Keel bolts - revisited!

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dur

dur

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www.gaff-rig.co.uk
Happy New Year All

Wind Song has a shallow long iron keel with a slot in it forward for the centre plate. Either side of the plate it is bolted with five pairs of 1/2" bolts (approx 10 1/2" long). Aft of the plate there is a mix of longer 1/2" and 5/8" bolts

Earlier in the year I removed one of the forward pairs and one of the aft singles (the 1/2" one)
(Earlier thread - http://www.ybw.com/forums/showthread.php?p=2062264 )
(Basically they were still serviceable)

I removed another pair before Christmas and as they didn't look very special have removed several more...

P1000353-2.jpg


The small bolts were replaced in 2005, the others 2006 and 2007.

I think I will replace all the bolts but have left some in for now as I don't want to break the seal between the ballast keel and wooden keel.

So to the questions:

- Why is the corrosion only where the bolt goes through the wooden keel?

- Why are two of the bolts pretty much unscathed (excepting the galvanised one) when the others are all badly eroded? All were still completely coated in the stockholm tar when they came out?

- Is it safe to galv all the bolts without risk to the boats copper fastenings?

Is there any merit in either epoxy coating the bolts before fitting or perhaps making a plastic sleeve? I had wondered about plastic shrink tube used for electrical connections. I guess the damage is principly galvanic erosion so presumably an insulating barrier would help?

All thoughts welcomed!
 
dur said:
So to the questions:

- Why is the corrosion only where the bolt goes through the wooden keel?

Usually the tannic acid in the oak-very corrosive

- Why are two of the bolts pretty much unscathed (excepting the galvanised one) when the others are all badly eroded? All were still completely coated in the stockholm tar when they came out?
Maybe the others are close to a copper fastening, or nearer a small leak. Probably black tar varnish.

- Is it safe to galv all the bolts without risk to the boats copper fastenings?
Yes

Is there any merit in either epoxy coating the bolts before fitting or perhaps making a plastic sleeve? I had wondered about plastic shrink tube used for electrical connections. I guess the damage is principly galvanic erosion so presumably an insulating barrier would help?
One usually just tars and greases them(lots) up. Bear in mind they should be a driven fit, as in any bolt or fastening on the boat. This is to peg the parts together. So if you do coat them (galv, powder, epoxy or tube) you will need to bore out the holes to allow for these coatings. I would ream the holes slightly anyway, in case there is somthing sticking out that will 'slice'the coating as you drive the bolt in. I would go for galv, as its probably the thinnest.
You could consider temporarily blocking off the bottom of the holes and filling with thinned linseed oil/cuprinol mix to keep the Tannin at bay. You should plug the holes anyway whilst the bolts are out as you will get accelerated local drying around the holes.

I must say I am suprised at how badly wasted they are after only 5 yrs.Where they greased?


All thoughts welcomed!
Click to expand...

Oh dear, my thoughts are in there somewhere!
 
Hi Nick

Thanks very much for your reply...

Seanick said:
Probably black tar varnish.
Click to expand...

It actually was stockholm (pine)tar. The bolts were hot dipped in it and then more poured down the hole before fitting. Some actually glooped out when taking some of the bolts out. Great smell!

I have a can of "black bitumen primer". Is this black tar varnish?

Seanick said:
One usually just tars and greases them(lots) up. Bear in mind they should be a driven fit, as in any bolt or fastening on the boat. This is to peg the parts together. So if you do coat them (galv, powder, epoxy or tube) you will need to bore out the holes to allow for these coatings. I would ream the holes slightly anyway, in case there is somthing sticking out that will 'slice'the coating as you drive the bolt in. I would go for galv, as its probably the thinnest.
Click to expand...

Well I think the holes are now slightly oversize plus the half inch bolts are actually 12 mm now. But a clean out is a good idea. Is it a case of running an appropriately sized drill bit up the holes?


Seanick said:
You could consider temporarily blocking off the bottom of the holes and filling with thinned linseed oil/cuprinol mix to keep the Tannin at bay. You should plug the holes anyway whilst the bolts are out as you will get accelerated local drying around the holes..
Click to expand...

OK will do.

Seanick said:
I must say I am suprised at how badly wasted they are after only 5 yrs.Where they greased?
Click to expand...

I think not greased because the tar was poured down the hole. Is ordinary thick grease the stuff to use? Or perhaps lanolin as an alternative?


Thanks very much for your help - once again!
 
fishermantwo said:
My guess is electrolysis. Stray current in the damp timber. Isolate batteries when not in use. Check anodes, maybe you have too many.
Click to expand...

Thanks...

I did put a new anode on last season and it has already lost a fair bit but it is under the prop shaft aft - close to the bigger bolts but not so close to the smaller ones. I have been worrying about the old electrics -especially to the auto bilge pump and I think some re-wiring is in order.
 
Seanick said:
Quote:
Originally Posted by Seanick
You could consider temporarily blocking off the bottom of the holes and filling with thinned linseed oil/cuprinol mix to keep the Tannin at bay. You should plug the holes anyway whilst the bolts are out as you will get accelerated local drying around the holes..

OK will do.
Click to expand...

Duly bunged up the holes and poured in the mix. 8 of the 9 holes were still full after half an hour with the 9th weeping out of the wood to iron keel joint. This seemed to slow after a second top up.
This seemed a reasonably positive result to me but I do have only half the bolts out at the moment as I want to preserve the joint. The new bolts are ordered so I shall have to wait a month or so before having a go at the others.

(I initially tried a 15 mm dowel to bung the 1/2" holes but it was just not quite tight enough so the holes are obviously oversize now. 17 mm dowel and a jack did the job.)
 
Thanks

I had found the real wrought iron guys, though I'm not sure if they will be horrifically expensive.
I'll ask them for a quote when I get an idea of the size of the keel boats on my Hillyard.

Abigail
 
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