Anodes

[Guest]

The wooden frames on my boat are stiffened with stainless supports welded into a stainless keelson. Around each frame white crystals appear and the wood is going soft. I am told this is due to over protection by the anodes. I have had the boat checked and I am assured everything is OK. I am tempted to remove the anodes completely. Any ideas as to how can I protect the wood and at the same time stop my prop and fittings from dissolving ?

 

[AlexHall]

Hi,
The setup isn't very clear, but as it is I would dare to say that it is not an anode problem.

I assume the stiffeners are bolted through the frames and all. If so how are they sealed from the outside? Stainless bolts? This could be problem area.

How long has this arrangement been in place? If its a while, remove one of the bolts with the most growth around it and inspect. There might be a surprise for you.

Your prop and shaft are not linked to your S/S keelson and frames, or are they?

In any case prop and shaft should have seperate anode on itself.

Your main preoccupation should be the soft timber around the fastenings for stiffeners. It could be that the timber is getting "burnt" but not by electricity but by chemical reaction between moist timber and fastening, especially if S/S.

Sorry

 

[johnlilley]

Anodes can cause extensive damage to timber on wooden vessels, particularly on the internal areas of hull wherever a particular metal item is fitted in the timber and has been wired to an anode. When the anode works, chemicals build up around the metal item being protected (electrolytes) and these cause extreme breakdown of the timber structure surrounding the metal. Look on the internal fastenings of the anode, sterntube, rudder tube etc. for signs of crystallistaion which eventually will cause softening and serious failure of the timber. Sometimes it is safer to cut the wiring, wash the internal areas with vinegar and fresh water and accept that it is easier to replace metal parts than the timber that surrounds them if that is the only option. My web site www.seasurveys .co.uk does give further info.
Regards John Lilley

John Lilley, John Lilley & Associates, Web site www.seasurveys.co.uk for osmosis /timber problems

 

[Mirelle]

Things are most definitely NOT "OK"

Stainless steel is not really a suitable material for use in close contact with wood structures, but you have got it so there we are.

Get rid of the anodes, and cleck your wiring very carefully indeed - you may very well have stray current electrolysis. Be religious about putting the batter master switch off, if you have an electric bilge pump, treat it with the gravest suspicion. Ditto a shore power connection.

 

[Peterduck]

You have a serious problem. The stainless floors/keelson is most unusual practice, and I suspect that this component may be reacting with the fastenings which hold the planking and frames together. These fastenings are usually copper or a copper-based alloy, eg. bronze, and are quite incompatible with stainless steel. The crystals are lye, a caustic salt, and as stated by an earlier correspondent should be washed away with vinegar. I really believe that the stainless steel keelson/floors will have to be removed and discarded. To repair the wood frames will depend on how badly degraded they are. Scrape or sand the frames back to sound wood and see how much wood you have left. It may be sufficient to laminate a veneer of wood on top of the remaining frame, or the section of frame may need complete replacement. Epoxy the new wood to the old and replace the frame/plank fastenings. You may also need to fit new floors, as the originl floors will have been removed by whoever built the stainless steel floors. Keep all fastenings compatible with whatever is holding the rest of the boat together.

 

[Guest]

Many thanks for the replies. You have now confirmed my worst fears. The boat is a 50 foot S&S ex Admirals cup, built 35 years ago in Utile with Acacia frames. She has a solid, and I mean solid stainless backbone complete with lifting eyes. The mast is stepped onto this backbone and the keel is also through bolted through it. The backbone has radiating frames that bolt (with SS bolts) fore and aft inside the boat to the real wooden frames, they also extend to the deck level to function as chainplates. This being the case I am not in a position to move or remove anything. It's where the wood and the stainless frames meet I have the problem. The hull fastenings are all silica bronze and in good condition. The confusing thing for me is the problem is localised in certain areas of the boat, often in places well away from any anodes or wiring. I'll take up the idea of removing the anodes, washing off with vinegar and having the wiring checked again. Is it possible to check your own wiring for stray current electrolysis ?