purpose of baby stay?

Ardenfour said:
VicS yes, lowers are inline. This (poorer) picture shows the lowers and caps on same plate. The reason the spreaders appear swept back slightly is due to the baby stay bending the mast.
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Thats OK but without aft lowers you have to be careful not to bend the mast more than the recommended amount.

Disconnect it only down wind or perhaps on a broad reach for gybing the spinnaker (if you had one) but keep it in place when beating to windward.

My rig, similar to dinghies, and common on small boats of the same age, has the lowers in line with the mast and the caps going aft over aft swept spreaders.

Tensioning my cap shrouds induces a bend in the mast. 35 years on I am still uncertain about setting it up correctly!
 
I have a detachable baby stay. I found when I removed it to mast foot that the mast was prone to pumping when head to wind in a blow. Gybing spinnakers didn't worry me too much. Having hoisted main on a mooring one day I looked up to see an alarming amount of mast pumping taking place. Baby stay was soon after replaced in its fore deck position and since then I have considered it an essential part of the rig in strong winds.
 
Ardenfour said:
VicS yes, lowers are inline. This (poorer) picture shows the lowers and caps on same plate. The reason the spreaders appear swept back slightly is due to the baby stay bending the mast.
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The baby stay is an integral part of the rig to stop the mast pumping in the middle. On other MH rigs this is achieved by having two lowers each side, one forward and one aft of the cap shroud.
Advantage is lower cost and removes the need for extra chain plates. Disadvantage is that it narrows the slot behind the forestay and makes tacking difficult, particularly if you have a large genoa that is common on many MH rigs. Therefore, somebody has made it detachable so that in light airs when it is needed less you can more easily tack your genoa. However it should be in place and tensioned in heavier weather otherwise you may find the centre of the mast pumps back and forth so altering the tension on the forestay.
 
If the rig on OPs boat is as designed then we would have to assume that the dmensions of the mast (fore to aft dimension) is sufficient to provide the necessary stiffness without support of the middle in the fore and aft direction. We can say that because there is apparently no pull of the intermediate side stays aft. Usually the chain plate will be mounted about 50 cms aft of the line abeam through the mast. Yet clearly OPs boat has chain plate in line with the mast.
The usual arrangement then on a mast head rig is for the intermediate side stays to pull the middle of the mast backwards while the baby forestay pulls it forwards. This pull forwards and aft then positively locates the middle of the mast in column. Even then it is possible to induce some mast bend (not much) middle forward to flatten the main sail.
So in the OP 's case with no restraint against the pull of the baby forestay (except the inherent stiffness of the mast) we would have to assume that its use is not citical.
So only to be used sparingly to bend the mast middle forward to flatten the mainsail. However be carefull as you would only do that when the wind comes up. A time when the load on the forestay can really load up the mast so you want it in column to best take the load. I suppose the baby stay will reduce mast pumping. (that is when the midle of the mast moves fore and aft rythmically) but that must be linited in value having nothing to pull against. Actual sailing experience will prove that so or not.
From my experience where I did lose a mast through failure of the aft swept spreaders to locate the middle of the mast on a fractional rig. If OP's rig were mine I would consider fitting additional chain plates for the intermediate side stays about 50cms aft of the main chain plates. Then I would always sail with the baby forestay tensioned unless it was very light conditions. This should give a well supported (located) middle of mast in a way that is very common on mast head rigs. However this will give much less mast bending possibilities.
Vic you say you are never confident about your rig set up. The amount of mast bend should be set to match the cut tof the main sail. So often a fractional rig main will have generous camber. It is expected then that the camber will be pulled out by mast bend when the wind comes up. The mast bend is induced by tightening the backstay which should be possible easily from helm position. Several modern designs of match racing boats here have the backstay tension brought out in a mid floor position next to the main sheet and vang so main sheet man can continually adjust backstay tension. In a gust pull on backstay then if necessary ease main sheet. The pulling on the backstay noticeably allows the top of the main sail to sag away releasing load as well as flatening the sail. More vang will reduce the amount of sag away.
Before you start bending the mast however with no backstay tension mast should be straight as set by cap shroud versus intermediate side stays. All reasonably tight. Some say it should have a little bend middle forward at rest. If adjustable the static amount of aft sweep of the spreaders might need to be increased to give more bend forward against the lower side stays. Just have a look at it all when reasonably well pressed (heeled) to see how the stays inter relate to hold the mast up. good luck olewill
 
William_H said:
Vic you say you are never confident about your rig set up. The amount of mast bend should be set to match the cut tof the main sail. So often a fractional rig main will have generous camber. It is expected then that the camber will be pulled out by mast bend when the wind comes up. The mast bend is induced by tightening the backstay which should be possible easily from helm position. Several modern designs of match racing boats here have the backstay tension brought out in a mid floor position next to the main sheet and vang so main sheet man can continually adjust backstay tension. In a gust pull on backstay then if necessary ease main sheet. The pulling on the backstay noticeably allows the top of the main sail to sag away releasing load as well as flatening the sail. More vang will reduce the amount of sag away.
Before you start bending the mast however with no backstay tension mast should be straight as set by cap shroud versus intermediate side stays. All reasonably tight. Some say it should have a little bend middle forward at rest. If adjustable the static amount of aft sweep of the spreaders might need to be increased to give more bend forward against the lower side stays. Just have a look at it all when reasonably well pressed (heeled) to see how the stays inter relate to hold the mast up. good luck olewill
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It's a MH rig not fractional, the lowers are in line with the mast and it has twin backstays which are not adjustable while sailing. The spreaders are shorter than is usual for a masthead rig

Tightening the cap shrouds causies a forward bend in the mast but since the lowers are square on to the mast they dont restrain the amount of this bend.
Tightening the backstays tends to reduce the tension in the cap shrouds and so far from increasing the mast bend as it would with a fractional rig it reduces it.

I normally set it up by tightening the backstays to give a decent amount of forestay tension. Then tighten the caps equally to give some prebend (ensuring they are equally tensioned so as not to cause any side bend) then tighten the lowers equally.

The vang is no more than something that prevents the boom lifting on a reach or a run.

The aim is to get the foretay adequately tight and a small amount of prebend in the mast induced by the tension in the cap shrouds. What I don't really know is how tight to make the forestay, how much prebend to induce or how tight to make the lowers. Its not a racing machine so the primary objective is rig that wont collapse.
 
sailorman said:
on a run with spi set, remove baby stay, remove pole from spi guy,dip pole below the fore stay to the other side & attach to the new guy, gybe the main & off you go trimming as req.
Or have 2 x poles
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I too have a Nic 30 (Hull No.9 - Jasrah III). I'm not sure that the baby stay on this boat was originally intended to be detachable - this may be the reason why they were originally supplied with two spinnaker poles, to negate the need to gybe the pole itself.

I'd have much preferred to see them with a 30 degree sweep back on the shrouds and spreaders.
 
VicS said:
Gybing the pole will be difficult by any method with a baby stay in place wont it.
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Yes, having a babystay does make gybing more of a problem, end-for-end is the only possibility, made somewhat easier by having a sheet and lazy guy system. The babystay also influences very strongly the selection of an inflatable dinghy, in our case we carry one that we don't especially like because its predecessor would barely fit on the foredeck.

Despite these problems it would not be advisable to remove the babystay, even temporarily, as it is preventing the mast from buckling aftwards. Doing it when carrying the spinnaker could prove even more regrettable when the pole loads acted in that direction.

A rule of thumb with babystay tension on masthead rigs is that the mast should bow forwards to half its longitudinal width, although I have no experience with the more complex version of the OPs boat.
 
All this confirms my view that Kipper's babystay is a later addition as a very bad conversion to cutter rig. I have forward and aft lowers each side that go to the same point on the mast as the babystay which has a halyard coming out of the mast at that point. The babystay gets in the way of everything, I'm going to remove it.
 
Just noticed the picture of your Nic - was it ever called 'Booby'? It looks identical to the boat which I learned to sail on in the early 1980s. If so, the babystay did not have any tensioning/removal system at that point.
 
Vyv,

I agree with the principle behind what you say, but if the baby stay is there to prevent the mast from "buckling aft", what's preventing it from buckling forwards ?..

Indeed, the compression on the mast applied by the combined tensions in the forestay, the backstay and the cap shrouds will induce a certain amount of pre-bend, with, or without tension any additional force applied by the baby stay - they therefore combine to cause the mast to buckling forwards to some (hopefully pre-determined) degree, and the mast is more than capable of withstanding it. Again, to a degree, it follows that if a hollow mast is perfectly straight, then the rig tension is most likely insufficient.

Best Regards,

DS.

I would suggest that given the chord length of the mast section, in relation to the height of the mast, the tension in the baby stay is more to damp out pumping action when beating into a chop.
 
Lazy Kipper said:
All this confirms my view that Kipper's babystay is a later addition as a very bad conversion to cutter rig. I have forward and aft lowers each side that go to the same point on the mast as the babystay which has a halyard coming out of the mast at that point. The babystay gets in the way of everything, I'm going to remove it.
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No - it's not a later addition - it was fitted by Camper & Nicholsons 40 odd years ago.

See extract from C&N GA sailplan at:

http://s121.photobucket.com/user/bajansailor/media/Yacht catalogues/Nicholson30P1.jpg.html
 
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Lazy Kipper said:
All this confirms my view that Kipper's babystay is a later addition as a very bad conversion to cutter rig. I have forward and aft lowers each side that go to the same point on the mast as the babystay which has a halyard coming out of the mast at that point. The babystay gets in the way of everything, I'm going to remove it.
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Rather than just remove it, why not shorten it slightly, reterminate with a staylock, and fit a highfield lever, or as Jim has done, a robust block and tackle, so that you can move it out of the way, but still have it as extra mast security when needed?.... wouldn't cost a lot, and would give you best of both worlds... plus, if you use a block and tackle, makes an excellent MOB lifting point.
 
Phoenix of Hamble said:
I'd be a bit concerned to use it in that role if the lowers are in column with the caps unless there were also checkstays.
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I used to have a UFO27 (straight spreaders, caps and lowers to same chainplate). The baby stay had a snap-shackle or similar for quick release and 4-1 purchase for tensioning. Other examples of the same marque I have observed with the babystay permanently fixed and adjustable with a bottlescrew. The quick release feature was much more user-friendly, as I found that I could unclip and stow it to the mast when sailing in light conditions to enable the huge genoa to be tacked more efficiently, whereas in stronger winds it could be deployed to bend the mast, bringing the draught of the mainsail forward. With the genoa rolled in a few turns, the babystay no longer interfered with the tacking of the genny. Once the babystay was tensioned up reasonably the backstay tensioner came into play in adjusting the shape of the mast. I don't think babystays are intended to have sails bent on, the tackle on mine would have made this quite difficult. My present boat has a removable inner forestay for use with storm, or other small jibs.
 
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I suspect that if shrouds are in the same plane as the mast, straight spreaders, then the baby stay tells the mast where it has to be. I was told years ago that the idea was that applying a force to the top of the mast via shrouds and stays lets the mast be floppy, so that small forces applied laterally will push it easily. Without a babystay it might go anywhere it wanted, within limits of the lowers of course.
 
Phoenix of Hamble said:
Rather than just remove it, why not shorten it slightly, reterminate with a staylock, and fit a highfield lever, or as Jim has done, a robust block and tackle, so that you can move it out of the way, but still have it as extra mast security when needed?.... wouldn't cost a lot, and would give you best of both worlds... plus, if you use a block and tackle, makes an excellent MOB lifting point.
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That's an excellent plan for a B&T.
 
345000 said:
Vyv,

I agree with the principle behind what you say, but if the baby stay is there to prevent the mast from "buckling aft", what's preventing it from buckling forwards ?..

......
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At various times, the spinny pole is pushing the lower part of the mast aft.
When reefed, the leach tension is pulling the upper part of the mast aft.
That's one of the times you need the babystay most, upwind in waves, reefed.
 
I don't understand why bend flattens the mainsail? Surely it makes the leach more baggy? Not disagreeing, just not understanding.
 
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