Sail Control: Outhaul and Inhaul

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Sailing Catapult


  The camber of the sail is set by lines running from the clew of the sail out to the end of the wishboom and then brought forward to the base of the mast, with v-jammer blocks allowing setting on the water, pictured below
 The outhaul:
 a 6 X 1 purchase block and tackle runs from the end of the wish-boom and clips to the clew of the sail (A)  The line then runs forward from the block on the boom (over a small block shackled to the clew, B) to the controls, photo (2) below.

  Also attached to the clew is the inhaul (the red looped line F in photo 1 below, and the upper line F in photo 2)


   As shown below in (2) the outhaul line runs to a block, and a 2:1 purchase (C , the yellow line below) giving a total purchase pulling the sail taut of 12:1 on most boats. The yellow line is controlled at a v-jammer block, D, pulling against a line looping around the mast (E) which secures the control lines, and allows them to be in easy reach when sailing.


catamaran sailing

  As noted above, the other control is the in-haul running from the clew forward towards the mast (F  in photos 1 and 2, the top red line in 2.)

 The purpose of the inhaul is to achieve a
slack sail foot sailing off the wind, when main sheet tension is released.

 As its name suggests, it pulls the clew inward, and the outhaul hence pulls against this tension (until full mainsheet tension pulls the boom down and slackens the foot.)

 Photo 3 shows the Outhaul line (yellow) and inhaul (red) around two Seasure v-jammer blocks (part number 00-13) which have been mated together with long clevis pins, as a neat solution to bringing the controls together. (They are shown fully-slack, see below.)


   A summary of the sequence setting up the sail

1) Raise the sail (more here) and take up the initial slack on the downhaul (more) to hold it.

2) Fasten the forward end of the wish-boom with the strop through the luff of the sail (Right)

4) Clip the block and tackle at the outer end of the wish-boom (A above) to the sail clew

2) Untangle and untwist the inhaul and outhaul, and slacken off fully at the v-blocks, and then loop the inner end round the mast (left loose.)

5) Clip the mainsheet onto the clew

 (Arrangements vary---on the boat in the top picture, it clips to the bottom of the small block B that the othaul runs through, while in the boat in Photo 4 below, the clip goes around around the inhaul and outhaul lines.)
catapult sail strop

    This is the position the rig will be left in when waiting to go, near the water.

o prepare for launching and the start:

6) Pull the loop round the mast down over the securing stud

7) Set the outhaul position. (This will probably be set tight for starting on the beat, but might be looser if there is a long run to the start.) (See below for comments.)

8) Set the inhaul. John Peperell comments: In-haul setup is a fine judgment. The easiest way of setting up is to apply full main sheet tension (so that the sail foot slackens) and at the same time just tighten the inhaul.

On releasing the main sheet the sail foot will remain slack, and probably wrinkled (folded) at the clue. The inhaul should now be eased a little to eliminate the worst wrinkles. This will give the basic inhaul setup and could be left unaltered for the time on the water.

    OUTHAUL SETUP  John: This depends more on your sail camber depth (and having enough
wish-boom length.) I like to start with my outhaul set up with full tension on the sail clue i.e. flat sail.

  I mark this point on the sail foot with red tape using the outhaul adjusting block as marking guide. I then release the outhaul making sure there is enough adjustment line to fully slacken the sail. I now mark this point on the sail foot again with red tape.

   This will give you the range of outhaul adjustment from full sail to flat sail. You could then use green tape to give you a medium sail camber setting.

  (If your outhaul at the clue is block to block at this stage, you will need to tighten the wishboom luff strop - not so tight that the wish-boom fouls the mast, or is awkward to get into place. For the Roundhead sail, the wishboom must be 2650mm overall minimum length.)   


These variations below are mainly to show the way the boat allows change and experiment (within the standard hull rig and sail.)

Photo 4
below shows how on this boat the inhaul (the thicker blue line above "G") is taken to the outhaul pulley block (rather than being separately clipped to the clew as in the boat above). The mainsheet clip then goes round the outhaul and inhaul, onto a small ring fastened to the clew ring, so that the two lines run freely through it.

    This was done to give one less attachment to make at the end of the boom when the sail is "live" The more usual way is as in the boat at the top, Photo 1, clipping the mainsheet to the bottom of the block B. (Mainsheet not yet attached.)

catamaran sailing rigging

    In photo 5, below, the outhaul (white) and inhaul (blue) finish in v-blocks as above. The outhaul has been modified to include an extra v-block carrying the 12:1 purchase. The inner v-block can alter the position of the outer one, and operating at less tension can move quickly. Alastair comments: This set-up was made for my previous flatter Dolphin sail, to have a greater range of camber and is probably too complicated in practice

  catamaran rigging sail control

     The ideas were firstly to have the outer control set for beating (tight to a greater or lesser extent depending on breeze) or reaching (fully released in one movement) while the inner control allowed a great deal more camber to be given (with no additional purchase needed, as the sail is already slack, although the line digs very tightly into the v-block under the load.)

 Secondly, it allows a great range of movement without a long "tail" from the 12:1 purchase hanging down to deck level. (I was about to tack in heavy weather at Rutland and noticed just in time that the "tail" was stuck firmly in the leeward frame bolts.)

  The elaboration was to also pull the inhaul further in and down when both are fully released----it certainly gives a spinnaker-like belly, and seemed to give some boat-speed at Marconi, but you need a very long downwind leg (as at Bala sometimes) and the inhaul is hard to release after being under high load. As said above, this note is more an illustration of playing around with possibilities.

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