IP Rig Tuning by Norm Pierce, Pierce Yachts
We have had several requests for our rig tuning sequence, so I shall give it a try. Be aware that this is
free advice, and we all know what that’s worth! Rig tuning is not a “black art” or magic; it is the
stabilization of the rig for the matching of the sailplan to the vessel and each step or movement is easily
understood by studying the cause and effect (make an adjustment and understand what it did). A
loose rig can result in difficulty in furling and unfurling the headsails, poor pointing & performance,
leaks at the chainplates and partners and induce or increase the shock loading of the rig in a seaway or
when tacking. A bent mast can make in-mast furling very difficult and possibly damage the mainsail,
put undue stress on the partners and mast step and enhance pumping in a seaway.
Understanding what each stay or shroud does is helpful:
-The headstays must be taught to give the genoa and staysail shape and that so the furler extrusions
will turn on them smoothly and easily. They are kept taught by the backstays, checkstays and aft lower
shrouds all pulling aft.
-The upper shrouds, checkstays, and fore and aft lower shrouds are there to keep the mast straight
and in column from side to side. They get tighter on the windward side and looser on the leeward side
as we sail and wind velocity increases. Without gauges you would check their tension under sail by
sighting up the mast and adjusting to keep the mast straight and in column.
-The forward lower shrouds also keep the center of the mast from pumping fore and aft in a seaway.
The shortest sequence is a “retune” of a rig already standing and sails bent: use the Loos
gauges and the IP specification charts for the ambient temperature at the time of tuning.
1) Ease the Boom Vang, Mainsheet and Genoa and Staysail
Halyards.
2) Check all turnbuckle threads to make sure they are clean
and lubed. (I prefer cleaning with mineral spirits and
lubing with Lan-O-coat)
3) Remove all cotter pins and discard. Check all upper &
lower shroud and checkstay turnbuckles to make sure they
are tight inboard on the chainplates so that the genoa
sheets do not catch on them.
4) Hoist a 50-foot measuring tape to the top of the mast
with the main halyard and secure the halyard.
5) Measuring from side to side from the top of the mast to
the chainplate pin of the upper shrouds; make sure the
top of the mast is centered in the boat, athwartships.
6) Adjust the upper shrouds to center the top of the mast as
necessary.
7) Check mast for straightness and rake, both fore & aft and
athwartships.
8) Adjust the lower shrouds to bring the center of the mast
in line with the top to achieve a straight mast.
9) Adjust the upper shrouds to specs.
10) Check the headstay (with sail on it) by sighting its length,
(it should not sag) and if no sag, shaking side to side. If it
should move with reasonable pressure more than 3” to 4”
from center in the center of its length the headstay may
need tightening.
11) Check the backstays and checkstays, if they are not to spec
then tighten both to spec. (Note: when tightening the
backstays as you tighten the 2nd one the 1st one will
loosen so you have to go back and forth between the two
to achieve correct tension.
12) Check mast for amount of bend. Make note of any bend
and how much.
13) If there is bend, loosen each backstay about 10 turns and
checkstays about 5 turns so you can adjust the headstay as
the backstays will, at full spec, put enough tension on the
furler turnbuckle to make it very difficult to turn, which
creates the danger of galling the threads.
14) Adjust the headstay in accordance with the furling unit
instructions (you will have to loosen or drop the sail on
most to adjust them) to shorten the headstay enough to
remove the bend in the mast when the backstays are at
full tension. This may take a couple of attempts so don’t
close the furler till you finish the tuning. Tighten the
backstays to spec and check for bend till you get it right.
15) Adjust the aft lowers and staysail stay furler to achieve a
balance of correct tension on both.
16) Adjust the forward lowers to spec. On the newer boats
the aft lowers are larger than the forward lowers to achieve
better balance of the staysail tension. What we have found
on the older boats with the same size fore and aft lower
shrouds is to lower the forward lower tension 5 points
from spec and increase the aft lower 5 points gives a much
better balance and staysail shape.
17) Recheck all gauge readings.
18) Install new cotter pins.