Anonymous wrote:

The simplest place to spot the lift and drag angles is at the Windex. The lift of the sail will by definition have to be at 90° of the arrows pointing direction, while the drag by definition points the opposite direction of what the arrow does.

Now, if we manage to point and sail the boat as closely as 30° from the apparent wind, then we can decompose the lift and drag  force vectors (Fl and Fd) into two sets of force components running along the ship’s CL, and at 90° to it (I cheat a little, disregarding the little leeway angle of the boat)

The sail’s lift, Fl, will produce
a boat driving force of Fl x sin30° = 0.5 Fl
It will also produce
a boat heeling force of Fl x cos 30° = 0.87 Fl

The sail’s drag, Fd, will produce
a boat braking force of Fd x cos 30° = 0.87Fd.
It will also produce
a boat heeling force of Fd x sin 30° = 0.5 Fd.

Only if the lift is sufficiently stronger, (say 3 or 4 times) than the drag, will this result in the boat going forward.

If I get my sums right, and I guess that
the sail’s lift/drag = 3.0, then..

The resulting net driving force will be
0.21 Fl  -  that is only 21% of the lift,

and the total heeling force will be
1.04 Fl  -  that is 104% of the sail’s lift.

It’s a wonder we can sail to windward at all...

Thank you Arne, I am about to sail from NW Spain, bound for England. A certain amount of the distance is likely to be to windward. I will look at my burgee with new eyes. (I had a windex, but it jumped off the mast).

Asmat

Asmat wrote:

 The fact remains that boats with cambered sails heel more than those with flat ones. They are also less close - winded, but I concede that cambered sails are more powerful and make better progress to windward.

I am not so sure about that. My first, flat junksail on my Albin Viggen, Malena, did never let me sail as closely to the wind as later cambered sails. Even when the wind was strong enough to be on the edge of needing a reef, we still pointed lower, although the performance gap was smaller in strong winds than in  light wind-conditions.

My conclusion was therefore that the flat sail could never produce as high lift-to-drag ratio as the cambered sails. That is still my view. 

Arne

PS:

The simplest place to spot the lift and drag angles is at the Windex. The lift of the sail will by definition have to be at 90° of the arrow's pointing direction, while the drag by definition points the opposite direction of what the arrow does.

Now, if we manage to point and sail the boat as closely as 30° from the apparent wind, then we can decompose the lift and drag  force vectors (Fl and Fd) into two sets of force components running along the ship’s CL, and at 90° to it (I cheat a little, disregarding the little leeway angle of the boat)

The sail’s lift, Fl, will produce
a boat driving force of Fl x sin30° = 0.5 Fl
It will also produce
a boat heeling force of Fl x cos 30° = 0.87 Fl

The sail’s drag, Fd, will produce
a boat braking force of Fd x cos 30° = 0.87Fd.
It will also produce
a boat heeling force of Fd x sin 30° = 0.5 Fd.

Only if the lift is sufficiently stronger, (say 3 or 4 times) than the drag, will this result in the boat going forward.

If I get my sums right, and I guess that
the sail’s lift/drag = 3.0, then..

The resulting net driving force will be
0.21 Fl  -  that is only 21% of the lift,

and the total heeling force will be
1.04 Fl  -  that is 104% of the sail’s lift.

It’s a wonder we can sail to windward at all...

   when sailing fully close-hauled, the main contributor to heeling the boat is the lift, not the drag. Surprise, surprise..

I am surprised. The fact remains that boats with cambered sails heel more than those with flat ones. They are also less close - winded, but I concede that cambered sails are more powerful and make better progress to windward.

Anonymous wrote:

In "Cruising Yachts: Design and Performance", Harrison Butler says that you can disregard the C of E and the CLR. What matters for a balanced helm is hull shape. A boat designed for good windward performance, with a lean bow and heavy quarters, will have more buoyancy at the stern when heeled, than at the bow. This will cause her to gripe.

Unfortunately, one disadvantage of a cambered sail is that as lift is increased, so is drag. More heeling is the result.

Jami, congratulations on your sail. I am impressed by what you have achieved.

Cheers, Asmat

That disadvantage, Asmat,

can easily be be put right by dropping a panel. I find that my boats are faster to windward with one or two panels down, if there is wind enough.

Btw, when sailing fully close-hauled, the main contributor to heeling the boat is the lift, not the drag. Surprise, surprise...

Arne

David, I did sew the sail according to your advice on the broadseaming and tucks. It's nice to hear that the job seems ok to your eye!

Arne, the boat seemed to have generous weather helm with the BR also. This surprised me, because the Galion was described as a very well balanced boat in all the testimonials I found.

A tiller lock would probably be of some use, but then again the boat likes to climb to the wind very eagerly, if I keep the tiller locked by hand. 

It could also be possible, that the boat is so directionally unstable, that I tend to take this as weather helm issue? 

To me excessive weather helm means the boat's tendency to turn to the wind very easily, with need to control the course all the time. At times the boat feels almost like a dinghy in this respect.

Strange.

The tiller forces don't seem too big, I think the rudder balance is ok as well as the ability to steer, even in the following wind and seas (although the boat starts to behave aggressively, as I wrote in an earlier post. Fortunately I don't like sailing ddw anyway :) )

I am planning to build a wind vane with David's plans, and a better balance/stability would probably make the system more stable as well?

Edit: Arne, no - I haven't shortened the top batten/s or the yard. I think the angle of the picture does a trick to the eyes.

Edit #2: The usntability is weird, because the Joe 17 I converted last year was basically a large dinghy, but I was able to put a simple sheet to tiller steering system and the course stayed for hours even in following wind.