Main Sheet Adjuster

The big cat, PlayStation, had a sort of triangular profile at the outboard end of its boom. The main sheet attached to a track mounted to the bottom of this angled section. This track seemed to allow the mainsheet to be adjusted up and forward or down and back along the boom.

More recently, I observed the same geometry on the back of a small cruising tri in photos of the Whidbey Island Race.

Can anyone explain the concept behind this set-up?

 

This arrangement was there to allow for traveling out the mainsheet car without having to make a corresponding adjustment in the mainsheet length itself. The end of the boom is moving in a circular arc as the traveler car is traversing a straight beam athwarships, thus easing the traveler normally would require a readajustment of the mainsheet. Placing a short traveler car on the underside of the boom and at a level horizon with the main traveler car keeps one from having to resheet the mainsheet each time the traveler is let out.

The first time I ever saw this used was on the first Formula 40 cat design for Randy Smyth by Gino Morrelli