Tuning The New C420 Sails
By Brian Doyle, US Sailing Development
Coach
and Dave Kirkpatrick, Vanguard Sailboats
Performance Product Manager
In the spring of 2003, the
Club 420 Class sails were redesigned to provide a better competitive and useful
lifespan. Now that several events have
been sailed using the new sail design, it is clear that the new sails will
provide unprecedented durability as well as excellent performance.
Because the new sails are
shaped somewhat differently than the old ones, there are several adjustments
that sailors should make when tuning their rigs. First, let’s have a look at what the major shape-affecting
changes are in the new sails.
Mainsail tack: The mainsail tack is now attached to the
mast by a slug which fits in the track, rather than connected to the boom by a
pin. This allows the tack to float up,
reducing the diagonal wrinkles you see in the main when going downwind.
Mainsail shape: The mainsail
is a bit flatter through the bottom and middle sections of the sail, and the
leech is a little looser.
Jib clew: The jib clew is
higher than on the old sails. The area
cut away in raising the clew is added back elsewhere in the sail.
Jib shape: The jib is slightly
flatter in the lower part, with a significantly more open leech, especially in
the upper section of the sail.
Jib luff wire: The jib luff
wire is slightly thicker than on the old sails, but is made out of slightly
stretchier wire. The luff wires on the
new sails are overall a very small amount stretchier than the old luff wires.
Rig Tuning Changes
Overall, the boat is rigged
the same way as before. The lines are
all strung as before, the mainsheet bridle remains unchanged, and all line
lengths remain the same.
Mast butt position can be moved one to two holes aft from the traditional “pin max
forward” position. Before, it was
mandatory to have the mast butt placed all the way forward in the step because
the mast was set up with so little rake.
This will balance the helm as much as possible. Most people sailing with the new sails have
noticed how nice it is not to have lee helm anymore. The mast rake, mast butt position and helm balance are all
closely tied together.
With the old sails, the game
was to set the mast without any rake (rearward lean) at all. Because the jib lead position on the C420 is
fixed, the old jib’s low clew made it necessary to have the rig far forward in
order to get proper leech tension for good pointing. The old jib was also quite finicky in that once you tensioned the
clew, it would very easily become over tensioned and the leach would hook to
windward. This is primarily due to a
design/construction detail which has been addressed with the new sails.
Because the old sails set up
with little rake, moving the butt forward “leaned” the rig back as much as
could be done, easing the lee helm that usually crops up when the rig is set up
with very little rake. Because the mast
is now raked significantly more, moving the butt backward one to two holes
provides a rig with properly balanced helm.
If you feel a lot of weather helm and, at the same time, feel a lack of
pointing (which is a very strange combination to have), you should try moving
your mast butt aft.
A benefit of having the mast
butt further aft is that you decrease the overlap between main and jib. While this doesn’t have a huge effect, it
will allow you to play the main a little more aggressively without having the
jib interfering with the main.
Rig tension
has a profound effect on how your sails will set. Simply, more rig tension will give you flatter sails with more
open leeches, while less rig tension will give you fuller sails with tighter
leeches. To simplify things a bit, this
just means that if you needed more power you would ease the rig tension and if
you needed less power, you would increase rig tension.
Because the mast on a C420 is
so stiff, the primary effect of pulling on more rig tension is to tighten the
jib luff wire. This flattens the shape
of the jib, and to a smaller degree will pull the jib draft forward. It will also loosen the leech of the
jib. Pulling the draft forward in a
sail and flattening the sail both contribute to loosening the leech. The magic of this, in a C420, is that this
allows you to trim the jib tighter (with both the leeward and windward sheets)
and thus point higher. With this kind
of setup you will have greater speed and pointing in fully powered conditions,
but will lack power, and thus speed and pointing, in lighter airs.
A Brief Warning About Rig Tension: Some sailors
have experimented with extreme rig tensions in their C420s. This tuning guide recommends a maximum
shroud tension of 350 pounds. Some
crews may wish to go slightly firmer than this. It is VERY POSSIBLE AND EVEN LIKELY that your boat (hull or
rigging) will suffer a breakdown if you use more than 400 pounds of rig
tension. The C420 was not designed to
sail under excessive rig tensions. Your
boat’s lifespan will be shortened if you regularly sail with excessive rig
tension. Before you go for that extreme
setting, ask yourself if you are willing to risk a possible regatta ending
breakdown by going for that extra amount of rig tension.
Mast rake in a
C420, as mentioned above, is a primary driver of jib lead angle. To help with understanding jib lead angle,
imagine your C420 rigged, with the jib trimmed in for going upwind. If the jib sheet points to the bottom of
the jib, you will be trimming the foot more and the leech less. If the sheet points into the middle of the
jib, you will be trimming the leech and foot about equally. If the sheets points up towards the top of
the jib, you will be trimming the leech more and the foot less. On the old jibs, in order to get any leech
tension at all, the mast had to be set up with almost no rake at all in order
to get the clew high enough to give any leech tension. With the newer sails, the clew is higher and
you get a much better lead angle with more rake.
More rake is also good for
opening the slot between the main and the jib.
Whenever the air leaving your jib is flowing into your main, it is
slowing you down. Having a wider slot
is better for windier conditions when you need to depower, but a narrower slot
will let you point higher in conditions where you can keep the boat flat. More rake = bigger slot + less power +
better speed + lower pointing. So if
you are having trouble keeping the boat flat, and are stuck pinching and not
going fast, rake back a little bit. If
you are feeling underpowered and have bad pointing, rake forward a little bit.
To measure rake, thread your
main halyard end through the end of a 25' or longer tape measure and hoist the
halyard to the top of the mast. With
enough pressure to pull the tape straight but not enough to bend the mast tip,
measure the distance from the top of the mast to the top of the transom on the
centerline. It is also important to
note that mast rake is measured with the rig fully tensioned. Pull up your jib to full tension, then
measure the rake. If the rake
measurement is too big, lower the pins on your shroud adjusters, re-hoist the
jib, then re-measure the rake.
Main trim with
the new sails is quite a bit nicer than with the old ones. Basically, with the old sails, you needed to
pull the mainsheet hard to keep the top of the sail sheeted in, but in doing so
the bottom 2/3rds of the sail would be badly over trimmed. With the new mains, the bottom 2/3rds of the
sail is a little flatter. Now you can
trim hard enough to keep the top of the main trimmed properly without over
trimming and closing off the lower 2/3rds of the leech. In moderate winds it is critical to trim the
mainsheet hard to obtain pointing and to keep the crew on the wire. In heavier winds, the new sail shape allows
the trimmer to obtain plenty of twist in the leech for depowering by using the
vang and mainsheet together.
RIG TUNE FAULT FINDER
Here
are some common symptoms and things you can do to help solve them. You should ask yourself these questions in
order as the earlier questions are easier fixes and more often incorrectly set.
Bad
pointing
·
Is your mainsheet bridle
too high?
·
Is your mainsheet trimmed
tight enough?
·
Is your jib sheet trimmed
tight enough?
·
Is your windward jib
sheet trimmed tight enough?
·
Is your mast raked too
far back?
·
Is your mast foot too far
forward?
·
Do you have too much rig
tension?
Bad
speed
·
Is your mainsheet over
trimmed?
·
Is your jib sheet over
trimmed?
·
Is your windward jib
sheet over trimmed?
·
Is your mast raked far
back enough?
·
Do you have enough rig
tension?
SETTINGS GUIDE
Here are some common settings
for the new C420 sails. All of these
settings are based on the mast butt being positioned 2 holes back from the
forward-most hole. These are based on
combined crew weight of about 250 pounds.
If you are much lighter than this, move up one range (use the 12-14
setup in 9-11 knots of breeze). If you
are much heavier, move your setup down one range. You should move down one range if there is significant chop.
0-4 Knots
Rake: 20’3”
Shroud Tension: 100 pounds
Centerboard: Full down
Mainsheet Bridle: Block sheave
top 21” from board cap
Mainsheet Trim: Top batten
telltale flying constantly
Vang: Loose
Outhaul: Slight horizontal
wrinkles along boom
Cunningham: Loose but only a
few horizontal wrinkles
Jib trim: Firm leeward sheet,
slight or no windward sheet
5-8 Knots
Rake: 20’4”
Shroud Tension: 140 pounds
(leeward shroud should be just a tiny bit loose going upwind)
Centerboard: Full down
Mainsheet Bridle: Block sheave
top 21” from board cap
Mainsheet Trim: Top batten
telltale stalling often
Vang: Very slight tension
Outhaul: Slight horizontal
wrinkles along boom
Cunningham: Loose to none
Jib Trim: Firm leeward sheet,
firm windward sheet
9-11 Knots
(this is the zone where you start to transition to trapezing)
Rake: 20’3”
Shroud Tension: 200 pounds
Centerboard: Full down
Mainsheet Bridle: Block sheave
top 20” from board cap
Mainsheet Trim: Firm
Vang: Neutral in lulls, slight
tension in puffs
Outhaul: Horizontal wrinkles
along boom
Cunningham: Very slight
tension
Jib Trim: Very firm leeward
and windward sheet
12-14 Knots
Rake: 20’2”
Shroud Tension: 230 pounds
Centerboard: Full down
Mainsheet Bridle: Block sheave
top 17” from board cap
Mainsheet Trim: As hard as you
can pull
Vang: Firm tension
Outhaul: Hard horizontal
wrinkles along boom
Cunningham: Tensioned
Jib Trim: Very firm leeward
and windward sheet
15-18 Knots
Rake: 19’11”
Shroud Tension: 300 pounds
Centerboard: Raised 1”
Mainsheet Bridle: Block sheave
top 16” from board cap
Mainsheet Trim: Pull hard
until you start to heel too much
Vang: Very firm tension
Outhaul: Hard horizontal
wrinkles along boom
Cunningham: Hard tension
Jib Trim: Extremely firm
leeward sheet tension, moderate windward sheet tension
19+ Knots
Rake: 19’10”
Shroud Tension: 330 pounds
Centerboard: Raised 3”
Mainsheet Bridle: Block sheave
top 15” from board cap
Mainsheet trim: Pull hard
until you start to heel too much then ease, hike, trim
Vang: Very firm tension
Outhaul: Hard horizontal
wrinkles along boom
Cunningham: Hard tension
Jib Trim: Extremely firm
leeward sheet tension, slight to slack windward sheet tension
03-0926