Antifoul preparation

DavidBolger

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Ladt Rowena gets lifted out this weekend for her annual wash and antifoul. Last year I noticed that some of the antifoul was flaking and I didn't have the time to prepare her. Should I prepare her better this season. How do I get all the flaking old anti-foul off. Do I use wet and dry sandpaper? She has been epoxied, does using sandpaper on her harm this?

Any suggestions, are most welcome.

regards


David
 

Twister_Ken

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In the past I've just scaped it off looser stuff using a scraper, either the wallpaper scraper type or a Scarsten (?) type. However, after a few years of doing this, the surface has become quite lumpy, so this year I'm biting the bullet and having a complete clean-off using slurry blasting.

Wet & dry is fine, but very tedious. I've also tried chemical strippers but been underwhelmed with their performance.
 

DAKA

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[ QUOTE ]
, , so this year I'm biting the bullet and having a complete clean-off using slurry blasting.



[/ QUOTE ]


Dont do it.

3 years ago at lift out a friend had his 1987 Fairline corniche at the side of my 1988 corniche.
He wanted me to join him for a slurry blast of 'gentle soda'.
I wasn't keen even when offered a two for one deal and declined.
My mate went ahead and I saw the damage the following weekend

Whole hull was riddled with small holes in the gel coat.
The whole boat had to be filled and epoxy coated.
At some stage a section of 1 ft by 2 ft on my bow had also been blasted.
It is unclear if
they started on the wrong boat.
they hit it by accident
they wanted to see if my hull would also be wrecked
they thought it was such a good job I would want mine done


My 'test' section was also covered with pin prick holes that I needed to fill.
I was pleased a small section had been tested as it confirmed to me that GRP shouldn't be grit blasted unless it needs an osmosis treatment.
A friend was then kind enough to clean my hull with an electric chisel, the old antifoul came off and left beautiful white shinny gelcoat with no visible signs of weakness.
It is clear that older boats have naturally occurring bubble holes deep within the gel coat that are created during the mixing. These bubbles are fine and will not cause a problem unless the Gel coat is overpolished with compound, over sanded or slurry/grit blasted.

The slurry blast had not made the holes but it had exposed voids that had been water tight for 15 years (moisture reading were very good).

The grass under the treated boat has still not grown back and turned into a bog for a while.

From my experience I would only have a slurry blast on a modern boat that had used a vacuum technique to mix the gel coat and so reduce the amount of bubbles.
 

DAKA

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Ive seen yours, it is fine.
a little bumpy but solid.
mine was flaking off so new was just falling off with the old.

I think it is a northern climate problem

antifoul absorbs moisture especially when several years of thickness build up.
frost expands and flakes of wet/frozen antifoul fall off.

As yours in kept nice and warm in your front room you will not have a problem /forums/images/graemlins/smile.gif
 

DickB

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How long did it take with an electric chisel for what size hull? I have tried with a scraper and it is a b_lls aching task!!! I wonder if it is worth buying this chisel or not?

thanks
 

DAKA

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Corniche is 31 ft and 11.7 ft beam.
Chines almost full length.

Yes it is worth getting an electric chisel.

I think it was two weekends of hard graft.

A weekends work in a boat club is very hard to put into hours sometimes you can get 8 hours talking in a day and the bar is open on Sundays /forums/images/graemlins/smirk.gif
 

chrisc

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Just spent two days scraping six years of anti foul back to undercoat a knackering job but the old stuff was just flaking off (in the areas that are really flaking scraping is very quick and easy) glad I have done it .now going for a bath and beer ,well deserved I think.
 

William_H

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Preparation of a boat for new antifouling is all a question of what you have the urge t do to it. if you just hose it down and slap on another coat then eventually the a/f will build up to the point where there is a step at the water line and the stuff starts flakig off leaving great steps in the smooth bottom.

You will know depending on how fussy you are when the time comes to do that terrible job of getting the old a/f off.

Me I would rather be out there on the water. Actually I try to put as little as possible a/f on and rub most of it off with in water scrubbing. But yes I use wet and dry samd paper and try to do at kleast a token gestue of old a/f removal each winter. olewill
 
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