Leeway - sail adjustment

[Magic_Sailor]

Is it just me.

Wanted to get as much as poss out of lig wind yesterday.

Moved mainsheet car right up to windward. Eased kicker. To allow mainsheet to be fuller.

Leeway seemd to increase a great deal.

Did it really? And if it did...why?

Magic

 

[Cornishman]

'cos you had your main too tight and all it was doing was taking you sideways. A common error - usually with the racing fraternity who think that sailing close hauled about 25 degrees from the wind looks good. No matter how many they have sitting on the windward rail with their yellow wellies hanging over the side the yacht goes faster sideways than it does forward. Looks good for the cameras, tho'
Ease your sheets (main and fore) just a tabnab, bear away about 5 degrees - leeway disappears and over the ground you will make better progress to windward.

 

[bbg]

Adjusting the sheet/traveller/vang will affect twist, not fullness. To make the sail fuller, ease the outhaul and the cunningham (or halyard). In really light wind I would have a bit, but not too much twist in the sail and the boom slightly to leeward, definitely not right on the centerline.

If you thought you had noticeably more leeway, it is could be because you stalled the main by bringing the boom too close to/above centerline.

 

[Rob_Webb]

Replies below pretty much cover it. Always better to foot it in the light i.e. drop down 5 or so degrees and sailing faster rather than higher. Only come up as apparent wind increases. If you're into your instruments and want proof that a lower faster beat can be better than a higher slower one then check out how your VMG (velocity made good) varies when you are beating towards a windward waypoint. Try different modes (combinations of sail and height of course) and see how boatspeed and VMG vary. All good stuff and not just for the racing boys. Can be important when cruising too and can the difference between making it home before the weather turns or not.

 

[Twister_Ken]

You can heave it up on the traveller, but let off sheet to keep the boom just below the centreline, and the top batten parallel with the boom. Let off other main tensions to make the sail fuller than normal (but not too full if the air is very light, or the airflow will not stay attached).

BUT, if you do this you also need to make sure you haven't opened up the slot too much otherwise it becomes counter productive, so you may also need to rig a barbour hauler on a tweaker to pull the genoa sheet lead inboard a little. If conditions are light enough to warrant this sort of fiddling, you might also want to move crew weight to leeward to induce some heel and help the sails fall into shape.

Trouble with this sort of set up is that it goes to pot in any sort of chop, so it's smooth sea stuff only. If there's a bit of a popple, it's worth just freeing off a few degrees with 'normal' sail tim and going for speed rather than pointing.

As to leeway, that's largely a question of a) whether there's sufficient laminar flow over the keel to prevent the keel stalling, and b) where in the sail plan the centre of effort is - too far aft and the sails are pulling the boat sideways, rather than forward.

 

[Magic_Sailor]

Thanks to all

To confirm - boom was a few degrees below centreline. Didn't adjust outhaul - (pain in ars on my boat).

Water flat.

Boat speed did increase markedly. But, probable closer to wind than I should have been judging from comment below.

Magic

 

[johnalison]

Re: Thanks to all

Glad to hear it. I used to think the seat of my pants would tell me all I wanted but now I have a VMG meter based on speed & wind I know better. In lightish winds, doing about 4kn, we do our best VMG much closer to the wind than feels natural as long as the helmsman is very sensitive and steady at the helm, since any marked use of the rudder is punished severely. In any chop I simply go for boat speed as I know from experiment that our VMG peaks with a speed of about 6kn. As long as speed is enough I can disregard leeway. In very light winds I put on the VMG meter, which is otherwise very tiring to follow.

 

[peterb]

Re: Thanks to all

Be careful. VMG has two meanings. One is velocity made good to windward, the other is velocity made good towards a waypoint.

If you have a wind instrument that is giving you VMG, then it is taking into account the wind angle and the boat speed to give you an estimate of the speed made good to windward. But it doesn't (and can't) take into account the leeway. As you bring the boat closer to the wind the speed through the water will drop and the leeway will increase. You don't have to stall the keel to get the effect, keel stall only happens when you have 10 - 15 degrees of leeway. But the wind instrument won't know about the increase in leeway, and will give you a false reading of VMG.

Most GPS sets can give you a reading of VMG, but in this case it is the rate at which the distance to the next waypoint is decreasing. If the next waypoint is directly to windward, then the VMG towards the waypoint will also be the VMG to windward, and this measurement will take into account the leeway.

It can be instructive to set up a waypoint a long way away to windward, then sail closer and closer to the wind comparing the VMGs given by the two instruments. The peak VMGs from the two are often from courses that differ by more than five degrees.