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Old 13-05-2021, 16:34   #1
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Halyard strength - Why so much

Okay, blame this one on lockdown boredom, brain freeze, or whatever. A discussion on another forum noted that the consensus for my boat is 3/8" for spinnaker halyards and 1/2" for main and foresail halyards. Right off I don't understand why the difference but it goes on.

And I'm going to have to check when I have access to the boat because I'm not sure that's what I have.

But in any case, this means lines with thousands of pounds breaking strength.

So, as a result of an "oops" moment, I'm going to have to go up the mast to retrieve a spinnaker halyard. I know from experience that this will require help because my wife isn't strong enough to winch me up the mast. But she can raise the main if she has to.

I weigh 145 pounds.

So why do we need a line capable of handling thousands of pounds when I know that we're not putting anything like that tension on it in other circumstances.

I'll repeat the apology because I sense that this is a really stupid question, but it has been a long winter and brain and body are currently in shutdown.
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Old 13-05-2021, 16:57   #2
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Re: Halyard strength - Why so much

Pressure on the sail puts additional tension on the halyard. When you get into heavy winds it can be very significant. Also, strength is often used as a proxy for stretchiness (sp?). If your main or genoa halyard stretches when you get heavy pressure on the sail then it will change the shape or get creases.

Also, as a cruiser I often go aloft using a halyard. If I get bouncing around in the bosun's chair trying to get a stuck bolt loose or whatever I don't want to have to think about the breaking strength of the line holding me 50' over the deck.
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Old 13-05-2021, 17:01   #3
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Re: Halyard strength - Why so much

Thanks for pointing out what should have been obvious. As I said, it has been a rough winter. (e.g. The spinnaker halyard is up the mast because I couldn't remember how to tie a sheet bend!)

Edit: added a useful word.
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Old 13-05-2021, 17:35   #4
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Re: Halyard strength - Why so much

Another reasons for halyards being bigger than necessary for strength is the human factor. Spectra 1/8" is strong enough, but do you want to hoist a sail pulling on slippery small diameter line?
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Old 13-05-2021, 17:49   #5
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Re: Halyard strength - Why so much

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Originally Posted by cal40john View Post
Another reasons for halyards being bigger than necessary for strength is the human factor. Spectra 1/8" is strong enough, but do you want to hoist a sail pulling on slippery small diameter line?
That said it's also easy to go too big. My boat had 14mm halyards which we've replaced with 12mm halyards because they run easier through the blocks and clutches. They still provide more than enough strength, and are easy to grip.

The 14mm line are now beautiful dock lines, albeit rather weathered.
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Old 13-05-2021, 17:50   #6
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Halyard strength - Why so much

I agree with the previous posters. Minimum size for stretch and hand. Maximum for blocks. And in the middle for clutches and self tailing winches. On a 30 footer that will likely get you all the strength you need. Bigger boats may need larger sizes for strength, but the stretch and hand will likely still control the minimum size.
I’ve got some big fat halyards. I do not like stretch. They have spectra cores.
Stretch is a performance and comfort killer in puffy or wavy conditions.
This is because stretch in a puff moves the draft back and adds depth to a sail in gusts. Exactly what you do not want.
Ps. Main halyard load is comparable to main sheet load. Jib halyard loads get up there too.
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Old 13-05-2021, 18:44   #7
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Re: Halyard strength - Why so much

Quote:
But in any case, this means lines with thousands of pounds breaking strength.
Several important points.
1. Breaking Strain (aka stress/strength)(BS) and Safe Working Load (SWL) are two very different things. SWL is frequently reckoned at 20-30% of BS ( 10% in many applications). Exceeding SWL can adversely the future strength of the rope.
2. A knot such as a halyard hitch can reduce strength by up to 50%
3. BS is "when new". A halyard that has had years of constantly varying loads will have a greatly decreased strength.
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Old 13-05-2021, 18:47   #8
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Re: Halyard strength - Why so much

Quote:
Originally Posted by AnglaisInHull View Post
The spinnaker halyard is up the mast because I couldn't remember how to tie a sheet bend!
Or maybe because you used a sheet bend instead of a Zeppelin Bend
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Old 13-05-2021, 18:51   #9
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Re: Halyard strength - Why so much

how else are you going to lift that diesel thru the companionway
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Old 13-05-2021, 21:06   #10
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Re: Halyard strength - Why so much

We went the opposite way when we changed our halyards a few seasons back. We went to 6mm dyneema, uncovered, for our halyards. The line breaking strength was 8000lbs. That seemed plenty strong and it sure saved some weight aloft. We kept the polyester covers on the dyneema where they went through the clutches and were handled.

All seemed well with this approach until this past season. We broke, in rapid succession, three halyards and a spinnaker pole lift. There was no sign of chafe (like from a bad lead or sheave).

So now we realize that factors such as UV can cause loss of strength and heavy winds can cause extreme loads on the halyards.

We have end-for-ended the broken halyards and moved the covers and I now have a 600ft spool of stronger dyneema. We will make new halyards soon.

A few of lessons: I will never go aloft on a single halyard again. I am going to run all my halyards up and into the inside of the mast when not in use, and I am going to worry about other use of these light lines (such as lifelines and running backstays).
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Old 13-05-2021, 21:16   #11
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Re: Halyard strength - Why so much

Wingsail makes a very good point— never go aloft on a single halyard. Use a primary and a safety and a bowline to attach each, separately, to your harness/ bosuns chair. Safe climbing!
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Old 13-05-2021, 21:53   #12
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Re: Halyard strength - Why so much

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Originally Posted by AnglaisInHull View Post
So why do we need a line capable of handling thousands of pounds when I know that we're not putting anything like that tension on it in other circumstances.
Suspend a 145 lb weight to the end of the line, raise it just enough to create a foot or two of slack, then let it fall. That should put over 1,000 lbs of force on the line. Probably less if you use a human as the weight, since they're squishy and will absorb a bit of it.

Similarly, tie a backup knot if using a simple bowline when going up the mast. Helps avoid surprises.
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Old 13-05-2021, 22:21   #13
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Re: Halyard strength - Why so much

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Originally Posted by requiem View Post
Suspend a 145 lb weight to the end of the line, raise it just enough to create a foot or two of slack, then let it fall. That should put over 1,000 lbs of force on the line.
It depends on how "stretchy" the line is.
At its simplest: Force = 2 * Weight * Height / Stretch

So for a 145 lb weight dropping 2 ft and stretching the rope by 6 inches:
F = 2 * 145 * 2 / 0.5 = 1160 lbs

But for a short "dyneema" line with little stretch, the load will be a lot higher.
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Old 13-05-2021, 22:31   #14
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Re: Halyard strength - Why so much

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Originally Posted by LoudMusic View Post
That said it's also easy to go too big. My boat had 14mm halyards which we've replaced with 12mm halyards because they run easier through the blocks and clutches. They still provide more than enough strength, and are easy to grip.

The 14mm line are now beautiful dock lines, albeit rather weathered.

I was taught that old halyards didn’t make good mooring lines because they don’t stretch significantly.
You want “just enough” stretch in a mooring line to act as a shock absorber.
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Old 14-05-2021, 05:01   #15
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Re: Halyard strength - Why so much

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Originally Posted by ChrisJHC View Post
I was taught that old halyards didn’t make good mooring lines because they don’t stretch significantly.
You want “just enough” stretch in a mooring line to act as a shock absorber.
Agreed. Good dock lines are far more stretchy than anything you'd use for a halyard. Even double braid nylon will stretch far more.
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