What is the evidence of the need to rebond the keel

[tillergirl]

Today with the aid of the yard, we investigated signs of dried salt around the nut of the No 1 keel bolt. This had been replaced 5 years ago when I drew all the bolts and replaced the lot. At that time the No 1 bolt had completely failed.

Trying to undo the nut, the bolt turned very slightly before the nut released so we decided to knock it out for a look. Going underneath we prised out the bedding (Polysuphide) that we had used to seal the bolt head socket underneath and as we did so out dropped a little water. I deduce that as this water has not found its way out until we prised out the bedding, it did not get there from underneath. That leaves two possibilities: water from the bilge (well there's always a bead of moisture isn't there) had found its way under the keelson into the bolt channel or water is getting in at the keel joint.

Further evidence: the keel bolt when removed has started the wastage process. It is years from failing - perhaps 20 years - but there is noticeable wastage of a little more than a sixteenth of the radius. Also at the keel joint, despite being cleaned two weeks ago, there is evidence of very minor salt 'efferversance' showing up. On the positive side, when we did the bolts 5 years ago, there was evidence of - what shall I say - 'over wet' timber around this bolt which is now back to rock hard.

I shall replace the bolt of course as the cost of that is pretty small in the scheme of things but should I be thinking that in a future winter I should separate the keel and re-bed it. Not an easy task and one requiring a pretty major shoring of the boat so the keel can be dropped.

So the question is what is the evidence that indicates that a rebedding of the keel joint is necessary? Any views anyone?

 

[Peterduck]

While the bolt is out of the hole, bung up the lower end of the hole (a wine cork or champagne cork, depending on your budget and the size of the hole) and fill the hole with water. If any trickles out from the seam between the wood keel and the ballast then that's where it will be going in. If you use fresh water it will also dissolve any salt which is still in there.
Peter.

 

[tillergirl]

Peter, thanks. I'll give that a try - got a couple of champagne corks handy (well hasn't everybody!) - although keeping the salt in there is good isn't it?

 

[Seanick]

Yes, keeping the salt in the wood is good, but not for your keelbolt!
Try galvanising the new bolt, very effective.
A few things,
If your keelbolts have tapered heads, and the keel has round counterbores then they should be filled not with lifecaulk but a tapered softwood end-grain bungs. I make them over-length, then put them in with an eight ton jack. This usually lifts the boat a bit. Saw off flush. The softwood will swell and make a seal 100 times more effective than modern goos.

If you leave the bilge full of water, and have external weeping between the wood/iron joint, then thats a sign that re-bedding is due 'in a few years'. You can extend this period, and decay of the bolts by injectin mastic into the void between bolt and its hole. I drill the wood keel with a 4mm long series bolt until I just touch the bolt, then screw in a grease nipple (not a word you see on this forum very often!). I mix butyl rubber mastic and white spirit untill it is runny enough to put ina grease gun and inject under pressure. Do it slowly or you can blow the keel apart......
Sprig the hole with softwood.
Do all the keelbolts.
You can also use this tecnique for rebedding any joint in-situ.

If you do rebed, leave the keel where it is and crane the boat off.
You may have to remove fore and aft deawoods-which will need new bolts.
Use normal roofing felt as a gasket, not sika, silicon etc etc....

 

[tillergirl]

The keelbolts are just studs with nuts on either end; the counterbores are square! There is also very little clearance between end of bolt/nut and the bottom of the keel. So the tapered softwood won't work - which is a pity. Mind you, it seems the mastic did work.

Like the mastic injection idea but I guess you get very little in?

As to the rebeding, I would be nervous about slinging so forward forward and aft to clear the iron keel. The keel extends from the middle chain plate to under the 'E' and the rear deadwood would have to come off first. What I fear is sagging. I know the keelson is pretty substantial but then there is a lot of weight in there and the slinging points would be pretty far apart.

 

[Seanick]

Re mastic injection some bolts have 2-3mm clearance, so you getb as much mastic in as is required to keep the water out.

to lift your boat the aft strop would go through the prop apperture, and the fwd strop would go nicely just in front of the ballast keel. Don't worry about sagging, your boat is stronger than you think. Compared to the loads imposed by sailing hard in a gale these loads are next to nothing. Any vessel that sags when lifted is close to un-seaworthy anyway, and due for major works.
Tiller girl looks relitively new, and a nice strong boat as well, so I would not worry!

 

[tillergirl]

That's reassuring. Her scantlings are of heroic proportions. I suppose when I think about it you must be right. The keelson is massive. Part of it was that I was thinking about avoiding having a crane in twice. A real issue is the aft deadwood which has a bronze bolt underneath which does not apear inside. I.e. it is under the rather massive internal shaft log(?) which sits on top of the keelson. More dismantling!

For now, I am putting new stuff back (launch a week Friday), taking a very careful note of the situation and shall inspect again at the end of the season.

Thanks for ther advice.