Backstay Tension 2?

[poter]

Sorry to be a pain but my first post on this subject went around the houses a bit.
Whilst I appreciate that the Backstay has many people, especially racing types, delving into the mysteries of mast bend & rig tension to achieve a particular sail shape.
All I am after is a sensible way of getting the correct tension to a mast head rig on a 1976 Moody, that as my name suggests will only be used for a 'Poter' Yes she will need to be correctly set up to avoid any problems in a blow & to fly a spinny, but there must be a simple & practical way to achieve the correct tension.

Note all the rigging is brand new.


poter.

By the way I will not sue!!!! who's Sue?<P ID="edit"><FONT SIZE=-1>Edited by poter on 25/03/2004 21:45 (server time).</FONT></P>

 

[maxi]

It's not just the backstay tesnion, but the juxtaposition of the backstay and the lower shrouds, particularly the forward lowers or babystay.

For a cruising or pottering boat, I would suggest that the right backstay tesion is that which provides a pre-bend of half the diameter of the mast. i.e that the section of mast approx half way up is forward of that at the foot by half a mast diameter, in your case maybe 3"



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[maxi]

Have just read my own reply - clarification required. We are looking for a degree of bend and not allowing the masthead to go forward of the mast step. So, in conjuction with what I suggested, I'd recommend that you also need to hang a plumb-bob from the main halyard which should hang approx 4"-6" aft of the gooseneck.

So set-up procedure = (1) establish mast properly amidships by use of cap shrouds
(2) establish correct rake by use of plumb-bob as above, using fore and back stay (3) tension capshrouds by equal amount either side thus maintaining midships orientation, (4) Set up baby stay or forward lowers to give required pre-bend also maintaining mast in column - looking up the luff slot to ensure absloute straightness, finally set up aft lowers to control lateral bend in the mast, also again ensuring that the mast remains in column.

Check it all whilst sailing, close hauled in approx f3 or f4, look up the luff slot to ensure that the mast remains straight (on both tacks) adjust accordingly if required.

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[bedouin]

I can recommend Ivar Dedekam's "Sail and Rig Tuning" as a good introduction that covers most aspects for a cruising sailor.

IIRC he recommends a backstay tension of about 10% of breaking load if you are not intending to adjust it while sailing (as most cruising sailors)

On a masthead rig the backstay does affect mast bend but only really influences the forestay tension, hence sag. On a fractionally rigged boat it is a lot more signifcant adjustment.

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