just sand off the rest of the remaining gelcoat and apply several layers of epoxy (Raka?), while finishing her off with 4-5 coats of Interprotect 2000 E, then gelcoat.

I attached a pic, though I apologize the pic is not that great.

Thanks in advance for any information/ideas you may have,
Chris

 

The big question is why you would want to do the difficult job of applying gelcoat after a perfectly good epoxy job ?

Although the data sheet on Interprotect 2000 E doesnt specifically say what can be painted on after, I would expect that a quality 2 part paint job would give better results and last just as long as a gelcoat.

 

I'd not be using gelcoat, the first job is to establish whether all that grinder gouging has affected the structural integrity of the hull. You probably got a discounted price because of it, every cloud has a silver lining.

 

If there are not blisters, just crappy prep work to remove bottom paint, then you just need to finish sanding, fill the gouges with epoxy, do any fairing with epoxy filler to the level you are satisfied with, then barrier coat with epoxy, then bottom paint and go sailing. By barrier coat I mean build up at least 10mils of epoxy, if you use a 100% solids epoxy such as West, Systems three, Epiglass, Raka, etc you will use less coats to get the thickness than products like interprotect which are full of solvents which make it easier to apply but need more coats, at least 5. The good folks at West have good info on how to do it but you don't need to use their products which are overpriced. You will not be using any gelcoat in the process.

Steve.

 

Conversely, you could just do the job the way most yards would, which is to remove any damaged gelcoat and laminate, bulk up where necessary, fair, smooth and re-gelcoat the area.

 

90% of people should never be turned loose with an angle grinder type sander. Seen plenty of timber houses seriously devalued by scored boards, particularly planed timber. Seems to be the same with boats.

 

I wonder what the chances of getting a uniform gelcoat colour are ?

The old gelcoat would be faded or discoloured, and then you have perhaps a dozen spots where you have to try and match the colour of that part of the hull.

On one boat, the gelcoat was never the same after having rubbed on an old truck tyre used as a fender for a couple of hours. The black never came out on that part of the hull no matter what treatment I tried.

 

Can't tell from the photos whether the whole bottom is in bad shape or only one small area. In any case, repaired areas needn't be gel-coated but matching color doesn't matter at all down there under anti-fouling paint. Epoxy would work well to seal it and gelcoat will be just as good or better than the rest of the bottom.
Your hull is very thick and well reinforced with floors and bulkheads especially down low and any superficial grinding will not weaken anything.
Dewax the area to be ground before grinding to avoid spinning it into the glass.
I think if I had to remove all of the gelcoat on the bottom I'd rent a special gelcoat-removing grinder and epoxy-barrier coat the bottom rather than gelcoating since you get a far better barrier with epoxy.

 

Welcome to the forum, Crocodile.

The photo looks like what I had to fix a few years ago. It looks like someone took the wrong tools to the hulls, probably busting open blisters and other defects. They weren't especially neat about it, but did get rid of the delaminated spots. Then they smeared gel coat all over the area, thinking is solved the problem, of course also leaving it bottom (in my case) very unfair.

I had to grind off all the gel coat in these areas, which had signs of cracking and bad prep all over. I filled and leveled the surface and epoxied, this time on a reasonably fair surface. Under bottom paint, you couldn't tell anything had been done.

It should be reasonably easy to tell what was used, if you take some 80 grit to the bad spots. Epoxy will have a translucent amber or milky white color after it's wiped with water. Polyester will look greenish or if it's gel coat the color will stay the same (white), again after a quick water wipe to make the scratches go way temporarily.

I think you know what needs to be done - the bad surface coating needs to come off, if only to find out how screwed up a job the previous owner has done. Filling the divots and gouges is straight forward enough and the resin system is your choice, though a novice gel coat job isn't easy to get right, let alone match. If you will use gel coat, stick with polyester resin systems and leave the epoxy alone. If using epoxy, stick with epoxy and just paint the boat instead, don't try to put gel coat over the epoxy.

 

You could always just patch it up so the laminate is sealed against water ingress, I doubt the difference in performance would be worth all the drama of restoring it to its original grandeur. Only the fish can see the imperfections when it's in the water. Big job otherwise.

 

The only things wrong with your plan is 1/ you don't need to remove all the gelcoat unless there is serious blistering/wet laminate and 2/ no regelcoating. What the hell is all this talk about matching gelcoat, nobody would reapply gelcoat below the waterline after doing repairs, you do repairs with epoxy and barrier coat(seal) with epoxy, then bottom paint. Above the waterline is a different story.

Steve.

 

Or just follow mr efficiencys suggestion, be sure to use epoxy or VE products.

 

Thanks for everyone’s input, it has been very helpful.

So I’ll keep the original gelcoat (hull has no blistering, just gouging…it’s not extremely deep, just deep enough to expose the fiberglass in areas).

I was told that this hull MAY have been laid up by the builder with epoxy on the outside (though not positive on this), and poly on the inside. Thanks for the info on how to find the difference between the two. I’ll have someone who is more in tune with this at the yard have a look at her regarding that.

I guess my last question I have (which seems there are varying opinions) is what’s the real difference between an epoxy resin coat and an epoxy barrier coat? I would imagine they’re pretty much the same thing?

My plan was as follows… after dewaxing, sanding, filling and fairing the gouges with an epoxy filler, I was looking at around 5-6 coats of epoxy below the waterline for peace of mind. I was told that I can simply do this with Raka 127 resin or Raka 900HP (same as West System, though much more affordable) and a simple layer of InterProtect 2000E over that to act as a primer for bottom paint. No re-gelcoating.

The reason for using 5 layers of Raka vs. 5 layers InterProtect is simply cost, though I don’t want to cut any corners. Does InterProtect have more flex/durability/denser than Raka? Is it not possible to reliably paint directly onto Raka 127 resin with a 2 part epoxy paint below the waterline before antifouling? Or just skip the 2 part paint and just put antifouling bottom paint directly onto the Raka or InterProtect?

OMG, I feel like there are 10 million products out there over complicating something that can simply be fixed with epoxy resin and paint reliably. Still, I want to do it right and at the moment I have the funds to do so.

Thanks again,
Chris

 

I am guessing there may be some improvements in the barrier epoxy to facilitate adhesion to Polyester, and thicknessing agents to enhance layup practice.

'Normal' epoxy goes to a bit of trouble to stay clear, something some applications require, but if they knew it was for sealing poly hulls, they could ignore this requirement. Epoxy formulations abound in wide variety to achieve various objectives.

The best place to get the real facts would be from the manufacturer. In the end, its the cost of each item versus the real benefits that you have to weigh up.

 

Thanks. Yes, I know that 'barrier coat' epoxy is thicker, or at least designed for less slumping when going on vertical. I've contacted several manufacturers regarding their epoxies, but it's hard to know what to believe when everyone is trying to push their product.