How much effect can fouling have?

My SR25 spent long periods stationary at HYCO in UK for years ... I would only use her on return to UK couple of times a year ....

Finally I decided to move her to Latvia and she was lifted. I had long before - years before - stopped wasting time with Anti Foul paint ... so expected to lift half of Chichester Harbour growth with her .... but :

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We were all amazed .... a quick powerwash and she was ready to go ...

Arrival at Latvian home ... 4 days later ... only having had that powerwash ... nothing more ...

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And for the record - I admit she's stayed Baltic and most time at bottom of garden in FW ..... since 2007 ... with occasional winter lifts and a home powerwasher only.

This is her when lifted for keel repairs :

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A hardish coating of scum like film ... but reasonably smooth.
 
I’ve spent the last year complaining that boats that shouldn’t be faster than my boat kept overtaking me under sail. Had the antifoul and prop clean done a week or two ago (after two years in water) and I’m blasting past all the boats now. Coppercoat next year then.
Once you are coppercoated you can save on lift out costs. My boat stayed in the water and I just had a diver to clean and grease the MaxProp occasionally.
 
Once you are coppercoated you can save on lift out costs. My boat stayed in the water and I just had a diver to clean and grease the MaxProp occasionally.
Indeed. Mine is a lift keel boat so very easy for me to dry her out on the beach too. I totally get that CC has mixed reviews, I’m just done with antifoul paint and it’s application.
 
I went out yesterday and found that I was down on motoring speed by about 1/4 knots. I didn't launch until June but used only one coat of cheaper a/f. The engine was running as smoothly as normal and I believe that the prop is still clean with its Trilux. Before I a/f-ed the prop I would find the engine sounding rough by this time of year with a fouled prop.

Fouling can have some odd effects. A few years ago at about this time the boat developed a strong pull on the helm to one side even as slow as 2-3 kn, whether motoring or sailing. By the time we lifted out I was seriously concerned that something had badly affected the rudder, in spite of no obvious reason for damage. By the time I saw it after being lifted it had been pressure-washed, but I was relieved to find no obvious fault, and at the spring launch everything was back to normal. An engineer once told me about a powerboat with c 500hp whose owner complained that it wouldn't plane and didn't believe that this was due to fouling until it was proved after cleaning. Apparently modern engines will go into anti-pollution mode if they detect an overload, and no amount of extra thrust would get the boat moving fast.
 
My boat - a Bav 30 - has suffered a marked decline in motoring performance, from a cruising speed of c. 6 kn to 4kn. (I can't really comment on sailing performance because we haven't been out enough to assess ☹️)

The engine has been thoroughly checked - fuel quality and lines, air filter, exhaust elbow, compression - all good. I'm now beginning to wonder whether a combination of foul bottom and prop (fixed 2 blade) could be the cause?
A fixed 2 blade prop with a bit of growth makes it pretty inefficient.

Maybe worth a dive to the prop for a quick clean, or at least a camera down to it it assess. If you can clean the prop you may be fine with the boat performance for the rest of the year. Stick a broom under the water and you will soon detect level of barnacles on the hull, though harder to feel softer growth - though you may well see what comes off as you bring the broom up. Is the prop antifouled?

Really, if it is after June (assuming a spring launch), and your boat is increasingly slow, it will almost always be fouling, either on the prop, or on the hull.
 
Sadler 32. Antifouled by builders, launched March. Easy 6knots motoring. Medway based. No mid season scrub. Lifted out October or November. Similar revs, down to 4 knots.

On lift out, found the builders hadn't antifouled where the cradle supports had been Four square patches covered in barnacles. (I had wondered when swimming why it felt particularly scatchy here and there).

More generally, found it was worth drying out to wipe the slime off before departing on the summer cruise. Otherwise we lost up to a knot of boat speed, particularly when sailing.
 
Cradle supports can be a problem. The usual thing in our yard is to leave the dregs of one’s a/f paint under the boat with a small manky brush, which the chaps will use to paint the patches at launching. I used the more effective Optima for many years but this needs an hour or two to cure before immersion and I had to get the supports lifted two at a time while in the cradle in order to paint the patches when doing the main a/f, which was a hassle. Better would have been to get the yard to paint the patches while in the slings and let it cure during their lunch hour.
 
9 kts sounds rather a lot for a 25' motor sailer.
I was thinking that. A displacement hull will do JUST over the square route of its water line length of 23 foot waterline so 4.8 knots plus a little bit say total 6 knots but he has a very big engine so perhaps it semi planes . Just a thought.
 
I was thinking that. A displacement hull will do JUST over the square route of its water line length of 23 foot waterline so 4.8 knots plus a little bit say total 6 knots but he has a very big engine so perhaps it semi planes . Just a thought.

You do realise that the waterline length formula is to determine the speed at which a boat will achieve without excessive 'thrust' ? Its a technical figure - that's all.

Try explaining why 'Barracuda' - anyone remember that boat ? The prototype was recorded achieving 25kts .. surfing on trip from north back to south ..

My 25ft 4 ton Motor sailer can achieve regularly 5kts under sail .... and has been logged at over 7kts ....
She has a 43HP Perkins 4-107 with large 3 blade fixed prop ... and cruises with that engine alone at about 5kts ... but will hit 9kts max throttle in calm waters.

Its same with any moving object ... there is a power figure that moves the object to a reasonable figure and then there is a 'barrier' - a resistance to pass that figure. It takes a greater increase of power to cross that 'barrier' than getting up to it. Each increase after that involves an even greater rate of power increase.

I love it when people call into question such as this ... with no factual back-up - keen to make comments !!
 
At my club, I can scrub off for about tenner so I didn't bother with antifoul for Jissel. I tried a load of different antifouls, including Coppercoat, as I got some for free, but nothing worked, so I saved £80+ a year and just scrubbed off a couple of times during the season.

On Jazzcat, the eroding antifoul I put on didn't work - not sure why I thought it might on the same drying mooring, so all the eroding stuff that hasn't eroded will be coming off this winter, a couple of coats of epoxy, then I'll try some hard antifoul, not because I think it'll work any better, but it may make scrubbing off easier.
 
Some boats on our river have so much growth, I doubt they will move at all.

Don't know if still offered .... but a famous Marina company used to offered a service where boat would be literally contained within an envelope of treated water alongside ... it being literally like a paddling pool affair the boat sat in - separated from surrounding 'normal' water ...

Offered due to the long term 'static' boats seen in all marinas.

I knew of many boats in UK - that Marina had a schedule set of lifting boats that had agreed / paid for such service on a regular basis - just to scrub off and then back afloat ... boats that literally rarely ever went anywhere ...
 
In Summer 2007 I anchored in Syracusa for about 3 weeks, on the way to Malta. When I lifted the dinghy it was covered in barnacles which took some shifting, and I could not get more than about 5 knots out of her on the flat calm crossing to Malta, (normally 7 knots was common at full throttle, and 6 knots at comfortable revs - Moody 44).

When she was lifted in Spring 2008, we found her hull thick with barnacles.
 
It's not only barnacles....

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Several 'well prepared' competitors had to retire from both Golden Globe Races due to the effects of fouling.

I helped move a 32' boat, laid up afloat for 2 years, upriver from the Tamar to Treluggan Boatyard, which looked like the above when lifted. We managed less than 1 knot over the ground, tide assisted.
 
Once tried to move a sailing yacht boat that had really heavy fouling. Max speed about 2 knots under engine, under sail in a breezy 15-20 knots wind could get about 3 knots. Steering and handling absolutely appalling.

At launch with a clean freshly (quality) antifouled hull I get 7.8 to 7.9 knots at max revs. By now in early Sept with minor slime and trace of weed at waterline I can only get 7.3 to 7.5 knots. This is a cruising boat, not a polished bottom racing boat. I use the max speed test to see if I need to persuade someone to swim and clean the prop. Prop condition makes a lot of difference: a lot of benefit from cleaning the prop, if you can do it.
 
Once tried to move a sailing yacht boat that had really heavy fouling. Max speed about 2 knots under engine, under sail in a breezy 15-20 knots wind could get about 3 knots. Steering and handling absolutely appalling.

At launch with a clean freshly (quality) antifouled hull I get 7.8 to 7.9 knots at max revs. By now in early Sept with minor slime and trace of weed at waterline I can only get 7.3 to 7.5 knots. This is a cruising boat, not a polished bottom racing boat. I use the max speed test to see if I need to persuade someone to swim and clean the prop. Prop condition makes a lot of difference: a lot of benefit from cleaning the prop, if you can do it.
I don’t use maximum power but I know that I should get six knots plus 0.1 for every 100 RPM over 2000 with everything clean.
 
Big thread drift here
The only benefit of Coppercoat is not having to get under the boat sanding down old A/F every year
In my mind that is a big plus
Also there is the ever rising cost of the A/F paint. Not to forget the ancilliaries , such as rollers, thinners, wipes, gloves, masks, overalls etc.
What one does have to do, after the launch at the start of the season, is budget for a mid season scrub.
I have spoken to a number of staff in St Helier, Burnham, Inverness, Dover & Shotley, who all say that Copper coat is no better- in some cases worse- than ordinary antifoul paint. None of them has said that it actually works as claimed. I have spoken to owners who are happy, but generally their form of "happy" is a thick film of speed reducing scum, all over the hull & long weed at the waterline. I have spoken to owners who are very disappointed I currently have long furry growth 50mm plus long, well below the waterline. I am far from impressed & if I had been able to continue my holiday, I would have had the hull jetwashed in Cherbourg.
I have never seen any claims about Coppercoat being a superior antifouling - just that it does not deteriorate in effectiveness over time and typically remains effective for up to 10 times longer than conventional antifoul. In heavy fouling areas it benefits from a mid year jetwash just like most other AF. That is all my Coppercoat needed in 6 years despite being in the water year round except for up to 2 weeks mid summer.
 
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