Wing-drive

I thing I lear is newer to trust annything befour I see some data from independant sorces.

I'm natural sceptical to everything new.

 

That kind of depends on your definition of efficient does it not?

Besides, the "Wing Drive" uses two symmetrical foils in a biplane configuration, giving a claimed CL of 1.0. Since soft sails can generate CL 2.0+, the Wing Drive must have double the area for the same force.

 

There is one important point to keep in mind. The soft sails can generate CL 2.0+ only when the sail trim is 100% right. The Wing-Drive CL 1.0+ is there all the time independent of wind shift and course changes.

 

Wing Realities

I am new to the forum but not necessarily new to wing forums as some of you may recognize me….. These threads seem to come and go.

What I want to add to the fray is the notion of model versus reality. Plenty of studies especially 2D models and a VERY few 3D efforts interpret wonderful possibilities and theoretical performances. All conclude their treatise with caveats that not all factors are considered, nor are all variables and interactions included. Models and mathematical equations are an attempt to simplify the physical world in ways we can better understand. Therefore all are wrong as they cannot adequately describe truth.

So when we compare wings to something else, models and mathematical representation will never provide a fair assessment. Tip vortices, vertical air movements, eddy effects (non-constant stream), heel, rigging drag, sea motion and dynamic responses to all environmental factors place performances at substantially less than mathematical prediction. Combine all those and add the human factor for sail trim, non-optimal sail shape, and equipment wear & tear…… and you can really see some less than stellar outcomes.

You can review how dynamic sail performance plays out in the 2002 study “Comparison of Wind Tunnel and Full-Scale Aerodynamic Sail Force” http://www.engineers.auckland.ac.nz/~hhei005/publications/HPYachtHansenJacksonHochkirch.PDF The study compares a model sailboat at 15% scale in a wind tunnel versus a fully rigged 33 foot IMS cruiser/racer equipped with high tech DYNA force measuring devices. Net results was CL never exceeded 1.8 main + spinnaker, never exceeded 1.2 for main + genoa.. While interesting is the difference, more interesting was the correlation of model to reality.

If reality is less than predicted by other 2D studies, wings must either have higher predicted performance or change the losses. Many studies have shown, symmetric wings will not provide better than a thin foil with sufficient camber. A wing with flap, CL 1.6, does get close to thin foil theoretical. So advantages come from loss reductions, such as CD from upwind sailing. Typical thin foils sails have L/D of 5:1, so 20% drag loss resulting in heel or direct reduction of upwind power. 30-60:1 L/D ratio is probable with a proper wing.

As Kjell has noted, sails have to be set & trimmed. Wings take out the human error, to which I have been guilty on numerous occasions. Wings will without fail, maintain orientation to proper angle of attack.

Sails bag, sag, fray, and otherwise wear out. I had to change mine every few years. Only new the first day. Rigid wings by nature should not be changing shape, and only require recoat with epoxy after 20 years for UV protection.

Rigid wings will not beat a spinnaker for a direct downwind run. CL for a spinnaker with its camber and eddy effect is very good, 1.6 to 1.8. However, for broad reaches, the marconi rig cannot rotate it’s boom forward of the mast. A wing can pivot 360 degrees, so at broad reach the lift vector for wings is closer to Cfx than is possible from a marconi sail rig.

Lastly, in light airs a sail will not hold its shape, flog, luff, bang and whatever else. Mr. Prentiss is correct, a rigid wing will generate lift at low airflows where a sail cannot possibly work.

I surmise Kjell’s premise is that wings don’t perform theoretically better, nor are they expected to win the race against professionals using the latest sail materials. However, for the rest of us, they are likely to provide lift force in the direction of travel Cfx commensurate to a 20-30% larger Marconi rig while having substantially less heeling and drag forces. We can have all of that plus wing “drive”management from the comfy of my padded helm chair. Proof will come to those who try, but it’s not easy with lots of wing dynamics, vibration, balance, CE, weight and response to address. Otherwise we would all have wings on our boats and John Walker would be the richest man on earth.

JT

 

What about when in a full storm?

 

Wings & storms

The only recorded account of wingsails and major storm is Walker Wingsail "Blue Nova" and it's encounter with Hurricane Claudette. As noted by Kjell, wings that are feathered have no thrust. Wings can be set for minimal thrust to maintain rudder control and required headway. Something a sailboat is hard pressed to manage in winds exceeding 50 knots. The question the link below answers is hurricane force winds cause for shaking the wings apart, due to minimal off-angle gusting. The answer is NO ! Do you have to take the wings down for storms, NO.

The voyage of the Blue Nova does not answer what happens to boat in dock when encountering winds over 50 knots. Kjell's testing says no problem, wings stay rock steady into the wind with no objectionable forces or wing loading.

See link below:

http://www.shadotec.com/leisure2.htm

 

This means that the 2.0+ CL for main and 150% Genoa and the 2.5+ CL for main and spinnaker that US Sailing's IMS VPP shows on my boat's polars is 40% Wrong?

If the target speed is based on a CL of 2.0+ and the true CL is only 1.2 that would mean that only 60% of the driving force is present. The boat speed predictions are based on the drive force. A 40% reduction in drive force would mean that no boat could come close to their target speeds. I haven't heard that people are missing targets by 40%.

Of course the same people that came up with a VPP that over estimates the drive by 40% could have also made an error and under estimated the force to drive the hull by 40%. That would explain boats being able to sail to their targets.

How likely is it that the IMS VPP is exactly 40% off one way on the sails and 40% off the other way on the hull?

Someones numbers are VERY wrong.

That would be a very neat trick ... a wing sail on a boat that outperforms a 30:1 AR competition sailplane. Probable? LMAO

30:1 AR for a 500 sq ft sail ... would have a 122 foot mast and a average chord of 4 feet. Just how are we going to see a L/D of 30-60 with an AR in sailboat range? Have you done the math?

Even using the suspect 1.2 CL from the link. That is still 20% more force from the same area soft sail. When you compare CL 1.0 to CL 1.2 x 130% Area what school of physics comes up with greater force?

At AOA of 15deg the Wing Drive has 100% force aligned with the direction of travel at somewhere around 75 deg apparent wind. On every other heading there is a heeling component that reduces the available drive.

The wing drive would have to be able to overpower the boat at 75 deg AWA in order to drive the boat on other courses where only fraction of the power is driving the boat. That requires area, since the foils operate at CL = 1.0.

The wing drive must have more area to equal the drive of soft sails except in the small subset of conditions where the soft sail cannot maintain its shape. In those conditions even at CL = 1.0, great area is needed since velocity is so small.

 

This relates to an aerodynamically perfect double surface outboard flexible wing superior to presently used kites, with my control system.

 

advanced sail prpulsion

This relates to an outboard aerodynamically perfect double surface flexible
wing superior to presently used kites, with newly developed control system.
Use for fishing: There is nothing on the deck which would interfere with fishing
equipment. The sail can remain in power near zenith, boat stationary.
Behaviour in heavy storm: Needs to be changed for small version. In the
unlikely case of capsizing the hull without mast and rigging is automatically
righted by the lines wound around it. It is more seaworthy, roll drastically
reduced, heeling eliminated.
Speed: It works above the wind gradient, in full blast of laminar air. The effects
of the sail force, its component forces and removal of unnecessary parts, on
one actual world records holding cross-oceanic sailboat will result in saving
approx. 40 per cent of displacement, on already fast boat.
Handling: Large size sail can be handled, including raising, control and
lowering by one person without much physical effort. It is self-adjusting,
Downwind use: One sail will perform in all modes, including spinnaker. Regular
spinnaker is an insult to the gods of aerodynamics. In very low wind, tandem
configuration can be used.
Other uses: As a backup powerful propulsion for motor yacht, hidden in a small
trunk.
Comparison to traditional sails: Any comparison could be interpreted as a
savage attack or disrespect for tradition.
Any comments, questions, encouragement / doubts?
I hpe I did not mess this up, I am a newbie, having hard toime finding how to make new thread.

 

Let' sailling on Wings!!!

 

I have one too..... see picture..... it is a keel. But seriously, this wing sail already have follower in the world? Very rare to see one......

How much to make one for a 65 ft monohull?

 

Wing Realities

Someones numbers are VERY wrong.

I agree someone has bad numbers…….. The 2002 report was published and presented in open forum. In spite of all that, no one ever seems to ever present the raw data for scrutiny. But what is of concern is an interesting comparison of both reality and model results. 2D studies cannot be corroborated with reality due to so many mitigating factors. CD, CL and so forth all rely on the assumption of infinite span length. I do modeling for my company and always require confirmation of assumptions do not degrade the usefulness of the model outcome. I suspect many aero studies when applied must go back and adjust to fit the environment. Tall masted Americas Cup boats may make close approximation of the study conclusion while shorter, smaller craft may be so confounded by tip vortice, surface effect, and hull interactions to make a mockery of the calculations.

That would be a very neat trick ... a wing sail on a boat that outperforms a 30:1 AR competition sailplane. Probable? LMAO

30:1 AR for a 500 sq ft sail ... would have a 122 foot mast and a average chord of 4 feet. Just how are we going to see a L/D of 30-60 with an AR in sailboat range? Have you done the math?

Eppler 472, Re 500000, CL/CD=50+, not sure why you think that 30:1 cannot be accomplished ? 2 wings 35 feet high 8 foot chord, not so much different than sizing for a walker wingsail. Weight 450 pounds, which also not so much different than Mast/boom sail & rig for similar sail area.

Not sure where the assumption CL of 1.0 comes from. CL max of an Eppler 472 & others is 1.2+ At Re 500000 and above.

Wings CF match Cfx at 112- 115 degrees AWA not 75. Anything beyond 75 or so my Marconi rig ends up smack against the shrouds and therefore loss of sail shape. CD takes over as the sails are bagged per normal sail management. I consider the wing an advantage as it continues to use normal lift and can pivot to apply that lift.

For light airs at 4 knots I have done the math, which puts my sail force for this typical light air application near a Honda BF15 outboard @ 2/3 throttle, which satisfies my needs. Someone else may not suffice, and turn on the iron genny. My 36 ft Jeanneau rig would only flop around.

Bottom line, it's within expected engineering feasibility to make wings adequate performers as compared to a properly sized sail plan. There are disadvantages such as live response at all times including dock, and who know if the birds plan to make nests on top, but that will be challenges after their application. I do believe John Walker did plenty of study and spent a huge amount of money on R&D to make performance commensurate with sailing rigs. I think for the rest of us we don't need the fancy computer control.

 

I've found that 3D lifting line theory agrees with the real world pretty well. Performance numbers and angles are close to what I have experienced on sailboats.

No argument that airfoil sections exist that have L/D > 50:1, but not entire aircraft. L/D > 35:1 is very good for a sailplane.

35 x 8? That is a AR of just over 4:1, correct? Plug in 1.2 CL and calculate the CDi, what L/D do you get? Not 30:1

The Wing Drive uses symmetrical foils and the designer uses CL=1.0 for calculations. I'll not argue with that number.

You are correct, I messed up my quick vector drawing last night. The CF = Cfx angle is 90 deg plus the AOA with a correction for drag. My error.

No argument about light air sailing. A rigid foil will do better than a soft foil when there is not enough wind to hold the soft foil's shape. However, the soft foil has variable camber, the Wing Drive does not. As soon as the sails are shaped properly the soft sails will develop more power. (for the same area)

 

http://www.cookeassociates.com/imagegallery.html

After that I was invited by John Walker to make a test trip with the Zephyr 43 I started a new point of view of how to use wind propulsion as a Safe-Simple-Sailing System and the WING-DRIVE was born.

 

CL of a soft wing

I am thinking of making a model using a soft wing approach what kind of CL could i expect. As it would form a asymetrical section. I dont need to worry about wether the boom will hit anyone or nesting birds just how fast itl go. i was going to make it with an AR of 3.7.
Will the low reynolds number mean that it is less efficient that a normal soft sail?