NORTH SAILS J-105 Guía de inicio rápido

Introduction

The J-105 began what J-Boats describes as the “J/Sprit revolution”. It was the first boat of this kind

introduced and has been followed by many models. The class has enjoyed great growth in recent years

through the quality of the boat itself and the strong involvement of its’ owners. Its attraction as a one-

design race boat is its high performance, strict class rules and limited sail inventory that promotes

extremely tight class racing.

The J-105 Class is part of North Sails Class Development Program. The “CDP” is designed to harness and

deliver to our Offshore One-Design customers the best sail designs and tuning methods that exist within

North Sails globally. We have begun by focusing on the Farr 40, Mumm 30, One-Design 35, J/120, J/105

and Farr 395 classes and plan to expand the Class Development Program to other Offshore One-Design

classes as we move forward.

“Through the Class Development Program, North Sails is coordinating sail development and rig tuning

like never before,” said North Sails Vice President Ken Read, who is the Director of the CDP. “Dedicated

class experts are consulting with our Offshore One Design customers on a regular basis and are

distributing the latest rig setups and trim techniques to North Sails lofts worldwide. Offshore One Design

sailors can go to any North loft worldwide for sails and tuning advice that is on par with the best in the

class.

The three sail inventory creates a challenge for sailmakers to produce fast sails that can perform well

throughout the complete range of wind conditions. North has put forth great effort to produce the

fastest, most versatile, easiest to use sails. Our constantly updated tuning guide provides “turn key

speed” for our clients. With the advent of North’s Offshore One-Design Class Development Program,

our J-105 program has seen significant developments over recent months. Class Leaders Tim Dawson

and Will Keyworth, with the help of several other North employees, have worked to further refine our

products through our class involvement and two boat sail testing sessions.

At North, we look at each sail with from a unique perspective and choose the best construction process

that we are able to produce within the class rules. We choose the best fabrics and construction

techniques that are commercially available, or develop our own through North Cloth where the proper

fabrics are unavailable.

This tuning guide has been developed over years of J-105 sailing and sail development. It is intended to

serve as a starting point for new boat owners and new North Sails clients. Once your boat is set up to

the basic principles of this tuning guide, you can use our Quick Tuning Guide to make on-the-water

adjustments to your rig to make adjustments for various wind conditions. This guide is not an absolute

truth, but will put you in the ballpark. As you get more advanced, you may find that slight alterations

better suit your sailing style.

Feel free to contact Class Leaders Tim Dawson or Will Keyworth if you have any

questions or comments about the information in this guide, or if there is any other

way that we can help make your J-105 sailing more enjoyable.

Contents

Part 1 — Rigging Preparation

Part 2 — Rig Set — Up

Part 3 — Mainsail Trim

Part 4 — Jib Trim

Part 5 — Crew Weight Placement

Part 6 — Downwind Sailing

Quick Tuning Guide

Part 1 — Rigging Preparation

The following recommendations are small changes that should be made to the stock J-105 to allow you

to get the most from your North Sails and make the boat easier to sail and set up.

Head swivel shackle: The North Sails jibs come with a webbing loop at the head. It is critical to have a

90-degree “twist” shackle to attach the sail to the swivel. A standard shackle will cause a hard spot at

the top of the jib as the sail is torqued.

Remove backstay toggle: Many J-105s come with a toggle that rotates the hydraulic cylinder 90-

degrees so that the handle faces forward. While it is nice to have the handle forward, this toggle

reduces the throw of the backstay adjuster too much so that you are not able to get enough tension in

heavy air. Some of the older boats actually need to have the backstay rod shortened to get enough

backstay throw.

Change to 6:1 Cunningham: The standard Cunningham is 2:1 and led aft to a cabinhouse halyard

stopper. This system should be replaced with a 6:1 system with the lower purchase with integral cleating

shackled to the ring on the top of the Quik Vang. This allows for easier and more precise Cunningham

control by a forward crewmember. Many boats then rig the asymmetrical tack line through the free

stopper. The tack line is much easier to work with in this placement than on the side of the cabinhouse.

Mark the tack line at the cleat: Put marks on the tack line at the proper range of settings. As you

approach the windward mark you can then pre-set the tack line so that when you extend the pole and

set the spinnaker the tack will be set properly.

Move mainsheet swivel base forward of the traveler: This allows for easier trim of the gross tune

by the main trimmer, especially when tacking.

Tapered SpectraTM spinnaker sheets: These sheets have a light uncovered portion that attaches to the

sail, with a covered portion that goes on the winch. The sheets should be 3/8” Spectra cored line with

the cover removed at the sail end of the sheet. These lightweight sheets are used in all conditions and

help downwind performance in light air. Heavy sheets pull down on the leech of the spinnaker in light

air, closing the leech too much.

Bypass the jib sheet turning block: The standard set-up for the jib sheet is to run the sheet from the

clew of the jib, through the lead block, through the turning block near the rail, and then to the winch.

This set-up makes the lead block lean over to leeward, increasing sheeting angle. In light and moderate

air, the jib will sheet tighter to the centerline if you lead the sheet straight to the winch from the jib lead

block. In heavy air, it can be faster to use the turning block to sheet the jib outboard slightly.

Part 2 — Rig Set-Up and Preparation

Tools and items required: Loos RT 10M Rod Tension Gauge, 2 crescent wrenches, spray lubricant,

bosun’s chair and 50’ metric tape measure.

Part of the success of growth of the J-105 Class is the tight class rules and limited sail inventory. With

the J-105s limited sail inventory of only one headsail, aggressive rig tuning is essential for performance

throughout the full range of wind conditions. By definition, the North Sails “AP” inventory is optimized

for 9 to 12 knots. This is actually the easiest condition to sail in, so the racing tends to be at its tightest.

Having really fast sails in this condition is key to gain a slight speed edge and the AP inventory is

designed to give you just that. The heavy air “HA” inventory is optimized for 13-20 knots. In the

extreme conditions of light and heavy air the rig must be manipulated to enhance the sail shapes for

those conditions. The result of proper rig tuning is the correct relationship between mast bend and

headstay tension to get fast shapes. The North inventory has been designed to make these transitions

easily with the correct tuning to be fast in all conditions.

Step 1 — Check Mast Butt Position: The measurement from the front of the forward bulkhead to the aft

face of the mast should be 24.46cm (9 5/8”). This is very close to the center of the step. For the HA

sails, the mast butt should be 26.00cm from the bulkhead.

Step 2 - Check J Measurement: The J measurement is the distance from the headstay intersection to the

deck to the forward face of the mast. This should be 4.11m (13’6”). Use mast chocks or SparTite to

achieve this position.

Step 3 — Set Mast Rake: Rake is controlled by headstay length. The headstay should be set at the class

legal maximum rake, 13.035m. Hoist a crewmember up the mast and have them hold the butt of the

tape measure at the center of the pin that secures the forestay to the mast. Measure to the to of the

furler drum (measurement A), then measure from the top of the furler drum to the bottom of the furler

drum (measurement B), then from the underside of the furler drum to the intersection of the stem and

sheer line of the boat (measurement C). The overall headstay measurement is then the sum of A+B+C.

Step 4 — Centering the Spar: Put a mark on the rail of the boat on one side even with the chainplates.

Measure this distance from the headstay attachment on the bow. Put a corresponding mark on the

other side, the same distance from the headstay. At this point the Upper Shrouds (Caps) should be hand

tight and the Intermediates (D2s) and the Lowers (D1s) should be loose. Hoist the tape measure to the

top on the centerline jib halyard. Measure to the marks on either side and adjust the Caps until they are

equal.

Step 5 — Tensioning the Shrouds: Tighten the D2s and D1s to hand tight. Add 8 full turns to the Caps.

Then tighten the D2s 6 turns. This should be done incrementally (2-3 turns at a time per side) sighting

the mast to be sure that the mast is in column. Add turns to one side and remove turns from the other

to bring the mast in column. This added tension that you have applied has probably made the D1s slack,

so double check to make sure that they are hand tight.

Step 6 — Check Shroud Tensions with Loos Gauge: Put marks on

the shrouds 2m up from the deck. Put the top post of the gauge

on this mark when measuring tension. Be sure to have the

backstay released when measuring tension with the Loos Gauge.

For the base setting for 10-14 knots TWS the shrouds should read

the following:

AP Sails HA Sails

Caps: 35 55

D2s: 10 25

D1s: 0 (10 cm play) 10 (hand tight)

You should double check to be sure that the mast is still in column

at the dock when the rig is at full tension. At the base setting, the

mast should sit with virtually no pre-bend up to the hounds.

You are now at the “base” setting and ready to go racing.

From here follow the Quick Tuning Guide to optimize your J-

105’s performance for various wind conditions.

Measuring Rig Tension with the RT-10m Gauge

Advanced Tuning — Beyond the Numbers

The North Sails J-105 Tuning Guide is very refined, and has been used to the letter

to win many events. In fact both the 2000 and 2001 North American Champions

use the Quick Tuning Guide as their bible. However, understanding the

fundamental concepts of how tuning affects the rig and sails is important to be able

to check that the settings are right for your boat, as well as customizing your own

tuning numbers for your sailing style. Keeping good records is the key. Keep a Wet

Notes pad on your boat and record your rig settings, wind speed, sea state, and

your speed and pointing relative to other boats. This will help you to see what is

working best for you and fine tune your own numbers.

North Wet Notes

Changes to shroud tension affect the rig in two ways: 1) headstay tension & 2) mast bend. Tighter Cap

shrouds generate more headstay tension by pulling back against the headstay. A good guide for Cap

(upper) shroud tension is that the leeward Cap shroud should just go slack in all but the heaviest of wind

conditions. Tighter D1 (lower) and D2 (intermediate) shrouds generate more h

tension by reducing mast bend and compression. The important factor of the D1 an

D2 adjustment is the relationship to the amount of backstay used in each wind

condition, which affects mainsail shape. Tight D1s and D2s will make the mast too

straight (main too full and draft forward) when no backstay is used, and conv

eadstay

ersely

loose D1s and D2s will allow the mast to bend too much (main too flat or even inverted) when a lot o

backstay is used. The final D1 and D2 rig tension will be dictated by mainsail shape.

The light air performance of the J-105 can be dramatically improved with leeward mast sag in under 12

knots. This is side-to-side sag from the partners to the hounds. This can only be seen under sail and will

not happen at the dock. The settings from the Quick Tuning Guide should generate this sag, but all

masts are a little different, so you may need to adjust your intermediates and lowers to achieve it.

Loosen the intermediates and lowers so that there is 1” of leeward sag halfway to the hounds in under 9

knots and ½” in 9-12 knots. In general the intermediates will need to be eased twice as many turns as

the lowers to achieve even sag.

J-105 Rig Side View J-105 Rig Aft View

The image at the right shows

what the mainsail will look like

with no backstay if the D1s and

D2s are too tight. The sail is too

deep and the draft is too far

forward. Rig is tuned for 15

knots and there was actually

only 8 knots. Mid stripe draft

location is at 35% in this photo.

Mid stripe target draft position is

42% to 45% when conditions

warrant no backstay.

This image shows a mast that is

bending too much, D1s and D2s

too loose for the amount of

backstay being used. The rig is

set at the base setting and the

backstay is pulled on all the w

The sail is inverting. Note the

diagonal wrinkles coming from

the clew towards the middle

the mast.

ay.

Part 3 — Mainsail Trim

The J-105 relies on much of it’s power from the mainsail with the class inventory. The mainsail is very

easily adjusted because there are many shape controls including mainsheet, traveler, backstay,

cunningham, vang and outhaul. Proper mainsail trim is achieved by balancing the speed and pointing

with its twist, angle of attack and overall power. Proper communication with the helmsman for the feel

of the boat and performance vs. the boats around you are the key to establishing the correct balance of

those three elements.

Mainsail Twist — The Sheet

The first and most important element of mainsail trim to set is the twist. Twist is primarily controlled by

the mainsheet. A tight sheet reduces twist and a loose sheet allows for more twist. Less twist lets the

boat point higher, while more twist lets the boat accellerate more easily. IMPORTANT — In order to point

high, you must be going fast first! By going fast, you increase water flow over the keel, which creates

more lift. If you try to point before you are going fast not enough lift will be generated by the keel and

there will be too much leeway making the boat actully go sideways. The general rule of thumb for the

median setting is to trim the sheet so that the top batten is parallel to the boom. At this setting the tell

tale at the top batten will stall about 50% of the time in moderate air. When you need to accellerate,

ease the sheet slighty while bearing off. Once you are up to full speed, trim in to the median setting or

slightly tighter and start to head up.

The proper amount of twist is dramatically affected by sea state. In flat water, where it is easy to keep

constant boat speed, you can sail with less twist. In waves or chop, the boat is in a constant state of

accellerating and decellerating and more twist is required in order to maintain speed.

Untwisted mainsail — top batten parallel Twisted mainsail — top batten open

ainsail Angle of Attack — The Traveler

tack

d depowering

e boat. Carry the traveler as high as possible without making the boat heel too much.

The traveler controls the boom angle to the centerline of the boat, which is described as angle of at

to the wind. Much like the sheet, a narrow angle of attack (traveler high) is used for pointing and

powering up the boat and a wide angle of attack (low traveler) is used for acceleration an

In light to moderate conditions the boom should be on centerline or slightly above. In very light air,

when the main is twisted, setting the boom actually above centerline will put the

lower third of the main parallel to the centerline of the boat. A good gauge for this

to look where the bottom batten is pointing. The bottom batten should point at th

backstay in very light air. If it is pointing to windward of the backstay, the traveler is

too high.

As the breeze builds, the traveler should be played aggressively to control heel and keep the boat on its

feet. If the boat heels too much, the boat will get too much helm and the helmsman will have to use

much rudder angle to keep the boat going straight. The optimum rudder angle to create the most lift is

around 4 degrees. There are times when more angle than that is unavoidable, but 5 degrees of rudder

angle should be the most that you try to use. Rudder angle can be monitored by putting a tape mark

the top of the wheel w

too

hen it is perfectly straight. The main trimmer can notice when the helmsman is

sing too much helm (or not enough) and adjust the traveler appropriately.

ainsheet vs. Traveler for Various Sea States

eler

ir only makes you lose height. With this style the traveler is played to

aintain the proper angle of heel.

ne is played to maintain the

orrect trim and angle of heel as the helmsman steers through the waves.

verall Power — The Backstay

st the

windy it is better to set the sails up flatter and sail with less twist. This will allow

ou to point higher.

ou to set up the sails as best you can when the wind changes and you are no

nger tuned correctly.

tay and 2) the mast will compress more so the backstay tension will not transfer as well to

e headstay.

hange. It is much easier to depower the J-105 than

is to power it up, so ALWAYS TUNE FOR THE LULLS!

One of the more difficult things to determine is how to depower the main in moderate to heavy

conditions. As we have learned, you can depower the main by either twisting the main by easing the

sheet or letting traveler down. The technique used should be determined by sea state, which will affect

how the helmsman has to steer the boat. In flat water, the helmsman should be able to use very subtle

steering changes. Hours of on-the-water testing has shown us that depowering by lowering the trav

and keeping a tight, untwisted leech produces the best VMG. You can point reasonably high in flat

water without slowing down and the tight leech will help with pointing. We have found that twisting

the main in flat water in moderate a

However in waves and chop, the opposite has proven to be faster. In waves and chop the helmsman has

to be more aggressive with the helm. With the wider range of steering keeping the traveler higher (wi

the car near centerline) with a more twisted main allows the helmsman to steer through wider angles

and accelerate as needed in the waves. With this style the mainsheet fine tu

The backstay is the most important sail control for setting the overall power of the sail plan. The

backstay is the universal control to modify the shape of the main primarily, but also the jib. The North

Class Inventory has been carefully designed so that backstay adjustment changes the shape of the main

and jib in unison. As backstay is applied the mast bends, flattening the main. It also pulls aft again

headstay, reducing headstay sag, which flattens the jib. By flattening the sails the boat’s power is

reduced as the boat becomes overpowered and heels too much. Flatter sails can be trimmed harder tha

full sails so when it is

As stated in the tuning section of this guide, having the rig set up properly for the wind conditions will

allow you to get the most benefit of adjusting the main and jib together with the backstay, but it is also

the control that allows y

With a loose rig the main will flatten out faster than the jib. This is because the loose D1s and D2s will

allow the mast to bend, which will flatten the main. However, since the mast is bending, the main will

get to a point where it over bends before you can bottom out the backstay. By not being able to bottom

out the backstay, the jib will still be a bit fuller than is ideal at this point since 1) you can’t pull on the full

range of backs

Conversely, with a tight rig, the main will stay fuller when the backstay is eased, while the overall rig

tension will keep the headstay tighter and thus keep the jib a bit flatter. It is important to understand

this relationship between how the backstay and rig tuning affects sail shape when you may not be tuned

correctly. If your rig is too loose, use more backstay to set the main up flatter, knowing that your jib will

be fuller than ideal. If your rig is too tight, use less backstay to set the main up fuller,

knowing that your jib will be flatter than ideal. In general, it is better to be set up

with a flat main and a full jib so it is better to err on the loose side of the rig tuning

matrix if you expect the wind to c

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