When will new ideas be adopted?

There have now been quite a few companies adding wind assistance to large ships. It's not a primary source of power, but just to save some fuel. Since they have not been tested very much they usually rely on computer models to predict how much fuel they will save and make their claims accordingly. It's becoming important to ship operators because of IMO United Nations rules which will take effect soon. They don't do tacking on these large ships, but just make use of the wind when it is favourable and coinciding to their intended direction. As far as I can see heeling does not occur or only very little. Neither have they fitted extra keels. More in formation here: International Windship Association | Promoting Wind Propulsion Solutions for Commercial Shipping https://www.wind-ship.org/en/grid-homepage/

 

Because they are towers and they suck! suck air that is.

 

There are 2 companies which use the "Turbosail" which they have re-named "Ventifoil" from the company Econowind and "Esail" from Bound4blue. Both these companies have done assessments and decided the "Turbosail" idea is the best way to go forward. Why don't they use them on aircraft? That's a very good question and one that I have asked myself.

Most of these new systems would take the effort out of sailing and would be a benefit to older people who are not fit enough to use normal rigs and the disabled. In other words make sailing easier.

 

I think, in many cases, winches would be a relatively inexpensive way to make conventional rigs easy for older people to use. Particularly rigs that aren't made for racing. Maybe a cat rig with some kind of roller furling and a wishbone boom.

Anyone who could afford a Turbosail for a recreational boat is probably slowed down by their fat, heavy wallet, so it ought to work for them.

Given that kind of budget, would a Turbosail be better than a two part wingsail? It ought to be able to handle one of those without much exertion.

Do you have any figures for the L/D of a Turbosail? What's different about them that would avoid the problems which aircraft have faced with powered lift, boundary layer control, etc?

It's probably not great for recreational sailors who don't want to put a lot of physical effort in, but I wonder if some kind of semi-automated power kite might be better as supplemental propulsion for ships. One advantage is that they can be stowed when there's a storm. Another is that the wind is much stronger higher up.

 

I don't have figures for Turbosail. But even if the lift to drag is better than a wing on a reach, I think the drag of the cylinder when head to wind would be a drawback.
I don't think you could buy one because no-one makes them. Needs someone to take a risk, test, and come up with a cheap example.

Even an effective single part wingsail is designed which would very easy to work without exertion. See www.windthrusters.net/simplicity.html

 

A single part wingsail with a symmetrical airfoil and no flap will be less powerful than a sail. It wouldn't be all THAT much harder to make it with a two or three element foil that changes shape. Then you'd have something.

 

The jury is out as to whether a symmetrical airfoil without flap is less powerful than a sail. Close hauled, the wing will score because of it's better L/D ratio.
Off the wind on a broad reach a sail might score because of greater lift and drag not counting any more. Several boats have been built and sailed successful
with single element wings. https://www.wind-ship.org/wp-content/uploads/2014/11/wwt_photo-700x325.jpg Saildrone and

These boats used single element for the sake of simplicity. But I admit a 2 element wing may be better in some respects especially off the wind.

 

Try the AYRS archives.
I define "average sailor" as someone who wants to use the boat in a general way, not for a specific purpose only like racing. The problems of the rigid sail remain the same since first tried: behavior in gusts, in high winds, at anchor, in marinas. All have to do with the ability to depower the sail effectively. Actually sailing a rigid sail under specified conditions is no big problem, all the rest is.
A saildrone does not have to care about crew comfort and you don't see them in marinas.
Operating a boat is a complete package and plenty of the limitations have nothing to do with pointing ability or speed.

 

As a members of AYRS myself I would like to refer you to an article on the "Catalyst" issue 49 by Peter Worsley about the his experiments with self-trimming
wingsails both in model form and fullsize it was found that there is no problem with behavior in gusts, high winds and at anchor. The wingsail system he
advocates works regulates and controls the wing in the same as an aircraft wing and they have no problem with gusts, or high winds. The Walker wingsail was of a similar design - it did
well and crossed the Atlantic several times. Saildrone have done nothing to fit their power system on any cruising yachts, maybe they should. Considering they
can work autonomously the use of their system would certainly make life easy for the sailor, particularly for anyone getting old and not so fit and the disabled.

 

and now do a recreational boat that gets 20-30h of engine time per year. If a real enthusiast maybe 150 hours.

Suddenly there is no time frame where such energy saving investments would ever pay themselves back.

Going slower would be the number one practical choose for energy conservation.

 

That's like asking how many average drivers have tried F1 paddle shifters.

 

No it's not. A sail can reach a much higher lift coefficient than a symmetrical airfoil. I suppose the wing might be more powerful if it was made significantly larger than the sail. Of course, that means a low aspect ratio. A suitable cambered wing, one with flaps, etc. will have a higher L/D than a symmetrical foil.

 

The sail can reach a higher lift coefficient than a symmetrical airfoil. But it cannot obtain a better L/D. Your graph does not include sails. Airliners typically use nearly symmetrical airfoils during cruise where the best L/D is required - without using their flaps. The B17 bomber of WWII used a symmetrical airfoil wing.

 

To me, the Eppler 378 bears a REMARKABLE resemblance to a sail. I tried increasing the leading edge radius to simulate a mast, but the L/D numbers were still much better than for that symmetrical foil. I'm sure if you went with an old gaff rigged cat with a mast the size of a tree, cut poorly, the L/D would be comparable to a symmetrical section wing mast.

I realize some aircraft used symmetrical foils, but a lot of aircraft, perhaps the majority, didn't. I don't think that proves anything.

Anyway, if the boat is able to carry a sail of a certain size, for equal power with a symmetrical airfoil, the wing will have to be much larger than the sail. Sails are pretty big already. When I look at these designs with symmetrical foil wing masts, they generally have less area than sails would, not more. So maybe your wingsail boat is going 2.5 knots at 35 degrees from the wind, 2.17 knots made good to windward, while the sailboat is going 45 degrees off the wind, making 5 knots, or 3.5 knots made good to windward.

A B-17 may have had a symmetrical airfoil, but plenty of other aircraft don't. As long as we're throwing famous airliners around:
DC-3 2215 root 2206 tip cambered
DC-4 23016 and 23012 cambered
DC-6 ditto
DC-7 ditto
We could also look at sailplanes, where L/D is king
RJ-5
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Oops. The computer ate my homework. Suffice it to say that the RJ-5, Schweizer 1-26, and Schleicher ASK-15 all used asymmetrical airfoils. So citing particular examples doesn't prove anything.

In any case, the word in question was powerful. A sail doesn't have to have a better L/D to be more powerful.

 

As you say the Eppler 378 does look like the "perfect" sail.
But there really can't be much in it that Boeing would choose it for their heavy bomber with a wing that was required to lift heavy weights of bombs.
Then there are aerobatic aircraft that happily fly around with symmetrical airfoils. I'm not saying that symmetrical are better just that they still work
much better than many people believe. There is another reason why a wingsail designer might use symmetrical - if they want the wing controlled
by a tail unit - symmetrical is better because the centre of pressure does not move unlike cambered designs. I hear what you say regarding VMG.
A symmetrical wing can be amazingly efficient as shown by this video by Peter Worsley the model boat
cannot be pushed back by the wind. Imagine if this could be achieved by a full size boat!