Removing Bottom Paint: How far is too far? - SailNet Community
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post #1 of 14 Old 08-24-2008 Thread Starter
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Removing Bottom Paint: How far is too far?

I have a 1973 Cal 21 that I have to do a complete refit on. The boat has many layers of hull paint and anti-fouling paint that I have decided to remove in order to do the job right. The old paint is flaking, peeling, etc. Here's the problem. The plan is to get as much paint off as possible, then sand and then re-paint.

However, I don't know if I have gone too far:

The visible paint is grey. I am using Peel Away, which is supposed to NOT attack the gel coat. However, it seems that the farther I scrape, the more layers I discover. I see what looks like virgin white gel coat on the hull, but scraping those areas (with a plastic scraper) exposes a red color. I don't think that the layup was red, though...... It might be that the red is on top of the white, it's a bit of a mess.

I fear that I have scraped past the gel coat. How far do I go before I stop?

How do I know that I have scraped hard enough? Is there any risk that I can scrape off the gel coat? Is everything lost if I do scrape off some of the gel coat?

HELP! Thanks,

Wes
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post #2 of 14 Old 08-24-2008
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Did you use peel away marine II or marine I or conventional peelaway? Marine II is recommended for older boats with perhaps porous gelcoat which may otherwise be damaged.

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post #3 of 14 Old 08-24-2008
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We love bottom jobs...

I'm not an expert but I have done the bottom on a 1974 27" O'Day twice and we are ready to apply barrier coat to a 1980 48' Soverel... On the O'Day I used 6" orbital sander (80 grit) until the powdery/flake bottom paint/barrier coat was gone, there were places I removed some gelcoat - I stopped there; I then smoothed the hull and filled blisters with West Systems, I did not apply a barrier coat ( I really should have and paid for it on the next bottom job blister wise...) and the used Trinidad S/R hard bottom paint - at the time I thought bottom paint was seawater proof - it's not. I saw a Cataline 30' in the yard with a ton of filler in it and the owner sanded down through all that and had a real mess and a rough bottom when he was done. The 48' Soverel had the gelcoat peeled at somepoint in time so we took it to fiberglass and found a lot of stuff we did not like; ground out and filled more than I care to talk about.

From the early 70's to the early 80's when fuel prices were high, manufactures were still working out the right formula for fiberglass resin costwise - these years have more problems with blisters than earlier and later model boats.

The Soverel is to take us around the world, the O'Day took us around the bay. The saying is "I have never heard of a boat sinking from blisters".

Keep it smooth and remove the flakey stuff, bevel out and fill the blisters with glass mat ( I like 1708 - mat on one side and wove on the other) and resin or West Systems /w filler or mat, use a good barrier coat like Interlux 2000E or similar. I used Primacon on the O'Day last time so I'm not able to tell you how it worked - Primacon is primarly for steel; I'm using Bar-Rust on the Soverel, another steel barrier coat - it came highly recomended and I'm willing to take the chance. It's used on oil rigs and ships ect to keep sea water from metal. One of the tricks of barrier coat is to make sure there are no loose glass/cloth fibers on the hull when applying your barrier coat, they "wick" water through the barrier coat to the hull - gelcoat is not saltwater proof, only resistant. Again, Trinidad S/R is what I use, it lasted 3 years on the O'Day last time and I could have gone 4 easily.

Other sailiors with more bottom experiance will most likely reccomend other methods.

Good luck on the bottom job!

Bruce

Last edited by BluewaterBruce; 08-24-2008 at 03:26 PM.
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post #4 of 14 Old 08-24-2008 Thread Starter
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Thanks for the response. I am lucky in that the hull does not have blisters. At least not that I can see, as the previous anti-foul paint is VERY uneven and rough.

I tried the Peel Away (I) (Blue Label) this time, but found better results with the Peel Away II (Red Label) on my last go 'round. The weird thing is that in places, the old paint came away super easy, on others, I really had to use elbow grease. I think I'll go back to the Peel Away II.

I already have the orbital sander and a grinder, so it looks like I'll be busy.

W
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post #5 of 14 Old 08-24-2008
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if you haven't gotten too far with the project, you may just want to get the whole bottom soda blasted. it will take the bottom right down to the gelcoat without harming it. i had it done this past winter. it was prepped, blasted, and cleaned all in one day for about $1500.00 (30' boat)

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post #6 of 14 Old 08-25-2008
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I'd second the sodablasting... saves a lot of time and effort, and generally well worth it...especially if you figure out how much time, effort and materials in stripping chem and such it will save you.

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post #7 of 14 Old 08-25-2008
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Try using a paint scraper (edges rounded) and a Random Orbital sander. Scrape the paint off and then use something like 120 grit to remove the final residue. Do not use a grinder on the bottom as it is far too aggressive.

Soda blast would be nice if you have 1500 to spend - otherwise I would suggest the scraper/sander method. Having never used chemicals I cannot comment on them.

The bottom job will be worth it even if only to make the boat look nice in the yard when ou of the water.

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post #8 of 14 Old 08-25-2008
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Mike-

If you consider how much time it will take you to scrape and sand the bottom, and the price of soda-blasting the bottom... the soda-blasting is very reasonable as an alternative... My boat only cost about $900 to soda blast, and I was able to use the time not spend scraping and sanding to work and pay for the soda blasting, paint, barrier coat and such and have money left over for a few other supplies.

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post #9 of 14 Old 08-31-2008 Thread Starter
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Well, I wish I could have it soda blasted, but my trailer is SHOT, and I don't plan on buying a new one for the boat until the refit is done, so I think it is out of the question.

I just spent 2 hours out on the boat with my orbital sander hooked up to my shop vac on some areas where I used EASY PEEL. The outer paint layers come off very easy, they seem very 'brittle' and get blasted away by the sander. There are definitely places where the paint gets removed all the way down to where I can see some mat, and colorless epoxy, which means I have gone through the gel coat. I don't think I applied too much pressure, I suspect that the gel coat had blistered or separated somehow.

The thing is, there are SO many layers, I STILL don't know which one is the gel coat........ I get to a blue layer that seems thicker than the others, and right underneath that layer is the epoxied mat. There is a red layer, a white layer, a grey layer, another white layer, and then a final grey layer on top.

Any advice on how to determine which layer is the gel coat?

Also, is 80 grit too aggressive to start with?
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post #10 of 14 Old 08-31-2008
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If you know you've sanded to epoxy, then you do not have gelcoat. Gelcoat is a polyester product and will not adhere to epoxy. However, epoxy will adhere to polyester.

I've just rebuilt a 25 footer which was polyester. I sanded through the three layers of antifoul, and the gelcoat. The gelcoat was in poor shape anyway. I then redid the gelcoat with two layers brushed on before reapplying the antifoul. If I were to do it again I'd probably use the high build epoxy barrier coat (interseal) I used above the waterline. It seemed like a better product.

As for the removal of the old, on a boat that small it would take me about a day and a half to remove the old paint. I'd stop at good gelcoat, but would feather any bad gelcoat areas before applying an epoxy. I sand with a 36 grit on a porter-cable random orbital sander (professional, not palm sander)to remove the majority of the paint, and then finish with a 80 grit before applying a thick coat of gelcoat or epoxy.

If you use gelcoat you must have an air-dry wax in it, otherwise it will stay sticky. The wax must be removed before applying the antifoul. The epoxy does not need an air-dry, therefore no wax removal.

Good luck and I hope you enjoy sanding
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