Am I losing power when the sail rests on the boom?

[DanWeiss]

Comment 1: Sail wrap. Whether a sail sits against the boom or wraps around slightly above and below is a function of desired sailing angle, average wind strength and the specific sail/board combination. The most significant influence is sailing angle.

Upwind, where the apparent wind is very far forward requires a leaner entry and flatter, less twisted overall profile. The choppier the water the more the apparent wind fluctuates, so often a flat entry with a deeper profile is best. The common way to achieve the first is to downhaul to flatten the entry but not so much as to kill power. One may achieve the second with a reduced outhaul and decent downhaul. The end balance isn't hard to achieve just by setting DH based on regular tuning advice based on wind conditions and playing the OH for power.

Downwind, hitting chop can slow the board and thus swing the apparent wind aft. More twist is required to damp the resulting power changes, so downhaul and less outhaul than pure upwind is usually the call. Of course, changing DH on the fly isn't likely to be available but to RS:X and Techno 293OD racers, so changing OH tension is the only option. Therefore, we tend to see sail wrap when the OH is dumped to achieve more leach twist because reducing OH tension also moves the draft back to a more narrow section of the boom. The balance can be well worth the speed loss.

Comment 2: Boom height. It's all about the angle formed between your harness hook, the boom and the mast base. Assuming you are properly tuned for fast and comfy beam reaching in flat water, raising or lowering your boom height often makes the common and respective changes also assuming no harness line changes occur. A lower boom will reduce the weight transferred to the mast foot but puts more pressure on your front foot. This helps control a board in choppier water and/or when overpowered. A higher boom increases mast foot pressure and reduces pressure on the front foot, usually allowing the nose of the board to ride higher.

In 1990, Anders Bringdal told me that he raised his booms a bit when racing slalom underpowered in order to get the board to "unwet." That remains ever more true with the higher aspect rockers of today. The idea that we exert more leverage "over the rig" usually suggests we could tip the sail over us more easily, thus loosing power. Yet the vectors in the tuning triangle say the opposite when planing. More force is produced downward through the mast base rather than to windward.

[GURGLETROUSERS]

As you say Dan, but your key point was 'assuming no harness line changes occur.'

I wear a seat harness, always, and use long 32 inch harness lines with, for normal conditions, the fixing points a foot apart, with loop elbow to wrist. If I raise the boom (not often -just if caught out overpowered) I drop into the water, unclip the clamp, thump it up a couple of inches with palm of hand, re-clamp, AND slide the harness line points closer to give a lower loop and same relative body lean, increased leverage, but sailing stance as before.

I always assumed, therefore, that I was sailing much as before, but under slightly easier control. I'm not certain if that is correct, except that over the years I've obviously adapted my sailing stance to FEEL that it is working, for me, bearing in mind that I'm old school lean out and cant the sail to windward when overpowered, just as pictures of Robby used to show him doing..

[NOVAAN]

You are not likely to plane in your stated wind range (8/10) no matter how you rig your 7.5 sail. The Ezzy web site has great rigging and tuning video's.
In any sport there are three main ways to create more power. Increase motor size, reduce weight and reduce drag. Windsurfing sails get most of the power by increasing size. By out hauling your sail you actually increase the measured size of your sail a bit. Most modern sails require positive out haul to help shape the sail. A very deep sail laying hard on the boom will create drag, feel heavy and be unstable. If your sail is just touching the boom, it should be ok. The Ezzy freeride sail requires a enough downhaul so the battens rotate to the opposite side of the mast with the corresponding amount of positive outhaul. See rigging video. The will create a lite feeling balanced sail..

[NOVAAN]

Never heard that rising the boom will increase your low end power. This is done to increase your control and leverage on an over powered sail. Putting the boom higher with the same length lines will cause you to pull the sail to the windward. Thus presenting less sail to the wind and decreasing your power. An up right and sheeted in sail is a powerful sail. Most of this is only going to make a small difference in the sails power. The best way to get the board up and going for a given sail size is to bear off the wind and pump the sail with your back and arms and the board with your legs. It takes more wind to get you going than it does to keep you going. let the board run down wind and get up to speed before heading back up wind. That said, probably not happening in 8/10

[DanWeiss]

Well, what can i say? I didn't make it up.

Raising booms often means that the original height was too low to keep the nose down. As far as not lengthening harness lines when raising the boom, of course we do. But discussing the variable of boom height seemed more helpful by keeping everything else constant. Assuming correct harness line length in the first place, we agree that raising the boom should result in a commensurate lengthening of harness lines.

[brynkaufman2]

Just as a follow-up I did raise my boom and that was helpful.

I did some tests yesterday by letting the sail rest on the boom vs. using more out haul and having it almost touch to boom, and I felt the more out haul in this case actually increased the power to drive the board forward. When I used less out haul and it pressed on the boom, it felt like a lot of pull, but for some reason it did not translate as well to forward speed.

So in light winds I will no longer rig where the sail rests on the boom and I will continue to keep the boom in the higher position.

[dllee]

Yeah, sagging outhaul FEELS more powerful, like no downhaul also feels, but actually kills low end by softening the leech TOO much, and killing any chance for high performance sailing.
You see that a lot with beginner short boarders, loose outhaul, sail wrapping/touching 10" of inside of boom, VERY slow sailing.

[Sailboarder]

[DanWeiss]

[Sailboarder]

Thanks Dan, quite informative.