Aluminium Mast - how strong?

[BOATYBOATY]

One of my winter jobs is to move the the Main Sail halyard sheave from the current port side of mast to the centre aft position of mast, it will be about 12" lower than present position. This will involve cutting a slot in the mast about 3" vertical x 1" wide. Do you think this will weaken the mast considerably? How can I add strenth to the existing slot, I was thinking of riveting a plate over it, what do you think. O' yes reason for moving it is so that I can work the Main Sail from cockpit without going on deck.

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[Robin]

Sorry, I still don't understand why working the main halyard from the cockpit means changing where the sheave is, unless you are just talking about the halyard exit at the lower end of the mast?? If this is the case and you want to cut a new halyard exit, there are S/S plates available via riggers that rivet in place over the cut slot and have a smooth path for the hayard to run over.

<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>

 

[steve_l]

Maybe I'm missing the point, but couldn't you just add a turning block at the base of the mast below the existing sheave and then lead the halyard aft to the cockpit through a deck-organiser and some form of clutch which you will have to use anyway.
No need to do anything remotely drastic with the mast in that case...

-steve-

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[Gunfleet]

<<through a deck-organiser and some form of clutch which you will have to use anyway>>
Don't forget the winch you'll need because you'll have introduced so much friction!

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[steve_l]

Agreed. But depends on the size of boat. Mine's just under 26ft with a full battened main and I only use the coach-roof winch to set the final luff tension. Otherwise the main's up by hand in a few seconds from the cockpit.

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[dickh]

I agree with steve in that a turning block which will lead the rope aft - they are called deck organisers I think, usually available with two or more sheaves or, like mine a double one on top of the other. Then lines led aft thro clutches and the winch. Works well, I can raise the fully battened main almost all the way and then winch the final few inches.
Just reread your post - you will also need a vertical block for the rope to go from vertical to horizontal at the base of the mast, often can be shackled to an eye on the mast base or shackled to an eyebolt thro' the deck(with a good backing plate) and then thro' the deck organiser, then aft.

<hr width=100% size=1>dickh
I'd rather be sailing... /forums/images/icons/smile.gif

 

[BOATYBOATY]

Sorry, I wasn't very clear, the halyard is internal of the mast where it exits, on the bottom of a fixed sheave in the mast is at a very difilcult angle to rig other blocks to get it back to the cockpit. If I move the position it exits the mast I will only need one organiser, and of course the deck house winch.

If thats still not clear I have a photo, thanks for advise so far.

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[boatless]

Oh - I get it now.

Would suggest that the height of the slot is as low as you can get it to keep strength up in the gooseneck area. Shouldn't be a problem, many masts have exit slots like this.

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[William_H]

There shouldn't be too much worry about the holes in the mast provided they are near the bottom and not all at the same level. (distance from the base). I did have a mast which failed in compression around the exit sheave holes they were all at the one level in the mast about 4cms from the bottom. Corrosion made it worse and the mast simply shortened itself by about 1cm. From my experience the best exit is about 1metre above the deck through a slot hole faired (or with a SS plate as suggested) down to a turning block attached to the cabin top about 10 to 15 cms out from the mast then if neccessary to another turning block to get around entrance hatches etc. You will certainly find it easier with all halyards to the cabin top winches near the cabin bulkhead.

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