headsail halyard tension

[scrambledegg]

**sorry, applies to mainsail, not headsail **

I've been having trouble hoisting my mainsail (~25 m sq) all the way to the top without using a winch, so I thought I would reduce friction by swapping the deck mounted plain-bearing 50mm turning block for a ball-bearing one of 60mm. It turns the halyard through 90 degrees.
I see now though that the ball-bearing blocks have lower safe working load that the plain-bearing ones. The one I bought says 300kg on the packet (but 500kg in the spec on the website, confusingly).
I mainly cruise the boat but I'm hoping that the racers on here might know what are normal luff tensions for mainsails, related to wind strengths.
Thanks

 

[olly_love]

It is quite dependent on the rope and sail as well

and old dacron main with a polyester halyard will show less load through the block
whereas 3di with a SK90 halyard will put the full loading through it

i would suggest that 300 is very low? i dont think even the light weight harken blocks are that low?

i would suggest using a plain bearing or roller rather than ball for halyards as they are mostly under a static load which will cause the balls to fail

 

[michael_w]

Does the sail have slides or a bolt rope? probably a bigger source of friction than the halyard sheaves. A squirt of McLube often helps. That said, what state is the masthead sheave in?

 

[scrambledegg]

Thanks for those thoughts so far.
Probably the ball-bearing block is a bit under-specc'd, but then it appears to be a fraction of the price of other bb blocks with working loads of 1000kg or so. My trawls of the web seem to show that nobody actually measures their rope tensions (or, confesses to).
It's a mainsail with slides, and, right enough, those other sources of friction need attention.

 

[olly_love]

Harken have lots of usefull bits here
https://www.harken.co.uk/How-To-Choose/

 

[flaming]

To be honest, the block at the base of the mast would be the last thing I looked at if trying to reduce halyard friction. As long as it seems to turn, i.e isn't completely jammed, then it's very unlikely to be the major source of your friction.... It's just the easiest to change....

Other sources of halyard friction worth investigating are jammed masthead blocks, sticky sliders or debris in the track, and twisted halyards inside the mast.

 

[scrambledegg]

Harken have lots of usefull bits here
https://www.harken.co.uk/How-To-Choose/

I've looked through their material. The approach they take with halyard blocks is to say: here is our range of blocks, "midrange blocks" for instance, this range of blocks suits boats up to certain maximum I and J measurements.

They have ducked the question of how much halyard tension is expected for a given sail area/wind strength. If it does also depend on the sail material and the halyard material there is no way of adjusting the purchasing decision accordingly. This will result in buying a block that is stronger than is probably necessary.
Interestingly, if you're buying a sheet car they do have calculators that relate the sheet tension to the area and the wind strength.

 

[anoccasionalyachtsman]

What power ratio is your winch, and how many kgs/lbs d'you reckon you're putting into the handle? Multiply those two and that's what's in the halyard as it leaves the winch. If your new block turns the halyard 90 degrees, multiply that tension by 1.4 and that's how the block should be sized. Double it for the masthead sheave because it turns the line through 180 degrees.

But, as mentioned, a can of lubricant sprayed onto the luff as you hoist it makes an almost unbelievable difference. (As will giving the groove a good scrubbing out on an elderly boat).

Lastly, a Cunningham tackle is the preferred way of getting good luff control on racing boats - no winch required.

 

[scrambledegg]

What power ratio is your winch, and how many kgs/lbs d'you reckon you're putting into the handle? Multiply those two and that's what's in the halyard as it leaves the winch. If your new block turns the halyard 90 degrees, multiply that tension by 1.4 and that's how the block should be sized. Double it for the masthead sheave because it turns the line through 180 degrees.

An interesting alternative way of looking at the loading question. However, I think the question is how much tension is needed (max), not how much can I apply - though I can see there is merit in spec'ing the blocks so that they won't break under the stress of maximum winching effort.

 

[anoccasionalyachtsman]

An interesting alternative way of looking at the loading question. However, I think the question is how much tension is needed (max), not how much can I apply - though I can see there is merit in spec'ing the blocks so that they won't break under the stress of maximum winching effort.

Well kind of. My main is hoisted with one 'man pull' which must be about 50kg because it's flipping awkward. That gets it to the top with about the right tension for 7kts of breeze. Then I use a 12:1 tackle on the cunningham when I need more. I only pull a few kgs on that, so say 50kg, and that gives a total of 100kg. 30ft racing boat with a newish dacron main.

@olly_love and @flaming's boats have much bigger mains, but I don't know if they grubby themselves with pulling ropes.

 

[scrambledegg]

What power ratio is your winch, and how many kgs/lbs d'you reckon you're putting into the handle? Multiply those two and that's what's in the halyard as it leaves the winch. If your new block turns the halyard 90 degrees, multiply that tension by 1.4 and that's how the block should be sized. Double it for the masthead sheave because it turns the line through 180 degrees.

ok, I'm going to run with this method.
My winch is a single speed Lewmar. Guessing a bit but I think it's equivalent to a 15ST, which has a power ratio of ~16 (assumes the winch handle is a standard length?).
I see elsewhere on the web that 16kg force is a typical sustained winching load for "most people" (
https://www.harken.com/article.aspx?id=12821)

That would make the max halyard tension = 16x16 = 256kg
I suppose also that a person could generate considerably higher winch force in a short burst of effort. If I say twice as much, 32kg, that would take the max. halyard tension to 512 kg -> and the block loading to 512 x 1.4 = 717kg

So, my newly purchased BB block with safe working load of 300kg isn't going to have enough margin.

 

[flaming]

@olly_love and @flaming's boats have much bigger mains, but I don't know if they grubby themselves with pulling ropes.

33sqm. So not a lot bigger... New boat has a 2:1 main halyard though. Not because it needs lots of umph, but simply to reduce the load at the clutch so that you don't need to leave the halyard on a winch upwind.
Feels really weird to be bouncing that halyard but the main only going up half as fast....

 

[lw395]

Halyard tension when sailing with be much the same as leach tension/sheet tension.
I.e. if you have 6:1 mainsheet, it will be around 6X the actual tension in the sheet rope.
So, what no you think that might peak at in a gust?
I would go for the biggest plain bearing block that gives a good lead.
Check the masthead sheave and any 'organisers'.
Also check the halyard does not touch the deck under tension.

 

[scrambledegg]

Halyard tension when sailing with be much the same as leach tension/sheet tension.
I.e. if you have 6:1 mainsheet, it will be around 6X the actual tension in the sheet rope.
So, what no you think that might peak at in a gust?
I would go for the biggest plain bearing block that gives a good lead.
Check the masthead sheave and any 'organisers'.
Also check the halyard does not touch the deck under tension.

Yes, looking at the geometry I can believe that mainsheet tension when close hauled is quite closely equivalent to halyard tension. That's good, one of those online sheet force calculators might get quite close to the answer. Thx
PS Harken's mainsheet force calculator yields 500 kg for my mainsail in 20 knots of wind. I wouldn't carry full mainsail in 20 knots, but could experience that in a gust. Interesting that force figure agrees well to my estimate of max achievable halyard tension by winch effort.

 

[Daydream believer]

My boat is 31 ft with a laminate mainsail. 8mm dynema halyard. I adjust it often to suit wind strength so it is not just a case of pull it up hard. In fact i just take the tension out of the luff to start with. However wind puffs put strain on the halyard & with no stretch it puts load on the blocks
This is what happened to the sheave at the mast head

No idea what the SWL is, but Sparcraft would be expected to get it right

 

[scrambledegg]

You're the first I've heard of with a masthead sheave failure. You should have fitted an under-rated block on the deck to act as a weak link like I nearly did .
You suggest that your low-stretch sail/halyard contributed to the breakage. Maybe there's truth in that.

 

[lw395]

My boat is 31 ft with a laminate mainsail. 8mm dynema halyard. I adjust it often to suit wind strength so it is not just a case of pull it up hard. In fact i just take the tension out of the luff to start with. However wind puffs put strain on the halyard & with no stretch it puts load on the blocks
This is what happened to the sheave at the mast head
View attachment 79439
No idea what the SWL is, but Sparcraft would be expected to get it right

TBH that looks as if it wasn't exactly brand new and shiny when it broke.
The low stretch of dyneema doesn't really affect the tension in the halyard much, a stretch halyard would make the sail fuller in gusts and increase the load.
Still, I wouldn't wanted to have been up the mast on that when it broke.

 

[Daydream believer]

TBH that looks as if it wasn't exactly brand new and shiny when it broke.
The low stretch of dyneema doesn't really affect the tension in the halyard much, a .

14 year old mast from new
I was not suggesting that dynema affected tension, only that i do not really over tighten the sail most of the time. Some FCL sails need a high luff tension for instance.
I do, however, have to load it up when reefed.

 

[lw395]

14 year old mast from new
I was not suggesting that dynema affected tension, only that i do not really over tighten the sail most of the time. Some FCL sails need a high luff tension for instance.
I do, however, have to load it up when reefed.

Plastic, in particular white plastic, sunlight 14 years, plus wear. Not really a short life on a racing machine?

 

[Aquaboy]

I thought the main loading on your halliard comes from the Cunningham.
I sail off and on moorings all the time and with lazy jacks the method is let the halliard go as you approach and the sail stays up fine on its own. Its not until you swing head to wind and release the mainsheet the pressure comes off and it drops. The mainsheet tension through the leverage of the boom is actually pulling the sail away from the mast and jamming the slugs or bolt rope in the groove. Puffs wouldn't increase the downward force on the sail either, quite the opposite.
If you have a multiplying Cunningham then any halliard tackle needs to be sized accordingly though its a static load that's being applied so plain bearings