On the water lesson (log entry below). A couple theory items first…
The instructors took advantage of the medium-high winds to talk about surfing. The idea was to learn to catch a wave while running and have the wave increase your speed. The instructors recommend watching your transom, and (when a wave is about to hit) giving the sail a “pump” to try to catch the wave, and ride it.
The Laser boom can be let out all the way to 90 degrees (and even past!). This is a blessing, and a curse. A blessing, in that it give you lots of options. A curse in that one of those options is to put the boat into “death roll” mode.
Imagine you’re going along downwind. You have your boom out 90 degrees to the centreline of the boat (on port tack) and your sail controls are loose (to generate as much power as you can). The bottom of the sail (blue, in the diagram below) is happily generating tons of forward power. The top of the sail however twists off in front of the mast (red). It’s generating power too.
Where we normally expect the boat to be heeling to leeward (starboard, in this example) so we’re probably sitting on the windward side of the boat (port). But the top of the sail is actually pushing the boat to windward (port) which will cause the boat to heel to port. Our natural reaction, when the boat starts to heel will be to move closer to the centreline, to do it “too much” and the boat will get into an osculating back-and-forth rolling pattern (will can capsize you pretty quick).
So, how do you recover if you feel your boat starting to roll? You have a few options, all of which are valid and easy (as long as you recognize what is happening and respond quickly):
- Sheet in — get the top of the sail pointing forward, and the bottom pointing a little bit to leeward. This stabilizes you real quick and allows you to balance the boat
- Head up into the wind slightly — this will cause the top of the sail to luff and stop generating as much power, meaning you can organize the bottom of the sail before heading back downwind.
One you have avoided the death roll, there are a few things you can do to discourage it from happening again:
- Sail with the sheet in slightly (maybe the boom is out 80 degrees instead of 90)
- Put a bit of boom vang on — this costs a bit of power, but prevents the top of the sail from twisting so much, and you can recover some forward power from that area
You can see in this youtube video a sailor who is blasting along downwind with his sail at 70-80 degrees for most of the video. At about 28s into the video he lets it out to 90, and you can see how quick the death roll happens if you’re not ready to sheet in (or head up)
Weather Forecast: cloudy, steady 10 knots from W
Observed: partly cloudy, wind 8 knots from NW, with occasional gust in 12-15 knot range (from either N or W)
On the water: waves died out meaning it was tough to find a trough to surf the boat in. Windward beats were good, although my roll tacks were particularly sloppy today. To work on next time — stay on old side of boat longer through tack, and do a smoother sit down on new side. Give larger pump when wave approaches to initiate surf.