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  1. #11
    Join Date
    Nov 2015
    Location
    Portsmouth
    Posts
    230

    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.
    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.
    Last edited by scrambledegg; 01-08-19 at 12:37. Reason: missed a bit

  2. #12
    Join Date
    Mar 2004
    Posts
    10,484

    Default Re: headsail halyard tension

    Quote Originally Posted by anoccasionalyachtsman View Post
    @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....
    You never know, I might be right!

  3. #13
    Join Date
    May 2007
    Posts
    38,079

    Default Re: headsail halyard tension

    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.

  4. #14
    Join Date
    Nov 2015
    Location
    Portsmouth
    Posts
    230

    Default Re: headsail halyard tension

    Quote Originally Posted by lw395 View Post
    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.
    Last edited by scrambledegg; 01-08-19 at 23:35. Reason: Extra info

  5. #15
    Join Date
    Oct 2012
    Location
    Southminster, essex
    Posts
    9,415

    Default Re: headsail halyard tension

    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
    DSC_0019 (600 x 402).jpg
    No idea what the SWL is, but Sparcraft would be expected to get it right
    Last edited by Daydream believer; 03-08-19 at 06:15.
    It is all down to the fact that my wife does not understand me !!

  6. #16
    Join Date
    Nov 2015
    Location
    Portsmouth
    Posts
    230

    Default Re: headsail halyard tension

    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.

  7. #17
    Join Date
    May 2007
    Posts
    38,079

    Default Re: headsail halyard tension

    Quote Originally Posted by Daydream believer View Post
    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
    DSC_0019 (600 x 402).jpg
    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.

  8. #18
    Join Date
    Oct 2012
    Location
    Southminster, essex
    Posts
    9,415

    Default Re: headsail halyard tension

    Quote Originally Posted by lw395 View Post
    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.
    It is all down to the fact that my wife does not understand me !!

  9. #19
    Join Date
    May 2007
    Posts
    38,079

    Default Re: headsail halyard tension

    Quote Originally Posted by Daydream believer View Post
    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?

  10. #20
    Join Date
    Jun 2019
    Posts
    53

    Default Re: headsail halyard tension

    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

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