Overview:
The JY15 performs best to a certain sailing style: boat
flat and footing, sails eased, and the rig raked. To understand why this style
is fast, first you need to take a look at some of the distinctive features of
the JY rig.
The JY15 has a smallish centerboard. Because
of this:
If you heel the boat upwind, the centerboard is less
effective. You must sail the boat
flat especially in a breeze. For a
small centerboard to be effective, you must get water flowing over it. You need to ease the mainsail and foot;
you must keep the boat moving fast.
If you try to pinch, not only will you be moving slower, but your leeway
will increase as well.
The JY15 does not have an adjustable
traveler. Because of this:
The traveler is always centered. Also, the mainsheet has
3:1 purchase. These factors make it very easy to over trim the mainsail. You
have to keep the sheet eased and the boom at least halfway between the
centerline and the leeward quarter.
Otherwise, you cannot foot the boat and you will be forced to pinch
which will tend to stall the centerboard.
Since you can’t trim the mainsail hard, the only way to
control forestay sad as the wind increases is by tightening the shrouds and
adjusting the mast chocks.
Sailing the boat “loose and level” leaves
the helm feeling “mushy.”
Very slight weather helm is fast when sailing to weather
because it means the rudder is generating lift. But you cannot get weather helm by heeling the boat or over
trimming the mainsail because this had been proven to be slow.
The best way to generate a slight weather helm is to sail
with as much rake as possible.
This is why you set your head stay as long as possible.
Traveler
Check the length of your traveler. The length of the rope, before knots
are put in it, should be the maximum allowed 48”. This raises the height of
your traveler and allows you to sheet the sail without as much leech
tension. This is important for
light air speed.
Main Halyard Tension
Lead the main halyard down the front of the mast so that
the halyard is forward and inside the shroud. This minimizes the tendency for
the halyard to go slack as the mast bends. Mark the halyard and put a scale on the side of the mast. The total tension range is 3” with the
tension gradually increasing as the wind builds. Set the halyard so that there
are small wrinkles in only the lower third of the sail’s luff. A Cunningham may be rigged in case the
wind comes up suddenly, but otherwise should not be needed.
Outhaul
Tension the outhaul until a small fold just begins to
appear in the bolt rope tape in the foot of the main.
Vang Tension
Put the mainsail up on the shore in calm conditions. Reverse the vang so that the cleat is
at the boom. Take all the slack
out of the vang, but put no tension on it. From this position in the cleat, make four marks on the tail
of the vang. The first mark is 1”
from the slack position followed by marks at 3 ½”, 5 ½” and 8”
Setting the Vang:
0-5 knots mark #1
6-10 knots mark #2
11-15 knots mark #3
16 + knots mark #4
Jib Sheet Trim
One advantage of sailing with a lot of rake is that the
foot of the jib lays closer to the deck.
This provides a better end plate for the sail and makes it more
efficient. The extra rake,
however, does make the bottom of the jib sheet rather flat. We compensate for this by pulling
approximately 2” on the weather sheet in light to medium winds. This deflects the clew of the jib about
1” inboard and adds curvature to the bottom of the sail.
Setting up the JY15
Tuning the rig:
- Set the forestay as long as possible.
- Set the shrouds on the second hole down from the top in
the “gross adjuster.”
- Put one chock behind the mast and one in front, and with
someone hanging on the main halyard to pull the tip of the mast toward you,
attach the shrouds to their deck eyebolts.
- With the forestay lever tensioned, and the boom off the
mast center the mast in the partner and sight up the sail track. The mast should be straight
sideways. If it isn’t then one
shroud is probably longer than the other.
Adjust the relative tensions until the mast is straight.
- With this setup, your shrouds should have approximately
250lbs of tension. This is a good
all purpose rig setting. If you
are not quite at these numbers, try adjusting the fine-tuning holes on your
shroud adjusters.
- You can fine-tune the rig for special conditions: light or
heavy air. For light air, try
loosening the shrouds one diagonal hole on the “fine adjuster,” and putting
both partner chocks behind the mast. In heavy air you can tighten the shrouds
one diagonal hole from your all-purpose setting, and put both chocks in front
of the mast. (In windy, flatter water conditions, try leaving the chocks
centered and tighten two “fine” holes.) Although adjusting the shrouds is not
recommended while you are out on the water, don’t be afraid to move any chocks,
as my adjustment is of benefit.
Basic Rig Settings:
0-10 knots ease shrouds one “fine” hole both chocks behind
5-20 knots shrouds 250 lbs./forestay 100 lbs. chocks
centered
15-20 knots tighten shrouds one “fine” hole both chocks
ahead
Mainsheet Trim
Tension the compression batten gently, so that there
aren’t any significant wrinkles in the sail along the length of the
batten. Be careful of over
tensioning the batten as this can make the top of the sail too full and the
batten to difficult to tack in light winds. Take a piece of dark tape, or a magic marker, and make a
dark line to mark the last 12” of the batten pocket’s length. This gives you a trim reference.
When trimming the mainsail, tension the sheet so that this
last 12” of the batten are parallel to the boom. You will have to get down under the boom and site up the
leech to get a feel for this trim.
The sail will look quite twisted to the eye and the top telltale will
always stream aft, except in near drifting conditions. If the tip telltale stalls, you are
drastically over trimmed. Take
your jib sheets and either sew or tie them permanently to the clew of your jib. Mark each sheet at 17 ½,” 19,” 20 ½,”
and 52.” Your first three marks are used for reference for primary sheet
tension. When these marks become just visible as they pass out of the aft side
of the ratchet block, you are at each trim setting.
The fourth mark, at 52,” is used for “weather sheeting.”
In light to medium air, take the weather jib sheet, and trimming through the
weather ratchet block, tension it so that the mark is centered in the weather
cleat.
Jib Sheet Trim
0-5 knots mark #1 add weather sheet tension in 4-10 knots
6-12 knots mark #2
13-17 knots mark #3
18+ knots mark #2
Jib Halyard Trim
Mark the jib halyard and put a scale on the side of the
mast. The total range of jib
halyard tension is 2”. Set it loose in light air and gradually tension it as
the wind increases. Set the
halyard so that you just pull out the scallops that appear between the jib luff
links.
Reaching
When sailing downwind, keep the weight well forward in the
boat. When racing, set the vang to
make your 12”batten mark parallel to the boom. Hold the jib sheet by hand to leeward. Position your hand so the sail luffs
evenly from top to bottom when the boat is turned into the wind.
Running
When running, ease the vang more, so that the top batten
is perpendicular to the wind. Even
though the boom is restricted from being let out by the shrouds, you can still
“let out” the upper half of the sail by easing the vang. Be careful not to over
ease the vang in heavy air, and make sure the crew has a hand on the
centerboard, ready to put it down before you lose control in the biggest puffs.
Wing the jib to the weather side.
In winds under 5 knots, easing the vang will not open the upper leach
due to the weight of the sail and the boom. In these conditions, you should not
wind the jib, but instead sail on a broad reach with the jib trimmed to leeward,
and jibe back and forth to the leeward mark.
Good luck and good sailing with your JY15 and North Sails!
Thanks to Ed Adams for compiling the information for this
guide.
Download a PDF version of the JY15 Tuning Guide
Parts List, provided by Hunter Marine
JY15 Line Chart
Repair Guide
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