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Re: [SabreSailboat] Mast Pumping

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  • Peter Tollini
    John - Those are really generic, conservative, do-no-harm suggestions. If your manual is available, Sabre provides the design forestay length, which sets the
    Message 1 of 8 , Jul 4 7:12 AM
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      John -
      Those are really generic, conservative, do-no-harm suggestions. If your manual is available, Sabre provides the design forestay length, which sets the design mast rake. Probably greater than 12".  Moderate prebend is necessary, but it needs to be controlled, mainly by the fore and aft lowers acting as checks. 
      Shroud tension should be verified either with a gauge or using Dedekam's ruler and feeler gauge method.
      Without a backstay adjuster, you'll need to find a happy medium to set the turnbuckle.
       
      Bottom line, backstay tension, with snug, but not tensioned, aft lowers should control pumping.
       
      Pete

      On Wed, Jul 4, 2012 at 8:10 AM, JOHN CALLIS <jsts@...> wrote:
       

      Last year I  went through mast tuning several times, and followed the procedure mentioned here best I could.

      You mentioned a couple of things that may be a problem for me.

      1.  my mast has more than 12 inches of rake, if I  remember right it is 16 inches or maybe 18 inches (measured by hanging a heavy weight by my main halyard).
      2.  I have no back stay tensioner other than a turnbuckle.
      3.  I have plenty of pre bend.

      John
      S 34 MKII


      On Tue, Jul 3, 2012 at 10:01 PM, Peter Tollini wrote:

         John -
      I have a similar rig on the 30 MkIII and haven't experienced that at all.  I suggest using Ivar Dedekam's book to set up your rig, but in a nutshell,first tighten your backstay. then here is the process.

         1.  Remove the wedges at the partners.
         2.  Use a 100' steel tape pulled to the mast head to position the masthead in the center athwart ships, measuring to the rails. 
         3.  Use the same tape to set your forestay length (should be in the manual from Sabre). If not, rake the masthead @ 12" aft. Sabres like rake.
         4.  Add moderate tension to the backstay. Consider a tensioner if you don't have one.
         5.  Tension the upper shrouds.
         6.  Tension the intermediates to keep the mast straight (side-to-side)
         7.  Tension the forward lowers to induce @ 1 mast section of prebend.
         8.  Tension the aft lowers - no slack, but not loaded.  These should limit mast bend and prevent pumping.
         9.  Replace the wedges to hold the mast in place.
         10. Tension the backstay when you sail (if you have a tensioner) or moderately with the turnbuckle if you dont.
         11. Go sailing. Hard on the wind in 12-15 kts, the mainsail tack shoul be arrow-straight side to side.  Leeward lowers should be untensioned, but not sloppy loose.
         12. If you need to, adjust leeward shrouds & lowers to remove slop, take and adjust the other side an equal number of turns.
         13. Get Dedekam's book or download Selden's guide.

      Pete
       
       
      On Tue, Jul 3, 2012 at 4:53 PM, fs3873 < jsts@...> wrote:
        The mast on my Sabre 34 MKII is a double spreader rig, and pumps when we are at dock.

      Last year the boat was new to me, and we soon noticed that the rig would pump forward and aft sometimes when we were at dock. I started taking note of when it happened, and I was surprised that it would take very little wind (7 – 10 knots) to cause it. I made several adjustments to the rig, which included increasing and decreasing shroud tension, and increasing and decreasing prebend in the mast. The situation is a little better, but I am still worried that something is not right.
      Have others had a similar experience?

      Thanks
      John
      S34 MKII



    • john kalinowski
      Pete s advice is spot on.   And John, how many foot pounds are you running side shrouds, fore/aft lowers, and backstay when you crank in the adjuster? ...
      Message 2 of 8 , Jul 4 8:57 AM
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        Pete's advice is spot on.
         
        And John, how many foot pounds are you running side shrouds, fore/aft lowers, and backstay when you crank in the adjuster?

        --- On Tue, 7/3/12, Peter Tollini <pete@...> wrote:

        From: Peter Tollini <pete@...>
        Subject: Re: [SabreSailboat] Mast Pumping
        To: Sabresailboat@yahoogroups.com
        Date: Tuesday, July 3, 2012, 10:01 PM

         
        John -
        I have a similar rig on the 30 MkIII and haven't experienced that at all.  I suggest using Ivar Dedekam's book to set up your rig, but in a nutshell,first tighten your backstay. then here is the process.
        1. Remove the wedges at the partners.
        2. Use a 100' steel tape pulled to the mast head to position the masthead in the center athwart ships, measuring to the rails. 
        3. Use the same tape to set your forestay length (should be in the manual from Sabre). If not, rake the masthead @ 12" aft. Sabres like rake.
        4. Add moderate tension to the backstay. Consider a tensioner if you don't have one.
        5. Tension the upper shrouds.
        6. Tension the intermediates to keep the mast straight (side-to-side)
        7. Tension the forward lowers to induce @ 1 mast section of prebend.
        8. Tension the aft lowers - no slack, but not loaded.  These should limit mast bend and prevent pumping.
        9. Replace the wedges to hold the mast in place.
        10. Tension the backstay when you sail (if you have a tensioner) or moderately with the turnbuckle if you dont.
        11. Go sailing. Hard on the wind in 12-15 kts, the mainsail tack shoul be arrow-straight side to side.  Leeward lowers should be untensioned, but not sloppy loose.
        12. If you need to, adjust leeward shrouds & lowers to remove slop, take and adjust the other side an equal number of turns.
        13. Get Dedekam's book or download Selden's guide.
        Pete
         
         
        On Tue, Jul 3, 2012 at 4:53 PM, fs3873 <jsts@...> wrote:
         
        The mast on my Sabre 34 MKII is a double spreader rig, and pumps when we are at dock.

        Last year the boat was new to me, and we soon noticed that the rig would pump forward and aft sometimes when we were at dock. I started taking note of when it happened, and I was surprised that it would take very little wind (7 – 10 knots) to cause it. I made several adjustments to the rig, which included increasing and decreasing shroud tension, and increasing and decreasing prebend in the mast. The situation is a little better, but I am still worried that something is not right.
        Have others had a similar experience?

        Thanks
        John
        S34 MKII


      • JOHN CALLIS
        My Sabre manual states that my upper shrouds should be tensioned to a reasonable degree of tension -2500 to 3500 lbs. maximum . I bought a loos gauge (model
        Message 3 of 8 , Jul 5 6:43 AM
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          My Sabre manual states that my upper shrouds should be tensioned to a "reasonable degree of tension -2500 to 3500 lbs. maximum".  I bought a loos gauge (model PT-2) and the highest the tension reads is 2000 lbs which is 24% of the breaking strength.  Since I had read that shrouds should not be tensioned more than 20% and my shrouds, yet in good shape are possibly original to the boat, I settled in on about 1600 lbs. which according to the gauge is 20% breaking strength.  I had the feeling that the Sabre manual may have been off on there recommendation, and Glen Chapman kind of agreed.

          My backstay and lower forwards are about the same as my uppers, and my lower aft are a little less, but about 1300.

          The mast looks good under sail, and the forestay does not seem to sag too much, but my problem is that I may not have enough experience to tell.

          Thanks
          John

          On Wed, Jul 4, 2012 at 11:57 AM, john kalinowski wrote:

             Pete's advice is spot on.
           
          And John, how many foot pounds are you running side shrouds, fore/aft lowers, and backstay when you crank in the adjuster?

          --- On Tue, 7/3/12, Peter Tollini <pete@...> wrote:


          From: Peter Tollini <pete@...>
          Subject: Re: [SabreSailboat] Mast Pumping
          To: Sabresailboat@yahoogroups.com
          Date: Tuesday, July 3, 2012, 10:01 PM

            John -
          I have a similar rig on the 30 MkIII and haven't experienced that at all.  I suggest using Ivar Dedekam's book to set up your rig, but in a nutshell,first tighten your backstay. then here is the process.

             1.  Remove the wedges at the partners.
             2.  Use a 100' steel tape pulled to the mast head to position the masthead in the center athwart ships, measuring to the rails. 
             3.  Use the same tape to set your forestay length (should be in the manual from Sabre). If not, rake the masthead @ 12" aft. Sabres like rake.
             4.  Add moderate tension to the backstay. Consider a tensioner if you don't have one.
             5.  Tension the upper shrouds.
             6.  Tension the intermediates to keep the mast straight (side-to-side)
             7.  Tension the forward lowers to induce @ 1 mast section of prebend.
             8.  Tension the aft lowers - no slack, but not loaded.  These should limit mast bend and prevent pumping.
             9.  Replace the wedges to hold the mast in place.
             10. Tension the backstay when you sail (if you have a tensioner) or moderately with the turnbuckle if you dont.
             11. Go sailing. Hard on the wind in 12-15 kts, the mainsail tack shoul be arrow-straight side to side.  Leeward lowers should be untensioned, but not sloppy loose.
             12. If you need to, adjust leeward shrouds & lowers to remove slop, take and adjust the other side an equal number of turns.
             13. Get Dedekam's book or download Selden's guide.

          Pete
           
           
          On Tue, Jul 3, 2012 at 4:53 PM, fs3873 < jsts@...> wrote:
            The mast on my Sabre 34 MKII is a double spreader rig, and pumps when we are at dock.

          Last year the boat was new to me, and we soon noticed that the rig would pump forward and aft sometimes when we were at dock. I started taking note of when it happened, and I was surprised that it would take very little wind (7 – 10 knots) to cause it. I made several adjustments to the rig, which included increasing and decreasing shroud tension, and increasing and decreasing prebend in the mast. The situation is a little better, but I am still worried that something is not right.
          Have others had a similar experience?

          Thanks
          John
          S34 MKII


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