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  1. #1
    Join Date
    Nov 2015
    Location
    Portsmouth
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    234

    Default headsail halyard tension

    **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

  2. #2
    Join Date
    Mar 2012
    Posts
    181

    Default Re: headsail halyard tension

    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

  3. #3
    Join Date
    Oct 2005
    Location
    Fuctifino
    Posts
    4,569

    Default Re: headsail halyard tension

    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?

  4. #4
    Join Date
    Nov 2015
    Location
    Portsmouth
    Posts
    234

    Default Re: headsail halyard tension

    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.

  5. #5
    Join Date
    Mar 2012
    Posts
    181

    Default Re: headsail halyard tension

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

  6. #6
    Join Date
    Mar 2004
    Posts
    10,506

    Default Re: headsail halyard tension

    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.
    You never know, I might be right!

  7. #7
    Join Date
    Nov 2015
    Location
    Portsmouth
    Posts
    234

    Default Re: headsail halyard tension

    Quote Originally Posted by olly_love View Post
    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.

  8. #8
    Join Date
    Jun 2015
    Posts
    1,730

    Default Re: headsail halyard tension

    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.

  9. #9
    Join Date
    Nov 2015
    Location
    Portsmouth
    Posts
    234

    Default Re: headsail halyard tension

    Quote Originally Posted by anoccasionalyachtsman View Post
    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.

  10. #10
    Join Date
    Jun 2015
    Posts
    1,730

    Default Re: headsail halyard tension

    Quote Originally Posted by scrambledegg View Post
    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.

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