Originally Posted by babylonlarry
Redbopeep, thanks for the link - good stuff there.
Silver Raven, Info on my boat and it's bottom:
She's a Tartan 37 not all that big. I have previously used ablative paint and three gallons did not get me a third coat at waterline and rudder. She seems to sit more than move so I have decided to go to a hard modified epoxy paint. I figure more is better as I do not haul out very often. I will look into tetracycline, maybe in addition to pepper. Can't use TBT. The only commercial biocide additive I found was from seahawk Bio-Boost ZPT Anti Fouling Bottom Paint Additive
The active ingredient is zinc omadine
They claim that it may cause instability in other brands of paint ???
Larry. I've been in the marine & chemical business all of my life - of course they would claim that - that's how they sell more product. That's a no-brainer, for sure & probably not all that close to the truth.
As I've always been required to apply a very smooth antifouled bottom - finished product - - I've always thinned my base antifouling & usually sprayed in on - - thus probably used less material for a greater surface area. Better or not is not the subject here.
I've always applied a few coats & then let them dry until firm to the thumb-nail push test. Then a few more coats - etc etc.
With hard or semi hard antifoulings - it is extremely important to let the solvents escape & not get trapped in under the dried surface & not be able to excape. The more solvent escapes - the harder the antifouling gets - the harder the antifouling gets - the longer it lasts. All of these 'little' details argue well for great cost effective job completion.
Is the coating - 'hard modified epoxy paint' an antifouling - as such - or just a modified epoxy for underwater use? I personally - would have some reservationsw about adding anything to an epoxy formula without have done a test - prior to mixing-up the whole lot. Can't see why it wouldn't work but it is wise to remember that the biggest factor in play with all jobs that are imnportant is that - MURPHY is always in charge - not you - regardless of how hard you tell 'him' otherwise.
Unless 'modified epoxies' are used very carefully they rarely achieve their top level of quality, especially so with the attention to detail in the preperation of the surface you are wishing to apply them onto. That is critical.
If the 'modified epoxy' is in fact an antifouling then it already has several additives & a few more (all in moderation - of course) shouldn't mess with the formula doing its best possible job.
I agree that you sure do need that 3rd coat around the waterline & especially on the rudder, if not a 4th coat - - they sure are high-growth areas.
TBT is good but not all it was cracked up to be - a bit like the old copper additives in an ablative antifouling - - & - there is not doubt that both were screwing up the oceans.
I've twice used a product out of the UK called 'Copper-bot' which I remember as being a highly ground copper powder that I added to a clear antifouling. The 2 chaps whose yachts I did were sailing around the world in the rally - at that time. Both contacted me several years later (4 to 5) from England - & said the antifouling that I'd applied here in Cairns, Far North Queensland - was still working - & so well that they weren't even getting 'slime' on their boats bottoms (gota be careful wording that) as they were both retired Admirals in the British Navy.
I agree with you that - more is better - however the 'more' needs to be applied at the top end of 'properly & ALL the solvent must be allowed to exit the solids of the antifouling coating left on the bottom.
I'm sure you're off on the right track & wish you good progress with your task. Ciao, james