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Old 25-09-2012, 06:30   #1
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Forestay tension?

Just how tight should a forestay be? mines a bit wobbly just now i can see it moving a fair few inches with the wind catching the furled jib, i dont have adjustable backstays and the mast has pre bent rake in it.
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Old 25-09-2012, 06:51   #2
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Re: Forestay tension?

Don't know is the answer but that sounds a bit loose if the wind can move it more than a few inches. That said your forestay is probably 15m so even bar tight it's going to move a bit in the middle. I can probably move ours 6" in the middle but only by giving it a good shake standing on the pullpit.

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Old 25-09-2012, 06:52   #3
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Re: Forestay tension?

I think it depends on the rigging some.

On my boat with the B&R rigging I also felt the forestay seemed loose. But I went to the rigging manual and it was suppose to be the way it was.

But on my last boat with an adjustable back stay if the forestay got loose I would pump up the tensioner to tighten it and put some rack in the mast and it would make a big difference in perfomance.
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Old 25-09-2012, 06:59   #4
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Re: Forestay tension?

I don't have the answer for your particular setup, but I usually judge the fore stay tension by the sag to leeward when the head sail is set and it's blowing fairly well..

Yours sounds too loose to me..
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Old 25-09-2012, 08:35   #5
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Re: Forestay tension?

You dont really tune your rig by using the tension of the forestay, you do so by adjusting the tension of your shrouds. Obviously the forestay tension increase as well but forestay length is used to control the rake of the mast.

Detailed rigging tension is usually specific to a given mast manufacturer and sail designer.

A good ballpark method:

  1. Make sure backstay and any runners are fully off
  2. Set the forestay length so that the mast is vertical fore and aft
  3. Increase all shrouds tension until they are hand tight and while doing so make sure you center the mast athwartships.
  4. It is really important to make sure the mast is square before increasing tension. If you are using either a halyard or a long measuring tape to check level the wind can play havoc with your attempts to be accurate. Take your time and it is worth doing it on a light wind day.
  5. Measure up from the deck 2 meters and put a pieces of tape on your shroud. Do this for both shrouds, this is where you will attach a loos guage to measure - dont have one borrow one. if you do this right you wont have to do it again for a long time, worth doing it right.
  6. Once the mast is square slowly increase the tension on the uppers to approx 15% of their breaking load. You can find breaking loads in a decent quick tuning guide from Selden Masts HERE. Do this by adding an equal number of turns on each side in small sets of 3 or 6 depending how close you are to the final tension. After each set of turns check that the mast is still centered and check the tension on both port and starboard uppers. Sometimes they will go up unequally and you most compensate for this without taking the mast out of center.
  7. Middle Shrouds: If you have middle shrouds their tension is usually dependant heavily on sail shape. However a baseline would be: If they are the same thickness as your uppers to set them at half the tension of the uppers or if thinner than uppers than to set them at 10% breaking strength
  8. Lower Shrouds: Lowers are relatively easy - hand tighten them and then go sailing - to check them - you want them just tight enough to help the mast to not pump.
All this is dependant on the rake of your spreaders - where the shrouds hit the deck, etc. But that should get you a base setting.


When you are adding tension to the lowers and mids make sure you put the side of your face on the mast looking up sail track on the aft side with all lines out of the way - this will tell you very accurately if the mast is bending in the middle while you are tensioning.


Such a huge topic but hope that helps...




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Old 25-09-2012, 08:52   #6
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Re: Forestay tension?

Quote:
Originally Posted by stevensuf View Post
Just how tight should a forestay be? mines a bit wobbly just now i can see it moving a fair few inches with the wind catching the furled jib, i dont have adjustable backstays and the mast has pre bent rake in it.
Your boat has split backstays. It's a fairly easy matter to add a split backstay adjuster, and there are several models on the market. I know that Harken makes a 4:1, an 8:1, and a 6:1 double-ended split. I would not recommend the 4:1 on your boat.

Adding such an adjuster, which should take a rigger less than a couple hours, will enhance performance significantly.
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Old 25-09-2012, 09:00   #7
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Re: Forestay tension?

Are you replying Don Lucas or the OP? OP asked about the looseness of his forestay. A picture I found of the Gib Sea shows a masthead rig that isn't B&R. B&R rig with no backstay, the shrouds will adjust forestay tension. Rig with swept spreaders, the shrouds will adjust prebend. With chainplates a little aft of the mast the shrouds will pull on the forestay some, but the backstay will be the main control. and a rig with non-swept spreaders will have forestay tension entirely controlled by the backstay.

OP, is there at least a turnbuckle on your backstay?

Also prebend and rake are two separate things. Rake is how far the mast is tilted fore and aft. Prebend is how much bend you have in your mast sitting at the dock due to the rigging. A babystay, foreward lowers, or swept spreaders adjust that on most rigs.

John

Quote:
Originally Posted by foolishsailor View Post
You dont really tune your rig by using the tension of the forestay, you do so by adjusting the tension of your shrouds. Obviously the forestay tension increase as well but forestay length is used to control the rake of the mast.

Detailed rigging tension is usually specific to a given mast manufacturer and sail designer.

A good ballpark method:

  1. Make sure backstay and any runners are fully off
  2. Set the forestay length so that the mast is vertical fore and aft
  3. Increase all shrouds tension until they are hand tight and while doing so make sure you center the mast athwartships.
  4. It is really important to make sure the mast is square before increasing tension. If you are using either a halyard or a long measuring tape to check level the wind can play havoc with your attempts to be accurate. Take your time and it is worth doing it on a light wind day.
  5. Measure up from the deck 2 meters and put a pieces of tape on your shroud. Do this for both shrouds, this is where you will attach a loos guage to measure - dont have one borrow one. if you do this right you wont have to do it again for a long time, worth doing it right.
  6. Once the mast is square slowly increase the tension on the uppers to approx 15% of their breaking load. You can find breaking loads in a decent quick tuning guide from Selden Masts HERE. Do this by adding an equal number of turns on each side in small sets of 3 or 6 depending how close you are to the final tension. After each set of turns check that the mast is still centered and check the tension on both port and starboard uppers. Sometimes they will go up unequally and you most compensate for this without taking the mast out of center.
  7. Middle Shrouds: If you have middle shrouds their tension is usually dependant heavily on sail shape. However a baseline would be: If they are the same thickness as your uppers to set them at half the tension of the uppers or if thinner than uppers than to set them at 10% breaking strength
  8. Lower Shrouds: Lowers are relatively easy - hand tighten them and then go sailing - to check them - you want them just tight enough to help the mast to not pump.
All this is dependant on the rake of your spreaders - where the shrouds hit the deck, etc. But that should get you a base setting.


When you are adding tension to the lowers and mids make sure you put the side of your face on the mast looking up sail track on the aft side with all lines out of the way - this will tell you very accurately if the mast is bending in the middle while you are tensioning.


Such a huge topic but hope that helps...




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Old 25-09-2012, 14:49   #8
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Re: Forestay tension?

there are ten stays in all, 2 back ,3 either side , baby stay and forestay, the baby stay is taught, all the othet stays can be wobbled slightly, but i had a guy do some work on the lower furling gear and he did play about with the turnbuckle, im sure after which the play was greater, all stays have turnbuckles on them, should i just give the forestay turnbuckle an extra couple of turns to retighten it, im sure hes loosened it somewhat
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Old 25-09-2012, 15:49   #9
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Re: Forestay tension?

I have struggled with this problem in the past and the only thing I have found as a good indicator of forestay tension is how hard is it to roller furl the head stay. When the forestay was too loose it was a devil of job to furl the jib and I often had to put the line on a winch. When I tightend the forestay, it became much easier. I also noticed that I was able to point a bit higher with the forestay tightend. For me it has been a trial and error process.

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Old 25-09-2012, 16:16   #10
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Re: Forestay tension?

In terms of sailing performance, a relatively loose forestay is great for downwind sailing and light wind sailing, but lousy for heavy weather sailing to windward and will reduce your pointing ability.
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Old 26-09-2012, 01:23   #11
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Re: Forestay tension?

thanks rich, the genoa has been a bugger to furl, i think you are spot on!
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Old 26-09-2012, 01:30   #12
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Re: Forestay tension?

Do you have a Loos gauge? we have but have to admit I haven't used it yet. Might be useful to measure the tension before you start fiddling so they can be reset if something doesn't work.

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Old 26-09-2012, 02:32   #13
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Re: Forestay tension?

yeah i have one, still in the box granted, but looks simple enough to use.
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Old 26-09-2012, 02:47   #14
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Re: Forestay tension?

Just because the forestay is loose, doesn't necessarily mean that it's adjusted incorrectly. It could be mis-adjustment of the backstay or shrouds for example. Always think of the rig as a whole.

Setting up a rig is a bit of a black art, but selden do an OK guide to the basics.
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Old 26-09-2012, 06:12   #15
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Hands on expirence of an old salt would be a good idea. Someone at your dock may be able to give you good advice. Remember, it is not a guitar string.
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