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Old 18 April 2012, 05:31   #11
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I'm with Alan P here. Heat+aluminium+grain distortion+stress=dismasting.

It'd be a different story if it was steel, but it's not and there's no way to regain the grain structure in the metal in the welded area. It'll look pretty when done if welded, but the mast is very likely to fail with the grain boundary or heat affected zone of the weld as the start point.
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Old 18 April 2012, 10:17   #12
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Quote:
Originally Posted by Nos4r2
I'm with Alan P here. Heat+aluminium+grain distortion+stress=dismasting.

It'd be a different story if it was steel, but it's not and there's no way to regain the grain structure in the metal in the welded area. It'll look pretty when done if welded, but the mast is very likely to fail with the grain boundary or heat affected zone of the weld as the start point.
I'm with you there. I've taken up aluminium casting as a hobby so have got a real feel for how aluminium and heat mix. I might trust a weld for something lower stress or non critical, but not your mast.
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Old 18 April 2012, 10:54   #13
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Originally Posted by rik_elliott View Post
I'm with you there. I've taken up aluminium casting as a hobby so have got a real feel for how aluminium and heat mix. I might trust a weld for something lower stress or non critical, but not your mast.
That's an interesting hobby,perhaps you could cast him an insert that could be bolted in place?
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Old 18 April 2012, 11:57   #14
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I used to wled as part of my job, ALWAYS ask can a mechanical fixing be used, gnerally it is superior.
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Old 18 April 2012, 13:24   #15
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Thanks for the advice. Decided to put bigger stainless plates on and bolt through with 4 fixings per side. Mark at Marine Fabrications is on the job (did my A-frame). I suppose that will be a whole day with a spanner on a stick trying to locate zinc chromate clarted washers and nuts on threads up inside the mast. The bottom of the mast has more fixings than swiss cheese but probably not much worse than an typical aircraft wing.

I think I would have been OK though. These masts are oversized to give buoyancy when capsized so would have been strong enough even with a 36mm hole right through (except the water would run in!). Saw one turtled boat and crew lift right out of the water on its mast in big waves off Abersoch - didn't snap. The hole is so close to the base that there is little stress here. Only a beach cat after all. Not crossing the atlantic anytime soon.

Dismasting's not so bad. It all floats down quite gently even if you are cracking on. Bust a lovely carbon mast last year on the other cat. Luckily it was a free-be. Just a little embarrasing as the whole pile drifts along like in Jaws 2.

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Old 18 April 2012, 14:42   #16
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Try putting your post on this forum. They are a good bunch of tekky lads and lassies on there.
MIG Welding Forum
There is a TIG section as well as MIG and other stuff.
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Old 18 April 2012, 15:55   #17
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Ally TIG welding is the preserve of Yoda like geniuses, not for the amatuer unless they are coded in Ally on TIG ofcourse. Sounds like he's sorted though.
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