I have just noticed on a Wharram forum that someone was wondering about our use of copper powder and epoxy as the final coat beneath the waterline. Although Tom has explained our reasons for this method in a comment on our blog, it is not that visible, so I have reproduced it here:
Good Day Dan,
Thank you for your comment, we very much enjoy the internet feed back and interaction as we are quite isolated from other builders.
We have put this mixture on mainly because it is a very hard and robust surface with very good sealing properties. The process is also a recommendation in Bob’s plans. Bob suggests on completion of bottom fairing, quote “This next bit is optional, I do it on my own boats, you make up your own mind”. He then recommends 50/50 by weight and to not to get it any where it should not go as it is, Quote “a bugger to get off”. We also have found that it is very, very hard, therefore in our climate, and I guess in yours, we note application should be done all at once as sanding down once cured would be bloody difficult. We found the 1:1 ratio is about the limit of copper that can be kept in suspension, and then only if continually stirred during application.
I don’t know about the effectiveness over time, however we saw Bob’s Mango about 18 months after launching and it only had thin slime evident. Please note that Bob’s boats are designed to be dried out regularly and therefore a quick wipe down with a 3m green pad (in the hands of all crew and guests) as the hulls dry out would take little time and suffice to slightly expose the copper. Obviously not an easy option for hulls that draw more than 500mm.
On ‘Binary” we have not touched the copper/epoxy surface, however the copper is leaching slightly as there is a greenish oxidization happening. This very evident where the hulls have been splashed with water at the front of our “shed”. During a second look whilst taking these photos, if I wiped my hands on the surface away from the splashed areas, I noted the surface is all leached and a green powder came off on my hand. This pleases me as it means little effort if any, would be required to release the copper. Please note the epoxy used is regular West System RD105 resin and HD206 hardener. Although I called this antifoul, I only think it is meant to be just a hard finish with some antifoul properties. It does however exhibit good properties and I will give it a go.
Considering the leaching I have found I am happy with the epoxy not needing any assistance to expose the copper. Please see photo.
Regards, Tom
The Scrumble Project 