Need for running backstays

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SouthPark

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I have a furling staysail fitted to an inner forestay - added by the previous owner of the boat. After reading the YM article on sailplans this month I'm wondering whether this is safe. I have only a single backstay supporting the top of the mast. The inner forstay is attached well below the top of the mast - and the YM artical suggested that if you have a rig like this you need running backstays to resist the forward pull of the inner forestay in heavy weather. As the staysail is my primary heavy weather gib (I have a storm gib too but would hope to use it only in storm force winds) I'm a little concerned that I may be chancing rig failure.

Opinions?

Southy

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Do you have forward facing spreaders or a jumper strut, thingy? You may not need running backs.


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The Moody 376 has straight spreaders and a 2 spreader mast I believe. So if the inner forestay is attached well down from the masthead (normal would be a the 2nd spreader height) then you will need runners IMO with a sail set on this. If the inner stay goes from near the masthead then the existing backstay should suffice.

We do have a removeable 2nd forestay at the 2nd spreader position to carry either a staysail or a storm jib, but we also have running backstays to use when this is in use, they and the extra stay are normally stowed by the shrouds.

<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>
 
I have a removable inner forestay on a masthead rig, but it is attached within 12 inches of the top of the mast. I agree with Robin that if your forestay is attached well down the mast you will need runners or risk rig failure.

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Running backstays are well worth having and are a good insurance policy against rig failure, particularly in heavy weather.

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Yes, I think you should fit running backstays. My boat is a similar size and has a furling staysail with running backstays. I don't have a backstay tensioner but there is a goodish bit of pre-bend in the mast. Like most furlers the inner one isn't particularly tight but it's amazing how it hardens up with only a modest amount of tension on the running backstay. This is good if, as you say you will use this stay in strong winds. Two reefs in the main with the staysail makes a very snug rig. The importance of the runners was demonstrated to me once when one of the blocks in the tackle gave way with a bang - indicating that the mast ws doing some pumping.

They are of course a pain to live with, and how to manage them is another subject. When deciding where to position the deck fittings consider whether the stays will be clear of a bimini should you ever fit one. (Actually I think your boat has a centre cockpit so this might not be problem).

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The worst bit is stowing them so they don't rattle. Ours are clipped on an eye right forward on the genoa track, then tensioned by hand using the integral tackle, then tied back to a a stay with webbing which tensions them more. Our tackle system doesn't include a jamming block which would be much better, in use they are held on the free S/T sheet winch. I keep looking at suitable jamming blocks but so far have baulked at thr £80 each required! In use ours go to deck eyes back by the forward pushpit foot which clears the bimini etc fine. I keep looking at the raceboat systems with a view to adopting their shockcord 'pull the lazy one out of the way' technique, so I would agree with your comment this is a topic for another separate post - hver to you, how about it?

Robin

<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>
 
Not knowing the boat or the mast section with which it is fitted, any opinion has to be blindfold.

But assuming the rig designer has used the normal 1:1.8 factor, if the forestay is within 1% of the free-strut length, you probably have nothing to worry about. If more than 10% you definitely need additional staying.
In between in depends on the sweep-back of your spreaders, more than 20 degrees you're less at risk than if you have straight spreaders.

The risk is of the mast fatiguing due to the pumping action caused by the inner stay and will be highest without any mainsail or if the mainsail is reefed, unless of course you have in-mast roller reefing which exacerbates the problem dramatically.

Using jumper stays will exaggerate the action and that's not a move to be recommended.

I would take an experienced rigger for a windward bash in a F6 sea, using the inner stay - he'll have no difficulty in forecasting the likelihood of a gravity storm.

Failure is unlikely to be sudden and catastrophic, most likely points are, on a keel-stepped mast, just above the coachroof and on a pin-joint mast at the base of the lower spreaders.

You might want to have an ultrasound test done on the mast to check for crystallisation - one of the few occasions it's valid. Unfortunately induction testing will probably be a waste of time.

PS. Daughter kindly modelled this one for me on the Soton mainframe after I had a fatigue failure mode off Cabo Gata in 2001. I was trying to persuade the insurers to pay up, but had to agree their view, that the failure was due to a design error, was justified.


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You appear to have been given some good advice, so just a point to dwell on.
My Trapper TS 240 has a very slim mast with pre-bend. Other similar models I have seen have no runners but mine came with them.
I thought they were mainly used for racing and I was going to remove them.
However I found that she sails very well and balances nicely with the 130 % genoa whether or not the main is reefed. I found also that the runners had been fitted in such a way that, with two reefs in the main, I can tack without touching the runners at all (very handy single-handed)
You may find it possible to achieve the same result.

Merry Christmas and Regards Briani

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