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Lazy Jack
05-17-2001, 04:42 PM
I need some advice from those who have had more experience with small boats and their rigs than I.

My gunning dory is gunter rigged with a horizontal sprit instead of a boom. The foot of the sail becomes sort of its own vang. There is a small jib foward which, when trimmed well seems to add a disproportionate amount of power. It seems to be well balanced with a light helm, I don't have to be dragging the rudder to keep from rounding up.

My question is about sailing to windward. Does there come a point when the sails drive to windward equilibrates with the windage of the hull and rig? I started out today with about a fifteen knot breeze and a reef in my mainsail. I was able to attain hull speed on a beam reach (all of about six knots)heeled over smartly. Every so often, an added gust would accelerate the boat noticably. However as I rounded up to about 45 degrees off the wind, the boat slowed although I still had enough wind to heel me over as much as I thought useful. The sails were sheeted in all the way but drawing nicely with the telltales trailing aft. But the gusts that had accelerated me before did nothing to my speed and only served to heel me over more.

Now perhaps 45 degrees off the wind is too optimistic for a dory with a gunter rig, but from my observations, it would seem that there comes a point when more wind or more canvas does nothing for you. The boat has a speed it will go for any point of sail closer than a beam reach, and no amount of wind or canvas will bring it to hull speed. If I am correct, it would seem better to reef early and sail comfortably with less sail than to strain the hull and rig with more canvas than the boat has use for.

Can anyone provide me perspective or steer me in the right direction?

Thad
05-17-2001, 04:55 PM
Sounds like you're doing good to me. Sounds like good sailing. With a centerboard as you heel you loose lateral resistance. The more you sail upright the better the "dig" of the board and rudder, not to mention less way lost in the gusts. Generally in boats of this sort you don't want to sheet in too close either, though your telltales may be telling you are getting good drive you should play with a slightly looser sheet and see if your true windward achievement is better or not. Fun.

ishmael
05-17-2001, 05:17 PM
What Thad said. I'm no expert, but probably the biggest mistake people make with these kinds of rigs to windward is to pinch. The boat will perform much better, and get you there faster, if sailed a bit off the theoretical highest point of sail, and with sails a bit less than completely sheeted in. That said, your approach of going out and getting the feel for it is really where the heart of it is. Sounds like you are well on your way to sensing how sail set, reefing, and how high you are pointing effect performance. It is one of the joys of a small boat with a simple rig that the feel is more intimate, and if you pay attention you develope a sense of what the boat likes more quickly than in a larger craft. Keep at it, and have fun.

P.S. Another little trick. If you find you've got too much sail up going to windward, and, for whatever reason, you don't want to reef. By easing the mainsheet, and leaving the jib sheeted in, the wind off the jib will deform the foil of the main and de-power it.

[This message has been edited by ishmael (edited 05-17-2001).]

Greg H
05-17-2001, 06:50 PM
I don't have much experience in little boats, but I'm learning. I've got one with the same rig but no jib and she doesn't like to be trimed in to tight. Try shifting your weight forward a little bit going windward. Also in a puff, fall off and ease the sheet just enough to gain momentim and pinch her up again. Keeps me busy, have fun.
Greg

PugetSound
05-17-2001, 08:10 PM
Jack,
45 degrees off the wind is pretty good for this type of rig. The gunning dories (and any other dory for that matter) are primarily pulling boats (according to Gardner) which often were fitted with sails for reaching and running.

John B
05-17-2001, 10:10 PM
This is twice today I've been able to say this.
In a puff spring a luff, in a Lull keep em full.
Sounds like you are right into the age old dilemma of high and slow versus low and fast. You need to find the compromise which suits your boat best.
6 knots!!. thats tramping in a small boat.

Lazy Jack
05-17-2001, 10:21 PM
Well that, I suppose, is the most responsible position to adopt. I've been so engrossed in designing this rig, having sails made, building spars and rudder systems and finally putting it all together that I probably lost sight of the fact that this boat, like you said, was never really designed to be a sailboat. Reaching and running is truely exhilarating but any progress to windward in a hull with such narrow after sections and high ends like a dory has should be considered a bonus. So I'll consider myself content with the ability to progress upwind at all!

Now I'll go build me a sailboat...

Todd Bradshaw
05-17-2001, 11:55 PM
I think what you found is pretty normal. Even if everything is trimmed, balanced and working perfectly, almost all boats will be slower as you approach their maximum upwind sailing angles. Bearing off a bit and easing the sails is almost always noticably faster.

It's possible that the extra "power" provided by the puffs as you sailed upwind went mostly unused as the airflow became detached. The higher you try to point, the trickier it gets to trim things for it and the boat is often sailing on the verge of a stall. Also, with the sails trimmed in tight, less of the wind power is converted into energy that will pull the boat forward so a puff really needs to be strong to push the hull noticably faster, and while it's doing it, it's also creating more drag. This is why making a tack and immediately trimming the sails all the way in is usually bad. You need more power to get the boat up to speed. As the boat speeds up and the aparent wind shifts forward you can then trim in to match it. If you try it without bringing the boat up to speed, it'll just lean over and go slow or stall.

Once you're up to speed, it's all about V.M.G. (Velocity Made Good) and figuring out whether your boat will get from point A to an upwind point B faster by sailing higher and slower or lower and faster. The same is true sailing downwind - broad reaching vs. running. These days, a cheap G.P.S. with a V.M.G. readout is the best way to really nail it down. You can read your boatspeed and see how much of it is actually getting you where you want to go.
Even America's Cup boats have limits. They almost never sail them as high as they will point or as fast as they can go. Instead, they have "targets" which are predetermined boatspeed/angle of attack combinations that get them to the mark in the least amount of time for the conditions at hand. About the only times you will see them pinch up above the targets are when avoiding a right-of-way boat or when trying to squeeze up and make a mark without having to make another tack.
The good news reguarding all this theoretical BS is that you need to do a lot of research to figure it out...go sailing and have fun.

T.E.B.

Ian McColgin
05-18-2001, 09:59 AM
Can't wait to get yours & Leeward side by side. It sounds likely that your rig is more powerful and better balanced than my currently jibless version.

As for the sailing, Probably best sailing 5 or 6 points off the wind rather than pinching up to 4 points. Tacking through 90 degrees or less is perfectly normal for many modern and traditional boats, tacking through 100 degrees or more is not that odd.

Racers do a polar diagram of point of sail to speed and then transferr speed for the course to course made good on your rhumb line to determine the best effectivre course.

To take an extreme example that you can do in your head, contrast tacking through 8 points (90 degrees) v. 12 points (120 degrees). To make whatever distance to weather, you have to go about 40% further if you can only make 6 points off the wind. So you'd need 40% more speed. This is unlikely in normal conditions but once flogging down from Boston to the Canal in Grana into the teeth of 45 sustained with much higher gusts, we found that isosolese triangles was the only was.

Small course deflections are often advantageious. Five degrees further off the wind only requires a few % increased speed to justify. If we do hook up, I'll show you a table on this.

G'luck

Mike in SC
05-18-2001, 03:45 PM
Ian- would love ta get a gander at that table- where'd you get it? I'd ask further if it's teak or mahogany, but then ya wouldn't take me seriously. Happy Sails!

Ron Williamson
05-19-2001, 05:42 AM
Don't forget the racer's maxim,"If the windshift heads you,tack"
R

Todd Bradshaw
05-19-2001, 10:25 AM
You can see a polar plot at
http://home.pacbell.net/dtsails/C22-Spin.htm

There are some buttons at the bottom of the page that bring up more info, though I'm not sure how much as I didn't play with them very long. Polar plots have to be created for each boat design, so there is no universal plot that will fit generic boats. US Sailing sells polar plots for hundreds of common sailboat classes.

The best book discussion that I have seen on the subject is in Dennis Connor's book "Sail Like A Champion". It isn't a long section, but it helps make some sense of the plots that you see. Pretty good book, too.

Ian McColgin
05-20-2001, 11:46 AM
The polar plot is built on careful practice with a given boat. The table I referenced is in Don Street's "Ocean Sailing Yacht." I'm looking at Vol 2 where it and a companion table on leg lengths for upwind are at pages 578 and 579.

Example - a useful one for traditional boats that don't pinch up too much.

If your original angle to the TRUE wind is 50 degrees and you alter angle to:
% you may decrease(-) or increase (+) to maintain rate of advance.
(I don't know how to format colums here but the lables should be figuable.)

30 -25.8%
35 -21.5
40 -16.1
45 - 9.1
50 standard
55 +12.1
60 +28.6

This info is helpful in looking at actual conditions of the day. You may have found that 50 off the wind is your generic best place but for a given sea state, and this may vary from tack to tack, you can gain 15% speed by cracking off another 5 degrees while on the other tack it may make sense to lose %5 of speed pinching up to 45 degrees.

The table is built on true wind to make a constant for wider conditions. The polar is usually built from apparant since it's measuring pure boat speed rather than rate of advance. The faster you're beating to weather, of course, the more the apparant wind leads the true.

He also has a fun table for tacking down wind (p579).

Fun with trig.

John B
05-20-2001, 03:23 PM
Vector Victor.

Ian McColgin
05-21-2001, 10:22 AM
Over, Under.