Where do you get keel bolts?

[Robin2]

I know I don't have them in a catamaran but ...

A friend has a 1952 long keel boat and he is wondering where to get new keel bolts. Do they have to be specially made, or can you buy them ready made? His bolts are about 1 inch diameter with a tapered end where they sit in the keel.

The keel is cast iron and the timber at the bottom of the boat is oak. Is mold steel the right material for keelbolts, or should they be made from stainless or bronze?

 

[iangrant]

Most metalwork shops will turn you up a few keel bolts, but not on the cheap.

I had a set made in Chichester can't remember the name of the place but on the industrial estate.

NOT Stainless - use mild steel - stainless will rust when starved of oxygen and shouldn't be used for keel bolts.

Ian

 

[Tranona]

I expect that the originals were forged to get the tapered head - in those days boatyards would have a forge and blacksmith. You could go down that route if you can find a blacksmith. Have them made a bit overlength and then get the thread cut to match and then cut down. If mild steel they could be galvanised or dipped in hot pitch just before they are installed. They can be turned, but depending on the taper this could be very wasteful.

Mild steel is the usual material - bronze would be used with lead. I have successfully used 316 stainless (at least I think it is successful as they have been in for 14 years), but I had the keel off and bedded it down well so water cannot get in the joint. The original galvanised bolts were in for 25 years, but two had waisted where they went through the oak keel and came out in two bits. The next set were mild steel pitch coated and had started rusting after 6 years. I replaced them because I put a new wood false keel in.

When I researched the subject the belt and braces answer seemed to be galvanised mild steel and pitch down the holes to try and isolate the steel from the oak.

Has your friend got the old ones out yet as this is usually the worst job, particularly if they are long and have waisted. Sometimes the top half comes out with the nut and then you have to drift the bottom half out.

 

[cliffordpope]

Bolts through an iron keel should be wrought iron, which is much more resistant to rust than steel - that is why the SS Great Britain survived when a steel hull would have rotted away.

I got mine made specially by Coventry Boatbuilders - I don't know whether they still exist. I was told that there is actually a difference between marine grade wrought iron and ordinary blacksmith grade. The former is unobtainable except by re-working rare sources of salvaged old iron. That may be untrue, but it was a good story, and they just happened to have had a load in.

The traditional way of isolating the iron from the oak is to have a strip of tarred canvas between the iron keel and the wood, and to dip the bolts in tar before fitting.
Galvanised bolts of course would have a smaller steel cross section to allow for the thickness of the zinc, and a less precise fit in the holes.

 

[Robin2]

I looked up wrought iron in Wikipedia - fascinating. But I don't think we'll bother with it.

 

[Niander]

Can you let us know how you get on?
Ill have to have a go at unscrewing one of mine...and have a look!
some of my keel bolts have a round top with a round hole that a bar could pass through is this why they are made this way?

 

[Robin2]

Is the hole for the bar inside the boat, and is it to stop the bolt turning while you do up the nut?

It will be a week or so before there is any progress. I'll try to remember to report back.

 

[Niander]

Yes inside on top of bolts i havent seen where there are nut slots in the cast iron keel and its not painted so i asume they are bolts into tapped keel....