Monday, 25 June 2012

Modified Drascombe Lugger Mainsheet

[Disclaimer for the traditionalists, I'm not suggesting this is a better arrangement than the original setup, only that it works well for me!]

The original John Watkinson design for the Drascombe Lugger mainsheet:
  • End of the sheet attached to an eye on the aft deck starboard of the mizzen
  • Sheet runs up to a parrallel double block at the clew of the main
  • Back down to a single block on the traveller back up to clew of the main
  • Down to an upright singleblock on the aft deck port of the mizzen
  • Sheet led forward through fairlead under traveller track to fairlead on base of tiller
  • Cleat, if used, is further up on the tiller
I found this unnecessarily complicated, and with all points of resistance given to the mainsheet, spilling wind became a bit haphazard, especially as the centre falls from the clew to traveller had a nasty habit of twisting. I also found that leading the mainsheet back to a fairlead on the base of tiller interfered with the helm.

On Ondine, we've converted the mainsheet to an arrangement I was already used to from our previous Wanderer, and seems common to aft-sheeted dinghies.

Essentially, we replaced the parallel double block on the clew with an inline double block, and replaced the single block on the traveller car with an inline double-block and becket. The fixing and upright block either side of the mizzen are redundant:
  • The mainsheet runs from the becket on the traveller block
  • Up through the top wheel of the clew block
  • Down to the top wheel of the traveller block
  • Back up to the lower wheel of the clew
  • To the lower wheel of the traveller block
  • Out to the helmsman's hand
More than sufficent purchase for the sheet, but no danger of it twisting and little resistance so it's easy and instantaneous to spill air from the sail in a gust. We've got a jamming cleat on ours, and found early on that it was essential to set the angle so that it required a definite action to set and would release on pressure from the helm without thinking of it in a rush.

We've been sailing with this setup in some, at times, quite boisterous conditions for over a year now, and haven't found any disadvantages to it.


photocurio said...

Does a 74 sq foot sail really need a four part purchase?

tatali0n said...

No. It's a case of we had it so we used it.

I manage more sail area in my Enterprise's mainsail on a two part purchase with only an 8mm mainsheet, and I know a couple of other Drascombes that use a similar arrangement but with only a two part purchase. And, more often, without the cleat.

In the case of our boat, we already had the cleated fiddle block which we'd removed from our previous Wanderer.

I don't know why the Wanderer's previous owner had installed it. A two part purchse system is more standard. We removed it and substituted a single ratchet block and becket before we even lauched the boat so it was kicking around in our box of spares.

That said, the four part purchase does make sheeting in to trim the sail a breeze even in quite stroppy weather, and doesn't seem to impede the free running of the mainsheet when spilling air in a gust.

It's not exactly delicate, but then nothing about a Drascombe is delicate.

Of course, halving the purchase would reduce the size and weight of the block on the clew, which would be no bad thing, but overall I'm quite happy with the system as it is.