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Mainsail Trim

Yesterday’s race was a perfect chance to practice what I had learned in San Diego.  The weather was lovely, the wind was fairly steady, and the lads had everything else under control so I could just concentrate on the mainsail.

In a nutshell, the advice worked!

  1. IGNORE THE LUFF.  I just focused on the trailing edge of the sail.  We had the outhaul on hard in only 10 knots of wind, and I used a bit of backstay.  There was still some back winding at the luff, and I just ignored it!
  2. TOP BATTEN ANGLE.  I focused on this instead, and it was fascinating to feel the effect of sheet and traveler.  Once a tack was complete and we were powered up, I used the following approach
    1. Brought the traveler up so the boom was on centerline
    2. Used the course end of the main sheet to bring the top batten parallel to the boom.
    3. All the tell-tales were flying
    4. In these conditions, balance was good and Kiwi only had weather helm in the puffs
    5. Using the tweaker, I could make fine adjustments to the top batten angle that translated into a few degrees of pointing ability. This helped us climb up to Battlewagon’s line at a critical moment in last night’s race.
  3. CONTRASTED to last year’s sail shape (where we chased away the backwinding by twisting the mainsail a lot), the sail was much less twisted, but it also wasn’t closing back on itself.  As a result, it felt like we were pointing nice and high.  When we tacked onto the lay line, and got up to speed, I could confidently offer Kiwi a bit more ‘height’ to make sure we made the mark.
  4. BACKSTAY performed like it did in San Diego.  To achieve this, I’ve got the shrouds tensioned more than last year, especially the cap shrouds.  As a result, the forestay only tightens slightly when the backstay is applied.  Instead, the leach opens a bit.  In a way, the backstay and the tweaker had opposite effects:  the backstay opened the leach at the top of the sail, and the tweaker tightened the leach along its entire length.  Somehow these two interact to refine the shape of the trailing edge of the sail, a lot like how the halyard and Cunningham both affect the luff tension but at different heights.  I need to play with this more!
  5. HALYARD and CUNNINGHAM.  Yeah, we still had this nice and snug.  Hard habit to break!

I also had a chance to think about TACKING.  The goal is to leave the tack with a fuller, more powerful sail shape while sailing a slightly lower angle until the boat gains speed.  This is especially critical in light wind, less so in moderate wind and beyond.

GOAL: to END the tack with the traveler a bit lower and the mainsheet a bit softer.

APPROACH:  just prior to the tack, draw up the traveler a few inches and ease the mainsheet a few inches — in other words, shift to a more twisted profile.

EFFECT: After tacking, this translates into a traveler that is low and a mainsheet that is loose.

POWERING UP:  First I raised the traveler gradually until the boom was on centerline.  Then, as the boat began to turn up, I trimmed on the main until the top batten was parallel to the boom.


One thought to “Mainsail Trim”

  1. Will be interesting to see how these lessons continue to play out over the course of the season. Was fun to actually gain on Battle Wagon while going upwind.

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