Optimal Heel Angle

[Bandit]

What is the optimal heel angle fo sailing to weather?

[GreenLake]

Looks like nobody wants to step forward with an answer. Which is a shame, because its a great topic.

Could it be that we don't feel our racing expertise is rarefied enough to attempt an answer, or could it be that we don't quite know what you are after?

Are you sailing with and inclinometer on your boat and really want to know whether to go for some precise figure, like 8° or 15"? Or are you looking for a more qualitative prescription, like full, partial or none? Are you coming at this from more of a basic perspective, or do you consider yourself experienced and are looking for the last bit of fine tuning?

And finally, as with everything in sailing, any answer would come with a large helping of 'it depends' --- on wind, boat speed, sea state, and so on.

I can tell you want I would do in the circumstances I encounter predominantly. But I don't have an inclinometer, and I don't sail in a one-design fleet, which makes it a bit harder to dial in optimal technique or to crank it down to a single number. But I'm happy to share what I'm doing and why I think that works. Let us know if that's something you might like to hear.

PS: Some keelboat designs have specific heeling angles that their hulls were designed for. At those angles, the effective waterline is longer than the one measured by whatever rating rule these boats were designed for. That is something that doesn't exist for the DS: racing is generally one-design, so there's no rule you can cheat to get a better handicap.

[Alan]

Since the Daysailer's hull is capable of planing, I think people were recommending that it be sailed pretty flat. Talbot, who spent a lot of time on the water in his DSII, had this to say:

Re: New to the site - angle of no return

Post by talbot » Fri Aug 29, 2014 2:30 pm
Yes, the boat can sail up at 45 degrees of heel, but it would be a lot faster to reef the main and keep the rail down. Most people say 0-10 degrees of heel is optimal. With an eye on the GPS knot meter, I think up to 15 degrees is OK. When you pass that, the speed falls off dramatically. Ditto what people said about the jib. A stuck foresail will prevent the boat from rounding up. At extreme angles of heel, there isn't much rudder in the water any more, so the sail is really in control.

[GreenLake]

I don't race, I "race" in beercan events. And the winds tend to be quirky and light, more often than not. With that said, let me add a bit from my perspective.

So I have lots of experience heeling the boat to leeward going upwind in light airs. At slow boat speeds this really helps. The theory for that is that lifting part of your hull out of the water reduces the wetted surface, and at low speed, surface friction contributes strongly to the overall drag. (Heeling to leeward also allows gravity to help get your boom and sailcloth in their proper shape, something that wind pressure may not be up to).

As to the precise angle, I usually settle for a heel angle that "feels right", which to me is bit short of balancing on a knife edge. I go a bit more conservative if the light patches alternate with stronger puffs. Don't want to be caught too far over on the wrong side if the wind picks up.

I'm thinking that this calls for some measurements on a calm day. With an electric motor and a GPS it should be possible to get the boat moving to some steady speed less than 1 knot, and any loss in drag from heeling should be apparent by some increase in speed. I'll see if I get a chance to try that out sometime. (I have done measurements of the affect of fore-aft balance, and found that to have an effect of up to almost .5 knots in the 3 knot speed regimen).

The reason fore-aft balance matters is that a stern heavy boat will drag the transom through the water. Now, if you heel your boat to leeward, the immersed part of the hull gets narrower, and some part of it will dig into the water at the stern. So, if that effect gets stronger the faster you go, then at some point you'll benefit from sailing the boat flat. (And later it helps in transitioning to planning, but that's not an upwind thing for the DS)

Which is perhaps the source for conventional wisdom for boats like the DS to sail them flat. I think that by 3 knots of boat speed the gains from surface friction are proportionally much less than what you lose from not sailing the boat flat (by having more drag from an inefficient shape). I tend to allow a few degrees of heel even then, because it seems to give me better feedback.

I've seen other experienced dinghy sailors do the same with dinghies of similar size. I'd estimate less than 10°, but I don't have an inclinometer. For comparison, the design heel for keelboats would be 15° or more. At least on boats I've been on.

There is another effect of a heeled boat in that it tends to want to turn the boat. Depending on whether that causes you to apply less or more rudder pressure to keep going upwind it could affect overall drag positively or negatively. Those contributions are harder to simulate without actually sailing because the sail plan itself tries to turn your boat into the wind. However, it should be possible to get some data points on how heel angle affects the main contributions to drag by making some measurements at constant speeds.

And Alan already mentioned that the rudder is more effective when the boat is flat - that alone might help speed things along as you'd need less rudder deflection for the same steering response.