Bolts for alluminium stanchion base

[Robin]

Are these S/S or an alloy? The bolts were very corroded yet the aluminium wasn't, this area had been damaged before we bought the boat and there were some rust stains which suggests they are S/S and maybe there was crevice corrosion on the bolts where they passed through the deck, although there were no leaks inside.

I have just managed to fall into the guard rails (don't ask!) and sheer off the bolts holding a stanchion base down. It is one that forms part of the aluminium toerail and after 4 hours struggling to remove woodwork below it seems to be bolted through a plate and glassed over inside as there are 2 'bumps' maybe covering nuts, but the outer 2 bolts may have been tapped into the plate as they are so close to the hull sides? Boat is a 1988 Jeanneau Sun Legende.

Anyone done a similar repair? The deck appears undamaged but the remains of the bolts are still in the holes

 

[Bodach na mara]

Stainless, preferrably A4 grade, with a smear of Duralac on the threads.

 

[VicS]

[ QUOTE ]
Stainless, preferrably A4 grade, with a smear of Duralac on the threads

[/ QUOTE ] Coated with Duralc where they are in contact with the aluminium but well sealed with the sealant of your choice where they pass through the deck to prevent crevice corrosion.

 

[Robin]

Thanks guys you have confirmed my own thoughts. I was a bit surprised because all 4 bolts sheared (about 5mm dia I guess) and because there was no obvious corrosion of the aluminium base whhen usually it is the aluminium that suffers in contact with S/S.

I'm still struggling with what to do about removing the old bits. As yet I have only succeeded in getting very limited access underneath (enough to get a hand in with a nut and washer) as far as removing the 2 that looked to be glassed over, but that still leaves 2 going through the deck very close to the edge (in the hull/deck join it seems) with no 'bumps' visible so these may have been tapped into some kind of backing plate. I don't doubt there is a plate in there of some kind because the centre cleat and genny track are close by and both have massive plates backing them up which ARE visible. I could drill down from above and hope there is a) someway of getting a nut/washer on or of tapping into the hole. I'm a bit reluctant to make things worse than they are.....

 

[Searush]

Try a small hole drilled into the bolt with a l/h threaded extractor perhaps? No expert, but what I would probably try myself if unable to get them out with "normal means".

 

[William_H]

Yes use an extractor (easyout) into a suitably sized hole n the broken piece of bolt. Often the heat of drilling the hole will help to loosen the corrosion etc of the thread to enable removal. If the extractor fails then keep drilling and retap the hole in whatever it is underneath be it nut in glass or backing plate. Be carefull you don't snap off the extractor so use one as large as practical. good luck olewill

 

[Robin]

Thanks all. I have some Easyouts all ready to go and will give it a try today with all fingers crossed!

 

[Robin]

Re: update

Thanks all, job all done bar replacing all the woodwork down below, it only took 6 hours to remove so hopefully no more than 8 hrs to replace tomorrow! Actually it will go back in a more suitable manner for easier removal - just in case. Not Jeanneau's fault re the access as this was added on stuff carrying all the electronics done very neatly by pro woodworkers so that not one screwhead showed, and there were 32 screws eventually found.. Two of the sheared bolthead with nuts glassed over below were ground off and punched out from above, the other two resisted all attempts with an eazyout until it broke, after which a friend and I drilled them out and re-tapped threads into the plates below.

As a bonus I have now removed the Navtex aerials which were hidden behind some of this woodwork and MIGHT just now work a bit better when mounted somewhere else.