PLATU RIG TUNING.
WITH THE BOOM OFF OR AT LEAST UNWEIGHTED AND NO CHOCKS
1/ Set forestay length (your own top secret measurement).
2/ Centre the rig using V’s (D 2s hand tight and mast straight) and the jib
halyard, marked and pulled down to alternate gunwales to ensure the rig is
vertical and not off to one side.
3/ Hand tighten D 1’s and connect the backstay.
4/ Now you can start tuning by tensioning the V’s a half, one or two turns at a time, first one side and then the other.
5/ When the V’s are reading just under your desired magic tension you can start
to work on your prebend by tensioning D 1’s one turn at a time, side to side.
This will take your V’s up closer to your magic number.
6/ Keep checking the rig tension.
7/ Pull on backstay to check mast bend. If there’s too much in the second panel
of the mast then tighten the D 2’s one or 1/2 turn at a time side to side.
CHOCKS Use the chocks to artificially alter the natural bend induced by your rig tensioning/tuning. An example of this is possibly chocking behind the mast in very light conditions to help in easing the mainsail leech / flattening the main, or alternately chocking in front of the mast to reduce bend when power is required in light/moderate and choppy conditions. Experiment to see what works for you.
In lighter winds you want to be able to keep some fullness
(not too much) with very little leach tension and light forestay tension
(this is why you set up the prebend.)
Medium winds (up to fully powered up) you need to have enough mast bend to get
maximum drive from top to bottom on the Main and medium forestay tension for pointing
In slightly overpowered conditions you need to bend the upper mast and flatten and depower the top of the main until the boat is balanced.
You pull the rig forwards if possible when sailing downwind but don’t let it distract from
the more important issues of trim and tactics. It is good to not let the mast jump around in waves as this stops the wind from attaching to the sails and will slow the boat . Better to have tension in the backstay.
Note… Fit elastic ‘preventers’ to stop the kite being trapped in corners where shrouds meet shrouds or mast.
Loos gauge settings for a PLATU
Wind speed V’s D1’s turns turns
0 to 5 8 5 -1.0 -1.0
6 to 8 11 8 0.0 0.0
8 to 10 13 11 1.0 0.5
10 to 12 15 13 1.5 1.0
12 to 14 16 14 2.0 1.5
14 to 16 19 16 2.5 2.0
16 to 18 20 19 3.0 2.5
18 to 20 21 20 3.5 3.0
20 to 22 22 22 4.0 3.5
22 plus 23 23 4.5 4.0
For Pattaya we use 6 to 8 knots as the base setting. Use the above
figures to adjust for wind changes from the base setting.
Remember, clockwise turns reduce tension.
D2,s can be set with minimum tension and for club racing can then be left alone.
Enjoy your racing and have fun.
Thanks to Gary Baguley and John Weston for help with input to the above.
Ferret News February 2012