Hi PitchPolePhobie!
Here's a link you might find interesting:
https://www.bottompaintstore.com/blog/b ... tom-paint/
just one of several articles out there on the subject....
When we had Over Easy done the professional yard they used an abrasive wet blast done by a certified professional to clean off as the marine crud , crustaceans and old unprimed bottom paint that may have been 20 years old and in bad shape.
Then several coats of an epoxy barrier coat of
Interlux Interprotect Epoxy Barrier Coat followed by several coats of
Interlux ACT Ablative Antifouling Bottom Paint.
This type ablative lasts whether one is in Fresh Water, Salt Water, Both (alternating between Fresh & Salt Water) and when drying out on the the trailer without needing to sand to reactivate (like copper coat type products). The copper type materials work by basically generating copper-sulfates in reaction to water...particularly more so salt water...which is aqueous (liquid) in nature and denser near the generating surface. Copper-Sulphates are toxic to most biologic (marine) organisims and plants. When copper type materials are removed from the water the air reacts with the copper to form copper oxides, including cuprous oxide, cupric oxide, and cupric hydroxide which are relatively stable (the green film color that forms on copper when exposed like on old buildings) and resists further degradation. Once the oxide forms further anti microbial / anti marine growth characteristics are inhibited . Hence the need to keep copper coated hulls in water and the periodic re-exposure of the copper base material granules just prior to re-immersion into the water for it to be effective.
The multi-environment and dry-out capability an important characteristic to note when selecting an ablative coating.
It goes directly to the basic chemistry aspect...
> An Epoxy barrier seals and protects the fiberglass hull from potential water migration and the resultant blistering that can occur.
This is of interest to us trailer sailers is that our hulls are by necessity a thinner animal and osmotic blisters can have negative impact.
This also prepares the surface to better bond with the ablative coating. (unlike the unprepared surface that was under our original).
By itself and Epoxy barrier does not really inhibit marine growth other than making a smooth surface (depending on how it is applied).
> An Ablative coating is designed to chemically dissuade marine growth and ALSO micro-flake away as the hull moves through the water.
The chemical aspect makes the coated surface a non-inviting / non-viable surface to marine organisms.
The micro-flake aspect allows what marine growth that does form to detach and fall/peel away from the surface due to the drag forces as the hull moves through the water. It does not sheet off, it ablates as tiny flakes. As such it periodically needs to be reapplied.
The frequency of re-application depends upon how the vessel is used but generally heavily used saltwater environment vessels that also sit for long periods of time can generally expect to get 2 to 3 years before needing a touch-up or reapplication.
Surface prep for re-application of an ablative coating with an intact Epoxy barrier layer is simple...Gentle power wash or light scrubbing with a hose and medium/soft brush...let dry throughly...and brush on.
Ablative coatings tend to be rougher than a plain gelcoat or painted surface but realistically one will not see any appreciable difference in top-end speed (inspire of what the pu99rists might be inclined to prognosticate as the hull of a MacGregor (like any sailboat) is primarily a displacement hull. Drag is relativistic to velocity and at the top speed of of about 25 MPH for the average Mac the drag co-efficient is not going to be significant due to the general boundary layer shear effects. Worse case I suspect (as no one has done a definitive hydrodynamic side-by-side or before-after controlled test) You might see a possible 1 or 2 MPH difference between a smooth surface vs an ablative surface. The drag and associated damage of marine growth is much much much more of an issue.
So far we have more than a year on our epoxy-barrier primer & ablative coating and have spent over 2,100 hours in water both in slip
and out cruising without any measurable marine growth in a full mix of Fresh Water / Salt Water and about 8,000 hours on the trailer (gotta get more time on the water!). ((Note: A 365 day year equals 8,760 hours))
We only do a light pressure wash at a distance of about 2 feet or more when we do it at all.
The Ablative surface looks as intact as it did when first applied.
The only thing we'd change would be to re align our waterline slightly higher in the stern as with the dual batteries and A/C (and all our stuff) it sits an inch or two lower than the 'from factory' applied waterline and some 'tea-staining' has become evident but that has
nothing to do with the effectiveness of the ablative coating...
Just relating our experience and opinion so far in our journey with Over Easy and what we've learned along the way...still more to learn and experience. Hope this helps some.
Best Regards
Over Easy
not sure what it is was or but has flaked substantially in last 2 seasons. I am on an Ohio lake docked for 5 to 6 mos that has zebra mussels. The park system experimentally partially treated the zebras this year so I didnt get hit at all. I am interested in reapplying an ablative barrier coat this winter to get ready for traveling next summer. What do you all recommend. I see barrier and ablative are different. I think I need an ablative coat.