International 420 Class Tuning Guide
Produced by Paul Eldrid
Quantum Sail Design Group WA
Congratulations on purchasing your new Quantum International 420 classsails. These sails have been at the forefront of national and international
competition for many years and our latest designs will give you the opportunity
to sail with speed and confidence. The following guide may vary from boat toboat and also your local conditions, but should give you a comprehensive
starting point and get you on the pace.
YOU WILL NEED-TAPE MEASURE-LOOSE TENSION GUAGE-PERMANENT MARKER-PEN, PAPER, & THIS GUIDESTEP 1.
MAST STEP
2790 - 2810mm
Measurement from the inside of the transom to the pin retaining the aft of themast heel.
STEP 2.

SPREADERS

L = Is the length of the spreader from theside of the mast to the side stay.
P = Is the Poke or deflection of thespreaders, measured using your top
batten across the shrouds at yourspreader tips to the back edge of yourmast.

MAST TYPE
Proctor KAPPA
Superspar M7
Proctor STRATUS

WEIGHT 115 – 125 KG
L
470
460
450

P125135145

MAST TYPE
Proctor KAPPA
Superspar M7
Proctor STRATUS

WEIGHT 125 + KG
L480470465

P115
120125

STEP 3. PREPARING FOR CALIBRATION
1. Hoist the tape measure up your mast. Adjust the halyard and lock it when
the tape reads 4900mm to the top of the black band near your goose neck.
This is very important!

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2. With no chocks (CHOCK) in the mast gate, pull the rig tension (TENS) on
until it reaches approximately 40 on the Loose Gauge. Now take the tapemeasure to the transom and see if it measures between 19’101/2” to 20’0”.
If not, adjust your chainplates (CHAIN) to achieve this ball park
measurement. Most chainplate fittings have 2 sets of holes, and the front
ones should be referred to as F and the back as B.
STEP 4. CALLIBRATING YOUR “HOOK”
Once done, then pull the rig tension on until you get the most uprightrake setting to suit your weight as listed below (diagram 1.2). At thispoint, you should put a mark on the side of your mast where your jib
halyard connects to your rig tension system. THIS IS THE “HOOK”. From
this mark, working downwards put 4 additional marks every15mm andworking upwards an additional 5 or so. Then number each of the marks
from top to bottom. Alternately, you can use “stick on” calibrations thatmany fitting companies sell.
STEP 5. CALLIBRATING YOUR RAKE & TENSION SETTINGS
Now simply work your way down each RAKE setting, recording yourCHAIN, HOOK & TENS on the draft easytune chart provided. If you
cannot achieve ball-park tensions for the rakes prescribed, you may haveto change your CHAIN until you get it right. (go down for more tension,same rake or up for less tension, same rake)
Diagram 1.2
WIND
0-55-1212-1515-2020-2525+

CHAIN
F4F4F4F4F4F4YOU FILL IN HERE

WIND
0-55-1212-15
15-2020-2525+

CHAIN
F4F4F4F4F4F4Weight 115 – 125kg
HOOK
TENS
1043941
740639
537
436

RAKE
CHOCK
020’0”
619’111/2”
519’101/2”
419’91/2”
319’9”
219’81/2”
CHOCK
See step 6

APPROXIMATE SETTINGS

Weight 125kg +
HOOK
TENS
1244
1144
1041839
737
636

RAKE
20’1”
20’1”
19’111/2”
19’101/2”
19’91/2”
19’9”

CHOCK
066543CHOCK
See step 6
YOU FILL IN HERE

APPROX SETTINGS
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STEP 6. PREPARING TO CALLIBRATE CHOCKS
Once your settings are finalised, tip your boat on it’s side, and with yourmost upright rake setting, measure the mast bend, with NO chocks at thespreader level. This is done by placing your main halyard to your gooseneck at the aft side of the mast, and tension it. Then measure the bendfrom the aft side of the mast to your halyard. You should have at least
30mm of bend with 0 Chock. If not, wind your spreaders back a little.
Remember, every boat is a little different!
STEP 7. CALLIBRATING CHOCKS FOR MAST BEND
This “0 Chock” setting at upright rake has now become your 0 – 5 knot
setting. Next, go to your 5 – 12 knot setting, and add chocks until the mast
becomes straight – 10mm of bend. Record the number of chocks on yourchart required to achieve this. From here, simply remove 1 chock for eachincreasing wind range.
PLEASE NOTE – Chocks control mast bend and therefore mainsail
depth. The above settings are guides only and you may have to adapt
how much “POWER” you get from your mainsail “DEPTH”, via the“CHOCKS” to suit your weight, sea state, wind conditions etc.
STEP 8. CALLIBRATING THE CENTERBOARD
While your boat is on it’s side, pull the centreboard all the way down. Youshould notice that it is raked forward in this position. Put a mark on theback of the C/B “handle” on the inside of the hull at this maximum down
setting and label it “8”. At 30mm increments mark another 3 settings
labelled “7, 6, 5”. Now pull it up until there is 400mm protruding under thehull. Put a mark or draw a line on the centreboard, on the INSIDE of yourboat to record this position, and label it “4”. Repeat the process at 300mm,200mm and 100mm.
THIS WILL ALLOW YOU TO GET A FEEL FOR C/B POSITION. AS A
GUIDE:
0 – 14 KTS
814 - 18 KTS
7–618 – 22 KTS
6–5+
SETTINGS WILL CHANGE WITH CREW WEIGHT, SEA STATE,GUSTINESS OF WIND, AND POWER IN THE RIG. TRIAL AND ERRORWILL SEE YOU BECOME FAMILIAR WITH YOUR FAVORITE“NUMBERS”!
STEP 9. STICK IT ON!
Simply complete your easytune chart, cover it with clear ‘contact’ or have it
laminated and stick it on the inside of your hull where it’s easy to refer to.
Don’t forget to take a copy of your numbers to add to your sailing file!
STEP 10. SAIL WITH CONFIDENCE!
This guide, along with practice should see you as fast as any other
Quantum boat on the water, and faster than our competitors!
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SAIL SETTING AND TRIMMING TIPS
MAINSAILTop Batten

Just tight enough to remove wrinkles from the pocket,
until over 15 knots, when it should be quite firm.

OuthaulLIGHT
MEDIUM
HEAVY

Firm
Eased a little so the foot shelf just “falls in”.
Very tightCunningham

LIGHT
MEDIUM
HEAVY

Just enough to remove major wrinkles
Remove most wrinkles
Tight to very tight.

Main Sheet

LIGHT
MEDIUM
HEAVY

Top ribbon to flow at least 50% of the time
Top ribbon to flow around 70% of the time
You will be vang sheeting now, see below

Vang

LIGHT
MEDIUM

Take it off the boom & clip it to the shroud
None, get all your leech tension throughmainsheet. Start using vang when easing
main to de power.
Continue to pull more vang on to control
leech twist, and aid mast bend. More andMore!!!

HEAVYJIBHeightThe tack of the jib, when tensioned should be no higher
from the deck at the forestay fitting than 40mm.

Luff Tension

Always enough to remove any wrinkles, except for very
light winds (off) and heavy wind (lots on)

Sheet Tension

In nearly all but heavy winds, the jib must be not only
sheeted, but also “barber-hauled” using the windward jib
sheet to bring the sheeting angle of the jib closer inboard,
resulting in greater height and speed.
LIGHT – with crew to leeward or in the middle of the boat,
trim the jib so it is barber-hauled, with the sheet eased toallow the leech ribbon and top leech telltales to flow.
MEDIUM – Pull the jib sheet in firm, then barber-haul very
tightly. You will now need to ease the sheet to get theribbon and leeward telltale to flow 90% of the time. Thecrew, if on trapeze, should be able to “walk forward” andcheck it out while on the wire.
HEAVY – As you vang sheet, and start easing the boom
off centreline, you should start using progressively lessbarber-haul, until it’s blowing hard and your using none!

GOOD LUCK, FROM THE QUANTUM SAIL DESIGN GROUP

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INTERNATIONAL 420 CLASSTUNING GUIDE

Where sailmaking is a performing art