best vmg

Can anybody tell me what gives the best vmg upwind. No steering or no sheet or a mix. What mix?

short answer: It's a combination of both that depends heavily on sea state.

I don't have the time at the moment for the long answer

I'm used to sheet my sail to the right place, cleating it and then steering to keep it in the groove.

This works well on the flat pond I sail on usually but it failed spectacularly two week-ends ago in the short chop on the Blackwater estuary. I found there that steering for the waves and playing with the sheet to keep the main in the groove worked better. Way better. Average speed was 6 knots trying to steer around and jumped to 9.5 knots once I figured out I needed to change the technique.

No easy answer, watch the Alinghi guys in the 1st AC race to see the debate going on.

a medium answer: you need to steer slightly as when the boat is fully (over)powered, it will benefit from sailing slightly higher without loosing much speed...but not a whole lot higher and not grabbing that bite to windward too quickly. The sail needs to be eased to accommodate the immediate need for depowering while the helm eases up a little bite to windward slowly enough that the turning action doesn't slow the boat. When the puff relinquishes, the sail comes back in (with anticipation!) and the helm can bare back off slightly. The timing for this between the crew and the helm is very important and not an easy thing to get right.

If it's light to medium wind conditions, you can survive with some speed by cleating the sheet and steering to the wind although you will find that some small sheeting changes will greatly enhance your speed. If it's medium to high wind conditions and choosing between one or the other, you're better off holding the helm steady and sheeting the mainsail in and out....but again, to do both in concert is faster.

With a gust the apparant wind veers aft. For that reason you can wind up. However you have to wait for the boat to accelerate. The apparant may turn back and luffing is useless. In heavy wind it may be a bit different as the boat do not accelerate as much as in medium wind.

????

Draw the vectors Paul; Best way to understand this is take it to extremes.

If we are sailing up wind (at say 45 to true) in 1 kt of wind and we are travelling at 0.5kt; this will result in the apparent wind being somewhere forward at (guess) 30 degrees. Now make the wind jump to 20kts and the wind component vs boat speed component means the apparent will move aft (the angle will increase).

Simon, thanks for that - I hadn't considered that effect properly myself either.

It's commonly called a "velocity lift". The reverse effect - when you sail into a lull, is known as a velocity header.

Regards,
Eric

When you sail in a lull it is useless to fall off as the headwind turns with you. The best is to go on and wait till the wind picks up again. So not the opposite of what you could do with a gust (luffing).

Hi Leo,

that's true, however it is less pronounced as on monohulls. Most beach cats have a very flat up wind vmg curve. That means it doen't matter if you go 50deg or 60deg to the true wind direction, the vmg will be pretty much the same. Also due to the high speed of a cat, the changes in apparent wind direction are smaller. Loosing speed due to excessive tiller action is far more worse.
I try to do steering as a fine adjustment of heeling angle and waves and do the big stuff with the sheet.
Keep the speed up, more speed is more lift from the foils. With speed you can point higher, with speed you can manouvre more quickly and with speed the boat behaves better in waves. Go first for speed than for hight.

Cheers,

Klaus

I'm no expert but my understanding is that by sailing a little bit lower in the lulls you will pickup a puff earlier as they move down the course.
IMHO sheeting, operating the cunningham, and steering as little as possible is the fastest.

Tony has it spot on, it is a concert between driving / sheeting and cunningham.

In a puff, ease main (talking inch or two MAX), point up a bit ( a degree or two). We generally ease main slightly delayed from pointing (i.e if point is going to take more then a degree or two, ease). If the main is constantly eased (i.e two inches of main sheet out more then it should be), cunningham goes on a bit to de power main.

On the F18 (at least C2 / Capricorns) the crew does main and cunningham as they can sheet in and out faster, this also requires a lot of practice and good communication with skipper. The skip takes the main in lighter air (and of course downwind).

Side note: if the cunningham is max on and you are still overpowered, take a look at diamond tension, probably could be tighter.

This is a great discussion, I've been trying to come up with a good 'rule of thumb' for how to handle this myself and had been under the impression that you want to keep the sheet on and play the traveler in the puffs to prevent the main from getting too much shape, power, and drag. Playing the traveler can be tricky, I've found that it doesn't always want to move when the sheet is fully on, looking forward to playing the sheet this coming weekend instead. Thanks guys!

Erm, ease the traveller. Diamond tension does a number of things depending on spreader rake.

Also note that with a straight traveler in-line with the rear beam, the action of releasing the traveler down the beam actually sheets the mainsail in tighter.

1) set diamond wire tension for the conditions anticipated that day
2) upwind sailing, work the downhaul to control power in gusts combined with some light helm corrections.
3) upwind sailing, when the downhaul is no longer enough to control the power in the boat, the crew needs to set the downhaul in a moderate to upper position and start working the mainsheet in and out slightly...again in conjunction with some light helm correction.
4) when it's getting really sporty upwind, and the crew is having to really saw the main in and out deeply, it's time to drop the traveler an inch or two and leave it there. Continue working the mainsail and helm.

And if that’s not enough; bring the plates up a little might help. If it get really sporty; max downhaul; and de-rotate the mast.

you would think that with all this emphasis on playing the downhaul, they'd make that line a little more forgiving on the hands.... But maybe it's just me and my house bi*ch hands...

Great thread. I also have been playing the travler w secondary adjustments by steering. I will be going out tomorrow and will try using the downhaul and sheet activly and leave the travler alone. I just doubled my purchase on the downhaul, so I think this is more viable now. Thanks for the info.

not sure i know what the upper position of the downhaul means (#3)

How would you set the downhaul in situation 4?

situation 4 give the downhaul all the cowbell you have. MORE COWBELL!

make the top of that sail flap in the breeze ,make the mast look like a banana, and the sail flat as a pancake?

hm, I don't use the downhaul without using the rotation. Pulling the downhaul only opens the leach and the lower part of the sail stays full. Thats good in waves and chop, but in most cases it is better to make the whole sail flat (=rotation plus downhaul) not just the top. But this might be different from boat to boat, sloop or uni, conventinal or wing mast.

Also I don't play the downhaul/rotator all the time (again depends if you are single or double handed). Better concentrate on course, sheet and pitch trim and only correct the big stuff with the sail trim. Maybe not the fastest way, but works for me.
Cheers,

Klaus

gotcha thanks

Mine is 16:1 on a cascade system. Works very well.

As you pull the DH you also SHEET IN that flattens the sail.

yes, but mainly in the top, because the lower part of the mast is still stiffend by the diamonds, if rotated out.
Here is a link to Landenberger sails: trim guide , which fits well to my mast. When I remember back on the Tiger, we used the rotation only between up and down wind, but not with different downhaul setting. Not clear if it because of the jib or the mast profile or because I sail better now (at least I think that I do).

Cheers,

Klaus

hm, it is maybe of the straighter leech...

For those new to these adjustments...here's what found out when first learning them (Charlie Ogletree's advice to me):

1. Stay off the downhaul until you're double-trapped and still unable to depower easily with an arm's length of main sheet out. If the hull is popping up rapidly, then start inching on the downhaul until you find more control.

2. On many boats, as you apply DH, inch by inch, be sure to sanity check how much you've applied. If you put too much on for the conditions, boat will be slow, flat and require you to foot off hugely to get the hull out of the water...bad for VMG. In high wind days, Charlie stated my boat had the flattest sail in the fleet, we were footed 10-15deg lower than everyone and we were still popping the hull up (cause of the wide angle to the wind gusts). Note that when easing the DH, the sail may not actually move back up the luff track until the mainsheet is also eased momentarily...that's important! Otherwise you think you've eased DH...then crank on more at the next gust, then "ease" and repeat...ultimately you've got a sheet of plywood/barndoor for a mailsail and you've lost your race.

3. going to weather the crew sheets the main, anticipating gusts and lulls. When hull raises too far, crew eases just enough main to control the hull height...then immediately re-sheets BEFORE the hull starts to drop again...if you wait until it's on it's way down, it will likely hit the surface and slow you. If crew has to move more than 1 arm's length to maintain hull height, and you're double-trapping, then start inching the DH on.

When we starting mastering this technique, our performance went huge. Boat feels like it's on rails...each gust squirts you forward, not up in the air.

The flatter the sail, the more forward the liftcurve (lift versus draft) goes, the higher you can sail. However the forces are lower and it will not deliver the best vmg.

I'm with you.. I think keeping the sail in a contant shape is important. I like to run the traveler from the crew spot amd let the skipper steer and use the main as a last resort to depower.

Leave alone the traveller. It closes the slot. Mainsheet is better.