My
Rig
My Tanzer 25 came with a 179sf (P=32.57', E=11')
mainsail made by Sobstad installed on a tall, bendy, single aft swept spreader
fractional rig made by Francespar.� Some boats have ISOMAT
spars.� I�ve been experimenting with Mast
Setup and find that the S2 7.9 is a close starting point. I�m listing the S2 7.9
table below and as I come up with different numbers for the T25, I�ll fill them
in.� Tuning a bendy single spreader rig
is fairly simple.� I�ve listed
instructions based on multiple sources below.
������
1.
Step the mast.�
Once you have the mast standing, hand tighten your lowers so the mast
stays in the boat, now tighten the uppers. Just make the shrouds tight enough
to hold the rig in, place.
2. Measure
the base of the mast position from side to side on the deck.� Get it centered on the deck.� This is important in order to have equal
tension on the lower shrouds when you are done.
3.
Without any shroud tension slide the butt
of the mast forward or aft until the mast is straight and the head stay is just
taut. Mast should be straight at this point fore and aft (a little aft rake
will increase weather helm and is generally ok).� Putting slight tension on the backstay can help
pull the mast tip back and rock the butt forward.� Mast rake is determined by forestay length.
Rake affects helm balance - raking the mast increases weather helm.� To measure rake, tension the backstay
approximately 60%, then check rake with a weight attached to the main halyard.
(Boat must be floating level when you do this!). Adjust forestay as necessary
to obtain the desired angle.� I have no
idea what the rake should be, so I have the head stay turnbuckle tightened half
way.� Oh, BTW, my head stay is 32�3�
long.
4.
Check that the mast is upright athwartships in the
boat. Use the main halyard to measure from the masthead to the chainplate each
side. Adjust upper (cap) shrouds to get identical readings each side (but use
minimal tension in the shrouds).� Another
way to do this is to hoist a tape measure to the top of the mast and measure to
the center of the chain plate pin. Repeat as necessary.
5.
A certain amount of pre-set mast bend is desirable,
to stabilize the middle part of the mast and thus minimize rig pump in a
seaway.
6.
Ensure the lower shrouds are slack. Induce the
required amount of pre-bend in the mast by tensioning the backstay. (Make a
note of the amount of pre-bend by using the main halyard tensioned down to the
foot of the mast, and measuring the amount of bend at the spreaders). Tension
the cap shrouds equally, a few turns at a time, until the fore and aft bend
starts to increase. Check that the mast is still straight athwartships.
7.
Now tighten the lowers in the same manner as the
caps, until the fore and aft bend starts to decrease. At this stage the caps
should be tighter than the lowers.
8.
Release the tension in the backstay, check that you
are happy with fore and aft and sideways deflections.� (Once the rig is set up as described here,
tensioning the backstay whilst sailing will affect the curve in the upper part
of the mast only, as the area around the spreaders is fixed by the opposing
forces of the shrouds).
9.
Tension your uppers until you reach 25 on the Loos
Tension Gauge. Make sure that you have done this by taking up equal turns on
each of the uppers.
10.
Once again, you need to make sure that the mast is
in the boat, square. Do step 4 over.
11.
Look up the back of your mast to check for any �S�
curves that you may need to tune out. If there is a curve then you will need to
start tightening the opposite lower. You should also notice that there will be
only a small amount of pre-bend.
12.
Assuming that your mast is straight, (no �S�
curves), bring your lowers up to 20 on the Loos Gauge. This should again be
done with equal tuns to each lower. You should find that your mast pre-bend is
about 1� to 1 ��.
13.
Go sailing! Set full sail to windward in smooth
water in light winds (10-15 degrees heel to windward).
14.
Tension the backstay just sufficiently to
straighten the forestay.
15.
If the leeward shrouds are slack, tighten them, but
NO MORE THAN ONE and a HALF TURNS AT A TIME. Go on the opposite tack and do
likewise, then tack again and check if the lee shrouds are still slack. If so,
repeat the operation. DO NOT OVERTIGHTEN the lee shrouds, as you may bend the
boat or break the mast when you tack!
16.
Back at the dock, check that the mast is still
straight athwartships
17.
As a final check of the rig tune, measure the
tension on the forestay using the Loos Gauge, it should be around 17 with the
backstay off and 30 with it full on.
18.
Now you have set your rig up for your average,
middle of the road settings. These numbers are good from about 8-16 knots of AWS.
These are also the numbers that we use for club racing when race to race
changing is not a necessity. Now just slacken or tension as the wind dictates.� A full turn is worth about 2 clicks on the
Loos Gauge at these settings.�
19.
I�ve included the S2 7.9 tables below and running
at the BASE settings.� If anyone has any
better ideas, please e-mail me.
S2 7.9 Rig Settings
|
|
Knots |
Uppers |
Lowers |
|
||
|
|
|
Tension |
Numbers |
Tension |
Numbers |
|
|
|
17-26 |
880 |
30 |
26 |
620 |
|
|
BASE |
8-16 |
620 |
26 |
22 |
480 |
BASE |
|
|
0-7 |
480 |
22 |
17 |
360 |
|
Base
settings = At the dock, setup the uppers at 25 and the lowers at 20 this will
be your base setting. With the shroud tension at the base setting of 25 and 20,
the head stay tension should be 17 on the Loose Tension Gauge.� Headstay tension can be adjusted through the
backstay adjuster to a tension of 30.
� = Numbers are from the Loos Tension Gauge,
Model B.
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