KEEL BOLTS

[nemesis]

IS THERE ANY REASON WHY REPLACEMENT KEEL BOLTS COULD NOT BE MADE
OF STAINLESS AS OPPOSED TO MILD STEEL.
I NEED TO REPLACE 8 BOLTS IN A 1930 HILLYARD WHICH HAVE DECAYED FROM
A SHANK OF 25mm DOWN TO 10mm.
I DON'T KNOW IF THESE WERE THE ORIGINAL BOLTS BUT AS THEY ALL NEED REPLACING , TO DO IT IN A MATERIAL THAT WILL NOT DETERIORATE SEEMS
THE BEST SOLUTION.

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[Richard_Blake]

Afraid there is, yes. Stainless suffers from crevice corrosion under water (no oxygen) and can deteriorate a lot faster than the old ones you had in there did! Others will probably explain the science/chemistry, but the general rule seems to be don't use stainless below the waterline. I've seen stainless keel bolts pulled after about ten years max, and they were down from a half inch to a quarter or less.
Richard

<hr width=100% size=1>LowTech

 

[ccscott49]

Agree with Richard. Why not use bronze? Good quality bronze, with NO ZINC in it. Not your naval bronze crap. Try Classic Marine. or Anglia stainless steel.

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[Mirelle]

Agree with Richard and Colin. Stainless steel should bever be used for this - it is far too unreliable. Crevice corrosion is odd - it looks as if worms have been eating the metal. One tiny spot with no oxygen in contact with the chromium film and the steel gets eaten.

If the ballast keel is lead then I agree with Colin - bronze is best.

Assuming that the ballast keel is cast iron, which since we are speaking of a 30;s Hillyard it almost certainly will be, the best material for new bolts is not stainless steel but a far older material - wrought iron. This is indeed obtainable, in standard Imperial dimensions, I had a new set of keelbolts made from it three years ago.

Try The Real Wrought Iron Company, who supplied mine:

http://www.realwroughtiron.com/

Wrought iron, being a fairly pure metal, corrodes far more slowly than mild steel and does not have the dangerous habits of stainless steel.




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[ccscott49]

Is brionze no good for cast iron keels? or are you thinking cheaper? I would like to know, for the old memory banks. Wrought iron is a good material, with a little give in it aswell, doesn't work harden.

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[mickshep]

Years ago an old timer told me that they used wrought iron for keel bolts but just before fitting they heated them to cherry red before plunge cooling them in old sump oil, he reckoned it made them last even longer. Any thoughts on this out there? Mike.

<hr width=100% size=1>"Naaa mate, she's made of tin"

 

[wishbone]

I am pretty certain it hardend up the steel as opposed to using water which cooled them it too fast

Wishbone
Rolling, rolling, rolling keep them doggies moving!
Where’s me chuck wagon gone?


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[Peterduck]

As I understand it, the oil becomes "absorbed" micrscopically into the iron, thus retarding corrosion. Yes, there may be some hardening of the exterior of the bolt, but this is unlikely to persist in depth. As wrought iron is reasonably soft and quite malleable, this effect would probably not be noticeable. The reason for using wrought iron bolts with cast iron ballast is to keep metals as compatible as possible.
Peter.

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[Mirelle]

I recall a rule that you can safely fasten a large lump of "less noble" with "more noble", but I think there may be two caveats - one is that the more noble metal, acting as the cathode, will gradually build up alkalis round it (wood + alkali = paper!) and the other is that bronze is slightly less trustworthy stuff and can develop a sort of crystalline fracture, but I am no expert.

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[penfold]

Bronze is satisfactory but because it's a big step in terms of nobility, it can result in corrosion problems. Some books say it's fine, some say not. My best information sez that hotdip galvanized mild steel (better still, wrought iron if you can get it) will do the job well and cheaply if you have an iron keel.

cheers,
david

<hr width=100% size=1>This candidate has low personal standards, and continually fails to meet them.

 

[grant]

OK. I am a bit confused, how about a lead keel with bronze bolts? The keel I took off my boat was cast iron with stainless bolts. The boat is an '85 and the bolts seemed to be in fine condition, however I want to replace it with lead to get a bit shallower draft.

<hr width=100% size=1>grant

 

[mtb]

It's not cherry red it's the straw colour that tells you when to quench. You can also case harden using carbon powder. By heating to cheery red then quenching in water that aneals the materisal dont it !!.
We had to do this stuff when going through the marine craft fitting courses years ago, I've never had to do it since.

Personaly if I were changing keel bolts that had been in for a long time I would use the same material cos why try to believe you can improve on what works.

It's hydraulic steering today the steering head on Danbrit has a leak, trouble is the head is blooming big !!.

cheers
Mick


<hr width=100% size=1>Danbrit is for sale I'm spending all my time working on her with no time for play