keel bolts again

[EASLOOP]

I have heard and read so many stories of woe from people trying to get their keel bolts out and presumably their keels off that it makes me wonder. There are tales of sledge hammer, lump hamers, drilling, sawing off in-situ, greasing, oiling, heating etc etc.
So, if the bloomin things are so difficult to get off when one WANTS them to come off what are the chances of them just falling apart of their own accord?

Go on, call me a twerp.

John

 

[banana]

you know, i thought that myself. but it was one of those things that was always at the back of my mind. i wonder how many keels have fell off. although in pbo there was that bavaria. but i suppose here we are talking about proper boats!!!!!!!

only joking

 

[rjp]

How long do keelbolts last? I guess it's a bit like asking how long is a piece of string. Alysia has 7/8 inch silicon bronze keel bolts into a lead keel. As best as I can tell she's been in the water at most 30 years of her 40 year life. I haven't drawn any keel bolts as there is nothing to suggest any problem. What I have done so far is replace seacock bolts (silicon bronze) and a bronze rod that came up through the bottom of the forefoot to a beam in the chain locker (the function of this being to tie in the sampson post). In neither case was any wastage present. On this basis I think I'm pretty safe. Or is this wishful thinking? The problem with trying to remove a keelbolt to my mind is the risk of creating damage where none existed.

John

 

[Peterduck]

The problem is that a number of boats have been built with galvanised steel keel bolts, and the galvanising is now well past its use-by date. With the forces of gravity trying to lever the ballast keel from side to side as the boat sails on different tacks, the seam between the timber keel and the ballast can open sufficiently to let a little salt water in to get at the bolts. When steel corrodes, it expands up to around eight times its original volume, so the steel bolt is waisting [getting thinner] as well as wasting [corroding] and the oxide [a.k.a. rust] is jamming it tight in the hole. There comes a time when the rust is not strong enough to hold the ballast in place, and there isn't enough bolt to do the job any more. That's when the ordure hits the fan, so to speak.
If the keelbolts are non-ferrous, there is a good chance that they are OK. However, a good friend of mine spent nine years building his pride and joy. For his timber keel he used a recycled bridge beam. When he launched his boat it was the first time that this beam had ever seen water close-up, and it swelled, as timber is prone to do. Several bronze keel bolts were shorn-off at the top of the ballast within a few months of launching. The sterntube was similarly torn apart in the middle, as was its replacement. Boats have an infinite number of ways of trying us out!
Peter.

 

[rjp]

Your anecdote about your friends bridge beam is very interesting Peter. It confirms that, even if I were to draw a keelbolt (and I'm not planning to unless some fussy surveyor gets awkward), then I would have to be extremely careful not to overtighten on replacement, Alysia having been away from the briney for at least 5/6 years as far as I can ascertain. Best left alone I feel! Where I have replaced the bronze rod I mentioned I have deliberately left the top nut a tad loose as I thought expansion of the timber might be a problem

John

 

[Peterduck]

It's one of life's little mysteries that so many people go to so much trouble to over-tighten bolts. I've seen them swinging on the end of lengths of pipe over a spanner, when they only needed the spanner. Too many folk think that a torque wrench was designed so that they could get the bolt tighter, when in fact it is designed to stop at the correct tension. It's another example of "if some is good, more is not better". My friend's keel problem was not due to overtightening, but in part due to wood swelling, and in part due to bronze having no ductility before failure. He had arranged the bolts in a zig-zag pattern along the keel, alternately to port and starboard of the centreline. This is held to be first-class practice. However, the timber swelled up across the grain and shore the bolts off. Australian hardwoods are hard enough to do that. His remedy was to replace with copper bolts, which have a little give and are still strong enough, and to drill all the bolt holes along the centreline. The timber continued to swell, but the bolts now defined a point of no movement.
Peter.

 

[delamaree]

I have a 53 year old timber ketch with 1" copper keel bolts - had them x-rayed and they came up new. Would I use bronze if I could use copper - no way. Would I remove them and risk damage - no way.

 

[Mirelle]

Re: keel bolts again - how long to they last?

Mirelle has had her iron bolts renewed regularly, every 10-15 years or so, apart from the one under the mast step, put in when she was new and forgotten about.

When it was found, 65 years later, during the replacement of said mast step, it was heavily corroded at the top and the nut would not come off - cold chiselled the nut and soon afterwards the bolt plinked out onto the concrete under the boat!

 

[tim3057]

Is it possible to just drill a few new holes and put new bolts in to save removing the old ones? You'd then have the keel held in place with new bolts, which you can replace more easily, more regularly, until the old ones rust away completely and can then be knocked out and filled over?