Vang purchase poll

Discussion in 'Laser Talk' started by GeoffS, Jun 9, 2003.

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What purchase do you have on your vang?

  1. < 8:1

    7 vote(s)
    7.4%
  2. 8:1

    19 vote(s)
    20.2%
  3. 12:1

    14 vote(s)
    14.9%
  4. 15:1

    54 vote(s)
    57.4%
  1. Braecrest

    Braecrest Member

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    I used to have the old style vang rigged with spectra line for 8:1 purchase, but I upgraded to the new harken setup, which is far more purchase then I really need, it's a little bit on the overkill side, but it doesn't bind up when it blows heavy.
     
  2. drLaser

    drLaser Member

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    Geoff writes:
    > I think the max-on to max-ease line length difference is maybe 12 inches.
    > I guess I could see how twice that might get to be a bother around the
    > mainsheet block, etc.


    Add to that length of line you need from the vang camcleat exit to the rail, to your hiking position, when the vang is almost all the way slack, and you are aft in the cockpit. You need that length so that you can throw the line over to the low side before each gybe and have it ready for you after the gybe for adjustments while hiked on broad reaches, or just in the middle but at the back of the cockpit on dead runs.

    Of course, if I don't want to have the opportunity to make vang adjustments without moving forward while sailing downwind , that's my prerogative.

    Same goes for upwind sailing, too. You don't want to come in from your hiking position and reach for the vang line to make adjustments. The vang line should be long enough to reach your hiking position, right next to your knees. But upwind sailing is less critical for determining the proper length of the free end of the line, since the vang will be tighter upwind, creating mucj of its own needed tail.

    With that noted, let me also claim that Geoff's statement that 12" is all the extra line you need from drum-tight to maximum slack may be an understatement. And the degree of understatement depends on the power ratio of your vang.

    In particular, The boom pivots around the gooseneck; the vang pivots around the vang tang. Drawing a circle centered at the gooseneck with a radius of around 45 cm (the max. legal distance from boom front end to end of vang strap is 482 mm), you can approximately trace how the vang strap hole will rotate as the vang is tightened. Drawing another circle centered around the mast tang hole with a radius of 62 cm ( the vang vang length, or the vang tang to vang key distance when the boom is set perpendicular to the mast, or about parallel to the water), you can see how the vang key on the key-block would rotate by itself, unattached to the boom.

    Then, if the latter circle were drawn with a radius 1" shorter (i.e., shortening the vang length by 1"), you can see that the first circle (the one centered at the gooseneck) and the second circle (the one centered on the vang tang hole) would now intersect at a point GREATER THAN 1" lower down than the original strap position (i.e., when boom was perpendicular to the mast).

    This is the beauty of the such vang designs fixed at the bottom of the mast: you lose power and efficiency because you are pulling at an angle, but less line needs to be pulled in to bring the boom down by one inch (compared to a vang fixed to the deck on a circular track following the projecyopn of the strap on the deck.)

    So, now we can get back to double blocking a Laser vang. (I'm just guessing these numbers from the Measurement Diagrams, but that's not important.) The boom end must come down by about 23" (58 cm) to be able to double-block, starting from a "parallel to water" state. How much of a downward movement at the vang strap does this require? Assuming a non-bending boom, it's a downward movement at the strap of about 4". And that's achieved by shortening the vang length by about 2.25".

    With serious boom bend, we are probably talking about shortening the vang length by 3". With line stretch at max vang, we are probably talking about 3.5". Which means that on an 8:1, you should need to haul in more than 2' of line, not just one foot, to go from slack on the vang to drum-tight.

    On a 15:1 (as in the new Holt and Harken vangs), we need to haul in more than 4 feet of line. So, the amount of "line in the cockpit" (or rather line "freely dangling from the camcleat exit") can be anywhere from six to nine feet when sailing upwind in strong air with the vang drum tight.

    Unless you constantly attend to your control lines (as you should at specific intervals, all other opportune moments while racing, and before all roundings), there is a significant likelihood that that vang line will find itself where you don't want it! Sucked into your ratchet block and blocking it, or pulled into any untaped stand-up spring underneath your camcleat, or on the wrong side of the boat, pulled to leeward either by its own (waterlogged?) weight and/or your shiny topsides.

    Some of these happen to me regularly if I'm not careful.

    I have not yet figured out what works best for me. The decision variables are:
    - The power ratio of your vang,
    - The length of the free end of the control line when your vang is at max slack, and
    - The brand/type of vang control line to use.

    Complementing these is a fourth new option: The opportunity to temporarily "tie" any control line to "any deck fitting" (however that's really defined by ILCA), as now allowed by Rule 3(b)x. It is of some interest when coupled with Rule 21 (Clips and Storage Bags)...

    Shevy

    PS. This is written on the run. Don't count on the correctness of the specific figures. I just looked at the Rules Book for measurements, and did not make any computations.
     
  3. rockingaswake

    rockingaswake New Member

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    This post refers to both the discussion of the new 15:1 vang system and a new discussion on the legality of storage of the free ends of control lines. Rule 21 of the laser bylaws stated "CLIPS AND STORAGE BAGS
    Clips, ties or bags to stow or secure safety or other equipment may be used on the deck, in the cockpit, or around the mast." Does this include the storage of the extra line needed in the cockpit while using the new 15:1. If this is legal I was thinking about storing all of the extra line from the vang in a bage i would make to hang from the mainsheet ratchet block fastener. Is this a good idea? I'm not sure there would be much chance to put the line in the bag but this was just a thought. I have seen this arrangement on a Hobie 33 Magic and that's where I got the idea from.
     
  4. Overdraft

    Overdraft New Member

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    GeoffS is spot on... If you've got some muscle and some loops you can fold your rig up very nicely with an 8:1, but you sure can't get it undone! Thus, in order to have a vang that you can release when necessary you've got to pay the big money for one of the approved systems just to get the cleat feature! (see my rant 'ILCA misses the mark?' under Politics)
     
  5. ChrisSmith

    ChrisSmith New Member

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    With the end of the vang control line tied to my centerboard, I never have trouble with there being too much line using the 15:1. One thing I like about 15:1 is that it's easy to get the vang nearly as tight as you need it for the beat without 2-blocking the main. And a co-effect of more purchase is finer control. Fine-tuning the leech offwind is easy with 15:1.
     
  6. Teeftie

    Teeftie New Member

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    i use a 12:1 using only the old bottom block and everything else new ball bearing blocks, its wickid, im only 140lbs, 5'11'' and a radial sailor so i dont really see the need for any more purcheses but i would like to have the new cleating system
     
  7. Rob B

    Rob B Active Member

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    I just tried out the new 15:1 vang in my back yard. The bend you can put in your mast in just a static test is scarey! The new vang is smoothe like melted butter too! Robbie likey. Will get to try it out in racing conditions this weekend. Hope I don't break anything!
     
  8. macwas16

    macwas16 New Member

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    You shouldn't break anything if you have your vang on tight as long as you have your main sheeted in...just remember once you finish a race to windward or something that you let it off.
     
  9. Darryn

    Darryn New Member

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    I use 15:1, I cant see any point in reducing the purchase to make things harder, the boat is hard enough work as it is. I broke a top section on purpose to find a ballpark limit, I put a mark on the vang where it broke. I find I dont have to go anywhere near that mark to sail the boat upwind in 25knots+ at a moderately competitive pace.
    Darryn 169711
     
  10. Siege

    Siege New Member

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    I use the 15-1 Harken vang system because it's what came with my boat. I find it's quite easy to pull on and I can get as much on or as little as I want with no problems. This is a good thing because although I sail a radial rig i'm still a little on the light side and have to de-power when the wind gets too much. Apparently some of my idiot friends down the club find it easy too since I often come back after leaving my boat alone on the beach for a while to find the vang pulled on quite tight...man these Aussie masts are good! :D

    Adrian
     
  11. GeoffS

    GeoffS Member

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    No, no. They're not idiots, they're just helping "work harden" your top section for you! ;-)

    Cheers,

    Geoff S.
     
  12. Rob B

    Rob B Active Member

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    Just back from my first outing w/the 15:1 vang. Loved it!, (actually loved all of the upgrades). Very easy to adjust, (all of them) on all points of sail in all conditions. Also, upgraded my tiller extension to the 48" carbo stick. Also, a must have over the standard length.
     
  13. seamonkey

    seamonkey New Member

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    I recently put together a 20:1 vang using the old vang base.
    -----Theory--At a certain wind-range,,,before you're sheeting-off upwind,,it may be possible to cleat the mainsheet,and play the vang in the puffs,with similar loads as mainsheet.
    -----Setup--1 line is attached at the mast end,with 2 tails making a double cascade,with a 5:1 pulling on that,so there's an extra block attached to the vang base,,and a double sheave at the top,pulling on the cascade.--to make this system work,it's important to develop a top-block which is very short,such that there's about 1/4" between the boom-tang and the block itself,,in order to get full function,,,and have the lines adjusted so that there's neutral leech pressure at fulll ease.
    ----------Function--with a concentration on using small blocks to give maximum play,,the vang goes from zero leach tension to the end of boom being ~9-10" off the back deck('redline' for topsection bustin'!!),,so it provides FULL adjustability range,with the added benefit that you CANNOT take the vang past the max load you identify,,which CAN happen (in the heat of the moment) with 12:1 and 15:1 vangs.
    ----------On the water---I've only tested this once so far(it's friggin' cold here these days!!),,,in ~18-25 knots,,so I was sometimes sheeting off in puffs,,but in the lower end of the breeze,,was able to test my usage theory a bit....and it seemed to hold true.......though the jury will of course be out until next race season!In the short sail I had (55min),I didn't have any immediate issues with the 'tail-length',,but have been used to dealing with a 12:1 already.
    ----------I'm a fatboy,,but methinks the lighter a sailor is ,,the more they want to be able to fully use their vang for flattening,de-powering their sail upwind,,,and the extra tail-length you have when 'cranked on' is only there when you want it in a breeze,upwind.....
    -------If you're not a tinkerer,,but have decided you MUST have one of these vangs,,,let me know,,and I'll develop a package!.....cheers!.....seamonkey.
     
  14. sailor327

    sailor327 New Member

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    i upgraded to the 15:1 because i had a lot of trouble getting the vang off at the windward mark.

    P.S: this might sound like a noob question but how do you find the purchase of a certain setup
     
  15. 144679

    144679 New Member

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    i have roosters version of the XD stuff, the kickers 15:1, n its harken deck cleats, cos in europe u get "Holt" if u buy the XD from laser,

    i want to ask the same question
     
  16. seamonkey

    seamonkey New Member

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    ......this dr lazer link should help..............

    http://www.drlaser.org/NEWRIG-sys.html
     
  17. 144679

    144679 New Member

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    since Drlaser is off line at the mo, can anybody tell me a general way or working out how much purchase a kicker or cunningham or anything wud have, i persume u can just look at the kicker 4 example and c what purchase u have, what does it mean 15:1 is the one the tail? (like one line out)
     
  18. Chumley

    Chumley New Member

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    A 15:1 is a 5:1 and a 3:1 combined, i.e. 5x3=15.

    Likewise a 4:1 is often a 2:1 with another 2:1 doing the pulling, i.e. 2x2=4.

    Try here and follow the links for a (relatively) straightforward explanation of mechanical advantage :

    http://www.technologystudent.com/gears1/pulley7.htm
     
  19. Baja

    Baja New Member

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    Added a block to my vang to get 8:1 this weekend and it is so much easier than the 3:1 that I had rigged originally. I think maybe too easy to pull on. It isn't difficult for me to release either. I may change my mind as time goes by, it was only my fourth time in the boat.
     
  20. computeroman2

    computeroman2 Member

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    I'll add to the disadvantages-If the vang line is too long and not tied to something, i find my line will get tangled with the mainsheet upwind and when i release to round the mark, the sail stays in because it's knotted with the vang and i waste precious seconds undoing the knots.
     

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