How much Antifoul ?

[max_power]

Have you noticed in recent years that the amount of antifoul needed is creeping up when looking at the tins ?

Flag antifoul for instance seems to have a good write up and a keen price. But do you need much more of the stuff ?

I lifted below from their website the recommended litreage :-

The first figure on the left is the length of boat in feet. Then Fin, Full Keel and Motorboat. All in litres and decimal points.

20 2.9 4.4 2.9
26 4.1 6.2 5.4
30 5.7 8.6 8.5
35 6.8 10.2 12.8
38 8.0 12.0 15.0
44 9.4 14.1 17.3

 

[tillergirl]

Well I've always used Blakes although I swapped between Tiger and Titan (now back to Tiger) I get one coat out of 2.5 litres on my 32' long (but admittedly shoal) keel. In fact, keeping the bit left over each year and using it the next, I was able to put an extra free coat on her last spring as I had something like 2 litres left over from the previous year. I see from my little book I used only 2 litres in 1993, but usually 2.5. I know I'm sad writing this down but when it comes to the topsides (I'm wood you see) I can never remember how much undercoat etc.

 

[Twister_Ken]

Point taken

Mine's 28' long keel using Blakes and they recommend 5 litres.

With your fellers, I'd need an extra 2.5l tin.

 

[oldsaltoz]

G'day Max,

Perhaps a look at the % of solids in each brand will throw some interesting light on this subject.

Avagoodun Old Salt Oz [kool]

 

[Gaffer]

The problem is that no two people apply paint to the same thickness. One owner I spoke to used 3 litres for one coat on his 22 ft fin keeler, and another used less than that for two coats on his 36 foot long keeler.

Eroding antifoulings only work if there is paint there to erode. The more you apply the longer it will work, and if there is any left on the hull at the end of the season it will still be active for the following season. If you have any left in the tin the best place to put it is on the boat, go round the waterline, leading edge of the keel and rudder where the most propeller wash is.

Hard leaching antifoulings will loose their activity as soon as the boat is hauled out and overcoated, which is why they always build up over the seasons.

Generally speaking the manufacturers recommend a wet film thickness (WFT) of 100 microns. If I am not mistaken that means a coverge rate of 10 square metres per litre. Per coat

You can calculate the surface area of your hull with the use of a formula which takes into ccount the waterline length and beam, but the best thing to do is to ask the boat's builder or designer who will give you the most accurate figure.

If you can find out what the total solids (or what is called in the industry as non volitile) of the product is then you can calculate what the dry film thickness (DFT) will be.
IE. paint 50% non vol...... WFT 100 Mu .... DFT 50 Mu.
paint 40% non vol......WFT 100Mu........DFT..40 Mu

Hope you find this of assistance

 

[dickh]

I used 5 litres of Flag on a Jaguar 27 fin keel - 2 coats. With about ½ litre left over which I put around the waterline, front of keel & rudder.

dickh
I'd rather be sailing... /forums/images/icons/smile.gif<P ID="edit"><FONT SIZE=-1>Edited by dickh on 20/01/2003 13:14 (server time).</FONT></P>

 

[PeterGibbs]

Biggest factor in my experience is whether you are mainly moored in a marina or stream, followed by how much the boat is on the move - since this affects how well the paint can do its job. For marina moorings with their concentration of biocides, one good coat overall, doubled up on the leading edges and on the top 30 cms at the waterline where light can encourage growth. But for river moorings, at least two full coats all round and then be prepared to brush off growth a couple of times a season.

For marina mooring, I find the second tier products perfectly acceptable, leaving only a slime at the end of the season (my standard of effectiveness). But for river moorings, the higher percentage of solids in Blakes and International will probably pay off.

Experimentaiton is the order of the day because application instructions are, as you realise, only averages, and then weighted in favour of the producer's margins!

Incidentally, over-painting is not only a big waste of money, but leads to flakely buildups that require disagreeable scraping to render the surface even for the next season - as we all discover eventually.

PWG

 

[jimi]

I always find I actually need about half a litre more than I actually buy!