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Extending the mast


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I'm looking at extending my mast by a metre and wondering whether a it would be expensive to manufacture a tapered piece that could be bolted to the top of the original extrusion. (so far, unable to get a piece of the extrusion.)

The original extrusion has an internal track which could be an issue, but surely I could find an extrusion that could be butchered to suit.

Any aluminium welders care to comment?

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Nothing is impossible....if you have enough money to throw at it of course :wink:

 

OK, first question, what are all the measurements and it would be even better if you could include a Photo of the extrusion.

Second question, is the want of extending due to wanting more sail? or some other idea??

Is the Mast Anodised or painted or plain. Anodizing creates a slight problem. See the note (a)

 

Butt welding the section can be done. It will always be a weak point. An internal sleeve would be needed to ensure a real strong join. (a)An internal sleeve and both sections riveted would also work OK, but you see the join is all. Probably best scenario if the mast is anodized.

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You will find that a lot of production boats have joined masts. (Look at Bavarias for an example). They are joined with an internal sleave and rivets. I would not weld anything. The days of welded on spreader shoes and similar seem to be over due to failures at the hardened weld line. The internal sleave should be tapered so that there is no "hard point".

If you use Stainless rivets then you need to use Durolac or a similar anti electrolysis goop.

 

....just my 2 bobs worth.

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Wheels,

I need more sail area and the mast is I think anodised.

Because it is at the top of the mast, and because there is less load up there I was thinking of manufacturing something with lugs about 100 ml longfront and sides at the bottom that could be bolted/screwed/rivetted to the top of the existing mast.

It's a rotating mast thats about 200 ml by about 100ml. The spreaders will be bought up the mast, but will still be on the original extrusion.

Danaide,I know about Zen, but he had the right extrusion available.

Idler boat, I agree with welding to original mast but what about the welding on the extension, that should be ok though?

And Andrew, cat 1 and 2 not a problem, but what about cat3?

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If the rigging attachment points are above the join, then the join "see's" the same load as any other point along the rest of the mast. So if you have the chance of folding it anywhere, it will be at the weakest point. In saying that though, a join can be made strong enough to take the load. So it comes down to where the best place to make the join is. So a little thought here, can you actually make the extension at the opposite end and lift the mast up. My question here would be, is she Deck steeped or Keel. If she is Keel stepped, then the addition could be any section capable. This is also presuming the Track is all the way down the section to the Keel or at least Deck. This would mean you can leave the mast head and all attachment poins alone.

If Deck stepped, I would assume you would not have a metre above the deck to Goosneck fitting, so adding a metre there is probably not an option.

 

So what did you want to weld exactly??

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Wheels, the part I was talking about welding would be the manufacturing of the piece to be added. I thought of tapering it.

Also, the rigging attachment points will be below the connection, so the only loads will be the sail loads.

If I had an extrusion piece I would add it to the bottom, but because it would need to be made up, it seems best at the top.

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OK, so what size are we talking? I happen to have a bit over a metre of section with internal track. It maybe too big for your needs though. It is a big section.

 

The problem with anodizing is that it is not conductive and is an oxide, so will not weld. So that coating has to be ground back to ally again. It can be re anodised, but it requires some skill and I doubt many places would take it on. Plus any welding will always come up a different colour to the non welded, so you see the Weld.

 

In regards to the stays terminating at the same point and the extension being above those points, that is beyond my area of knowledge and you would need to ask a spar maker about that one.

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If you are welding up the mast as in a taper then it should be ok, but welding around the mast is not a good idea. A sleave to the goose neck will place a huge amount of stress to a very vunerable place. Most comercial joins seem to be about a meter above or below the first spreaders.

As an aside, a boat I know dismasted in light winds. It had a sleave section to the first spreaders to increase the moment, whilst using a lighter section for the rest of the mast. Crevice corrosion in one cap shroud allowed the stay to part and the load snapped the mast through the spreader shoe through hole. The joys of a swept back rig with only the minimum of stays and section. This boat was a very long way off shore........

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