Checking the forestay tension

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Alexis
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Checking the forestay tension

Post by Alexis » Tue Mar 12, 2019 5:15 pm

Hello,

I recently changed my headstay in the furling system and I am wondering if there is a method to check the tension of the stay?

According to the boat manual the mast angle with the deck should be 94 degrees. Is that also an indication of the forestay tension? (I.E. 95 deg is not enough tension VS. 93 is too much?)

Somewhere else in the documentation it is said that the turnbuckle must be tighten down until the rig is "really snug". What does that even mean?

kurz
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Re: Checking the forestay tension

Post by kurz » Wed Mar 13, 2019 2:59 am

Hi
I copy-paste here the info from Bluw water yacht. I cannot find it actually on their page but I saved it earlier. Very good thought I think.

In order for your MacGregor to perform to its potential, you must keep your rig (mast, shrouds, and stays) properly tuned. These suggestions are designed to give you an idea of how to shape and tension your rig. Included are some notes on specific sailing conditions and various boat models.
For these instructions, we are assuming that you trailer your boat and want to be able to easily pin the headstay when raising the mast. The additional performance gained by making the rig tighter than we are suggesting is small -- and the additional hassle is a trade-off not many people want.
VOCABULARY
The main terms used on these pages about rig-tuning:
Shrouds: The wires that run from the sides of the boat to the mast. MacGregor's have four shrouds -- an upper and a lower shroud on each side. (The forestay/headstay and the backstay are not called shrouds in this context.)
Lowers: The shroud on each side that goes from the deck to the point at which the spreader meets the mast.
Uppers: The shroud on each side that goes from the deck through the ends of the spreaders and then attaches to the mast. At the top on M19 & M22, about 4 feet below the top of the mast on most other Mac's.
Spreaders: The aluminum tubes extending away from the mast, about halfway up, that hold the uppers away from the mast.
Headstay: The wire from the bow of the boat to a point near or at the top of the mast.
Forestay: Another word for headstay.
Backstay: The wire from the stern of the boat to the top of the mast.
Fractional rig: A boat on which the headstay attaches to the mast below the top. The M26, M26x, and some M19s are fractional.
Masthead rig: A boat on which the headstay attaches to the top of the mast. Most M19s are masthead rigged.
Other terms you may hear in advanced tuning guides:
Partners: Small wedges used to position the mast where it goes through the deck on a boat with a keel stepped mast. Many larger, non-trailerable boats have masts that go through the deck and sit on the keel, books about tuning may talk quite a bit about the partners, but you don't have to worry about this, no Macgregor (except the 65!) has them.
Hounds: The point at which the headstay attaches to the mast, especially in fractional-rig boats. We refer to this fitting as the Headstay Tang.
Mast Position: Mast position is the angle of the mast (fore and aft) relative to the top of the deck with no bend in the mast.
Most MacGregors sail well with about 3-6 degrees of aft rake. (That is, the mast is slanted backwards slightly.) If your boat tends to round up (tack by itself) in a stiff breeze, shorten or tighten the headstay to bring the mast tip forward (less rake). If it turns away from the breeze, lengthen the headstay.
Mast Bend (General)
MacGregor masts, like most aluminum masts, are meant to bend somewhat (with the middle of the mast curved toward the bow of the boat). By changing the amount of bend, you can change the way the boat sails. Note: The 26M sets up with the mast nearly straight.
Mast Bend (Light-Wind Areas)
The mast should be almost straight (very little bend). Tighten the lower shrouds to pull the middle of the mast aft -- but never so much that you pull it beyond straight. Even for the lightest-wind areas, the mast should always bend at least a little bit.
Mast Bend (Heavy-Wind Areas)
The center of the mast should bend 2-3 inches forward of a chord from the mast tip to the mast step. (To help see mast bend, you can pull the mainsail halyard tight to the where the back of the mast touches the mast step on your deck.) To push the middle of the mast forward, tighten the upper shrouds. You may need to first loosen the lowers a bit if the rig is already fairly tight.
Backstay Tension
Masthead boats:
If you don't have an adjustable backstay, make the rig as tight as you can put up with when pinning the headstay. This minimizes headstay sag and improves upwind performance.
Fractional-rig boats:
The backstay should be just snug for normal sailing. (On a fractional rig, the backstay contributes very little to headstay tension.) On windy days, if you have an adjustable backstay, tighten it an extra inch or so in induce mast bend. (This flattens the mainsail a bit and also spills some wind from the top of the sail, both of which will make the boat heel less.)
How Tight Should The Rig Be?
This is somewhat subjective. A good rule of thumb for easy trailering plus good performance is that the shrouds should be tight but not quite tight enough to "play music" on them. If it is very difficult to pin the headstay when you raise the mast, the rig is probably tighter than it needs to be. The balance of tension between the upper and lower shrouds is determined by how much bend you are trying to preset into the mast.
Alignment Side to Side
The procedure described here should work well for anyone but the hard-core racer (who's likely looking for that last 1/16 inch, that extra 1/10 of a knot).
Make certain that the upper shrouds are in the same holes in the adjusters on each side of the boat before you start.
Sight up the sail slot in the back of the mast; if it appears straight, you're home free.
If the mast bows left in the center, you need to tighten the starboard lower and/or loosen the port lower.
If the mast bows right in the center, you need to tighten the port lower and/or loosen the starboard lower.
Boat Specific Notes
MacGregor 19:
You may need to have the uppers tighter than the lowers in order to keep some bend in the mast.
Typical mast rake is 6-8 degrees (more than most trailerables).
MacGregor 26 daggerboard:
Shorten the headstay to the limits of the turnbuckle or adjuster. This will reduce helm pressure, these boats are really fast, but very prone to weather helm.
MacGregor 26X:
Typical mast rake is 7-10 degrees (a lot more than most trailerables).
MacGregor 26M:
The new airfoil mast on the M is very stiff, and sets up very straight as it is really hard to bend it very much.


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Tomfoolery
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Re: Checking the forestay tension

Post by Tomfoolery » Wed Mar 13, 2019 6:42 am

In a nut shell, you don't set the forestay tension directly. You set the side stay tensions, and since they're countered by the forestay, it will be correct. Or it will be what it will be, at least. If you increase the forestay tension, the side stay tensions will also increase, since they're swept back and counter the fore/aft component of the forestay force. So in essence, you tension the forestay indirectly. But you change the length of the forestay to adjust the mast angle to the deck.

If you have a furler for your jib or genoa, then you can't check forestay tension directly anyway, since you can't put a Loos gauge on it with the foil in the way.

Personally, I think the 4 degrees of rake off the flat part of the cabin roof in front of the mast is too much, and I have mine standing a bit taller (forestay turnbuckle turned in more).

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Re: Checking the forestay tension

Post by Neo » Wed Mar 13, 2019 2:32 pm

Tomfoolery wrote:Personally, I think the 4 degrees of rake off the flat part of the cabin roof in front of the mast is too much
And in practical terms (Specifically for the 26M) how would anyone measure that angle accurately anyway? .... The straight line measurement (72"up the mast, 156" down to front edge of rubber rail at the Bow) is the most practical way to set it all up ... and works great too. :)
I don't use any de-tensioning tools on my Shrouds/"Stay adjuster channels" to adjust them. I keep the Baby stays on the mast (as a backup), detach the Forestay and just loosen the MRS to the point where the Shrouds are just starting to go slack. I then adjust the Shrouds one at a time. .... This is not a method for a very windy day but it is quite safe :D ... and it's much quicker to have one person on the ground and another by the MRS.

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Re: Checking the forestay tension

Post by NiceAft » Wed Mar 13, 2019 7:38 pm

Neo,

Do you have a roller furler?

Ray

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Neo
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Re: Checking the forestay tension

Post by Neo » Wed Mar 13, 2019 9:04 pm

NiceAft wrote:Neo,
Do you have a roller furler?
Ray
Yep I do!... Does that make a difference?

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Re: Checking the forestay tension

Post by NiceAft » Wed Mar 13, 2019 9:40 pm

Well,

In the post that Kurz sent, I thought I read that a roller furler length can not be adjusted because of the foil. I was just wondering about that with your system.

Ray

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Re: Checking the forestay tension

Post by Neo » Wed Mar 13, 2019 9:55 pm

Well all I know for sure Ray is you can on the common FF2 Furler.
Take out the pin, slide back the drum and it reveals the turnbuckle.
Image

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Re: Checking the forestay tension

Post by NiceAft » Thu Mar 14, 2019 6:36 am

I went and re-read the postings. What I was confusing with in my head was in the post by tomfoolery:
If you have a furler for your jib or genoa, then you can't check forestay tension directly anyway, since you can't put a Loos gauge on it with the foil in the way.
Ray

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Re: Checking the forestay tension

Post by Tomfoolery » Thu Mar 14, 2019 7:09 am

NiceAft wrote:What I was confusing with in my head was in the post by tomfoolery:
Story of my life. :D :D

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Re: Checking the forestay tension

Post by Neo » Thu Mar 14, 2019 1:58 pm

Tomfoolery wrote:If you have a furler for your jib or genoa, then you can't check forestay tension directly anyway, since you can't put a Loos gauge on it with the foil in the way.
I often speed-read/miss-read things Ray (that's the story of my life :D ) but on this occasion the above made perfect sense to me :)

Anyway is it time to "Check your forestay tension" yet?... or still too cold over there?

All the best guys.
Neo

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Re: Checking the forestay tension

Post by March » Thu Mar 14, 2019 3:06 pm

I guess I never bothered with a "properly" tensioned forestay, Since every time I attach the forestay, I keep yelling to my helper: "Come on! Crank it up two more inches! You can do it!" and I have a merry old time attaching the pin, duly celebrated immediately after with the first beer, I have always assumed it is tensioned right.

Side stays: taut and checked. Forestay: taut with a very slight curve owing to the weight of the furler The rake may be adjusted from the backstay, if needed, but I never felt I did. I couldn't even tell much of a difference whether the pin goes into the first hole, or the second one. I insert the pin where it goes first, like the impatient dope that I am.

That being said, I always check very carefully the connections to the roller furler, both ends, before launching, making sure the crimps are in place and no stray wires show. And I always attach the free spinnaker line to the pulpit as a back-up stay, just in case.

How much of a difference does the first or second hole makes? I mean, truly meaningful difference?

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Re: Checking the forestay tension

Post by Tomfoolery » Thu Mar 14, 2019 3:18 pm

March wrote:How much of a difference does the first or second hole makes? I mean, truly meaningful difference?
None. The manual shows using the forward hole, because a hanked-on head sail needs the aft hole for the tack. I use the aft hole so that I have the forward hole available for the spinnaker tack connection.

But if you notice, both those holes are at the same radius from the forestay hound bolt, so it makes no difference as far as forestay length goes, and no practical difference for furler line angle or force vector through the forestay chainplate..

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Neo
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Re: Checking the forestay tension

Post by Neo » Thu Mar 14, 2019 3:54 pm

March wrote:I always check very carefully the connections to the roller furler, both ends, before launching, making sure the crimps are in place and no stray wires show.
Now here's a process I need to implement too :wink:
Sounds like you :macx: guys have a tough time attaching the forestay :| .... No Backstay on an :macm: so when the rigging is all set up correctly attaching the forestay is not so bad. 8)

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Re: Checking the forestay tension

Post by NiceAft » Thu Mar 14, 2019 3:59 pm

Neo asked:
or still too cold over there?

Getting closer, but not there yet.Image

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