Hough's Marine Tuning Guide, reprinted with Randy's
permission. Although originally developed for Catalina 27
owners, much of this material is relevant to C34 owners, as
well. Randy cautions that this tuning guide should be used
only for boats with riggin in good general condition; he
doesn't trust any rig that's over 7 years old!
Basic Rig Tuning for
Single Spreader Rigs (mast head / non-bendy spar)
You will require:
- Wrenches to fit the turnbuckles
- Lubricant for turnbuckle threads
- Your boat in a slip
- Flat calm (early morning)
- Your first mate or other crew (requires more beer)
- A piece of piano wire at least two feet longer than the
luff of your main
- Loos (tm) tension guage
- run around the boat and put a few drops of lube on the
threads of each turnbuckle while you are making sure your
- loosen the shrouds to just short of floppy
- center the masthead athwartships, use the main halyard
to measure to the cap shroud chain plates on either side
of the boat. Adujust the caps until the measurement is
equal P & S. Then tighten an equal number of turns
until the caps are taught. (about hand tight on the
- sight up the sail track on the aft side of the mast, it
should be dead straight athwartships. Use the lower
shrouds to bring the mast in column. Check for fore / aft
bend. The mast should be straight, or have a very slight
forward bow (masthead aft of spreaders). Tighten all lower
shrouds an equal number of turns checking to make sure the
mast is still straight, until single lowers are a little
*tighter* than the caps, or double lowers are a little
looser than the caps.
- have a beer, the mast is centered and straight!
- Use the spinnaker or jib halyard to heel the boat 20
degrees (listen for the china or television hitting the
cabin sole) count the turns as you take the slack out of
the "leeward" cap shroud. Note if the mast bows
out of column athwartships, and which direction
("weather" or "leeward"). Measure and
note the tension in the cap shroud while heeled with your
guage if you have one. Check it against the rated breaking
strength of the wire, it should be under 20% of breaking
strength. If its greater than 20% STOP! the
rig is not the correct size (unlikely on production
boats), you haven't figured out how to read the guage
correctly (likely, it takes some practice), or the boat is
too tighly moored or aground. Ease the halyard.
- Clean up the broken china or TV. Tighten the other cap
shroud the same number of turns that you took on the first
cap. Use the main halyard to assure your self that the
masthead is still centered
- If the mast bowed to "leeward" at the
spreaders, tighten the lowers (about half the turns you
took in the cap)
- Heel the boat the other way to 20 degrees (listen for
Chapman's, Bowditch and your wine hitting the cabin sole)
If you counted correctly the new "leeward"
shroud should be just taught. The mast should be straight
athwartships at the spreaders. Note any athwartships bend.
Ease the halyard.
- Clean up the mess below (sheesh don't you *ever* learn?)
If the mast was bowed to "leeward" at the
spreaders tighten the lowers some more, the forward lower
should be tighter than the aft lower. Sight up the mast to
make sure it is still straight, use the forward lowers to
straighten it as needed. In the unlikely case that the
mast bowed to "weather" loosen all lowers an
equal number of turns, keeping the forward lowers slightly
tighter than the aft lowers.
- Secure below deck items (before you trash the sextant
and binocs). Heel the boat to 20 degrees, make sure the
mast is straight, and none of the "leeward"
shrouds are loose, if they are, count turns until they are
just taught. Heel the boat the other way, and take up the
same number of turns on the other side.
- Have a beer, promise first mate to replace the china and
TV, and pump wine out of bilge.
- Go sailing. check the mast for athwartships bow and use
lowers to correct as needed (not likely). Tighten the
backsaty adjuster, and sheet the main in hard, the mast
should be dead straight fore and aft or have a slight
(1") forward bow at the spreaders. The aft lowers
should be looser than the forward lowers. Turn downwind.
Ease the backstay and main. Take the spare jib halyard to
the stem fitting and crank it tight. The aft lowers should
be tight. There must be *NO* aft bow in the mast. If there
is, ease the aft lowers equally, and take up the forward
lowers the same mumber of turns.
- Have a beer, your rig is now tuned better than 90% of
the rigs in your marina. Look at your notes, you should be
able to create a tuning guide for your boat: Hand tight
plus X turns for each shroud. If you have a tension guage
take 3-4 readings on each shroud and note the most
repetable one. (you didn't do all this work and not keep
notes did you?)
Note: Your rig will must likely be tighter than most, and
almost for sure tighter than the builders guide. Don't worry!
Any well designed production boat that does not have a
reputation for shedding masts, will sail all day heeled to 20
degrees. The tension in the loaded (weather) shrouds while
sailing will be the same at 20 degrees of heel if the shrouds
are loose or taught at rest, since the force to heel the boat
remains constant (heeling force is transmitted to the hull by
the rig). Sloppy rigs are slow and *increase* shock loads on
the shroud system (the same twine that cuts your hand before
breaking under a constant strain can be snapped with a quick
Take all the junk off the boat, fill the water and fuel
tanks about halfway, pump out the holding tank. Look at the
static hull trim. The boat should have no list (tilt) to port
or starboard. See what you can move to correct the trim if
needed. Fore / Aft trim is tougher, the boat should sit on her
lines with normal crew in normal positions. Light boats where
crew is a bigger percentage of total displacement will lie bow
down (transom up) when unladen. You can go as far with this as
you like: Lighter is better, move heavy items as close to the
center of the boat as possible. If you need to correct trim,
it is better to remove wieght from the heavy end /side than
add wieght. Take everything you haven't *used* on the boat in
a year off (save them for the next swap meet).
Light air adjustments
More bow down trim, crew below or just forward of mast,
both anchors on the rollers (disguise yourself as a cruiser).
Only enough water and fuel on board to get through the day.
This trim decreases wetted surafce area on most hulls,
reducing skin friction.
Mast Rake / Prebend
Tie that big rusty wrench that you never use to one end of
your piano wire, hoist the other end to the masthead on the
main halyard, to create a huge plumb bob. The wire should lie
behind the mast, slap a piece of tape on the boom and mark
where the wire crosses. This is your mast rake. Adjust mast
rake using the *forestay*, longer to increase rake (wire
further from mast) shorter to decrease rake (wire closer to
Start with minimum rake. 0"-1" Your boat should
have 2-5 degrees of weather rudder angle when sailing upwind.
The higher the angle of heel, the more rudder angle is needed
to balance the boat. More rake (masthead aft) creates more
weather helm, less rake creates less or lee helm (leeward
rudder angle *kills* upwind performace)
A good all around setting is 5 degrees of weather rudder at
15 degrees heel. Adjust rake (using the forestay) to get the
balance right. Every time you change the rake, check the fore
/ aft bow (prebend) of the mast and adjust lower shrouds as
needed to avoid inverting the mast (aft bow).
Light air adjustments
Increase rake to give more weather helm at low heel angles,
the rudder must *never* have leeward angle when sailing to
weather. Loosen the lower shrouds to allow the mast to sag to
leeward at the spreaders to power up the main a bit.
Heavy air adjustments
Decrease rake to give no more than 7 degrees weather rudder
just before you reef or shorten sail. (18-20 degrees heel max)
Keep lowers tight so the mast is dead straight athwartships.
More tension on forward lowers to prebend mast and flatten
(de-power) the main.
Backstay tension controls jib / genoa luff sag and mast
bend (depends on mast section) More sag = fuller sail (more
draft, more power, points lower) Less sag = flatter sail (less
draft, less power, points higher) Forestay length controls
Ease the backstay, the forestay should almost flop. This is
Tighten the backstay about halfway, measure the tension in
the forestay and note it.
Add measured ammounts of backstay tension logging the
forestay tension each time. Check mast bend also, if the mast
bends more than 20 - 25% of the fore / aft demension od the
section STOP. Tighten aft lowers to limit bend.
At some point you may notice that the forestay is not
getting tighter when you add backstay, this is because the
hull is bending . STOP , mark the backstay adjuster at this
point (we call it banana trim... think about it...) this is
100% backstay. (if you have hydraulics, note the pressure)
Don't worry if you run out of adjustment before the boat
bananas, good stiff boats won't under normal loads, and most
non-hydraulic adjuster systems don't have enough purchase to
bend the boat
Mark the adjuster for 25, 50, and 75% backstay (or make a
Upwind: 25-100% backstay as needed to control luff sag /
power to balance the boat.
Downwind: 25-0% backstay to let the rig move forward .
Keep a rig tuning log. Note changes and the boats
performance. $40 buys a rig tension guage, these are great for
returning to known settings and for catching problems early
(after initial strech shrouds should maintain tension, if one
is loose every time you check it, you *will* find something
wrong with the rig).
Multiple spreader rigs are more complex to tune, but the
order is the same. Center mast, cap shrouds first, then
intermeiates and lowers.
Please send your
comments and feedback to Randy Hough
Important: The opinions expressed here are those
of the individual contributors to this page, and not those of
the Catalina 34 National Association or Catalina Yachts, Inc.
Additionally, this material has not been reviewed by Catalina
Yachts, Inc. for technical accuracy. This page's maintainer
cannot guarantee the accuracy of this information or the
desirability of suggested modifications or upgrades. Please
obtain assistance from a competent marine mechanic or boatyard
prior to making any significant modifications to your vessel.