Anti fouling a bottom like this

[Rum_Pirate]

Port and starboard bows


Both sides of rudder


Is it recommended, after a light sanding to put an ‘anti fouling primer’ on the hull and rudder and then antifouling

OR

just sand, clean dust and apply antifouling?

 

[Jonny A]

The latter, for me.

 

[Rum_Pirate]

The latter, for me.

Forgot to add: It is going on a Corsair F-27 trimaran which sailsat 12 knots plus, so good adhesion is paramount.

 

[geem]

Coppercoat would be my choice but lots more prep required

 

[Rum_Pirate]

Coppercoat would be my choice but lots more prep required

Unfortunately it is not available here.

Considering Antifouling, Islands 44 Plus Black Hard Gal
Antifouling, Islands 44 Plus Black Hard Gal - Budget Marine

 

[Spirit (of Glenans)]

Port and starboard bows
View attachment 146697 View attachment 146698

Both sides of rudder
View attachment 146699 View attachment 146700

Is it recommended, after a light sanding to put an ‘anti fouling primer’ on the hull and rudder and then antifouling

OR

just sand, clean dust and apply antifouling?

There should be no dust. Dry sanding of antifouling is unkind to the environment, abhorred by neighbouring boat-owners and deleterious to your health. It should be wet-sanded.
A primer (such as Primocon), is only required if the a/f is being applied to bare gelcoat, or when patching spots where it has flaked off.

 

[Spirit (of Glenans)]

Forgot to add: It is going on a Corsair F-27 trimaran which sailsat 12 knots plus, so good adhesion is paramount.

Normal a/f usually adheres pretty well, particularly to surfaces it's not intended to be on?

 

[Neeves]

If you have the need for speed, or are going to race her - keep her on the trailer and dry sail. However you will need to sand and polish the hull (but once completed - will serve for years).

There are commercial AF used for high speed vessels - so they offer AF characteristics but do not wear quickly. Jotun sell their's under their Sea Quantum brand and the other big AF manufacturers offer competitive product. Jotun have 4 formulations, differentiated by vessel speed, under the SQ brand

But these products are professional application only - and need some persistence and guile to source. You also need to use the yacht, frequently, and sail at speed (which is the reason you chose an F27).

If you did not buy for speed - you chose incorrectly.


I'd favour - dry sailing.

Jonathan

 

[Chiara’s slave]

Dry sailing a 1.5 ton tri is bloody hard work, or expensive. Any hard racing antifoul will do for the job. I definitely would use the antifoul manufacturers recommended primer first, after a wet sand, 240 grit. A little fouling is to be expected, but in your neck of the woods, taking her to a gently shelving sandy beach and giving her a scrub isn’t a hardship. I recommend the brush in your right hand, beer in your left.

 

[Spirit (of Glenans)]

Dry sailing a 1.5 ton tri is bloody hard work, or expensive. Any hard racing antifoul will do for the job. I definitely would use the antifoul manufacturers recommended primer first, after a wet sand, 240 grit. A little fouling is to be expected, but in your neck of the woods, taking her to a gently shelving sandy beach and giving her a scrub isn’t a hardship. I recommend the brush in your right hand, beer in your left.

...and don't splash a/f into your beer?
But seriously, I was given to believe, following the oft-repeated discussions on these fora, that if the new a/f was compatible with the existing, no primer was necessary. I have been slapping the same brand on for many years with no primer and no problems.

 

[Chiara’s slave]

...and don't splash a/f into your beer?
But seriously, I was given to believe, following the oft-repeated discussions on these fora, that if the new a/f was compatible with the existing, no primer was necessary. I have been slapping the same brand on for many years with no primer and no problems.

That boat was last antifouled years ago, no idea what they put on her. A barrier is very much the thing to do.

 

[Spirit (of Glenans)]

If you have the need for speed, or are going to race her - keep her on the trailer and dry sail. However you will need to sand and polish the hull (but once completed - will serve for years).

There are commercial AF used for high speed vessels - so they offer AF characteristics but do not wear quickly. Jotun sell their's under their Sea Quantum brand and the other big AF manufacturers offer competitive product. Jotun have 4 formulations, differentiated by vessel speed, under the SQ brand

But these products are professional application only - and need some persistence and guile to source. You also need to use the yacht, frequently, and sail at speed (which is the reason you chose an F27).

If you did not buy for speed - you chose incorrectly.


I'd favour - dry sailing.

Jonathan

If you are situated anywhere on Britain's Irish Sea coast, make the occasional foray across to Ireland, and prefer Jotun a/f, it would be a good idea to drop in to Howth and buy a few cans ( or drums) of Jotun from the chandlery opposite the fish market, where its sale is unrestricted. (No connection to either the manufacturer or the vendor)

 

[Spirit (of Glenans)]

That boat was last antifouled years ago, no idea what they put on her. A barrier is very much the thing to do.

Agreed. In that case that's the best practice

 

[Chiara’s slave]

Agreed. In that case that's the best practice

£50 worth of primer, it's a no brainer. As you can see, we have a similar kind of boat. We had an F27 years back. That’s how I know what a bastard they can be to recover to the trailer in a cross wind.

 

[Neeves]

In the grand scheme of things a barrier coat is not expensive (see Chiara's post) is easy to apply and removes any doubts over incompatibility.

Its not only best practice but a no brainer (though might be different - on a tiny island in the Carib).

Ideally you buy the primer from the same manufacturer from whom you buy the AF (but primers tend to be very forgiving of what the final product might be).

Jonathan

 

[Rum_Pirate]

...and don't splash a/f into your beer?
But seriously, I was given to believe, following the oft-repeated discussions on these fora, that if the new a/f was compatible with the existing, no primer was necessary. I have been slapping the same brand on for many years with no primer and no problems.

I don’t know what the brand is of the original AF.

 

[Chiara’s slave]

I don’t know what the brand is of the original AF.

So, a coat of primer first. We used to wiggle 2 oil drums under the ends of each float, 1 at each corner unfolded, then gently pull out the trailer with the car. A bit of ingenuity and cranking on the jockey wheel can lift the boat off the pads. Then you have the entire main hull available for sanding and painting. the floats are easy.

 

[gordmac]

Is it hard or soft? I would imagine putting soft on hard would be ok without compatibility issues, ask the makers? Hard on soft is a no go I believe. In the grand scheme of things 12kn isn't fast, I doubt any soft type would have a problem with that. Easy enough to get one that would be ok and just paint it over what is there?

 

[Chiara’s slave]

Is it hard or soft? I would imagine putting soft on hard would be ok without compatibility issues, ask the makers? Hard on soft is a no go I believe. In the grand scheme of things 12kn isn't fast, I doubt any soft type would have a problem with that. Easy enough to get one that would be ok and just paint it over what is there?

12Kn is for pottering. I have a photo of an 8 year old girl steering ours with the log in the background reading 17.5. Soft is unsuitable additionally because the boat can take the ground.

 

[gordmac]

My boat does over 30kn and cruises in the mid to high 20s, soft af works fine if you get the correct one. Taking the ground is a different matter, I don't know what that would do to the life of the stuff on the bottom.