Aluminium fillet weld or patch on mast ?

[Alfie168]

I had an accident with the mast on my moored boat. It ended up over the side when I was away and apart from bad scratches appears OK except for where the railing wire has acted like a bandsaw and cut a small nick in it, which has penetrated the mast wall, though only just.

My initial idea was to get the nick fillet welded, but mindful of the hardening of the metal that can take place round a weld I did wonder whether a simple riveted plate might be better. I think I'd prefer a neat weld visually, but thats less important than structural integrity of course.

I am qualified as a lead welder and have had training as an arc welder many moons ago, but alloy welding is not my scene at all and is quite specialised. If there is anybody out there who has experience I'd appreciate their input.





Tim

 

[jerrytug]

I had a much worse crack, and I cut a patch out of stainless steel sheet, bent it to a close fit, using a hammer, round bits of wood etc, and rivetted it on with monel rivets using lazy tongs and plenty of Duralac.
It's best to drill a couple of holes at one side of the patch, then put the rivets in them.
Then move the clamps, drill two more holes,and put the next two rivets in, and so on. Doing it that way, you get a tight fit which must make the repair a lot stronger.
If you drill all the holes first, some of them won't line up and you have problems.

It's been fine for 18 months so far, I have given up keeping an eye on it.
Welding would cause more stress as you say.

Another thing, get the exact proper size new drill bits to match the rivets, tight fitting rivets are much stronger.

 

[Rigger Mortice]

It looks so small that it's probably no different than a slot for sheaves or the ends of the rigging. Why not just file off any sharp edges and corners to make sure that there is no stress point for a crack to start from? Then fill it with some epoxy and keep any eye on it for the rest of the season. At least you'll be able to see if there is any movement which you won't be able to see if a plate is covering it.

 

[cliff]

1) Aluminium does not harden during welding as steels tend to do.
2) The weld in the aluminium will soften the area around the weld.
3) There will be little or no residual stress in the weld due to the low yield strength of the weld/surrounding area
4) The welded area will have lost its anodised finish and be prone to corrosion - both on the internal and external surfaces of the mast
5) you will need AC GTAW (or GMAW) - my preference would be GTAW
6) For all the damage I would forget welding, rather I would clean / dress any sharp edges and fill the groove with epoxy. I would mix the epoxy with powdered aluminium toi give a aluminium coloured exopy paste, apply the paste, cover with a plastic mixing spatula pressed tightly over the groove 'til the epoxy has hardened. This will give a smooth finish with no need to rub down and hence possibly damage more of the anodising.

 

[Alfie168]

Thanks for your replies. I still can't make up my mind, but there is a bloke with a workshop who welds alloy only 20 yards from the boat, so I might ask him for a quote.

Thing is, I can see the differing points everybody has made, for which thanks, and in some respects all the advice is 'right'. I can't see the hole being a problem, but all the same I can't help thinking that a drop of weld nicely finished off might be the best solution, as long as he doesn't want mega bucks to do it.

I hadn't thought of stuffing it with epoxy. Epoxy doesn't like UV so won't last,but I could slop a bit of aluminium silver paint on it to protect it.

Thanks for advice in any event. Its all being mulled over by the brain cell!

Tim

 

[30boat]

The damage is slight and as was pointed out it's no worse than a halyard slot.However I would have it TIG welded shut.The metal becomes a bit soft in that area but that won't be problem because it's small and there are no stresses on the weld.I wouldn't worry about corrosion.Marine alumimium alloys very quickly create an oxide film that prevents future corrosion.