Proper keel bolts

[Captain_Bunsby]

Cautious Clara requires a new bronze keel bolt. The original has a head that seems to have been forged: the bolt diameter is 3/4" which tapers out to 1 1/8" over a distance of 1" at the end. Several people have offered to make one by turning down a piece of 1 1/8" rod, but does anyone know where we could get one like the original?

<hr width=100% size=1>Captain Bunsby was a character in Dicken's novel Domby and Son. His ship was the Cautious Clara.

 

[Peterduck]

If I were faced with that problem I would make a wooden pattern and get a few cast [you may need to replace others later on]. How many would depend on the cost and your ability to bear it. You could make the moulder's job easier by making a follow board to match the pattern or by making the pattern in two halves, split longitudinally. Ask your foundryman about how to make a follow board. If you go for the two halves method, split the 3/4" dowel off centre, so that one side is a true half, and use two lengths to get a proper circular cross-section. Heads are often made in a pyramid shape rather than a cone, as this resists turning when you tighten up the nut. A pyramid should be split from corner to corner rather than through one side, so that it releases from the mould more easily.
Peter.

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[pelorus32]

I've just been through the process of having quite a number of keel bolts fabricated. Assuming that your keel is lead - and therefore that you want bronze bolts. We used Nickel Aluminium Bronze (AB2) rod and simply cut it to length. Then we made nuts out of larger diameter stock and ran threads on to both ends of the bolts in the lathe.

To install the bolts we drove them through from the bottom with the nuts on the bottom (and secured) and then placed and tightened the top nuts with the relevant cotton and black jack in the relevant places.

I would be most reluctant to get bolts cast as small cracks and flaws are common in castings. This is particularly so where the dimension of the casting in cross section is small compared to its length. We had substantial trouble with some straps we wanted to cast. The long items are "pinned" in the mould at either end by the place where you pour and the riser and as they contract (3/16" per foot of length) they crack and fracture. As for the unusual flare - cut it on the lathe maybe.

Regards

Mike

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[DRW]

Hi,

www.gtc-direct.com supply a wide range of silicon bronze and A2 and A4 stainless screws bolts stud etc.

They are helpful and if you bolt exists, they would probably be able to sell you one. They also have no minimum order, so you just get what you need. They also have a really useful catalogue for free.

But I have a hunch you may need to turn down some rod on a lathe.

Good luck.

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[dickh]

The easiest way is to get some ¾" Dia. rod and turn threads in each end; with a tapered nut on the lower end, with the end rivetted over the nut to stop it turning or pinned. By far the cheapest and strongest method. Or as you have said use larger diameter rod, turned down to the correct taper and the other end threaded. Don't go for a casting - it will not be as strong and could have flaws in it.

<hr width=100% size=1>dickh
I'd rather be sailing... /forums/images/icons/smile.gif

 

[Mirelle]

It's an "upset head" which has been "jumped up", just as an iron keel bolt is made - basically the bar is heated and then banged down on the floor until the tapered head is formed.

I do know that this was common practice with bronze bolts, as it still is with iron ones, but I know nothing of metallurgy and could not say whether it is a Good or a Bad Thing.

<hr width=100% size=1>Que scais-je?

 

[Transcur]

Nickel Aluminium bronze makes really good keel bolts. Problem is cutting the thread, its very tough. You may need to get a specialist firm to cut the threads. CA103 is admiralty spec. A 3/4 bolt will have a ultimate stress load capability of well over 10 tons each!!!!! Do not forge the ends as the bronze will loose strength. Pocket (socket into keel)the lead keel using an old chisel to accept hex bar stock. Its quite expensive to buy ,standard lengths are 10 ft.
Atco qualcast did my bolts for a bottle of wine and some cigars, Knackered the die box.
Have fun

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[Captain_Bunsby]

That's the sort of thing I had in mind, though I thought I'd need some form of mould or die the shape of the head that could be clamped around the rod before hitting its (heated) end, rather than just banging it on the floor (which of course would be much simpler and cheaper). Maybe I'll try that before investing in a mould. Although I called it a keel bolt, this one is actually through the lower stem, holding the second floor, so the wood might be more forgiving of variations in shape than the ballast keel would be.

Whether its a Good or Bad Thing at least its historically correct! (although the alloy used might not be..)

<hr width=100% size=1>Captain Bunsby was a character in Dicken's novel Domby and Son. His ship was the Cautious Clara.

 

[Peterduck]

When you come to deform the end of the bolt into a head, DO NOT HEAT THE BOLT! In one of those curious quirks of metallurgy, heated bronze is very, very brittle. I tell you this after trying to straighten a bent 3ft long bronze chainplate some years ago. At the first blow I had two 18" lengths of bronze, and a chainplate is not something that I would want to have brazed. I had to get a new one cast up. To make things worse, cold aluminium bronze is, I think, very resisitant to deformation. Gunmetal might be easier to swell, but it is still not easy. A press and forming dies may be necessary.
Peter.

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[Captain_Bunsby]

I was intending to use silicon bronze. Larry Pardy describes making bolts (albeit with a flat head) by heating silicon bronze rod until blue and then hammering the end. The rod has been ordered so I'll give it a go and let you know the result.

<hr width=100% size=1>Captain Bunsby was a character in Dicken's novel Domby and Son. His ship was the Cautious Clara.

 

[Mirelle]

Cross refer to Transcur\'s post

Pete Thomas knows a good deal more than I do about these things and he is against heating bronze.

I've taken Pete's advice for 20 years and always found it good.

<hr width=100% size=1>Que scais-je?