Anti-fouling - Orwell Mooring

fredrussell said:
Well Im up at Debbages. I hadn't considered this before but It must be pretty brackish up there, at least half the day anyway during the ebbs, as the Gipping is flowing out straight past my beloved boat. Is this likely to be a good or bad thing re fouling?
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Did you know that Lord Haw Haw claimed the Germans had bombed Dagworth Dock
 
Various views here and interesting to hear Tradewinds comment on aluminium anodes - we have used them in salt and fresh and not just brackish and prefer them. That said I am wondering whether to g for zinc or Ali as we are moving from fresh to salt.

Putting a different dimension on the anti-foul question, anyone gone for coppercoat and have any views on whether it is worth the expense?
 
Greg2 said:
Various views here and interesting to hear Tradewinds comment on aluminium anodes - we have used them in salt and fresh and not just brackish and prefer them. That said I am wondering whether to g for zinc or Ali as we are moving from fresh to salt.

Putting a different dimension on the anti-foul question, anyone gone for coppercoat and have any views on whether it is worth the expense?
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Aluminium anode - yes in seawater and brackish water
Antifoul - seajet shogun 33 - was on the Orwell half of last season, then Thames - hardy any growth
Copper coat - if it's a new boat then yes as you can be sure it's dry. Old boat - only if you can be 100% sure it's dry as you don't want to lock moisture in. If any doubts then antifoul and regular keeping ashore over the winter to ensure it dries.
 
STOL71 said:
Aluminium anode - yes in seawater and brackish water
Antifoul - seajet shogun 33 - was on the Orwell half of last season, then Thames - hardy any growth
Copper coat - if it's a new boat then yes as you can be sure it's dry. Old boat - only if you can be 100% sure it's dry as you don't want to lock moisture in. If any doubts then antifoul and regular keeping ashore over the winter to ensure it dries.
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Yes, I have some sympathy with the point about the epoxy locking moisture in but I have heard it said that whilst it may do just that it also prevents further moisture ingress whereas traditional anti-foul will not do anything to prevent further moisture ingress.
 
Greg2 said:
Yes, I have some sympathy with the point about the epoxy locking moisture in but I have heard it said that whilst it may do just that it also prevents further moisture ingress whereas traditional anti-foul will not do anything to prevent further moisture ingress.
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If the hull is wet as the majority of old boats are then you want to be able to see if blisters develop and take them out in situ. At the same time you want the anti antifouled hull to dry regularly when on the hard.
Osmosis is a problem as much from the outside as it is with bad ventilation on the inside.
If you were to seal a wet boat on the outside and osmosis does develop eventually then the osmosis will no longer be cosmetic below the gelcoat but deeper in the laminate.
Therefore, I believe it not prudent to copper-coat an older boat or to buy a copper-coated boat that hasn’t firstly been copper-coated when it was still new.
 
If moisture can get in to the GRP very slowly from the outside surface, can it not escape very slowly from the inside surface (assuming it's not a closed-cell foam sandwich)? Unless you lock it in with epoxy on both sides that is. Just a thought.
 
MikeBz said:
If moisture can get in to the GRP very slowly from the outside surface, can it not escape very slowly from the inside surface (assuming it's not a closed-cell foam sandwich)? Unless you lock it in with epoxy on both sides that is. Just a thought.
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Moisture doesn't simply travel through the hull and can be attracted from the inside and outside.
The below is from Westsystem and explains the process in detail:
Blisters occur when water that has penetrated the laminate dissolves water soluble materials within the laminate and accumulates in voids or cavities below the gelcoat layer. The solution of water and water soluble materials, through the process of osmosis, attracts more water to the cavities to try to dilute the solution. The pres- sure of the accumulating water enlarges the cavities to form gelcoat blisters.
When water soluble materials in a polyester resin laminate mix with moisture that has pen- etrated the laminate, it creates an acidic fluid. This acidic mixture can attack the polyester resin throughout the laminate, severing the chemical bonds that hold the resin matrix to- gether, as well as the resin-to-fiber bonds. This process is known as hydrolysis. Once hydro- lysis has started in a polyester hull, the hull’s strength has been compromised and the potential for serious additional hydrolysis will never go away. If you own a fiberglass boat built with polyester resin, you should be aware that the potential for this problem exists. Gelcoat blisters can often be repaired before the laminate is damaged by hydrolysis. Keep in mind that gelcoat blisters can be an indicator of hydrolysis, and that hydrolysis can occur without the appearance of blisters. - hence my view of copper-coating.
 
My thoughts were prompted by comments about the epoxy 'trapping' moisture in the laminate. For it to be permanently trapped you would have to permanent seal both sides. I'm not advocating epoxying a damp hull.
 
I keep my boat on a mooring at Woolverstone. I’ve used Witham’s Admiral for years; the only anti-fouling with a Royal Warrant. It was brilliant as it lasted for two years with no fouling at all. Whatever they put into it was not so brilliant for the environment as it was stopped as it did not comply with EU law. I changed to their “Traditional” and that did not work at all so I now use Hempel Tiger with mixed results. I wonder whether Hempel change the formula because in 2017 it hardly worked but in other years it has. I now required a mid season scrub on the posts though as a green slime tends to form which never happened with the Witham Admiral.
 
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