Before I get into a couple of other topics later this week, a few thoughts about spinnaker trim prior to BBR.
Spinnaker trim is a thing that's often mystifying to people for a long time, and then they kind of get it. With more boats moving to asymmetrical sails, it's becoming a dying art. One of my favorite roles on big boats used to be trimming the guy, it was something I did well enough to get asked onto good boats to do. Now the big boats I'd like to sail don't have a guy to trim. C'est la vie.
When you are reaching, there are a few things about spinnaker trim. You need to keep the pole LOWER than you would running, as this gets the leech of the sail to twist open. If you have the pole too high, the leech will close. If the leech closes, the jib will interfere with the spinnaker leech and if you ease the main, the main could even hit the spinnaker. If it's light air and these things happen, the spinnaker will collapse. If it's heavy air and these things happen, you'll probably flip over.
If your spinnaker luffs, you need to trim the sheet, let the pole forward, head down, or some combination of all three. When your spinnaker is luffing, it is a lively flapping.
If your spinnaker collapses, you need to square the pole (try that first), ease the sheet, head up, or some combination of all three. When your spinnaker collapses, it is not a lively flapping.
The difference between luffing and collapsing is that a luffing sail is flapping all around and acting like an excited puppy. When it collapses, it just droops and hangs there, like a very very very old dog.
This 470 isn't actually close reaching. If they were close reaching in this much breeze, the skipper would be hiking hard on the windward side. But it's the closest pic I could find for what I want to show. The jib is very much under trimmed. Your jib must not ever be over trimmed downwind. It is deadly. The vang is eased enough that the main sheet doesn't have to be eased very far to depower the main. This keeps the main far away from the spinnaker leech. And the pole is low, opening the spinnaker's leech and keeping it away from the main, and promoting good flow across the spinnaker.
This is a 505 close reaching in medium conditions (505s are much more powerful than 470s). Notice that the pole is at a low angle, and the jib is eased. Notice also that the main is trimmed quite hard. The worst mistake you can make reaching is to have the spinnaker over trimmed and the main ender trimmed. Over trimming the jib would simply be another terrible thing to add to that. Notice also that the pole is just a tiny bit off of the forestay. If you let the pole hit the forestay, the pole will bend around the forestay. This effectively shortens the pole's extension (because the pole is bent) and it allows the spinnaker to rotate too far to leeward. The leech hooks back to windward, pointing right at the main when you do this. Very very slow. This boat shows how you want to look. Coincidentally, this boat is the world champion.
This picture (go Stu and Dave!) shows good heavy air running technique. Look at how high the pole is! The pole acts a lot like the cunningham. It moves the draft forward toward the luff (the guy side) and opens the leech. Simple. When you run, you want the draft away from the luff, and you want a relatively closed leech. If it was lighter, they could pull the pole back more, but it's obviously almost scary windy here so they keep the pole a little farther forward for stability and to make it easier to steer the boat in the waves. Jib is very eased.
This picture shows light air running. I believe that they could pull the pole back (or "square the pole" as we actually call it) both to get more spinnaker projection, and to get the spinnaker leech away from the main. But who knows because it's one picture taken at a moment in time. In very light air, you can't run with the spinnaker all the way squared - it's like sailing a school 420 when it's too light to go wing-and-wing. But it looks like there is enough breeze here to wing, which means there is enough breeze to go full square. When you go full square, your limit is that you want to keep the clew to leeward of the forestay. This sail shape actually doesn't look very good to me. I'd like pole more squared and maybe a bit higher.
Again, this isn't meant to be a full encyclopedia of spinnaker trim but just a few general ideas on it, with some pictures to show how it looks when it's done right and maybe not so right.
