Bottom sanding job seems to be going sideways on me

[Sandero]

Originally Posted by sailorchic34

Epoxy is not needed over the gelcoat, just a light sanding and wipe with acetone. Epoxy is used under a gel coat where blisters are.

Haulouts are always way too much fun...

Usually...

After many years of applying bottom paint.... it was clearly too thick and too heavy and needed to be removed. I hired a soda blaster... but unfortunately went through the gelcoat in a few places. So I decided to do an epoxy barrier goat. No blisters in the gel and so barrier coat was mostly double protection against moisture infusion.

The removed paint was over 500#.

[Ziggy]

Originally Posted by gamayun

[...]Apparently, one coat of paint was applied at the factory back in 1988. Now I know there's no barrier coat! At least the bottom is good with no blisters so I could clean it well, then plan to do the rest of the sanding next time I haul. [...]

Blistering was a serious problem in many boats built in the 70s and 80s, but Tillotson-Pearson, the builder of Freedom yachts, switched to using vinylester resin sometime in the early 80s. Vinylester is a lot less susceptible to osmotic blistering than the conventional polyester resins that were commonly used at that time, perhaps as resistant as epoxy, or maybe even better. So I think epoxy barrier coat is probably redundant in your case. Just be careful not to get too exuberant sanding, so you don't go through the gelcoat.

By the way, one advantage of epoxy barrier coat like Interprotect is that it's very hard, so it's a lot less likely that you'd go through it when sanding. But when I had my boat's bottom soda blasted a couple of years ago, it went through the barrier coat in patches, even though I asked the contractor to preserve it. At least it help preserve the gelcoat.

[rbyham]

I agree with advice given to OP along the lines of freshening current bottom paint and going over with new ablative. That and epoxy barrier on rudder parts which look to be down to gelcoat.

I do not mean to hijack this thread but with the pic below expand the conversation...

Let me add a picture of a hull I saw yesterday at a local yard. I am hauling in two weeks. This will be first haul. I have seen my bottom from in the water but am guessing it will look a lot like the picture I have attached.

Looking at the pic just how bad a job would it be to get back to gelcoat followed by two layers of barrier and two of ablative paint?

What tips would folk here have for someone facing this level of hard growth on a hull which much like the picture shows very little indication of antifouling paint. I am thinking scrape/sand with 36 grit or scrapers to sped things up but are there others out there with experience of a hull this bad?

Please don't suggest media blast. That is not in the budget.

Thanks...

[Nicholson58]

Originally Posted by gamayun

Oh man, though I am still miserably sick and coughing, Arg

Invest in a proper canister mask with good fit. The crappy paper ones - are just that. Goggles when you really get throwing stuff.

Photo - Big scraping job - Use a big tool & keep it sharp. We finished with a hired sand blaster but the black (tar) had to be scraped.

[IRG]

Quite so. It never ceases to amaze me how many people don't know that the humble scraper is the fastest, cheapest and safest way to get anti-fouling paint off a bottom. A 2" blade and a long handle and you can take off half a square foot off per stroke and no small particles to breathe.

Originally Posted by Badsanta

I found that a carbide blade paint scraper with a long handle for two handed scraping helped alot before sanding.

[Nicholson58]

Originally Posted by IRG

Quite so. It never ceases to amaze me how many people don't know that the humble scraper is the fastest, cheapest and safest way to get anti-fouling paint off a bottom. A 2" blade and a long handle and you can take off half a square foot off per stroke and no small particles to breathe.

The tool I am holding is a linoleum floor scraper. Its 4-feet long with padded handles. I use a fine belt sander (600grit) to keep the edge sharp. You get about 3 sq-ft per sharpening. Keep the tool handle close to the boat so the blade doesn't dig in. It is fast but a work out. Way better than sanding - BUT - it does make some breathable fines if the bottom is dry. I also have a spare blade sharpened convex for the inverse curve by the keel.

If I was going to sand, I have a 7" diameter -# 4 grit terrazzo floor diamond wheel. We faired the entire bottom in one day with that beast.

[darylat8750]

Originally Posted by Sandero

Usually...

After many years of applying bottom paint.... it was clearly too thick and too heavy and needed to be removed. I hired a soda blaster... but unfortunately went through the gelcoat in a few places. So I decided to do an epoxy barrier goat. No blisters in the gel and so barrier coat was mostly double protection against moisture infusion.

The removed paint was over 500#.

500# !!!! On a 36 foot boat. I would not have guessed!

[Cadence]

Originally Posted by gamayun

Finally hauled my boat for first time in the 3 years since buying her in San Diego. As part of the purchase, the bottom was painted with Interlux Ultrablue. I have no idea what other paint is on the bottom. Now that I am taking a closer look at it, there are places where the paint seems exposed all the way to gelcoat. No blisters though. Also, in my agressive approach to sanding through several layers of bottom paint, just past a flaky brown layer that really seems like it needs to go, sometimes it immediately exposes the gelcoat like nothing was sticking there. It's my understanding that I need to epoxy the gelcoat patches somehow, but that epoxy won't stick to the paint that's still there. I don't have the time, money or inclination to strip it all to gelcoat (which probably needs to be done to do it right) so what's the next best approach as I continue this really difficult job and try to not do more damage that could make my life any worse right now? (I also came down with a cold so itchy/runny eyes, sneezing/coughing and blowing my nose while wearing a respirator, goggles and Tyvek hood is just a real PITA.)

Just my humble opinion. Don't cut into the Gelcoat by sanding. See if you can fine a paint stripper then use a scraper. The Gelcoat is your friend as far as blistering. A good coat of epoxy on it prior to fresh bottom paint and you are good to go. Probably be doing your lung a favor also?

[ronakke]

My boat was hauled out last Fall and the original barrier coat was soda blasted off. With the barrier coat removed there are small areas where the gelcoat is exposed and visible. The boat yard is going to smooth out the rough areas with an epoxy before applying several new coats of Interlux 2000. I called Interlux directly with any questions and they were very helpful.

[Iaangus]

Why does the accumulation of anti fouling pain need to be removed only to re apply more? Why not just scrape barnacles and sand to a fresh smooth finish, touch up of any spots where gel coat is visible, fair those spots with sanding and call it good? i have no practical experience, I'm just wondering why this isn't recommended. If it's stuck on why take it off?

[Sailor Doug]

Scraping and sanding risks penetrating gelcoat. Penetrated gelcoat invites blisters and that should be avoided. I power wash and then after it dries use a scotch bright pad to clean up untied areas. Power washing evens out ablative paint.
Last boat I had I had bottom blasted and epoxy coated. Then you can start painting bottom again with paint of your choice.


Sent from my iPad using Cruisers Sailing Forum

[Cadence]

Originally Posted by Sailor Doug

Scraping and sanding risks penetrating gelcoat. Penetrated gelcoat invites blisters and that should be avoided. I power wash and then after it dries use a scotch bright pad to clean up untied areas. Power washing evens out ablative paint.
Last boat I had I had bottom blasted and epoxy coated. Then you can start painting bottom again with paint of your choice.


Sent from my iPad using Cruisers Sailing Forum

Sounds like good advise.

[Nicholson58]

Originally Posted by darylat8750

500# !!!! On a 36 foot boat. I would not have guessed!

There is an interesting calculation. Estimate square feet; apply data - dry paint density; estimate thickness - calculate an impressive mass. I know that adding paint to bombers reduces the bomb load & likewise, capacity on commercial liners. I am sure modern aircraft paint is as light as possible. On a boat, that paint is very high density. A gallon feels like a pale of concrete. It takes three gallons/layer on our boat.

We have been using VIVID. After about three years, the stuff gets friable and is easily flaked off with a plastic (ice) scraper. It lets loose at the Interprotect - very convenient - no damage. I use a furniture plane to keep a piece of Lexan sharp. Wear a respirator. It explodes from the hull in a shower of flakes & dust. I have learned to dilute the antifouling & apply several thinner coats. Our local PETTIT rep is extremely helpful & has directed us to different techniques than on the can.

[Lancerbye]

Originally Posted by Iaangus

Why does the accumulation of anti fouling pain need to be removed only to re apply more? Why not just scrape barnacles and sand to a fresh smooth finish, touch up of any spots where gel coat is visible, fair those spots with sanding and call it good? i have no practical experience, I'm just wondering why this isn't recommended. If it's stuck on why take it off?

One does not remove the previously applied bottom paint if it is sound with no blisters showing. After many layers of bottom paint flaking can start happening , where big chunks of multiple layers start coming off the bottom. At that time it is time to remove it all and start over. I had to have this done in 2009. It took 2 young men 3 weeks of scraping, chemicals, sanding etc to get the stuff off down to gel coat. Another week to apply 5 coats of barrier paint and 4 coats of bottom paint. the bottom was totally tarped in and it was 80 degrees outside. The bill totalled 18000. The two men probably got paid 15 dollars an hour. Blasting was not permitted in that yard. This is not a fun job and not for the faint at heart. I was not happy having to spend that kind of money but when you own a boat you sometimes have to bite the bullet

[gamayun]

Originally Posted by Lancerbye

One does not remove the previously applied bottom paint if it is sound with no blisters showing. After many layers of bottom paint flaking can start happening , where big chunks of multiple layers start coming off the bottom. At that time it is time to remove it all and start over. I had to have this done in 2009. It took 2 young men 3 weeks of scraping, chemicals, sanding etc to get the stuff off down to gel coat. Another week to apply 5 coats of barrier paint and 4 coats of bottom paint. the bottom was totally tarped in and it was 80 degrees outside. The bill totalled 18000. The two men probably got paid 15 dollars an hour. Blasting was not permitted in that yard. This is not a fun job and not for the faint at heart. I was not happy having to spend that kind of money but when you own a boat you sometimes have to bite the bullet

OMG, if I had read about your experience yesterday, I would have walked away from my boat! I must say that it's not turning out as horribly as I thought it might. TPI was a great boat builder. I have such a solid boat and I'm truly thankful for that. The bottom has no barrier coat, however; but after 28 years, no blisters. A Valiant that was hauled here a couple of days ago has blisters larger than my fist and after a sanding, has now been painted. The bottom is weeping through the paint. My problem is that I can't get to good paint on my boat. When I try to sand the rough paint, it goes straight to gel coat. After another 5 hours of two of us sanding today, we almost got one complete side stripped clean. I think we have another 10 hours total to get it ready to apply Interprotect, which will require 3 days to get 7 layers down. Then barrier coat. I am thinking of using Tropikote by SeaHawk, but maybe I'll talk to the Innerlux rep on Friday. I'll be sailing over with a friend on her Santana 22 for the Gary Mull celebration. Coincidentally, my F38 is also a Mull design

When I get on my computer later, I'll post a pic of today's work. I'm really impressed at the progress and feeling pretty good about it all. Now, when I haul in the future (3-5 years, I expect) all that'll be needed is a light sanding and painting.