Headstay Tension, and why no winch?

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Signaleer
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Headstay Tension, and why no winch?

Post by Signaleer » Wed Aug 12, 2015 9:51 pm

First, thanks to all the help from this friggin awesome forum, we GOT THE MAST RAISED and PINNED! We built a new forestay at West Marine with new turn buckle etc. We have not yet reinstalled the furling system. We will do that tomorrow. So.... YOU GUYS ROCK, and I am going to quit saying the normal things I do about you...

1. I have read the forums. I just replaced the head-stay with the standard 1/8 inch 1/19 wire from West with a swag fitting at the turn buckle (completed by a local rigger with that tool for 20 bucks), and 2 ea. Nicopress fittings with the 1/8 thimbel at the top. Is the standing rigging tension for this headstay 270 lbs static? (Got from other thread).

2. The lowers shrouds should also be 270 lbs? 1/8 1/19 stainless steel rigging? And the uppers should be above that? What tension?

So, I need a loose gauge to get this right. I'll get that tomorrow I hope.

Finally, to get the head-stay pinned with correct tension, why has no one put a block near the front of the bow, and winched the mast forward with say the spinnaker halyard? This is above the fore-stay and would be better to assist in pinning the head-stay no? And then release to the proper tension and easier pinning? I have searched the forums and not seen this. Using the mast raising system which attaches below the fore-stay would require a lot of tension to achieve the same results.

Wouldn't it be better to pull the mast from above the head-stay attach point?

Thoughts?

Ed.

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Re: Headstay Tension, and why no winch?

Post by Wind Chime » Wed Aug 12, 2015 10:02 pm

We use the spinnaker halyard to raise the mast, the spin halyard hound is 18 inches above the standard forestay hound. Also with an X we can loosen the adjustable backstay and snug-up afterwards.

There have been some threads about this so you may want to try some different search words. Mast raising system etc.

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kadet
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Re: Headstay Tension, and why no winch?

Post by kadet » Wed Aug 12, 2015 11:07 pm

Putting too much tension on a fraction rigged mast above the upper stay can snap the unsupported part of the mast or cause fatigue cracking in the bolt holes for the stay attachment. There is more support below for the mast raiser and with the winch it is not onerous to pull the mast forward that few millimetres to pin the furler.

But either way will work with care.

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Re: Headstay Tension, and why no winch?

Post by Tomfoolery » Thu Aug 13, 2015 1:03 pm

Posting from my little iPhone 4, so quoting is a challenge, but I'll just put this outt there. Not many folks actually know what the correct forestay tension might be. Because they don't have to.

The rig geometry is fixed (the standing rigging doesn't change length and the terminations don't move relative to the mast or boat) other than so e elastic stretch under load. So when the mast rake is set correctly, and the shrouds are preloaded to the required load, which is not the same for the inner and outer stays, the forestay will have some specific preload. Change the shroud tension, and the forestay tension will change, too. It has to - it's the only thing resisting the rearward force component from all those shrouds.

The sideways force components of the shrouds balance each other and cancel, but the forestay is the only thing that terminates forward of the mast. But that force isn't all that much, since it's only 1/8" wire against the less advantageous angles of all four 5/32" shrouds which are mainly working side to side with only a small component pulling back.

But the point is, the correct preload, whatever that force is, will be established by the shrouds (backstay slack), so whatever it is when the rake and shroud force (which also determines mast bend) are set correctly, that's what it is. If you then loosen the forestay, the shroud preload force will also go down. Like a tent pole with just three guy wires - tension in any one depends on the tension in the other two.

I use the old style MRS connected to the jib halyard at first but now to the spin halyard 18" higher (jib halyard removed) and just put some ass on it to make the pin. Most of the force is downward anyway and along almost the same line as the forestay. I calculated the bending force and stresses in the mast once, and satisfied myself it was t going to damage it if I didn't go crazy on it, and the holes line up without too much effort. You could always rig the main sheet or vang to pull directly on the forestay, which is a suggestion I read here a few times.

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Re: Headstay Tension, and why no winch?

Post by Signaleer » Thu Aug 13, 2015 2:48 pm

Tom,

Thanks for your reply.

We are going sailing but the only other time I raise a rig was on my P26 and it had very specific pre-loads (it was also a mast head sloop).

I completely understand the geometry of the B&R rig (is this technically a B&R rig) in which the aft positioning of the shrouds are the force to the rear.

I just want to get it right and 'tight but not too tight' and 'you shouldn't be able to play a tune on them' etc. ... well, it just makes me nervous. I was going to use a gauge, but we can't get one before tomorrow.

I used the spinnaker halyard to pin the fore-sail. I weigh about 200 lbs and had to apply a good amount of force from the spinnaker halyard to pin the head-stay. I pulled the spinny halyard forward to the bow-pulpit and as I applied downward force with that halyard, Nick pinned the forestay. My guess is that we are close. We'll see.

Thanks again.

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Re: Headstay Tension, and why no winch?

Post by dlandersson » Fri Aug 14, 2015 4:59 am

That's how I do it - takes two people. 8)
Signaleer wrote:I used the spinnaker halyard to pin the fore-sail. I weigh about 200 lbs and had to apply a good amount of force from the spinnaker halyard to pin the head-stay. I pulled the spinny halyard forward to the bow-pulpit and as I applied downward force with that halyard, Nick pinned the forestay. My guess is that we are close. We'll see.

Thanks again.

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Re: Headstay Tension, and why no winch?

Post by budgates » Fri Aug 14, 2015 9:57 am

I find a johnson lever to be the easiest and quickest way to tension the forestay. Another method is to use your mainsheet to pull on the halyard giving a big mechanical advantage plus the cam cleats hold everything in place while you attach the forestay. With a little forethought one person can use either method.

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Re: Headstay Tension, and why no winch?

Post by Don T » Fri Aug 14, 2015 12:18 pm

Hello,
I find the shroud tension to be just right when under the strain of the mast raising system I can barely pin the fore stay (back stay is slacked off of course).

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