Philippe on the subject of sail trimming and especially use of the gnav (according to him, an under-used tool).
Philippe is an an incredible sailor and an amazing instructor. We spent about half of the time on land with an RS Venture looking how the various sail controls affected sail shape and talking about what sail shape you want for what conditions (it was blowing over 15 kt. this evening, by the way, with pretty big seas - we had a lot of weight on the boat on land to make sure it didn't capsize into the cars parked near the clubhouse). On land, it was much easier to see the effects of various controls on the sail shape.
This is my lesson summary (feel free to comment):
Scope: Dinghies which generally don't have travelers.
- Sail shape is very important. The usual things about depth and power, and location of sail draft. With lighter winds, you want a fuller sail and a draft a bit aft. With heavier winds, you want a tighter sail and a draft forward.
- In heavier seas, you want more power, even with stronger winds.
- Tensioning the Cunningham brings the draft forward.
- The outhall affects the lower third of the sail.
- Several controls bend the mast aft, which tighten the sail and move the draft forward. Tightening the mainsheet and the gnav do this.
- In high winds, you don't want the boom near the center of the boat, as the lift from the sail is mostly sideways to the boat. But just easing the mainsheet induces twist in the sail. Tightening the gnav overcomes this, allowing the mainsail to go to a better angle, but preserving the sail tightness.
- Bearing off from close-hauled, you want to do several things. One is ease the mainsheet. Another is to keep weight on the windward side to help turn the boat downwind. A third is to ease the gnav (and then tighten it when on course).
- Blow the gnav before the gybe (this will depower the sail and cause the top of the sail to back-wind before the bottom of the sail, producing a gentler gybe).
- Weight the boat to windward to turn it down-wind through the wind. If you reach across to pull the boom across, you'll mess this up.
- If done correctly, the wind will gently pull the mainsail across. Grab the sheets as this happens to buffer it.
- Power up after the gybe by tightening the gnav
Then we went out and did it, both upwind and downwind. And it worked. I was prepared for hikiing really far out with the winds we had, but we didn't have to. And it was amazing how gentle the gybes were with this technique. Note that in bearing off and gbye-ing, you're doing what you would do rudder-less - moving weight to turn the boat. After the class, I discussed that with Philippe, and his opinion (as a racer of some renown) is that the more you can use your weight to maneuver the boat, the better (i.e. faster) you'll sail.
For me, this was an excellent complement to the Senior Study Group session by Saul on Advanced Sailing Theory (which was also excellent), and to the book Saul recommended - Tom Whidden's The Art and Science of Sails.
The Advanced Dignhy season could not have started better. Grazie, Philippe.