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Old 31-03-2009, 21:31   #31
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Originally Posted by s/v Jedi View Post
Welding: I would not worry about the new weld, that will be plenty strong. But I worry about the opposite side where the aluminium was bent out, and will be bent in again when welding the seam. This work hardens the aluminium and can cause failure easily. Just try it with a scrap piece of aluminium: it will quickly break in two pieces.

On construction: you are right, that is the way they taper extruded spreaders, masts, booms etc. I am now convinced this damage was caused by failure under compression, not from ice. With ice, you would see a change of shape everywhere before the weld fails.

On foam: don't worry about expanding foam breaking your welds ;-) If that would happen you should be a happy man and throw them away and buy new ones. The foam is nowhere near strong enough to do that.

cheers,
Nick.
Nick,

If you would just agree with me, I could get on with this!

Just kidding .
I will though take another picture which I haven't taken (tomorrow) which will show how wonderfully even the pressure must have been in order to do this. Perhaps the spreader was only 1/4 or 1/3 full of water when it froze.

One step at a time.

Regards,
Extemp.
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Old 01-04-2009, 17:05   #32
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FWIW Extemp,

One consideration not yet mentioned here: when the spreader was welded in the tapered area, there could well have been overzealous grinding of a (possibly poor) weld in order to make it look good. Then you not only have the original poor weld weakening the structure, but a goodly part of it being ground away as well. I find the ice hypothesis a bit hard to believe myself, but that is only a gut feeling from seeing a lot of busted gear over the years, and remembering the cream sticking up out of frozen milk bottles (how old fart is THAT?). but, whatever caused the failure, a proper welded repair should restore it to useable strength. Further I wouldn't worry too much about restoring it to its exact former shape (cross section). As long as it is straight and free from kinks after welding it should be fine.

As an aside, I remember when the old raceboat "Kialoa II" was in the tourist charter trade in La Paz (about 1987) she suffered a broken upper spreader. Frank Robbins (sp?), her then owner, went to the local chap who made axe handles and had him make a replacement out of Mesquite wood. It wasn't a pretty thing, not very straight and a bit lumpy, but when we next encountered them in Fiji in 1990, it was still in service! Considering that her cap shrouds were 7/8 or 1 inch in diameter, the spreader loads were, uhhh, considerable!!

Good luck with whatever you decide...

Cheers,

Jim
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Old 01-04-2009, 20:56   #33
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FWIW Extemp,

One consideration not yet mentioned here: when the spreader was welded in the tapered area, there could well have been overzealous grinding of a (possibly poor) weld in order to make it look good. Then you not only have the original poor weld weakening the structure, but a goodly part of it being ground away as well. I find the ice hypothesis a bit hard to believe myself, but that is only a gut feeling from seeing a lot of busted gear over the years, and remembering the cream sticking up out of frozen milk bottles (how old fart is THAT?). but, whatever caused the failure, a proper welded repair should restore it to useable strength. Further I wouldn't worry too much about restoring it to its exact former shape (cross section). As long as it is straight and free from kinks after welding it should be fine.

As an aside, I remember when the old raceboat "Kialoa II" was in the tourist charter trade in La Paz (about 1987) she suffered a broken upper spreader. Frank Robbins (sp?), her then owner, went to the local chap who made axe handles and had him make a replacement out of Mesquite wood. It wasn't a pretty thing, not very straight and a bit lumpy, but when we next encountered them in Fiji in 1990, it was still in service! Considering that her cap shrouds were 7/8 or 1 inch in diameter, the spreader loads were, uhhh, considerable!!

Good luck with whatever you decide...

Cheers,

Jim
Thanks Jim.
As I said earlier, one step at a time.
Even if I end up going with the welding fix, next winter, when the boat is on the hard, I'll get replacements.
Regarding whether it is ice or compression damage.
Substantial water poured out of the end cap when I took it off to take the trapped shroud off. So that part/component of that possible equation was present making freezing damage possible.
The freezing temperatures part of the equation was present making freezing damage possible.
Having lived in the North all my life, without exaggeration, I'm sure that I have seen ice damage 20 times, mostly in pipes but several in containers. I'm very sure that I would have noticed this last fall when the boat came out of the water and I un-stepped the mast. My wife is also sure that she would have noticed it. There are no remarkable occasions that occurred last sailing season when I could possibly imagine that there was enough stress to do this. Also in an over compression situation it would be odd/bizarre to me that with the degree of damage done, the damage would have stopped where it did. I think that with what I see, if it was compression damage and you consider that it had to damage a perfectly straight spreader to get to the point that it has, total failure would have occurred.

I could be wrong (but I don't think so).

That said, when it is at the machine shop, I'll ask them to look closely at the existing weld for signs of defect or deterioration.

Your aside story is interesting. Wood can be incredibly strong in compression.

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