Motoring under sail

[John Kogel]

I watch sailboats and wonder why the 'captain' has

sails up when there is no wind? They motor along with the mainsail up, or sometimes just a big jib.

Answers are varied, too lazy to drop the heavy sail, maybe the wind will pick up, boat looks better that way, etc.

Some of these fair-weather sailors actually claim this one -The motion of the air past the sail is pushing the boat. Is that hogwash, or what?

[kurt]

There is an effect in sailing called "apparent wind", where planing hulls/windsurfers/some multihulls, can sail faster than the actual windspeed, sometimes twice as fast. Moving through the wind, one can actually get up on a plane by sailing with apparent wind and not actual wind direction. It's kinda hard to explain, having to do with vectors, trigonometry, and lots of other stuff I don't understand, but its' real.

I was big into windsurfing for about 30 years. When sailing too tight to the wind, I might not be able to plane. I'd bear off a bit, pick up slightly more speed, then once planing, head back up to the original tack still on a plane. I was able to continue on a plane at a high angle of attack and speed due to the benefit of the apparent wind created by the faster speed.

There are those that think by having the mainsail up, one can get a little boost from apparent wind if they are sailing on the appropriate tack. The motion of the wind against the sail could be creating some apparent wind benefit. Maybe, I don't know.

We used to keep the main up because it adds stability to the boat. Deep keel sailboats are not comfortable when just under motor power; they pitch around and kind of bob in the water; very inefficient, they're not made for motoring. Add just a little stabilizing power from a sail, and they stiffen up and one can make better headway than just by motor alone. We never thought about apparent wind, we just wanted the boat to stiffen up and punch through the water efficiently.

Interestingly, the jib alone gives more stability than the main alone. The real driving force is the jib.

[John Kogel]

Stability makes sense and is probably the best reason.

I suspect the boat has to reach planing speeds to get any benefit from apparent wind. At the slow speed of a motor-sailer, I've got my doubts. May just have to buy a sailboat to find out. []

[kurt]

My rule is..... anyone with a boat gets to do whatever they want whenever they want to, and make up whatever reason they want for doing it.

[Tom Raymond]

I have found the best means of boat ownership; borrow someone else's. Bring them back cleaner than I found them, and with at least as much fuel. A day on the lake for $30 is hard to beat.

These are my parent's toys. There are kayaks on the trailer between the logs of the barge.

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[Charlie R]

Boats under sail have the right of way on the water over a prop driven boat so even if the boat is using a prop, if the sail is up, that boat has the right of way.

[Marc]

Boats under sail have the right of way on the water over a prop driven boat so even if the boat is using a prop, if the sail is up, that boat has the right of way.

That's the first thing in this thread that makes any sense to me but then I don't sail.

Marc

[John Kogel]

Boats under sail have the right of way on the water over a prop driven boat so even if the boat is using a prop, if the sail is up, that boat has the right of way.

That's the first thing in this thread that makes any sense to me but then I don't sail.

Marc

That is another of the multi reasons given for having sail up. It forces Motorboat operators to give the sailboat the right of way.

[kurt]

That's true. And sometimes, they even do it.

[John Kogel]

And does everybody that drives a boat know what this flag means?

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It means there is a diver in the water somewhere in the vicinity of the boat, right? So when I heard a horn going off the other day I couldn't believe I was witnessing a 40 foot motor launch passing within 20 feet of an anchored dive boat. It is lunacy out there. Yep, everbody does whatever. []

[kurt]

Yeah, it can get nuts on the water. My "rule" doesn't mean forgo safety or disregard others, but the average boater thinks it does.

When I'm on the water, my first maneuver is usually get far offshore ASAP to get away from the nutjobs.

[Garry Sorrells]

There are a variety of sailboat designs. The type of hull, the number hulls and the design of each hull makes a difference in what each boat is capable of and how it reacts under different conditions. Then you have to introduce the type and kind of rigging and sails as additional factors for each boat.

-Motoring with sail can add some stability.

-Sail may pick up some air and increase speed.

-Sail may pick up air and decrease fuel consumption.

-Sailboats have what is called max hull speed. Meaning that it only goes just so fast. To go faster you have to be planing/lifting of the the hull, which is very difficult on displacement hulls. Planing is far different in a sailboat as opposed to a power boat. Planing/lifting or surfing can occur with a mono hull going down wind under certain water/wave conditions. You also can exceed mono hull speed when surfing/falling/sliding down the back side of a wave.

-Not the end of an explanation just the meager beginning of the why sailboats do or how they work.

Kurt is right. It can get nutty on the water and it does not mean the lack of ability nor experience but only poor judgement of a situation that may cause a problem. Kurt may agree that one of the biggest concerns is what others are doing and how it will adversely effect you, always looking over your shoulder.

Then on the other hand for a few dollars you can go out and kill people and need little to no skill or ability.

OH.... The last question on OP. Pushing the boat (no wind-0mph) and using sail for increased speed from lift by air going over sail is basically poop. Can it be achieved? Yes but it will require what most boats do not have, sails that can be independently fixed shaped.