BENETEAU Boat User Manual page 132

13.16.2. Tuning
Before un-hooking the mast from the crane used to step the mast, for safety, make sure that the minimum
amount of thread of the turnbuckle is engaged. Ensure that at least 1-1/2 times the thread diameter is
engaged or that the holes for the split pins are visible through the turnbuckle body - this is refered to as
the minimum safety position of a turnbuckle.
When making any adjustments to the mast, always make sure that the mast is straight and that there is no
lateral or sideways bend. Fore and aft pre-bend is acceptable but must never exceed half the fore and aft
dimension of the mast section.
If, at any step, you are having difficulty keeping the mast straight you have probably over tensioned the
stays and shrouds causing excess compression loads on the unsupported mast panels between the stays
and shrouds. Reverse the steps and re-tension the stays and shrouds using fewer turns.
Always make sure that all turnbuckles are clean and properly lubricated with a non-graphite grease.
When adjusting a turnbuckle, it is best to make less than three turns of the turnbuckle before adjusting the
opposite turnbuckle.
• Set the rake of the mast by adjusting the forestay to the pre-determined length according to the
standing rigging specification sheet. TIP: Set the forestay to the correct measurement before
installing it on the mast and note the distance between the threaded stud and the turnbuckle body.
After stepping the mast you will be able to know the forestay length by comparing this measurement.
• Make sure the intermediates (D2) are released to their minimum safety position.
• Center the mast athwartships, using the capshroud (V1) turnbuckles. TIP: Using two pieces of
rigging tape, mark the port and starboard toe rails (opposite the mast) at an equal distance from the
forestay. Use a tape measure hoisted on the jib halyard (it does not need to be hoisted all the way) to
check the port and starboard measurements at the toe rail rigging tape mark. They must be the same.
When taking these measurements, ensure that you are taking a straight line measurement from the jib
halyard sheave to the toe rail mark and that no equipment is fouling the measuring tape overhead.
• Tension both backstays equally. This will introduce pre-bend in the mast and make it easier to tension
the cap shrouds.
• Tension the cap shrouds (V1) an equal number of turns on port and starboard. Do not allow the
intermediates (D2) to become tight. At this stage you will have more pre-bend than is required.
Oceanis 381
Rev. 01
TUNING A MASTHEAD RIG
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WARNING
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6/12/2008
9:16 AM