TUNING GUIDE
INTERNATIONAL
420
Produced
by Paul Eldrid
Sobstad Sails
Congratulations on purchasing your new Sobstad International 420 class sails. 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 to boat 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 GUIDE
STEP 1. MAST STEP 2790 - 2810mm
Measurement from the inside of the transom to the pin retaining the aft of the mast heel.
STEP 2. SPREADERS L = is the length of the spreader from the
side of the mast to the side stay.
P = is the Poke or deflection of the
spreaders, measured using your top batten across the shrouds at your spreader tips to the back edge of your mast.
WEIGHT 115 – 125 KG
|
MAST TYPE |
L |
P |
|
Proctor KAPPA |
470 |
125 |
|
Superspar M7 |
460 |
135 |
|
Proctor STRATUS |
450 |
145 |
WEIGHT 125 + KG
|
MAST TYPE |
L |
P |
|
Proctor KAPPA |
480 |
115 |
|
Superspar M7 |
470 |
120 |
|
Proctor STRATUS |
465 |
125 |
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 lower black band near your goose neck. This is very important!
2. With no chocks (CHOCK) in the mast gate, pull the rig tension (TENS) on until it reaches approximately 40 on the Loose Guage. Now take the tape measure 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 upright rake setting to suit your weight as listed below (dia.1.2) At this point, 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 and working upwards an additional 5 or so. Then number each of the marks from top to bottom. Alternately, you can use “stick on” calibrations that many fitting companies sell.
STEP 5. CALLIBRATING YOUR RAKE &
TENSION SETTINGS
Now simply work your way down each RAKE setting, recording your CHAIN, HOOK & TENS on the draft easytune chart provided. If you cannot achieve ball park tensions for the rakes prescribed, you may have to change your CHAIN until you get it right. (go down for more tension, same rake or up for less tension, same rake)
Dia 1.2
Weight 115 – 125kg
|
WIND |
CHAIN |
HOOK |
TENS |
RAKE |
CHOCK |
|
0-5 |
F4 |
10 |
43 |
20’0” |
0 |
|
5-12 |
F4 |
9 |
41 |
19’111/2” |
6 |
|
12-15 |
F4 |
7 |
40 |
19’101/2” |
5 |
|
15-20 |
F4 |
6 |
39 |
19’91/2” |
4 |
|
20-25 |
F4 |
5 |
37 |
19’9” |
3 |
|
25+ |
F4 |
4 |
36 |
19’81/2” |
2 |
CHOCK
See step 6
YOU FILL IN HERE APPROXIMATE
SETTINGS
Weight 125kg +
|
WIND |
CHAIN |
HOOK |
TENS |
RAKE |
CHOCK |
|
0-5 |
F4 |
12 |
44 |
20’1” |
0 |
|
5-12 |
F4 |
11 |
44 |
20’1” |
6 |
|
12-15 |
F4 |
10 |
41 |
19’111/2” |
6 |
|
15-20 |
F4 |
8 |
39 |
19’101/2” |
5 |
|
20-25 |
F4 |
7 |
37 |
19’91/2” |
4 |
|
25+ |
F4 |
6 |
36 |
19’9” |
3 |
CHOCK
See step 6
YOU FILL IN HERE APPROX SETTINGS
STEP 6. PREPARING TO CALLIBRATE
CHOCKS
Once your settings are finalised, tip your boat in it’s side, and with your most upright rake setting, measure the mast bend, with NO chocks at spreader level. This is done by placing your main halyard to your goose neck at the aft side of the mast, and tension it. Then measure the bend from 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 your chart required to achieve this. From here, simply remove 1 chock for each increased 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 centerboard all the way down. You should notice that it is raked forward in this position. Put a mark on the back 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 the hull. Put a mark or draw a line on the centerboard, on the INSIDE of your boat 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 8
14 - 18 KTS 7 – 6
18 – 22 KTS 6 – 5 +
SETTINGS
WILL CHANGE WITH CREW WEIGHT,
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 Sobstad boat on the water, and faster than our competitors!
Sobstad Sails
– First in Technology, First in Value!