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Hi have a 13 mtr 7/8 rig , and the forstay sag is getting me down. ,I have done the back stay bit , added a few turns to the fore stay , and still it sags , has dyform wire very good condition the fore stay , and caps all meet same at the hounds so I am feeling caps could help here and lowers to keep all straight ,, furler has sag around 8 inches sighting against the halyard The boat climbs so high , the speed is way up there, helm is perfect , main sets perfect , just the sag worries me , any idears

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Forestay length sets rake. Forestay tension is a function of both backstay tension and, provided you have swept spreaders, cap shroud tension. The amount of spreader sweep sets mast prebend. So, caps should be 15-20 % of break load, back stay should be 20% when going upwind. Do you have runners? How have you “done the back stay”?

You can get accurate tensions by measuring stretch in the wire, preferably over a 2m sample....

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Hi I added a furler last year rig was fine before with the foil on being the Alado model it seems to have the sag , the rigging wire is dyform so no stretch ,I am consuming what you are saying , spreaders are swept back yes ,back stay I can’t haul any more it just bends the rig ,so is it the caps. No running back stays. Y stay pull adjust vire blocks on the back stay

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Sorry, that is not correct. Dyform stretches under load, same as any other wire.

 

For example, an unloaded 2m section of 10mm dyform loaded to 20% of break will stretch to 2004mm. See https://jimmygreen.com/content/85-compact-dyform-vs-standard-1x19-wire-rigging for specs.

 

How you set the rig up is dependent on the rig type.

 

So to give you any decent info, first you need to tell us what the rig is.

 

7/8 ths, yep.

Swept spreader, ok, one or two sets?

Lowers, how many, terminate where, is there fore and aft lowers, or baby stay or what?

 

Aft lowers restrict mast bend. Its pretty easy to work out forestay tension from backstay tension, but rig measurement is required. Guessing and tensioning  till it feels tight is crap, and a recipe for poor performance or disaster 

 

A really good reference for all this is this book

Ivar Dedekam "Sail and rig tuning" 

Its available in PDF as well I believe, well worth buying and keeping in your reference library! 

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Ok iam in others hands here , single spreader , swept back ,one set of lowers swept ,set of caps swept both lowers and caps meet at the same chain plate no inner baby stay One fore and aft stay a 6 stay rig same as say Eliott 1050 etc

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You may also be worrying too much about forestay sag. There always will be some in a rig like this. The main thing is ensuring the furler rotates on the forestay cleanly. If it has too much sag, it can jam up, especially under load. As IT said, the forestay sets the amount of rake the Mast will have. The backstay sets the tension.

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8 inches sounds like a hell of a lot of sag on a 13 mtr rig, have you had a rigger check it? With a fractional rig like that without runners most of your forestay tension will be on the caps.

Depending on the boat you may or may not be able to get enough tension on them, some boats get to a certain tension then you start winding the boat toward the rig.

If however this amount of sag is normal for your type of boat the sail will be cut to allow for this, that fact that you have posted this suggests this is maybe not normal and could point to an issue elsewhere. If it were me I would get a rigger in to check the rig.

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OK, now we know what the rig is. Your choice is either to get a rigger to sort it, or;

 

Starting with rigging just hand tight, and rigging screws clean and lubricated.(easy to turn by hand unloaded)

 

1. Set forestay length to allow correct mast rake (start at 3 degrees if there is no info on your boat)

2. Check the mast is vertical, measure (or use a halyard) from masthead to chainplates

3. Tension caps to elongation of 3mm over a 2m section (measure from the bottom swage up 2m, mark shroud, then tension until it measures 2003mm) This will give you most of your forestay tension.

4.Tension lowers to limit mast bend, look up the sail track and ensure the mast is still in column

5.Tension backstay same way, mark the max tension (3-4mm stretch) on the adjuster. Release it when not sailing.

6. Go for a sail and check the mast is in column. When the boat is fully powered, the leeward shroud should JUST be loose (preload is used up), and the mast should still be in column.

 

These are general rules, some classes do it different for racing, but following this will give you a good start, and support the rig in the best way structurally. I dont like to prebend more than 1/2 of the mast measurement fore/aft, but some do.  

 

ANYONE, riggers included, who do a rig without measuring the loads is an amateur, and should not be relied on. Remember that the elongation is 3mm (4 on a real race boat) per 2m so it can be done by working out that for the full shroud length, then marking that on the shroud terminal. Also with a loos gauge. Pulling/Pushing on a shroud is NOT an acceptable way to ACCURATELY check rig tension, all it tells you is if it's really loose!

 

As mentioned above, some hulls wont allow proper rig tension, as the hull bends. If you can keep winding on tension and the measurement does not change STOP. Something is moving.... 

 

Here is another reference;

https://afloat.ie/resources/marine-industry-news/uk-sailmakers-ireland/item/38282-tuning-a-fractional-mast 

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At that amount of sag, if the performance is good, helm is good, and mast isn't pumping or moving around in waves, I'd say it's largely cosmetic and psychological - clip the halyard somewhere else, and you probably won't even notice the sag.

 

I'm with Native, backstay on a fraccy doesn't do much to the forestay, unless your mast is a powerpole.

 

If it really bothers you, tighten the cap shrouds slightly, but try not to bend the boat. Suddenly the washboards don't fit and the cupboards don't shut

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Yeah 8" sounds a bit much.
IT is correct about the tension, providing the stays are the correct diameter and not over sized.
So what you do.
Tie a small weight to the Main halyard and let is hang so the weight is free and just above the boom. Measure from the mast to that halyard at the boom level. You want a rake ruffly 5 to 6".
If you need to adjust this, then you will need to let all the other stays off so you can change the mast fore or aft.
Tighten the back stay and keep checking the rake angle and adjust the forestay to suit. As the backstay are ramping up in tension, the forestay is getting the exact same tension, so it will also stretch and thus mast will rake back to far, so you need to tighten the foretay to bring back the mast to the correct rake. But ensure that the back stay does not get over tension. So you have to continually take those measurements. You are too and froeing all the time.
As you do this, keep an eye on the mast itself, by getting your eye as close to it as you can and look up. You do not want to see the mast bending on it's own under what is called Compression load. The bend is done by the forward shroud. The aft shroud keeps both taught and locked in place. If the mast is bending too much without the shrouds, then you should not tighten the backstay any further.
How much pre bend you create is a little more difficult and is kind of the fine tuning side of it. You probably want a person with experience to take a look at that and adjust or advise.

Side stays or shrouds are tuned a little differently. Basically go for a sail in a stiff wind and on each tack, tighten the leeward stays till they are just tight, not loose and ensuring the mast is perpendicular and not being pulled off to one side.

 

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Wheels, his rig does not have fore and aft lowers, only Aft. On this rig spreader angle sets mast pre bend and forestay tension, lowers limit max mast bend and keep the rig in column.

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I spent a lot of time sailing wooden rigs and gaff rigs. That teaches you a lot about rig geometry and forces that affect a spar, because wood bends more easily and telegraphs( hahaha, unintentional pun)  whats happening by obvious and visible bend. They're actually easier to tune  because of that.

 People forget how important running rigging is . An example , on a gaff rig ( my mainsail was 600 ft, nominal and rounded , say  60 sq m) the main sheet actually is responsible for most of the forestay tension, more properly , the jib luff tension. There's a circle of force from the mainsheet , through the leech of  the mainsail , the peak halyard  attached to the gaff and the mast and then the jib halyard and jib luff. The running rigging is as important to the jib luff as the standing rigging

 

If you use that as an exaggerated  example to make a point, you can also see that forestay tension on a standard rig not only comes from the way the standing rigging is set up , but also how hard the jib halyard is set up , 

 

An Alado furler does not have a halyard  attached to the mast if I understand it correctly, its reliant on the foil or spar for static jib luff tension.

 

 Therefore it becomes totally reliant on standing rigging tension , whereas most  rigs  have halyards attached to the mast  and get  both standing rigging tension plus the bonus ' turbo' of halyard tension  to cut out the sag.

So it would be logical to assume that an alado set up needs  quite a bit more standing rigging tension than a standard furler or foil system to acheive the same amount of sag in similar conditions.

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Absolutely true John, The alado furler has no halyard to the mast. The halyard comes back down the forestay and terminates at the base of the foil, on the furler drum. It does rely completely on forestay tension to restrict sag, and will sag slightly more than a conventional furler. However, it also gives a much better visual on the forestay sag, as the halyard return provides a straight edge to view the sag against. So it might SEEM to be worse when the difference is actually small. Some Alado users remove the halyard, but I don't (yes I have one too), as I like to be able to remove the sail from the deck if required (removing it means a trip up the mast if the halyard is removed) .

 

No harm in checking that the rig tensions are right though!

 

Also, consider this. In a conventional setup, the jib halyard (hank or foil sail ) goes around a turning block at the top of the forestay. The load on that block is compressive on the rig, and the angle of that load is 1/2 of the angle the forestay makes to the mast, if the halyard is terminated at the deck. Quite a bit of that load actually reduces  the forestay load as it is in the same direction as the forestay load. Some boats using a wire (probably spectra these days) luff jib actually crank it in so it takes more load than the forestay!

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IT -interesting, haven't heard that method before. So you mark 2m above and then tighten. Would that mark then not measure less, as you are then stretching the wire down.?

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Tried to load a pic if the sag . Thanks all you guys the reading has been good I have learned a lot. As befor the rig has been good , I believe the rigger set it up right but I can’t remember if he did the measurement thing , but tell tails from the input here lend it is ok I think , the lowers just loose hard on wind Mast looks straight I do remember him using a gadget to true the mast , mast hard on the wind on both tacks has a small amount of sag over length The jib is in the sail makers yesterday having more kiwi slides fitted as they were a bit far apart as seen in the pic ,,,,,,922D13A9-2793-4276-A1F0-FF7156F57F50.jpeg

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Yes , and again using the vintage example which sets a flying jib  the mode there is to tension the halyard until you see the forestay sag away slightly.... the jib wire/ spectra luff effectively becomes the forestay.

 And you also get the same effect on cutter and particularly solent rigs when you tension one stay or halyard more than another. IE , tension  the staysail iup too far and the genoa will develop sag, because there's two wires sharing the load . ie only half( say , for simplification purposes) of the rig tension left available for the genoa.

 

 edit . oops 2 new posts while typing.

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Wheels, his rig does not have fore and aft lowers, only Aft. On this rig spreader angle sets mast pre bend and forestay tension, lowers limit max mast bend and keep the rig in column.

Arr righty. I should really have payed more attention to the topic header. Rigging Expert

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IT -interesting, haven't heard that method before. So you mark 2m above and then tighten. Would that mark then not measure less, as you are then stretching the wire down.?

Nah Vic, I obviously did not make myself clear enough.

The mark is 2m above the terminal swage on the wire, that distance will grow with tension as the terminal itself is drawn into the rigging screw. The wire stretches to allow this....

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