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The mystery of rig tuning

Discussion in 'Ask All Sailors' started by Phil Herring, Feb 4, 2019. Add this thread to a FAQ

  1. Phil Herring

    Phil Herring Dethroned Admin

    Joined Mar 25, 1997
    4,416 posts, 340 likes
    Hunter 450
    US Bainbridge Island
    Somewhere between a steaming cauldron and the wizard behind the curtain is the dark art of rig tuning.

    Its usually the territory of rig shamans, but some brave owners embark down this perilous path on their own.

    Do you tune your own rig? What tools and specs do you use, and how often do you check it? Your secrets are safe with us.


    TomY and Simon Sexton like this.
  2. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    4,489 posts, 2,440 likes
    O'Day 19
    US Littleton, NH
    Do you know what you can do with a sailboat that you can't do with a banjo? Tune it.
    I have tuned my own hobie 18 for years and now my Mariner 19. I thinking it is important to understand the basics of rig tuning when you own a trailersailer. On a bigger boat, I'd still do it myself because it's more affordable.
    Inspection of the the rig happens everytime I interact with it. I consciously and unconsciously look for loose cables, rust, missing pins, bent parts, cracked and dry bedding. On a trailer sailer, the mast head is easy to inspect everytime you secure the mast for transport or untie it to raise.
    Otherwise, I think I would want to go up the mast at least once a season.
    I would expect to get three or four years out of my stays if I were putting a lot of heavy sailing on them, like doing a lot of racing or long voyages in heavy weather. Otherwise, I would not be inclined to change them out until I noticed wear and tear or was prepping for a big voyage.
    For my fractional rigged hobie or Mariner, I tune by raising the mast in column so it is just supported by the stays. I first adjust the forestay until I have the desired rake. Then I tighten the backstay until I see a slight bend. I back that off to get the bend out (I've never sailed with an adjustable backstay, but this is how I would do it with one of those too. You need to start straight before putting the bend in).
    Then tighten the shrouds, lowers first so they feel tight when plucked. You should be able to deflect the cable just a little with modest effort. Make sure the mast is in column and not bent.
    The upper shrouds are last and tightened similarly to the lowers.
    The tension on the shrouds is fine tuned under sail. A beam reach in a good 12 knot breeze is perfect. Watch for dancing turnbuckles, then tighten both sides equally to just take the looseness out of the lee side a couple of extra turns, try the other tack and I'm in tune.

    -Will (Dragonfly)

    "Selah" likes this.
  3. LakeOntario270


    Joined Jan 4, 2013
    184 posts, 37 likes
    Catalina 270
    US Rochester, NY

    njlarry, "Selah" and DrJudyB like this.
  4. capta


    Joined Jun 4, 2009
    3,006 posts, 1,075 likes
    Pearson 530
    na Admiralty Bay, Bequia SVG
    We tune our own rig. As a matter of fact, we did so just yesterday. Quite simply, our object is to have the mast be perfectly straight (no fancy prebend or rake) and not moving around when sailing upwind in upwards of 20 knots of wind and 3 to 8-foot seas. We don't want slack shrouds on the lee side, even in a gust, especially when pounding into the seas.
    When I sailed The Bay, we did this under sail, tacking back and forth until all was perfect, but down here we can't get the wind without the seas, so that isn't practical. Instead, we watch the gear when sailing and tune when at anchor, a much more tedious and less simple way of doing the job.

    "Selah" and Will Gilmore like this.
  5. Joe Blizzard

    Joe Blizzard

    Joined Feb 5, 2009
    191 posts, 32 likes
    Gloucester 20
    US Kanawha River, Winfield, WV
    My owner's manual has this to say about rig-tuning:
    “The mast should be approximately plumb to the waterline and should not lean over the bow or over the stern. The forestay and backstay should be carried quite snug. The tension between the upper and lower side stays, or shrouds, should be adjusted so the mast is straight athwartships when sailing in a good breeze. In general, the shrouds should always be kept rather taut, but they do not have to be exceptionally tight.”

    I don't really know whether I have this calibrated correctly or not…

  6. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    4,489 posts, 2,440 likes
    O'Day 19
    US Littleton, NH
    My understanding is that the goal of proper tuning is to prevent slack that might then allow a sudden snapping of the rigging during an uncontrolled jibe while using the least amount of tension possible.
    Spend a little time sailing around older wooden boats and you'll see hogged shears that result from over tightening of shrouds over time. The turnbuckles that lay on the leeward gunnells are also seen from time to time. It doesn't take a gauge to fix those problems. In fact, a gauge doesn't know anything about those problems. Use stays that are not undersized for your rig and then adjust for the least tension to do their job.

    -Will (Dragonfly)

    "Selah" and Tom J like this.
  7. NYSail


    Joined Jan 6, 2006
    2,034 posts, 175 likes
    Beneteau 423
    US Mt. Sinai, NY
    I always tuned my rig on last boat.... using loos gauge and keep it column. Now with new boat have discontinuous stays and brackets that lock stay to spreader tips.... have to learn and will mess with it this spring as I do have a bend in mst up high.

  8. markwbird


    Joined Nov 26, 2012
    977 posts, 227 likes
    Hunter 34
    US Berkeley
    I do my own. It 's not really that it is mysterious so much that it is tedious. Start by getting the mast centered with the amount of rake you want. Then tighten to the proper basic tension while sighting up the mast to make sure it stays straight. Then go sailing and see how it behaves under load adjusting as you go. This is a long day or maybe even a couple of days.

    Don Crowther likes this.
  9. DougM


    Joined Jul 24, 2005
    1,625 posts, 208 likes
    Beneteau 323
    US Manistee, MI
    I do my own tuning, and check it often during the sailing season.
    I use a Loos gauge and go by the recommendations on the label which show numberes relative to the cable diameter of the shrouds and stays.
    The lower shrouds are adjusted first then the uppers while using a measuring tape hoisted on the main halyard and measuring side to side to the toe rail.
    There is no adjustability at all on the forestay of my Beneteau 323 short of taking the mast down and adding or removing a short tang at the masthead. Can’t do it at the bow because the roller furler leaves no room for a turnbuckle on the stay. So that adjustment won’t happen.
    The only other “fun” is adjusting the split backstays, and attempting to get enough rake to avoid lee helm.
    The whole process is a good way to use up an otherwise good day.
    If anybody has any good suggestions as to how to do it better, I’d love to know.
    Before anyone suggests doing the process while sailing which makes good sense, remember that when there is decent wind on Lake Michigan, it gets pretty choppy as well...and age conbined with a bionic knee makes safety an even bigger priority.

    "Selah" likes this.
  10. Pizzazz


    Joined Sep 11, 2015
    98 posts, 25 likes
    Hunter 31
    US Marina del Rey
    I have the B&R rig which is pretty easy to tune once the mast is stepped. You can even do it without a gauge, tighten per the instructions, then go sailing and remove the slack if any, alternating tacks. If you have a back stay, tighten it last as it is not supposed to be load bearing (in my case, it is just there for the SSB antenna). Other rigs require more effort.

  11. victorhoisington


    Joined Jan 22, 2008
    221 posts, 49 likes
    Islander Freeport, 41 Ketch
    US Longmont, CO
    So what do we do when the rig and boat are 40+ years young. My Islander 41 ketch has a rig (masts and shrouds) of unknown origin. To big for the standard Loos gauge and even then I'm not sure what setting to use.

    Earlier this year, I noticed significant pumping during high winds while at anchor. As noted by others, I believe I would have seen slack shrouds on the downwind side of the rig while sailing. After a rather uncomfortable night of the boat pumping during the wind storm I went topside and manually checked each shroud for tension. They all seemed to have about the same amount of soft tension, the mast was in column, but all shrouds felt equally loose. Out came the handy tools, 8 - 1/2 turns on each lower shroud, 5 - 1/2 turns on each center shroud. Everything is now much tighter, and better yet, no pumping of the rig during the next wind storm.

    I'm sure there is a better way, certainly a more precise way, but I'm equally week when pulling on each shroud so they all give about the same. As long as I can't tell the difference in tension and since I'm not racing, I'm sure the rig will handle the wind better and it "feels better" for cruising. No pumping while at rest means the rig isn't moving as much which means its less likely to develop a defect. at least that's my theory.

    If you don't have a gauge handy what options are there to be more scientific in my approach to rig tuning?

    SV/ French Temper

    All U Get likes this.
  12. Davidasailor26


    Joined May 17, 2004
    1,615 posts, 387 likes
    Beneteau Oceanis 37 LE
    US Havre de Grace
    Certainly not pumping is better than pumping, but a more scientific approach could be better still. Google the Selden tuning guide and it has a way to use a folding ruler taped to the shrouds to estimate their tension. As for balancing the tension from side to side, you'll probably find that unless the rig is wildly off both tensions will match, they just might both be wrong. Any difference in tension will just bend the mast to one side until the tensions balance again. The force of the mast trying to straighten itself won't add all that much tension of the shorter shroud.

    Now, as for that potentially 40+ year old rig of unknown origin - I'm assuming that at a minimum you do really good inspections routinely of the fittings that are holding it all up.

  13. vhoisington


    Joined Mar 13, 2011
    136 posts, 34 likes
    Islander Freeport 41
    US Longmont
    Yes, and good idea. I didn't mean that the rig it self was 40 years young, it's just the age of the boat. I have evidence that things were upgraded in 2003 or even 2007 and yes I check everything almost monthly to ensure no wear or tear.


  14. jssailem


    Joined Oct 22, 2014
    8,748 posts, 3,746 likes
    CAL 35 Cruiser
    US Salem, Moored Port Everett WA
    I too have a 40+ old boat. (Launched in 1974). When you do not have info you need to ask folks who might know. I got lucky. Found Bob Doyle. A Pacific NW Mast rigging legend. He was commissioned to replace my rigging and I got to ask all the necessary questions while he tuned and explained the tuning of the new rigging.

    One element. If the door to the head is jammed then the rigging is compressed to much. My rig is balanced port to starboard. I adjust the aft stay as needed to modify the forestay to tension and sail trim. Now when I grab the shrouds going forward I have a feel for the tension. So far the amount of tension had served my needs

    Last edited: Feb 5, 2019
  15. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    4,489 posts, 2,440 likes
    O'Day 19
    US Littleton, NH
    If the mast is in column and the boat is level (in the water, for example), the tension should be the same on both port and starboard shrouds. If you notice slack on the lee side while sailing, take up the slack evenly on both sides and when sitting still, check to make sure the mast is still in column.
    I can't imagine a gauge will give you a better tuning.
    The recommended 15% of breaking strength is suppose to be a maximum tension, not necessarily the tension you should actually put on the rig. Read your published tuning guide that comes with the boat. The ones I've read say something like, 'set the least amount of tension to do the job, not to exceed 15% of the breaking strength'
    The guide doesn't usually tell you what the least amount of tension is. Put a radar antenna high on your mast, the required tension will change. Switch to a full battened main or a bigger overlapping genny, the tension required will change. A gauge can only help tension to known values.
    If your cable is to specs, you won't have any problems. If it is not to specs, old or undersized, all you can do is guess and hope. If the cable is oversized, tuning to the recommended 15% means way over tensioning and putting extra forces on the hardware, chainplates, spreaders, mast, mast head and step, compression post, keel, garboards, freeboard and toe rails. Your boat will change shape and parts will fail sooner.

    -Will (Dragonfly)

    Whatfiero1 likes this.
  16. All U Get

    All U Get

    Joined Oct 2, 2008
    2,868 posts, 526 likes
    Pearson/ 530
    US Strafford, NH
    I have those baby stays that I was told would reduce any mast pumping. So far all they have done is chaffe the main sail and take up deck space.

    Bob S likes this.
  17. Sandy Stone

    Sandy Stone

    Joined Jun 2, 2007
    340 posts, 43 likes
    Beneteau First 375
    US Slidell, LA
    What kind of furler do you have? The Harken furler on my boat has an integral turnbuckle that adjusts the length of the headstay, but you would never know it without looking at the installation instructions. That being said, you would only adjust the headstay length to change the mast rake, not rig tension.

    jssailem likes this.
  18. Jackdaw


    Joined Nov 8, 2010
    9,933 posts, 2,977 likes
    Beneteau First 36.7 & 260
    US Minneapolis MN & Bayfield WI
    Wrong. 15% is TYPICAL number for set-and-forget. We adjust our daily and run ours up to close 25% on windy days, and that's recommended procedure. Honestly Will, correcting your errors based on you writing things you have no real world experience in is a full time job.

    jon hansen and Sailor Sue like this.
  19. DougM


    Joined Jul 24, 2005
    1,625 posts, 208 likes
    Beneteau 323
    US Manistee, MI
    I do have a Harken furler, and I guess I will have to look at the installation instructions more closely. I certainly didn’t see anything that resembled a type of turnbuckle adjustment when I put it together. I wish I had the instructions here rather than 1000 miles away.

    I realize that the adjustment only affects the headstay length, but that is what I need. The mast needs to be raked back slightly from where it is presently.
    The instructions I just looked up on the Harken website show the typical turnbuckle on the headstay, neither my original equipment headstay nor the new headstay I installed 2 years ago had a turnbuckle adjustment. Both headstays were products of US Spars presumably made to Beneteau specs.

    Last edited: Feb 5, 2019
  20. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    4,489 posts, 2,440 likes
    O'Day 19
    US Littleton, NH
    That's why it's not a good idea for you to take a break from this forum.
    I'm sure I'm not the only one who has missed your wisdom.

    -Will (Dragonfly)

    Scott T-Bird likes this.

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