J/105 Tuning Guide - Rig Setup

CDP CLASSES:
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Beneteau 36.7
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J/105
J/109
Melges 32
M30
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Swan 45

J/105 CDP:
Tuning Guide
Sail Descriptions
Client Testimonials
Class Rules

Tools and items required: Loos RT 10M Rod Tension Gauge, 2 crescent wrenches, spray lubricant, bosun's chair and 50' metric tape measure.

 
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"). Heavy air areas, such as San Francisco, should set the mast butt 27cm 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. Use mast chocks or SparTite to achieve this position. SparTite is recommended.
 
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.

Click HERE for the headstay measurement diagram.
 
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 RT 10M Rod Tension Gauge: Put marks on the shrouds 2m up from the deck. Put the top post of the gauge on this mark when measuring tension. For the base setting for 9 to 12 kts. TWS the shrouds should read the following:

» Caps: 35
» D2s: 10
» D1s: 0 (has 10 cm side to side play)
 
Double check to be sure that the mast is still in column at the dock. You are now at the "base" setting and ready to go racing.
 
From here follow the North Sails J/105 Quick Tuning Guide to optimize your J/105's performance for various wind conditions.
 

Below are links to three additional Quick Tune Guide to help you tune your J/105 rig:

» Quick Tune - Scrimp (PDF file, 60kb)
» Quick Tune - Pre-Scrimp (PDF file, 60kb)
» Quick Tune - Heavy Air Sails (PDF file, 60kb)