Beneteau First 40.7 Mast Tuning Instructions

  1. After stepping the mast, make certain that the mast butt is centered in the step and pinned in the center hole.
  2. All deck fittings should be secured into place and tightened securely. The rubber mast collar should be tightened.
  3.  Because the mast is locked at the deck in a centered position, it does not have to be adjusted as there is enough play in the step to adjust and correct the tuning depending on the weather conditions.
    Mast pumping struts below deck should be tightened and locked in place. Failure to tighten and lock these struts in place can cause catastrophic mast failure.
    Make certain there is NO TENSION on the backstay (all hydraulics released and the turnbuckle loose).
    PRIOR TO CENTERING THE MAST, ALL DIAGONALS SHOLD BE LOOSENED COMPLETELY (ALMOST OFF).  THIS IS CRITICAL AS THE DIAGONAL TURNBUCKLES, IF NOT LOOSENED COMPLETELY, WILL ADVERSELY AFFECT THE MAST TUNING AS THE PRE-BEND IS ESTABLISHED. THE VERTICLES WILL TIGHTEN AS THE BACKSTAY TENSION IS RELEASE.  Tensioning the rigging on the V1 is without any effect if you do not full take off on the D2’s and D3’s.  You must absolutely release dompletely the tension on the D2’s and D3’s before tightening V1’s. If this is not done, then any tension placed on the V1’s are transmitted to the D2’s and D3’s and this will place center part of the mast under tension without any tension at the top of the mast which is critical.
    The mast should then be squared in the deck using a tape run on the main halyard to port and starboard chainplates.
    Put approximately 3500 lbs of tension on the backstay or tighten until the masthead is back at least 30 inches.
    Once the mast has been centered, port and starboard cap shrouds should be tightened evenly.  The cap shrouds should be tightened until BAR TIGHT. (Note: this may seem unreasonably tight, however, it is imperative that the caps be extremely tight) Make certain that an equal number of turns are taken on each side so that the mast remains centered in the boat.  The cap shrouds are discontinuous rigging and therefore must be tightened with the diagonal turnbuckles completely loose.
    With the backstay still on, send a man aloft and tighten the upper diagonals until hand tight plus 4 turns on each side. Make certain the upper and middle segments of the mast are in column by having someone on the deck sight up the mast.
    With the backstay still on, lower the man aloft to the middle verticals and tighten hand tight plus 4 turns. Make certain the upper and middle segments of the mast are in column by having someone on the deck sight up the mast.
    With the backstay still on hand tighten the lower diagonals plus 1 turn on each side.
    Ease the backstay completely off. At this point, the mast should be in column and there should be about 3-4 inches of pre-bend in the mast.  With the backstay completely off, hand tighten the turnbuckle above the hydraulic backstay adjuster plus 2-3 turns.
  • It IS NOT necessary to adjust the general geometry of the rig as the rig was designed with racing rules in mind and to avoid runners which are heavily penalized.  There will be some level of pumping but this should be mitigated by tightening the mainsail leech upwind. Remember…set up the verticals VERY TIGHT and adjust the forestay length to the amount of rake for the wind conditions and play the backstay to tension the forestay!!Special notes:The Beneteau 40.7 spar has been designed from the original Farr sail plan in conjunction with Beneteau engineering.
    Approximate time to tune the mast: 3-4 hours
    Forestay length:  open length pin to pin is 16,311mm.  Tuning calls for the forestay to be located in the 3rd hole of the link plate (never shorter than this hole!!) which should be at 16,251mm. (53.513-53.316ft/642.16-639.8 in)
    Mast step should be in the middle hole.
    The headstay is Navtec-17 rod rigging with the lower assembly reference LRT-120 plus G100-17.  This should be replaced with Navtec turnbuckle C550-17, but the forestay will have to be taken off the boat to a local Navtec agent to be re-swaged.
  •  THIS IS A MUST for adjusting forestay tension with aft raked spreaders.
    The backstay turnbuckle CANNOT replace the forestay turnbuckle.  The backstay turnbuckle is necessary in order to pre-tension the backstay.  With the backstay cylinder fully released, the backstay must be tensioned. This will allow the backstay hydraulic cylinder to be very efficient and powerful.  This will also decrease the possibility of a mast failure due to the masthead moving forward of the mast step.