Making Ready 6

 

With Stargazer's new mainsail on its way (Making Ready 4), it is time to resolve a bugbear with the mainsheet (the 'block and tackle' which controls the boom and mainsail). The power of a 6:1 purchase is required, in order to handle the load generated by the sail. This has triple sheaved blocks mounted to the boom and cockpit sole. Necessarily, its falls (the lengths of rope running between the pulleys) are closely spaced (picture above). To the extent that, at inopportune moments, they can touch, and lock up under load. Preventing adjustment.

This is a known drawback, to high purchase sheeting arrangements. (Their advantage is that, without the use of winches, the sail may be controlled by hand). There are two schools of thought on how to overcome it. 

The first concerns the mounting of the blocks. Some swear by locking them in position, so that no twist is possible; and, in theory at least, the falls are held separate. Others swear by fitting them on swivels, which allow the blocks to take up a position of least resistance, determined by the pull from the falls. I have tried both approaches, as well as a hybrid, with one block fixed and the other swiveling. And found little difference in performance. In the end settling on a swivelling arrangement as ‘least bad.’

The second school of thought concerns the reeving (threading) of the mainsheet through the blocks. At commissioning Stargazer's mainsheet was rove to the Harken pattern (shown above). 

Because of the lock up problems, I had begun to doubt whether Stargazer's original mainsheet reeving was correct. An internet search confirmed that it did exactly match the Harken pattern. It also turned up a different method, on the Barton website (above). Following it alleviated, but did not completely eliminate, the mainsail control issue. Instead I evolved a technique, to free the jam, by grabbing the middle (upbound) fall and pulling it forward, hard. This has always succeeded in freeing a lock up. Not elegant, but it seemed that I had exhausted all of the known cures.

Until, in conversation with Alan, the sailmaker, I learnt of an alternative approach: The EasyMatic system (shown above). This removes the problem, of locking falls, in an elegantly simple manner. Although a 6:1 system, it eschews the problematic triple block. Instead there are double blocks, in a fore and aft plane, with a single block mounted laterally. This separates the falls and eliminates the twisting forces which bring them together. Thus (I hope) eliminating friction lock up at source. It has another trick up its sleeve, too. You may notice that it is double ended (actually an endless loop, spliced together out of shot). Pull both tails (ends) simultaneously and a great deal of sheet is moved very rapidly, at a 3:1 purchase. Useful for light wind gybes. Pull just one tail however and the full 6:1 purchase is engaged.

Vectran mainsail, EasyMatic mainsheet; and a super smooth hull (Making Ready 5). Stargazer is making ready to fly, in 2022.

Picture Credits

1,2,5   Me

3         Harken

4        Barton

5        Force 4 Chandlery