rossd 16 Posted September 27, 2015 Share Posted September 27, 2015 I am not to sure how to proceed here. I can understand damage history to the leading edge after 40 years but the hole is a bit of a mystery to me. Its about 20mm deep at deepest and the bronze keel bolt is exposed the lead is sort of powdery but I have got it mostly back to solid lead apart from one small hole going down. I was going to epoxy it up but not sure how to prepare the lead for epoxy. Also what has caused this and will it happen again? I was thinking of casting flaw or electrolysis. Quote Link to post Share on other sites
Island Time 1,235 Posted September 27, 2015 Share Posted September 27, 2015 Powdery lead is likely to be electrolysis. Are there any anodes on the keel? Quote Link to post Share on other sites
rossd 16 Posted September 27, 2015 Author Share Posted September 27, 2015 No, not when I brought it 7 years ago or since Quote Link to post Share on other sites
wheels 543 Posted September 27, 2015 Share Posted September 27, 2015 No prob. Just clean it back, mix up a plaster of some cement and sand and for a few bucks you are all.....oh ooops, wrong Forum It won't be electrolysis. That would be all over, not just one hole. Yes the white powder could be, but that is local to the Brass screw and Lead, not the cause of the hole. It is likely possible that the hole was for the screw/bolt and epoxied. The epoxy has leaked, and the corrosion has popped the epoxy plug out. Clean and fill again. Epoxy will not adhere perfectly to lead., but then nothing will really. You could try a soft filler like Sikaflex or similar. Quote Link to post Share on other sites
rossd 16 Posted September 27, 2015 Author Share Posted September 27, 2015 Photos didnt come up. Second attemp Quote Link to post Share on other sites
Island Time 1,235 Posted September 28, 2015 Share Posted September 28, 2015 No prob. Just clean it back, mix up a plaster of some cement and sand and for a few bucks you are all.....oh ooops, wrong Forum It won't be electrolysis. That would be all over, not just one hole. Yes the white powder could be, but that is local to the Brass screw and Lead, not the cause of the hole. It is likely possible that the hole was for the screw/bolt and epoxied. The epoxy has leaked, and the corrosion has popped the epoxy plug out. Clean and fill again. Epoxy will not adhere perfectly to lead., but then nothing will really. You could try a soft filler like Sikaflex or similar. Wheels, I'm not so sure about your comment re electrolysis. I had one patch of lead on my keel that always blew off the paint, was powdery and ate some of the lead. Tried filling it, and it did it again - several times. Filled it again and added an anode to the keel and have not had the problem since. I always assumed that the problem area must have had, for some reason, a lower resistance path to the sea than the rest of the lead, but that is just supposition... Ross, if it were me, I'd clean out the hole as much as possible, probably with a grinder. Don't damage the bolt though. Leave it rough, and while still shiney, fill the hole with epoxy... However, one of the real boat builders on here might have something to add/change or suggest? Quote Link to post Share on other sites
wheels 543 Posted September 28, 2015 Share Posted September 28, 2015 Arrr, a picture is worth a thousand words. It was awfully hard to visualise. Wheels, I'm not so sure about your comment re electrolysis. What do you call it, semantics is it? There's Electrolysis, which is chemical decomposition produced when passing an electric current through a solution containing ions. Galvanic corrosion which is an electro-chemical process where one metal corrodes in preference to another when both metals are in contact, in the presence of an electrolyte. Both related, both very similar, yet different and usually seen as a very different issue on a Hull.What we have here now I see a pic, is a Galvanic action taking place between the Brass and the Lead. And maaaybeeee, I say hesitantly just at the mo, but that laminated timber, any chance that is Tanalised?? It may also be part of the picture if it is and if it gets wet. It may just be the picture, but it looks like it is treated and the green tinge to treated timber is caused by Copper and often Arsenic.Adding an anode will stop the lead from being eaten away yes. But that is only because the anode gets eaten away instead. So you could say, the real problem is just being masked. Maybe that is an easy fix in the end. But...Obviously in this case, the "system" once worked, but isn't now. For Galvanic issues there has to be three parts to the story. Metal part A, Metal part B and an electrolyte connecting the two and bingo, you have a Battery but sadly no Bulb. Just like fire, remove one of the three and you don't get fire...I mean eating away of the metal. So if it can be properly sealed so no water ever gets in there, the two metals should not be able to get all frisky with one another.Another way of dealing with it and is why sometimes it is dealt with this way in some Boats, is to earth all the Bronze bolts inside the Hull so they are connected together and to the main Anode. That is like "shorting the battery", stopping the electrical flow. Or of course, as IT suggests, another anode on the Keel. Quote Link to post Share on other sites
Island Time 1,235 Posted September 28, 2015 Share Posted September 28, 2015 Yep, fair point. You know way more about this than me! Good to learn more... Quote Link to post Share on other sites
rossd 16 Posted September 28, 2015 Author Share Posted September 28, 2015 Well the holes quite big but the photos are huge! Thinking about this that keel has had a big whack in the past as there are repairs inside at the aft keel end so this probably opened things up at the forward end both between lead and dead wood (or whatever its called) and the laminate. This probably let water into contact with the bolt (although has always been dry inside) and started that galvanic action Wheels. Think I will put on an anode cannot do any harm? How do you work out what size? 400 kg each keel from memory. Quote Link to post Share on other sites
Chewing Gum 17 Posted September 30, 2015 Share Posted September 30, 2015 Bolts are probably silicon bronze. If they were brass it wouldn't last 5 minutes. Brass has no place on a boat. I have never seen corrosion of lead like that, I guess it could be tanalised timber as wheels says causing the problem. Anode on the lead could be worth a try. We do have all our through hull fittings bonded to the anode - seems to work. That bolt seems very close to the top of the lead, maybe it is just securing the wooden keel stub ? A longer bolt would probably be a better bet (either silicon bronze or monel - not stainless or brass). You could possibly fill the hole with lead ? (Clean existing lead back to shiny first and undercut so lead stays put) Quote Link to post Share on other sites
rossd 16 Posted October 1, 2015 Author Share Posted October 1, 2015 I think that sub keel would be kauri like the rest of the boat. Built 1974, I don't think it would be tanalised. Getting molten lead in there to a vertical finish would be a mission, bit more than making a sinker. Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.