Main Halyard Diameter Query

[savageseadog]

Dyneema.

We have a 38 footer with a main area of 453.64 ft2 / 42.14 m2
The Halyard is doubled back to the exit.
Currently we have 12mm racing dyneema and have wondered if that's over specced. It's a very bulky and heavy load of rope.
Perhaps 10 or even 8mm would do? What does anyone think?

 

[mrming]

With Dyneema I find it’s a trade off between what’s comfortable to handle, what doesn’t slip in the clutch and what is the best compromise for friction / weight / bulk. For me that’s usually a size down from what people usually choose. I don’t think you would have a strength issue with 10mm or 8mm but you might find 8mm would be too small for the clutch / unfriendly in the hand for the size of load.

 

[Kukri]

Do you need the two part halyard?

 

[savageseadog]

Do you need the two part halyard?

I have wondered.

 

[Kukri]

I have wondered.

Mine’s one part 12mm Dyneema, going to a Harken 44/2 winch. 508 sq ft mainsail. I won’t pretend that I can set it without the winch, but I can get it most of the way.

 

[Daydream believer]

I bought 8mm dynema & the breaking load was given in the specs as 4.5Tonne. So always handy if I want to hoist the boat out of the water by the tip of the mast. . So strength of a decent rope will not be an issue.
The main thing is friction reduction. I would imagine that with 2:1 halyard the load is quite small & the sail relatively easy to hoist. Regarding slip, that would be my main concern. As the load on the halyard will be less than a direct pull, then the clutches should be OK,- with the correct inserts. Depending on how the rig is set up one may be able to leave a turn on the winch.
Dynema halyards need to be selected with care. It is possible to get one with an outer casing that slips & causes bunching at the clutch, thus making it impossible to release. The enclosed picture shows our ( supplier says it was Marlow, not certain)14mm cruising dynema rope, which was on a cleat, holding a 2.5 tonne weight in water suspended on an airbag. When suddenly the casing broke & the core slipped through & off the cleat. The release mechanism narrowly missed someones head as the airbag jumped upwards, on releasing the load.

 

[dunedin]

Do you need the two part halyard?

Yes it does seem overkill to have 2:1 halyard on a 38 footer. Surely it would be very easy to change to 1:1 with the existing halyard and give it a try for a while. Will be a lot of excess rope but no need to cut until proven.
Indeed, if it really is a 2:1 halyard with 12mm racing dyneema the extra long rope must have cost an absolute fortune.

 

[savageseadog]

I'm all too familiar with rope sheath slip from my caving days, very alarming to be slipping down when hundreds of feet up a rope.
No. Breaking strength isn't an issue, I don't believe handling is either as long as the self-tailing winches and clutch will hold. I do think stretch could be a problem? The reason I asked about this issue is that better sailors than me decided to go for the setup. 30 odd metres of 12mm in the cockpit is a pain and replacement expensive.

I haven't really quantified what Halyard loads actually are. My guess is they would be similar to sheet loads. The jib is sheeted with a single sheet.

 

[Daydream believer]

I'm all too familiar with rope sheath slip from my caving days, very alarming to be slipping down when hundreds of feet up a rope.
No. Breaking strength isn't an issue, I don't believe handling is either as long as the self-tailing winches and clutch will hold. I do think stretch could be a problem? The reason I asked about this issue is that better sailors than me decided to go for the setup. 30 odd metres of 12mm in the cockpit is a pain and replacement expensive.

I haven't really quantified what Halyard loads actually are. My guess is they would be similar to sheet loads. The jib is sheeted with a single sheet.

I would imagine a reefed mainsail would involve the higher halyard loadings. I am sure mine do. Certainly more than a jib sheet. I expect that your mainsheet is 6:1 & possible you use a winch in heavy weather. All that puts downward load on the sail cloth.

 

[savageseadog]

I might ask Parker and Kay, now One Sails as they did the prototype sails and rigging.

 

[dunedin]

I'm all too familiar with rope sheath slip from my caving days, very alarming to be slipping down when hundreds of feet up a rope.
No. Breaking strength isn't an issue, I don't believe handling is either as long as the self-tailing winches and clutch will hold. I do think stretch could be a problem? The reason I asked about this issue is that better sailors than me decided to go for the setup. 30 odd metres of 12mm in the cockpit is a pain and replacement expensive.

I haven't really quantified what Halyard loads actually are. My guess is they would be similar to sheet loads. The jib is sheeted with a single sheet.

A 12 racing dyneema halyard is PLENTY strong enough for a 38 footer even in 1:1 setup (like ours, with 12mm cruising dyneema in fast cruiser). With to 2:1 it is massively over spec’ed - unless your 38 footer is an AC style foiling race catamaran or similar. But even then, a race boat would use halyard locks rather than a 2:1 main halyard.
(A 1:2 halyard, ie the opposite way rigged, sometimes used on spinnakers to get them up faster, but never on main)

 

[flaming]

2:1 halyard is absolutely the right thing on a boat like this. It's exactly what we have. Having a 2:1 obviously halves the load on the rope, and thus the clutch. This means the clutch alone is enough to hold the tension upwind, which is a big benefit when it comes to wanting to use the winch for other tasks.
It also reduces the compression load in the mast.

That said, 12mm feels a little overkill for a dynema 2:1 on a 38 foot boat. Check with a rigger, but I'd be looking at 10mm for that.

 

[Kukri]

The Racing Man has spoken. I’m sure he’s right and he’s confirmed the OP’s diagnosis.

 

[Birdseye]

It also reduces the compression load in the mast.

? How?

 

[flaming]

? How?

2:1 halyard reduces the load on the mast?

That thread explains it better than I could.

 

[savageseadog]

? How?

I was going to post something on this
I think it's a myth, oft repeated.
My analysis is that the load on the rope drop is indeed half of the luff tension on the main. The load on the return the return masthead is the other half of the luff tension. However the total load on the masthead equals half plus half of the luff tension.equals the luff tension and hence that amount of the maist compression.

 

[Daydream believer]

My analysis is that the load on the rope drop is indeed half of the luff tension on the main. The load on the return the return masthead is the other half of the luff tension. However the total load on the masthead equals half plus half of the luff tension.equals the luff tension and hence that amount of the maist compression.

Am I the only one who does not have a clue what you are trying to say?

 

[savageseadog]

Am I the only one who does not have a clue what you are trying to say?

Major wife says that a lot.

 

[anoccasionalyachtsman]

I was going to post something on this
I think it's a myth, oft repeated.
My analysis is that the load on the rope drop is indeed half of the luff tension on the main. The load on the return the return masthead is the other half of the luff tension. However the total load on the masthead equals half plus half of the luff tension.equals the luff tension and hence that amount of the maist compression.

If the luff tension is T, then the tension in each part of the 2:1 from crane to headboard is 0.5T. The tension in the descending halyard is 0.5T, so the total compression in the mast is 1.5T. With a normal halyard you have 2T.

 

[dunedin]

If the luff tension is T, then the tension in each part of the 2:1 from crane to headboard is 0.5T. The tension in the descending halyard is 0.5T, so the total compression in the mast is 1.5T. With a normal halyard you have 2T.

…… and with a halyard lock would be just T.