Epoxy or fibreglass over keel--need zinc?

[bill]

I originally posted on the catalina 22 forum but no reply. Perhaps this wider posting will get me some responses. Question is whether or not to put a zinc through a keel that has been covered with fibreglass=the new style C22 swing keel, or through the epoxy coating placed over old iron swing keel or over fixed shallow draft keel. Purpose of epoxy is to prevent entry of sea water an so eliminate keel corrosion.But if one now screws a zinc to the keel the screws penetrate the metal and make potential path for sea water to get to the metal. Wont this defeat the purpose of the epoxy, or of the glass covering over the new typse swing keel? On theother hand without a zinc there are metal parts at the pivot of the swing keel and of course there are the keel bolts on the fixed keel. The metal parts on the swing keel are below the water line--so without zinc on the keel how do you prevent their corrosion. On the fixed keel your alright as long as the epoxy remains intact, especially aroung the seam between keel and hull. But if this should leak then youve got water that can seep to the bolts.So what to do--do you fasten zincs through the keel? If so, what is the use of the epoxy or the glass ?

 

[Doug]

Reason for Zinc

Unless you are bonding your electrical system to the keel, I don't see why you would want to attach one. You whould have one on your outboard, and that should be sufficient for the boat.

 

[mg]

if i had a swing i,d put on a zinc

especially in salt water .you still have dissimilar metals and any loose current in the water will cause electolosis. there is quite a bit loose in most marinas. i think that if you epoxy that it protects from some oxidation of the keel but you need 5-6 coats depending on epoxy type to actually seal out the water. the fiberglass board i believe was simply for a better underwater shape. if i had an iron swing keel id put a kit in the pivot pin, epoxy the keel with VC TAR put a zinc as close to the pivot as i could. and go sailing with the thought i wont need to mess with it for the next 5-6 years unless i was eating zincs like crazy. good luck ng