Anti fowling - Hard on top of self polishing?

[Tim Good]

Question 1: is there a easy way to determine if I have hard or self polishing AF on my boat already?

Question 2: if it is self polishing, is it ok to paint hard on top?

Question 3: I intend to have the boat on a drying mooring for a few months in the summer in additional to a pontoon birth. Do I really need hard anti fowl?

Prizes go to those able to answer all three

 

[johnalison]

1 Ask the previous owner. Alternatively, if it scrubs off it isn't hard.

2 I don't think any hard antifouling can be out on soft, though sometimes the other way round. If in doubt, reprime.

3 You will need anti-fowl to stop gulls messing up your boat. The bottom will need antifoul which won't work very well and will need at least one mid-season scrub.

 

[VicS]

Question 1: is there a easy way to determine if I have hard or self polishing AF on my boat already?

Question 2: if it is self polishing, is it ok to paint hard on top?

Question 3: I intend to have the boat on a drying mooring for a few months in the summer in additional to a pontoon birth. Do I really need hard anti fowl?

Prizes go to those able to answer all three

1. I imagine you mean eroding when you say self polishing. Lightly scrub it with water and a brush or even a coarse sponge.
Eroding will come off easily. Hard should not.

2. Whether it's hard or eroding is not the main concern when over-coating. Antifouling manufacturers produce tables of compatibility and treatments necessary when over-coating different types. However if you do not know the type already on there you have a problem. You wont be able to tell if it can simply be over-coated with your chosen product, if it will require a barrier coat or if it will all have to be stripped off!
Simply over-coating is the most likely to be all that is required but ....?

3. The type of berth is, as such, not important. A hard type is likely to be required if the boat is on a drying mooring or pontoon berth.

.

 

[Twister_Ken]

Hard should not go on top of soft.

Soft can go on top of hard.

 

[Tim Good]

2 I don't think any hard antifouling can be out on soft, though sometimes the other way round. If in doubt, reprime.

Thanks John. So repriming will be ok rather than having to go the whole hog and strip everything off?

 

[Twister_Ken]

Thanks John. So repriming will be ok rather than having to go the whole hog and strip everything off?

Not sure I'd be too happy with that, coz the primer will be sitting on top of paint that is designed to 'wear out' and will, at least partially, be in a worn-out state which will affect its adhesion. Thus, some primer might flake off over a period, taking your hard a/f with it.

But why not try it and see for a season? Worst that can happen is that she'll get mucky and you'll have to strip it all off 2012/2013.

 

[VicS]

Hard should not go on top of soft.

Soft can go on top of hard.

It may seem logical not to put a hard antifouling on top of a soft or eroding one but this is not in fact reflected in International Yachtpaint's antifouling compatibility chart.
http://www.yachtpaint.com/LiteratureCentre/antifouling-compatibility-chart-gbr.pdf

What is the source of your statement that hard should not go on top of soft.

 

[nickf]

Have got to say I had hard put on top of 3 layers of soft some 3/4 seasons ago with no problems.

 

[Tim Good]

But why not try it and see for a season? Worst that can happen is that she'll get mucky and you'll have to strip it all off 2012/2013.

Fair point. I play to dry out on some beaches and stuff in summer when I can give her a scrub anyhow.

 

[Tim Good]

What is the source of your statement that hard should not go on top of soft.

PBO

Which is why I'm after a second opinion

 

[VicS]

PBO

Which is why I'm after a second opinion

I'd go with what the manufacturers say. Their advice will be compiled by coatings technologists, not journalists.

 

[Giblets]

I'd go with what the manufacturers say. Their advice will be compiled by coatings technologists, not journalists.

Ouch! That could get you put in the sin-bin, Vic!

 

[Twister_Ken]

What is the source of your statement that hard should not go on top of soft.

Experience using Blakes (now Hempels).