North Sails new J70 One Design Class Racing sails represent the leading edge of sail performance and are a result of North Sails unmatched design and manufacturing technology. For this new class, we have utilized our advanced North Design Suite of software to accurately model the aerodynamic flow, sail loads and rig geometry of the J70. This process has allowed to us create refined designs straight out of the box that are perfectly matched to the Selden Spars Carbon mast. The new J70 sails are also made from the revolutionary new North Radian™ sailcloth. Radian™ sailcloth uses a unique (patent pending) process to create the world’s first warp-oriented woven polyester to harness the power and low-stretch of radial construction.
Learn more about the North Sails J/70 sail development ►
J/70 Radian Race Mainsail
The North J/70 Radian Race Mainsail is a radial panel layout and manufactured from NorDac Radian 6.3oz Olympic Finish.
Mainsail standard features:
- Class insignia
- Sail numbers
- Epoxy battens
- Vision window
- Spreader window
- Leech line
- Leech tell tales
- Camber lines
- Long roll bag
- ISAF in house measurement
J/70 Radian Race Jib
The North J/70 Radian Race Jib is a radial panel layout and manufactured from NorDac Radian 6.3oz Olympic Finish.
Jib standard features:
- Epoxy battens
- Vision & tell tale window
- Leech line
- Leech tell tales
- Trim tell tales
- Camber lines
- Long roll bag
- ISAF in house measurement
J/70 Asymmetrical Race Spinnaker
The North J/70 Asymmetrical Spinnaker is manufactured in Dynakote 75.
Spinnaker standard features:
- Sail bag
- ISAF in house measurement
- Stock colours
Please contact the J/70 Experts
or your Local Loft or Agent
for additional information and questions about our products.
All prices include UK VAT at 20%, terms and conditions
The all new J/70 represents one of the most exciting developments in sailing to come along in years. An affordable sport boat made by one of the best names in the boat building industry the J/70 is sure to be a class for the ages.
At North Sails we are excited to help J/Boats to get the class going by offering high quality performance sails as part of the initial package for the boat. We have worked very closely with Southern Spars and J/Boats to develop a set of sails that will deliver top performance, ease of use and longevity. Using the North Design Suite (NDS) we have modeled and flown the sails on a loaded sailplan to simulate actual sailing conditions. By running iteration after iteration we have been able to fine tune the design of these sails.
The main and jib are made from a new, cutting edge material called Radian™. This is a warp oriented, patented, polyester material with its strength in the long direction making it perfect for radial sails. Radial sails align the load in the sail more accurately with the cloth orientation and make a lower stretch and longer lasting sail. Until the creation of this sailcloth it was very difficult, if not impossible, to use this type of construction in a polyester sail. The new J/70 will be the first large class to take advantage of this technology.
The drawings are screen shots of some of the modeling that has been done to develop the sails for this exciting new boat. The whole network of North lofts around the world looks forward to working with the J/Boat network to bring this exciting new boat to the forefront of sailing.
After just a few short months of sailing, training and testing the new J70 we are able to share with you with some tuning notes and tips to help you and your team get up to, race winning, speed quickly! As new information, regarding setup, tuning and trimming techniques, becomes available we will update this page.
The J70 has already proven to be a design that incorporates many decades worth of great ideas and puts them into a 22 foot package of fun and speed. The J70 incorporates the speed and handling of a top tier sport boat with the stability and reliability of a performance keelboat dinghy creating an sailing experience that accommodates all ages, abilities and sailing appetites. The J70 has proven to reward racers who sail tactically strong races and have great boat handling. We expect to see the J70 class crown a diverse group of champions in the coming years. Let North Sails help you be one of them!
Attached is our quick tuning guide that we have developed for the J70. North Sails worked in conjunction with Southern Spars and Selden Spars in designing our sails to match the characteristics of the class approved J70 mast. Using the North Design Suite, our design team was able to design the perfect sail and mast combination using the same tools and process we use for projects like TP52, Farr 40 and other high performance racing programs that choose North Sails and Southern Spars.
Where to Start
Starting tuning points-Rake and prebend
The headstay length that we have found works best is 8.45m pin to pin.
If your mast is up, unhook your headstay and pull it taut down the front face of the mast. Make a mark on the headstay (a Sharpie pen works best) at the top of the white band that is on the mast. From that “Sharpie” mark,measure to the centre of the pin in the furler. That measurement should be 1385mm.
We are always shooting for 65 to 75mm of prebend for the mast and utilizing the following will get you in that range:
Step by Step Tuning
Step the mast and connect the forestay.
. Measure from the top of the tape/permanent marker mark on your headstay to the centre of the pin where the forestay attaches to the furler. This should measure 1385mm.
. To aid in centering the mast laterally in the boat, place a pencil mark 2.4m back from the stem fitting at the shear on each side. Hoist a tape measure on the jib halyard and measure to the pencil marks previously marked on your shear (the hull-deck intersection) on each side of the boat. Adjust the upper shroud lengths correspondingly from side to side until the mast is centered in the boat. Be sure to adjust the lower shrouds as well, maintaining a straight mast as viewed from up the back of the mast slot.
. Tension the uppers to 22 on the PT gauge.
Tension the lowers so the mast is straight laterally when sighting up the slot at the back of the mast. The lowers should be tensioned at 11 on the PT2 gauge.
The above settings (22 uppers/11 lowers ) are considered your base settings. Download our rig tension chart shown here
Re-measure the side to side position of the mast to ensure it is centered. Using calipers, measure the distance between the studs on all five shrouds to ensure repeatability and to be able to get back to base quickly.
Check that you have developed the proper pre-bend in the mast (positive bend) by pulling the main halyard taught to the gooseneck. The distance between the back of the mast and the main halyard at the spreaders is targeted at 65 to 75mm.
After many hours of on water testing we were pleased with, not only the handling of the J70, but also the responsiveness of the boat to sail trim adjustments. The J70 has shown to be forgiving to sail trim mistakes while at the same time rewarding the trimmers who continue to make sail trim adjustments to the ever changing wind conditions. While many of the “basic” sail trim concepts have proven to be very competitive with the J70 here are a few trimming notes that we have found that will help you get up to speed quickly.
It is important that the mainsail is at full hoist at all times. Always make certain that the mainsail is pulled up to the white band at the top of the mast. We check this regularly between races.
The J70 main is equipped with a tack strap. It is important to make sure that the tack strap is tensioned so that it is taking the tack load. This will insure that the boltrope doesn’t chafe at the feeder.
Batten tension on the full length battens is a critical item for proper sail shape. We set our batten tensions so that there is enough tension to “just” eliminate any vertical wrinkles coming from the pockets. You certainly don’t want more tension that this. We also recommend backing the battens off when storing the sail between events.
A backstay flicker to help the mainsail leech pass through the backstay when light air tacking and jibing.
Trimming the mainsheet so that the middle full length batten is parallel the boom has proven to be the fastest base trim setting. At times, you will find you can trim about 2 inches tighter, specifically, when the boat is “up to speed” and you want a bit more point. Make sure the boat is fully up to speed though!
A key to great speed in the J70 is proper jib trim. One thing we have found is key is to always keep the jib leech tell tales flowing. The jib is very high aspect, and little adjustments in trim make a big difference. We have been trimming as hard as possible, just to the point where the telltales stall. If they stall, you will feel the boat slow down and we immediately ease to keep flow and the boat going fast. Few tricks for better jib trim:
Put a mark on the deck and on your sheets so that the trim is easily repeatable and something that can be done over and over again.
If the boat feels slow, try to ease the jib slightly. We found that the boat can easily feel bound up and most times it has to do with the jib being trimmed too hard.
In lighter winds, we will use the
windward sheet to help in haul the jib,
which allows for a closer sheeting angle.
We have had success windward sheeting
up to 75-100mm “in” (see pic).
Our goal is to set the jib halyard in all
conditions so that there is a slight hint of
wrinkles along the luff. Only in conditions
where you feel you need to depower
would we pull the halyard on enough so
the sail would just start to go smooth.
Think of the jib sheet as your gas
pedal. A small bit of ease, and pressing the bow down, will result in
acceleration and more speed!
Make sure the jib sheet gets
knotted through the jib block from the
inboard side of the car. This helps keep
the sheet as far inboard as possible.
– Upwind and
• Displacement mode - Constantly look
to see that the knuckle of the bow is just
kissing the water.
• Light air mode- you will want to
sit forward to reduce transom drag and
wetted surface as much as possible.
• Breezy mode- In breezier conditions
begin to move crew weight slightly farther
If you are downwind and planing,
you will want to sit father back, but be
sure not to sit so far back that the boat
will sit “artificially” bow up.
This sounds basic, but be sure to put
marks on your sheets, pole, tack line, and
halyards so settings are easily repeatable.
Spinnaker trim on the J70 is much easier
than that of a conventional poled boat.
There are a few tricks that can make
you faster downwind and make your sail
handling easier. Tack height on the sail
is important. Generally, we keep the tack
down tight to the pole end when reaching
(broad or beam). Letting the tack up on
reach will just move the sail to leeward
and increase heeling. When running
we can let the tack line off when the
tack will ride straight up or just slightly
to leeward. We have found this setup
to be faster in deep running conditions.
We will generally let the tack off in these
Two other topics that always come up
are whether to take the spinnaker down
between the shrouds and the mast or
behind them. The other topic is whether
to gybe the spinnaker inside it’s luff or
outside. We’ve found that it almost
always seems easier to take the spinnaker
down between the mast and shrouds.
This makes setting the spinnaker easier
as it does not have go all the way around
the shrouds which are pretty far from
the mast. When setting the spinnaker, it
is best to take the whole sail out of the
bag prior to setting. This makes it much
easier to hoist the sail. Normally, we’ve
found that it is just as fast and a lot safer
to gybe the spinnaker inside its luff. This
eliminates any chance that the lazy sheet
could fall in the water, it makes for a less
sheet for the spinnaker trimmer to pull in,
and it allows you to perform any of the
three takedowns at the leeward mark.
Gybing the Asymmetric Spinnaker
There are two types of gybes. The inside
gybe and the outside gybe. How you
hook up your tack line to your spinnaker
tack dictates whether you will gybe inside
or outside. By placing your tack line on
top of the spinnaker sheet when hooking
the tack line up to the spinnaker you
are setting up for an inside gybe, where
the spinnaker passes between the luff
of the spinnaker and the furled up jib on
the headstay. Hooking up the tack line
underneath the spinnaker sheet sets you up for an outside gybe. Most of the
time though, you will see teams gybing
inside. On the gybe, the fastest method
is to have the trimmer ease the kite as
the boat heads down, another crew
starts to trim the new sheet and the
forward crew overhauls the new sheet
just behind the shrouds. The forward
crew then pulls down on the clew to
untwist the head as the kite comes
around. Almost everyone is now
gybing inside and not using the outside
We have found that it is best to always
set the spinnaker from between the
shrouds and mast. This does mandate
taking the spinnaker down between the
shrouds, which is the easiest way for all
There are three types of takedowns:
the windward, the leeward, and the
The windward douse is used when
doing a port rounding and you are
approaching the mark on port tack.
The “Mexican” is for rounding a mark
to port but your approach is relatively
shallow on a starboard tack. The
leeward douse is for rounding a mark
to starboard while on starboard tack or
when you approach the mark at a very
sharp angle while on starboard tack and
you will have to gybe quickly around a
mark leaving it to port.
For the leeward douse, you can either grab
the lazy sheet off of the clew, or grab the
sheet just above the lifeline. The helmsperson
then must bear off slightly, the clew should
be pulled in between the shrouds and under
the mainsail to prevent the kite from blowing
over the leech of the mainsail, and then the
tack line must be blown off completely. The
halyard should then be fed down as the crew
gather the spinnaker.
For the windward douse, the skipper can sail
low, while the crew start to trim the windward
sheet to pull the kite around to the windward
side the forward crew should blow off the tack
to unload the pressure off the kite. The clew
should be trimmed all the way back to the
shrouds and then pulled between the shrouds
and the mast. The halyard can then be released
and the kite stowed.
For the “Mexican”, as you approach the
leeward mark on starboard, the helmsperson
should bear off into a slow gybe, the trimmer
will over-trim the sheet as the boat gybes
to port. Just as the boat is headed directly
down wind and the mainsail begins to gybe,
blow off the halyard. The spinnaker will blow
against the rig and fall on the deck. When the
sail is 2/3rds the way down release the tack
and stuff the spinnaker in its bag. Practice of
these three douses is vital to success on the
Always store your sails away from the sun and make sure they are clean
and completely dry.
Be sure that you always “roll “your upwind sails. This will help then last
longer and remain wrinkle free.
If you would like to discuss setting up your J/70 sails please contact the North
>> Download the full guide here
Check out the J/70 Boat Handling Tuning Videos with Tim Healy:
>> Video 1
Spinnaker Set Up
>> Video 2
Spinnaker Take Down
>> Video 3
Tack and Gybe