Tech Notes
Index

I have tried various mast tuning positions for my First 21.0 Classic (Hull #58). I feel the "Factory Commissioning Guide" in the owners manual ensures the proper mast tune. This "guide" is also posted here in this web site's library. In brief, the factory guide says to set up the mast this way: a) loosen all turn buckles to 3/4 open; b) center the mast athwartships (abeamwise) by measuring with a tape or halyard; c) tighten the backstay adjuster until there is 12 inches of bend in the mast; d) hand tighten the upper shrouds; e) release the backstay adjuster and you should have 4-6 inches of pre-bend in the mast; f) tighten the lower shrouds to ensure the mast is in column, that is straight up the center bolt rope slot and that it does not "pump" under sail. When done with these steps, I remeasured the distance from the masthead to the shroud chain plates. The distance was equal. I left the forestay turnbuckle pinned at 3/4 open. With that setting, the forestay is fairly "wobbly" with no backstay tension and nearly "band tight" with the backstay tensioned hard.

With this set up, my boat points as high as the Factory "polar" charts suggest and it sails true on all points of sail, with main/jib or with main and spinnaker. With this set up I have done best racing under my boat's PHRF handicap rating of 210 sec/mi. Here are the shroud and mast stay tension readings I measured using a LoosTens wire tension guage:

Backstay at Rest and 4"-6" mast bend:

5/32" upper shrouds = 420 lbs
5/32" lower shrouds = 380 lbs
5/32" forestay = 300 lbs
1/8" split backstay (2:1) = 0 lbs

With Backstay Tensioned and 7"-9" mast bend:

5/32" upper shrouds = 420 lbs
5/32" lower shrouds = 420 lbs
5/32" forestay = 800 lbs
1/8" split backstay (2:1) = 400 lbs

When the backstay is taught, the tension in the upper shrouds remains the same, tension in lower shrouds increase to same as uppers and forestay tension increases over 2.67 times.

Title: Beneteau 210 Rig Tension Guide 
Model(s): First 21 Classic; First 210; First 211 Spirit 
System(s): Rigging & tuning 
Author: Terry F. Ellis