When Bolts Go Bad
Replacing The Spreader Bracket Bolt With The Mast Up
Summer 2002
It was an easy sail in 5-10 kts. out the channel, so I took the opportunity to
check the mast and rigging visually. Something didn't seem quite right at the base of the
port-side spreader, but I couldn't see anything in detail, and there was no perceptible
movement, so we decided to continue with the day's sailing with caution. Of course, hindsight
suggests that real caution would have seen us drop the sails and turn around, but we got away
with it.
Later, closer inspection showed that the forward bolt of the pair securing both spreaders
to the mast had sheared off, and only a single bolt was retaining these strategic bits of
hardware.
The obvious solution wasn't very attractive; dropping the mast would be both time-consuming
and expensive, so I mulled the alternatives. Eventually, after sober consideration, I decided
that the job could be done with the boat in the water and the mast up - here we go...
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Port and starboard shots of the effect of the sheared forward bolt.
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I would be freeing the spreaders from their attachment to the mast, so I wanted to
provide temporary support elsewhere. I dropped the jib and used the jib halyard to one side
and the spinnaker halyard to another, winching them in tight; you can see the halyards
attached to the bases of the lifeline stanchions immediately astern of the pulpit. I didn't
loosen either pair of shrouds.
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I set up a self-powered block-and-tackle rig to ascend the mast; I've tried having crew
grind me up, but that's just too much work for all involved, and I wanted to try out a
solo option in a calm environment. I used a triple block attached to the main halyard
and raised to the mast-head,
and a pair of double blocks in series attached to the bosun's chair, with a cam cleat
on the upper of the pair of double block; the line is a retired mainsheet. This is
effectively my back-up rig for the mainsheet tackle.
Another in-mast halyard was used as the safety line, with my dear wife keeping the line snug
around a winch in case of a failure in the main rig; the girls in the cockpit did their
part, feeding the ravening ducks and swans so they didn't fly up and feast on me...
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Here the broken bolt and the brackets have been removed, and the spreaders held in place
with a piece of line. NOTE the plastic rod through the forward hole - this is
VERY IMPORTANT! There is a barrel running between each pair of bolt holes, inside
the mast; these prevent the mast walls being compressed when the bolts are tightened. If
the bolt is simply removed, the barrel will drop down and be impossible to
recover without unstepping the mast! To prevent this, I fed the plastic tube in as the bolt
was being withdrawn.
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Here you can see the sheared bolt, along with one bracket (the other is still on the mast
with the remaining bolt), and the rods that hold the spreaders in the brackets. The tools
for the job are pretty simple - well, until the replacement bolt goes in...
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To cut a long story short, the original bolts are (from memory) 5¾", but I could only find 6"
replacements. I over-optimistically thought "What's ¼" between friends?", and fitted the new
bolt anyway, but then found the extra ¼" obstructed the base of the spreader; it was
less trouble to haul up a battery-powered drill and cutting disk and trim off the bolt
in place, than to remove, modify and re-fit the bolt - mainly because I was having
nightmares about losing the afore-mentioned compression barrel.
Of course, it would have been least trouble to think "A ¼ inch too long is too long."
before fitting the bolt, but life would be awfully depressing without a dash of
optimism to spice things up.
Some final notes :
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Womble was berthed in a very protected marina; little traffic, virtually no wakes, and
no natural waves. In a berth that might have caused more motion, I would be less inclined
to do this work with the mast up; having said that, the mast itself, in concert with the
lower shrouds, fore- and back-stay, and the temporary stabilising halyards, should
be more than strong enough even with some boat motion. The assessment of risk needs to
include the gravity (ha ha) of the consequences, as well as the probability; in this case,
the risk goes up pretty fast as the probability of mast failure increases, because the
consequences can extend to loss of life as well as expensive hardware!
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I did, of course, replace both bolts; however, I did notice a flaw in one of the brackets,
so I'm planning to replace them as well in the near future.
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This is a good example of the principle of replacing hardware before failure; if
this had happened in heavy weather, we would probably have lost the mast. I am not the
original owner of the boat, but I suspect this bolt was 20 years old, and should
have been retired a few years ago.
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With respect to losing a compression barrel down the mast : a replacement barrel could be
made up and fitted through the access hole, but that doesn't seem much fun either.
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The rig used to ascend worked out at 4:1 purchase; I weigh about 180 lbs. and
am in decent shape, and found this ratio a nice compromise between strength needed to
lift and lifting rate. The safety line manned by crew is more than desirable, but in an
emergency situation, this rig can be used solo. I used the cam cleat as a precaution, and
also knotted the line to secure against release once I had reached working level.
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All lines used in exercises such as these, including the temporary stabilising halyards,
are in-mast; this means that any block or pulley failure on these lines will allow
the line to drop only an inch or two, rather than free-fall to the deck.
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