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Old 03-02-2009, 21:04   #1
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Tension on 4stay with Roller Furling

Tension on 4stay
Hi One more question ok more than one
I downloaded “Selden Rig tuning manual” one of the best I have seen one issue puzzles me when tensioning wire using the 2 meter approach seems good but how do you do this to the 4stay when it is surrounded by roller furling, you can reach the turnbuckle but not 2 meters of wire??? Also I have 2 5/16 backstays do I tension each only 1/2 the 15% as there is only one 3/8" forstay or do I tension both back stays to 15%
Also a separate question when I raise the mainsail I usually run out of rope halyard and begin 2 wraps of wire on winch which I suspect is not good should I shorten wire and by how much( when I say wire my rope halyard is spliced into wire for the last approx. 50 feet)?
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Old 04-02-2009, 09:56   #2
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Wire on winch

Cannot comment on your tension headache but can on the winch. My last 40 foot racer had wire/rope arranged so that had two loops of wire on winch with rope cleated off. After 25 years use, the S/S winch barrel was slightly worn but not unsightly and did not affect function. Minimal tension on the rope-wire splice which was in good order after years of hard service. Replaced the mast sheaves before the wire and rope. So I guess that says is not an issue to spend time on.
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Old 05-02-2009, 12:04   #3
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If you have a double backstay each leg get's half the tension. This is pretty much true of split (Y) backstays as well. Determining tension on a furler headstay is tough. Remember, that furler is heavy so it'll always seem loose if you just grab and shake it. Follow your tuning guide at the dock and then take it out for a sail for a dynamic tune. This probably isn't the answer you are looking for but with furlers it's about your only choice.

As for your wire to rope splice, that will result in wear on your winch drum (especially aluminum) and a much shorter life for your halyard. Ideally the tapered end of the wire inside the line should end above the winch so that only line is actually wrapped around the drum. It's not critical, your halyard isn't likely to immediately fail but it is hard on your gear and should be done correctly when you next replace the halyard. Worst case scenario is a worn out winch drum (especially if your drum is aluminum). When you do replace that halyard consider going with something other than the wire/rope combo. There are much better materials available now versus just a short while ago.
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Old 11-03-2009, 15:26   #4
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Better a late answer than never...
Basically you want the minimum amount of headstay sag without over tightening. A good way to adjust the headstay tension with a furler is to first check how much sag you are getting under sail. While sailing under moderate load, estimate how much luff sag there is at the midpoint. It helps to run a spare halyard down to the tack, parallel and as close as possible to the furler. This is used as a straight reference line. Then take up a couple of turns on the backstay turnbuckles (provided your mast rake is about right to start with). Sail again and recheck the luff sag. When the sag no longer decreases you have reached a point where it is no longer beneficial to tighten the headstay.

If you have split backstays it is easy to run a tackle between them and effectively squeeze them together for a sort of makeshift backstay adjuster. A vang tackle works well for this. This can be used to experiment with both headstay sag and to tune the rig for weather helm. Particularly if you have a cutter stay you can induce a little mast bend (very little) which often helps reduce helm pressure. It works quite well, I've used it extensively. I can give more detailed description if you need it PM me.

Cheers,
jim
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Old 12-03-2009, 16:57   #5
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Thanks for your advice seem practical and I will try next time I am sailing
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Old 12-03-2009, 17:29   #6
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Not all info in this thread is correct...

When you have two backstays, they share the load but they are also smaller diameter than for a single stay, so the stretch under load would roughly be the same percentage!

About that pre-tensioning: this is mainly done on capshrouds, lowers and intermediates and never on the forestay! Actually, the forestay is never tensioned by it's turnbuckle! The length of the forestay is adjusted to get the masthead to the right position. Tensioning it is done by the backstay or, lacking these like on Jedi, by the capshrouds and helped/tuned by special runners to the masthead.

The measuring of pre-tension by measuring the stretch over a 2-meter section works very well and is the same for all diameters (it's 20% of breaking strength and thicker wire needs more tension to get there, at which point is stretched the same length as thinner wire).

I don't know if this is in that tuning manual but use Lanolin (jars from Forespar) on the turnbuckle threads when tensioning. It prevents the galling better than anything else.

cheers,
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Old 12-03-2009, 17:52   #7
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Also, I think I need to elaborate more on capshroud, lowers and intermediate tuning:

before tensioning, the mast must be centered (and raked but that's part of the fore/aft stays and deck-level support for keel-stepped masts). This is done with the water-filled bucket on the main halyard, adjusting capshrouds until the bucket is hanging exactly midships and the capshrouds have some tension and feel equally tight. Now, the same must be done with the lowers, looking up the mast-groove to see if it's straight.

After that, the turnbuckles are loosened again, each the same amount of turns, until capshrouds and lowers are slack and the 2 meter section is marked. I just tape the tape-measures to the shroud. It's best to first tension the lowers if you have aft-swept spreaders. Each should be tensioned the same amount of turns so check that. Next while tensioning the capshrouds, check on the lowers again! Capshrouds on aft-swept spreaders bend the mid-section of the mast forward, tensioning the aft-lowers and loosening any fwd lowers! Adjust the lowers tension accordingly.

After all this, the intermediates are tuned to feel and you must go sailing to tune them further. This is why it is easier to have intermediates run down to deck-level instead of terminating at spreaders! While on a tack, tighten the leeward intermediate until it's not slack anymore, tack and do the same on the other side. Now look up the mast at the groove again (while sailing) to check if the mast is straight. Correct by further tensioning and repeat on other tack. Now stop sailing and loosen the intermediates again with the exact same number of turns until slack and do the 2-meter tensioning thing but each side must be tensioned the same number of turns!

Very good riggers manage to do all that while at the dock. They developed an extra sense for it. But they would agree that tuning under sail is better (more precise) but that would add too much to their bill and the competition is waiting to take over.

Finally, every rig is different and imo every cruiser should know how to tune it on their boat. I discovered that my mizzen forestays are too small diameter as they get much more tension than 20% of breaking strength when tensioning the capshrouds!

cheers,
Nick.
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Old 12-03-2009, 18:03   #8
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Ah, I must react to that wire-on-winch thing. This is really no good. The rope to wire splice and rope-part are (should be) strong enough. Also, the winch radius is small enough to hurt the wire or reduces it's strength.

Instead of shortening the wire-part: replace the sheave at the masthead and change to all-rope halyards, maybe even fancy ones like spectra or vectran.

For jibs: check that the anti-halyard-wrap mechanism works. Many jibs are not hoisted high enough for this to work with wraps and jib damage as the result (happened to me too). Adjust this height by a Spectra lashing at the tack.
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Old 13-03-2009, 19:36   #9
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Thanks Nick for the advice
This is a great sight which allows me to learn from the experience of others compared to trial by error.
Good point about the 2 back stays being smaller. Also the notion that the forestay is used to position the mast and the back stays are used to tension the forestay.
If I went to full rope for halyard why do you suggest changing the sheave at the top of the mast I believe the sheave is made to accommodate both the smaller wire and the larger rope halyard?
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Old 14-03-2009, 22:16   #10
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2 backstays: according to Brian Toss this is evil (it's on his website).

changing the sheave: it is either a version shaped like for rope with a slot for wire, or just shaped for rope but from hard material. The slot-version will chafe rope even when new and the other one too when it has some wear from the wire.

cheers,
Nick.
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