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Old 08-05-2013, 23:52   #76
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Re: Beating Home Alone and oh so Slow

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Originally Posted by ctl411 View Post
The Solent rig problem is a two against one thing. Two forestays one back and getting the balance of them plus no running backs to help. On a true cutter with running backs you use the runners to help balance the tension.
With a sprit you add the flex of that and there are very high compression loads pulling the sprit back. They can and do work but it's not just a simple bolt on.
Rig tension is set by percentage of breaking strength of the stays.
Hmm - I have a somewhat different take on this. I personally think the tension-related difficulties with solent stays arise from the fact of their being attached to the mast in close proximity.

In this it is similar to the problem with twin forestays (side by side), which were briefly popular on long distance sailing rigs a while back. These had a number of other problems, but the relevant one was to do with tension on the unused stay.

This turned out to hold true, even when the twin forestays were 'balanced' along the lines ctl411's plausible reasoning would suggest, by providing twin backstays, which also ran to the masthead.

The underlying problem turned out to be that the stay which was under load, from having a sail full of wind hanked to it, would deflect into a curve, as usual, under the luff load (acting in the plane of the sailcloth).

At the same time, that luff load would cause tension in the loaded stay, pulling the masthead forward (of course it tries to pull directly towards the bow, but the mast is stiff in compression, so it moves forwards)

Because the loaded stay is curved, even though the distance between the end attachment points of the stay is reduced by the masthead coming forward, the loaded stay is also effectively shorter, when measured in a straight line, so it continues to pull until equilibrium is reached.

The problem is that the OTHER (lazy) stay does not have any natural curve, and yet its attachment points are also displaced towards each other.

This means the lazy stay loses tension, quite drastically in strong winds, causing it to flop around as the boat pitches, and be prone to fatigue near the ends.

So the further down the rig the solent tang attaches the better, and ideally even a masthead rig will be tapered above this point, and a powerful masthead backstay adjuster fitted to allow keeping a bit of tension on the masthead forestay.

It's tempting to try to design a masthead box which transfers some backstay load directly through to the forestay without needing to induce mast curvature, with a simple (pivoting) crank arm, and resilient stops, but I personally think it's asking for trouble on an offshore rig.
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Old 09-05-2013, 00:08   #77
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Re: Beating Home Alone and oh so Slow

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Hello Cruisers,

I recently had a short jaunt across the Gulf St Vincent in South Australia with three of us on board a Swanson 42. The trip over was great, did the 35 nautical miles in 6 hours pointing the whole way, nothing to complain of except one of the crew got quite seasick. The next morning we set out home, a trip due East for 35 miles, but had to turn back when the crew member became quite sick again. For various complicated reasons this meant I left both crew members on the Westerns side of the gulf (to be collected by car) and sailed home alone, into a pretty grotty Easterly. I didn't get to leave till midday so I was looking at a very late arrival, but the boat has good lighting, good auto pilot and a radar so I was not too worried, and once you are half way across the gulf you can keep all shipping traffic to the south of your path so solo navigation was not a big problem. The weather forecast was for a number of days of similar or worse conditions, so waiting around on the Western side was not a great option either.

The unexpected problem I ran into was that the wind was gusting between 18 knots and 28 knots. To reduce strain on the boat and rigging during the 28 knot blows, I reefed the main down to about half size and rolled the jib back in to give a balanced helm. This stopped me worrying about the strong gusts, but I found that between the Swanson's rather "rotund" hull form, the suprising large seas coming from directly on the bow and the fact that with the sails reefed down that much there was barely any power when the wind abated to 18 knots, I made absolutely no headway all evening, and to cut a long story short, did not get home till 5:30 in the following morning.

Looking back, I feel there must have been a better tactical approach to this one. On the face of it, it was simply a matter of beating 35 miles into strong winds in fairly undemanding expanse of water (though it can get a bit scary if there has been a Southwesterly blowing for a bit of time.). I had plenty of sea room to the North and South of my course, though the area to the South does have some shipping traffic so I was keen to avoid it. The boat was certainly up to the task, but taking nearly 18 hours to do 35 miles is horrible and left me with the unavoidable need to take short sleeps between tacks, reinforcing my desire to keep the sail area to a minimum, and slowing me down even more. Vicious circle.

What should I have done?


Thoughts and suggestions welcomed, I'd really like to avoid another night like that one.

Matt
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Old 09-05-2013, 05:20   #78
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Re: Beating Home Alone and oh so Slow

E]
Quote:
Hmm - I have a somewhat different take on this. I personally think the tension-related difficulties with solent stays arise from the fact of their being attached to the mast in close proximity.
Which is why I thought the sprit solution would work better.

Still hard to see why it induces tension problems.
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Old 09-05-2013, 05:28   #79
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Re: Beating Home Alone and oh so Slow

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E]

Which is why I thought the sprit solution would work better.

Still hard to see why it induces tension problems.
OK: Think of it this way:

Imagine stringing a bow with two strings the same length.

Now draw the bow, with one string.

The other string will immediately go slack.
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Old 09-05-2013, 06:06   #80
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Re: Beating Home Alone and oh so Slow

I guess the problem is how you define " problem."

Yes there will be some varying tension, I get that, it is a bit of a compromise.

But it does help to resolve the "problem" of tacking through a small spacing and give you a wider range of head sail options, etc.

So any one "solution" begets a problem. Pick your poison.

I does strike me that the head tension issue is pretty manageable.

That said I am still looking at the rig after replacing the sprit, trying to assure myself that the small dimensional issues are resolved and the rig correctly balanced.

Edit...apologies if I come across argumentative, appreciate the explanation.
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Old 09-05-2013, 08:02   #81
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Re: Beating Home Alone and oh so Slow

Andrew, the tension issue (at least in our boat) isn't related to the lazy stay flopping about from sail loads on the active stay as you describe. Rather it is that if you load one stay with its rigging screw, the other one looses tension, and thus will have sail shape affected when it is in use.

I try to have them reasonably balanced, but it isn't easy to achieve. The outer stay is 10 mm Dyform, the inner is only 7 mm Dyform. The sail areas are roughly 550 and 200 sq ft, so the stay sailing loads are somewhat different. The final result is that neither stay has as much tension as our sailmaker would like! Everything is a compromise...

Cheers,

Jim
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Old 09-05-2013, 13:15   #82
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Re: Beating Home Alone and oh so Slow

Perhaps I wasn't blunt enough about the potential consequences if the attachment points are close enough (which is why boats no longer have side-by-side twin forestays)

when I wrote above: <<This means the lazy stay loses tension, quite drastically in strong winds, causing it to flop around as the boat pitches, and be prone to fatigue near the ends.>>

Even with toggles, the whipcrack action over time is likely to cause stainless wire or rod rigging to break, usually near the bottom turnbuckle.
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Old 09-05-2013, 17:35   #83
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Re: Beating Home Alone and oh so Slow

As I have a solent rig, so I have been following this discussion with great interest.

As an idea straight off the top of my head, what about this: single attachment point at the head of the mast; block attached there; twin forestays of dyneema, running through the block; tensioning turnbuckle on one of the forestays at the deck, tensions both forestays. That is, the twin forestays are made up of one length of dyneema, running through the masthead block.

I am trying to envisage the forces at work under sail load. Shoot me down..lol

Lee
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Old 09-05-2013, 17:45   #84
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Re: Beating Home Alone and oh so Slow

G'Day Lee,

Well, that set up might well equalize the tension on the stays, but I see some difficulties:

With the two stays so close together at the top, the interference issues would be greater.
And AFAIK, folks are not using furlers on Dyneema stays, and at least in my case, I have two of them to consider.
Finally, the load on that masthead block would be pretty substantial!

But it is an idea worth considering in the abstract!

Cheers,

Jim
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Old 09-05-2013, 17:51   #85
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Re: Beating Home Alone and oh so Slow

Lee

A neat concept. I once toyed with a proxy solution, using a 'balance beam' to bridge between the toggles of two wire forestays providing a single point of attachment, designed in such a way that if either one broke, the other would hold (although it would lose some static tension).

Yours would be one solution if you are wedded to a twin forestay (I mentioned there are other disadvantages: for instance: presuming hanked sails - and why else go for naked forestays ? - the working hanks are prone to hooking themselves to the lazy stay and jamming - even with old-school piston hanks, although it's hard to imagine - it seems the lazy stay can operate the release - but that seems unlikely with your proposal.

Wichard one-handed operation hanks, which are a much nicer option, are not viable with any sort of twin forestay, in my view)

The luff sag would be greater than with a single dyneema forestay of the same diameter, because although the masthead is more firmly fixed*, the elongation of the lazy stay adds to that of the working stay**.

However if you are looking specifically at eliminating flop of the lazy stay (and eliminating fatigue and greatly reducing inertial load issues) it certainly seems to me to answer those objections elegantly.

*(Because from the frame of reference of mast movement, the stays are in parallel)

**(Because from the frame of reference of extension of the working stay, the stays are in series)
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Old 12-05-2013, 14:38   #86
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Open class boats all have solent stays and furlers. I think they have a block and tackle at the base to tension individually? This would solve the problem of the luff becoming too curved in heavy wind and putting too much camber in the sail
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Old 12-05-2013, 17:27   #87
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Re: Beating Home Alone and oh so Slow

what you describe is the perfect scenario for motor sailing.
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Old 13-05-2013, 06:13   #88
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Re: Beating Home Alone and oh so Slow

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Originally Posted by Andrew Troup View Post
In this it is similar to the problem with twin forestays (side by side), which were briefly popular on long distance sailing rigs a while back. These had a number of other problems, but the relevant one was to do with tension on the unused stay.
Interesting, The two boats I sailed with that had twin forestays I found them to be pretty good, the slack unused shroud was not a huge drama except for the worry it might foul a hank (which never happened), and some chafe on the luff of the sail. I never recall them banging about in any way that worried me (and I am a worrier!). Maybe as simple as some very strong bungy or nylon could eliminate the shock loading without reducing the tension very much on the loaded stay?

This is my concern about any sort of balancing system, that it either reduces tension in the loaded stay giving much more luff sag, or it doubles the compressive loads on the mast from the forestays if you increase the backstay tension to compensate. It was sometimes common to put a little triangular monkey face plate at the base which might have equalised the loads slightly, and people talked about making them rotate so the loaded stay would always be to leeward. Both stays needed to be about the same size as a single stay would have been, doubling the weight of the system.

I think what really killed the twin stays idea was the improvements in furler (and sail) technology and the gradual acceptance of the newfangled device. coupled with the increased size of vessels and the weaker crews. For me the switch to rollers was as much to do with extra storage space as anything else. I hate having salty damp sails below, and drying sails after every sail is impossible. Now my spare headsails are dry and neatly folded under a bunk forward.

The biggest pain with the twins for those of us without a nice pair of identical sails was the need to swap the smaller headsail to windward each time you gybed. it got annoying pretty quickly even on a 28 footer.

I have seen a setup with a furler to port and a bare stay to starboard, the owner liked it. But I would worry about the wire getting caught in the furler one day, and chafe.

I am keen to use dynex dux for my next solent stay, the light weight will make it much easier to tie back to the mast, and take forward. It can be very hard holding the end of a wire in a seaway, the snatching tries to rip it from your hands. The soft rope will also reduce chafe of the other sail.
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Old 13-05-2013, 08:03   #89
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Re: Beating Home Alone and oh so Slow

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I am keen to use dynex dux for my next solent stay, the light weight will make it much easier to tie back to the mast, and take forward. It can be very hard holding the end of a wire in a seaway, the snatching tries to rip it from your hands. The soft rope will also reduce chafe of the other sail.
G'Day Ben,

I think this has a lot of merit, and would (for me, if I didn't have a roller on the Solent) be a great way to evaluate the use of Dux for sail-bearing stays. I know that Evans has done so for a storm sail, and I value his opinions, but it is so counter-intuitive that I need to do it for myself! At any rate, doing it on a Solent for evaluation means that should it fail at sea the mast stays up and you still have some sort of headsail.

And if you think that the snatching in a bare wire is bad at sea, try it with a furled staysail on a roller! When I move the Solent sail out of the way for better tacking in light airs I know that it will be there until we are again at anchor or it is really flat calm. Sometimes this worries me...

LEt us know if you pursue this idea, please.

Cheers,

Jim

PS: Has anyone tried using a roller on a Dux stay?
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Old 15-05-2013, 04:19   #90
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You're LUCKY!

I once had to sail around the world in a bath tub with only an rotted shower curtain for a sail, sailing upwind and against the current the whole way. I had only the plankton that would wash over the sides to eat, and had to pay $20 a day the sea monster who was chasing me.
Bloody Luxury !!!

I once had to circumnavigate the globe lying on a broken twig with a zip lock bag as a "jib" and a sticky note as a "main" during fair weather. Sadly, I couldn't use the main much, it was winter in both hemispheres. Meager portions of scales scraped off the back of passing fish sustained me, my dog didn't fair so well.
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