Folk Thats Had There Bottoms Off.

hlb

hlb

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OK there's been a few threads about removing anti fouling.

I've heard varying degrees of the differences, before and after. Some say the boat went five knots faster, others don't agree.

So some facts. MF was bought eleven years ago, the anti fouling had been stripped off when I bought her at ten years old. Why, I don't know. But she now has about 22 coats of anti fouling on her.

She's going progressively slower, down from about 24 knots flat out to maybe 18 to 20, mostly 18. She's had new props, about seven years ago, new turbo's three years ago, engines seem fine, with no oil lose.

I suspect that constant coats of AF causes a rippling effect. Lets face it, anything unsmooth down there causes a hell of an effect.

I've been told it's weight, but to be honest, I've never seen a difference, whether carrying 100 gallons of fuel or 200, water full or empty.

Yes I can see it will make a big difference on little boats where an extra ton is a huge percentage.

The guy slurry washing the fisheries protection boat said it had to be done, because it was using to much fuel and was using about half as much now.

What are your experiences.
 
If you doing a lot of miles every year your antifoul should erode away, if not then best to have it stripped, I find the farrow system best and after blasting its ready to prime without having to sand
 
Well I had Blue Fisher done by Master Blaster in Plymouth. Huge difference, gained about 10kts, used just a fraction of the fuel I used to consume, I ended up better looking, fish started jumping into the cockpit and the young ladies were waiting topless on the pontoon ready to tie me up.
So most definitely, go for it!!
 
longjohnsilver said:
Well I had Blue Fisher done by Master Blaster in Plymouth. Huge difference, gained about 10kts, used just a fraction of the fuel I used to consume, I ended up better looking, fish started jumping into the cockpit and the young ladies were waiting topless on the pontoon ready to tie me up.
So most definitely, go for it!!
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Never mind tops, I'm talking about bottoms. Anyway, you never did 10 knots in your life. Not as slow as Litle **** tho, she's brought a whole new demension to the word, Stopped!
 
More on Knobbly Bottoms.

When my boat was last surveyed the gentleman who dun it,did comment about the 50 layers of A/F clinging to the bottom of the boat.He reckoned it it looked similar to the surface of the moon and would definately slow me down and use more fuel.
However as removing all the old stuff involved either hard work and/or money decided to not bother as rarely go anywhere at more than 6-7 knots.
He mainly does commercial stuff and did say that on some small barges/coasters the effort is financialy worth it.
 
On a slippery hull 41ft sailing boat cruising under engine at 2000rpm would give 6.5kts and just heavy slime fouling at the same rpm would knock that down by as much as 0.75kt or need an extra 150rpm to overcome it. We used to pay for a diver clean (£35) just before going on our main cruise each year to have a nice clean bum, in our case so that we still made good progress in light winds under sail but losing 0.75kt over 24hrs is 18mls or nearly 3hrs longer!

In terms of the smoothness of the paint job itself it has to make a difference. Racing sailboats often burnish the antifoul (rub down the final coat with fine wet/dry used wet) for the ultimate finish, so it must be worth it. We have friends, ex-raggies, with a Nimbus 36 or thereabouts that are very picky about having a smooth bottom job, it might be a hangover from their sailing days but then again it might be worth the extra work!
 
hlb said:
OK there's been a few threads about removing anti fouling.

I've heard varying degrees of the differences, before and after. Some say the boat went five knots faster, others don't agree.

So some facts. MF was bought eleven years ago, the anti fouling had been stripped off when I bought her at ten years old. Why, I don't know. But she now has about 22 coats of anti fouling on her.

She's going progressively slower, down from about 24 knots flat out to maybe 18 to 20, mostly 18. She's had new props, about seven years ago, new turbo's three years ago, engines seem fine, with no oil lose.

I suspect that constant coats of AF causes a rippling effect. Lets face it, anything unsmooth down there causes a hell of an effect.

I've been told it's weight, but to be honest, I've never seen a difference, whether carrying 100 gallons of fuel or 200, water full or empty.

Yes I can see it will make a big difference on little boats where an extra ton is a huge percentage.

The guy slurry washing the fisheries protection boat said it had to be done, because it was using to much fuel and was using about half as much now.

What are your experiences.
Click to expand...

I had my Corniche done, you know the full unfortunate tale of the soda blast so I will not bore you with that again.
A friend took it back to shiny gel with an electric chisel, fantastic job, gel looked brand new.

I had to have it done cos the hard antifoul was so thick it just flaked off in huge chunks, painted over it so it was really uneven.

After it was stripped I applied Primer and two coats of hard, looked as good as brand new and it stayed on.

Performance wise, no change at all other than at the end of the season there wasnt any patches of fouling on bare areas that used to flake off.
I had the boat 6-7 years cruising 1700-2000, I knew exactly how much fuel I used and would have noticed a difference in speed and or fuel consumption but there wasnt any.
Volvo ADAQ41's

I guess your performance is down to weight, take all the stuff off you never use.

lift raft
dinghy
outboard
spare derv
spare props
kedge anchor
spare chain
spare warps
tools
spare filters
Drinks, alright thats going too far but could you cut down on the mixers ?:D
 
I have often wondered what a difference removing all the old AF would make. My Princess 560 must have plenty on here bum, (1993) Mind you when she first goes back in with new AF she will pull 25 knts in warm med waters, and with twin 485's thats probably not far off her original top speed.

Be nice to hear from someone who has done it
 
IMHO, removing 22 yrs of antifoul won't make a huge amount of difference. How much antifoul do you put on every year? Maybe 10 litres? Well that's about 10kg. Considering that some of that would evaporate on drying, some would erode and some would just fall off, I reckon you're adding less than 5kg per year to MF. So over 22 yrs thats about the extra weight of one fat bloke (eg ljs) on your boat and he's maybe worth 1 knot. OK removing the old a/f and repainting would probably make yer bottom a bit smoother but I can't see that making much difference. I reckon clearing the boat of 11 yrs of cruising detritus and refettling the props would make more difference
 
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