Mike Fox Posted March 25, 2006 Report Share Posted March 25, 2006 My fibreglass boat needs a permanent pear-shaped anode, but the anode bolts have now corroded too much to keep them. I've a horrible feeling that they might be original....1989 vintage. The bad news is that the bolts appear to be glassed in. I've removed the nuts (eventually), but the threads below the hull have wasted away. I sheared one of the inside nuts, taking some of the bolt with it. The current ones are now unuseable. The bolts look just like studded mild steel thread, but tapping them firmly with a hammer will not loosen the bolts as fibreglass resin/epoxy was used to bond them in! I can see a number of choices: - Bigger hammer hitting a replaced nut to avoid damaging threads, either from inside or outside (but risks damaging the hull); - Hacksaw them flush, then drill them out (might go off-centre damaging the hull); - Hacksaw them flush, cover over with epoxy filler, hope they don't corrode further till next winter when I can do a permanent fix, and make fresh holes for the new bolts; - Call in a marine engineer/shipwright who would do one of the above and charge me handsomely. Anyone got any sensible suggestions? Thanks, Mike Quote Link to comment Share on other sites More sharing options...
Newboy Posted March 25, 2006 Report Share Posted March 25, 2006 I might be miles off track, but why would a grp hull need an anode? I haven't taken much notices of other people's boat, but mine has only an anode on the outboard. Quote Link to comment Share on other sites More sharing options...
Mike Fox Posted March 25, 2006 Author Report Share Posted March 25, 2006 The bronze seacocks for the loo etc are through hull, and bonded to the anode. Would rather lose zinc than a seacock! Mike Quote Link to comment Share on other sites More sharing options...
Newboy Posted March 25, 2006 Report Share Posted March 25, 2006 Told ya, nothing wrong with s-ing and p-ing over the gunnel..... None of the options sound promising. Do you really need the anode, isn't bronze sort of metal you don't need anode? (or is it brass?) Quote Link to comment Share on other sites More sharing options...
Mike Fox Posted March 25, 2006 Author Report Share Posted March 25, 2006 Trust me...it's needed! Mike Quote Link to comment Share on other sites More sharing options...
TomBettle Posted March 25, 2006 Report Share Posted March 25, 2006 I am no engineer so a pinch of salt needed. Can you not get a wrench on the bolt, leberal squirts of silicon around the hole and gently twist and tap it out. If you did a little bit of minor damage to the hull it won't be impossible to repair to a professional standard and not as pricey as you think. The most important thing will be water integrity. And yes, you should have the anodes! Tom Quote Link to comment Share on other sites More sharing options...
Afishionado Posted March 25, 2006 Report Share Posted March 25, 2006 Bl00dy hell anyone would think that I never wrote about a 1000 words on how an anode works and why one is needed Kam! As for the problem at hand......... If you try and drill them out, you are right, unless you are VERY lucky the drill will drift into the softer material. I am assuming the boat is ashore? If so I sugest the best method is working from inside the hull.I would think that a heavy lump hammer and a drift will work once the epoxy/resin that was used to retain them sheers. A heavy hammer used slowly is much more effective than a smaller one used frantically, it's all to do with inertia and mass. They will indeed be mild steel studding or bolts. I also think that grinding them off flush will be a good idea before even starting with the hammer as the heat generated by the grinding will also help the surrounding sealing material to loosen up. Mad Mike Quote Link to comment Share on other sites More sharing options...
Mike Fox Posted March 25, 2006 Author Report Share Posted March 25, 2006 Thanks Mike, will see if my "Gentle Persuader" used cautiously has the desired effect. Mike Quote Link to comment Share on other sites More sharing options...
Afishionado Posted March 25, 2006 Report Share Posted March 25, 2006 Thanks Mike, will see if my "Gentle Persuader" used cautiously has the desired effect. Mike Don't worry if the GRP tears a bit, it's dead easy to repair and if needed I can give you some glass mat as I have some spare from another job. Mad Mike Quote Link to comment Share on other sites More sharing options...
Mike Fox Posted March 28, 2006 Author Report Share Posted March 28, 2006 Thanks for all offering advice! Due to the uneven nature of the fibreglass around the anode bolts inside the boat, I decided to chisel it away carefully. There was a nut under the glass matting, that had been painted over. I chiselled the matting away carefully, then removed the nuts, getting down to what looked like bare hull. Remembering advice about big hammer being better than small, the "Gentle Persuader" was used. However it just wouldn't budge it, from above or below. I tried hacksawing a notch in the bottom of one bolt, and using big screwdriver and big adjustable to get extra torque, I leaned into it. All I achieved was twisting the bolt. Lacking an angle grinder and being worried about drilling off centre, I ummed and ahhed, and called in professional help. They fixed the problem in an hour. The bolt had a square mounting plate on it...but it had been fitted internally instead of externally as normal, and had been glassed over as well. When I had removed the glassed-over nuts, I thought I was down to bare hull, but I was wrong. Well, they used an angle grinder to cut away the glass matting around the mounting plate, and then tapped upwards gently, which broke the mastic seal. New anode bolts and an anode have now been now fitted in a more conventional style. Thought I'd let you all know, in case others ever come across something like that! Mike Quote Link to comment Share on other sites More sharing options...
Swainiac Posted March 28, 2006 Report Share Posted March 28, 2006 Mike, who did you use, and what did they charge? Call outs etc?? Rich Quote Link to comment Share on other sites More sharing options...
Mike Fox Posted March 28, 2006 Author Report Share Posted March 28, 2006 Rich, Have sent you a PM. Mike Quote Link to comment Share on other sites More sharing options...
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