New Wing Sail

[Manfred.pech]

VPLP - Van Petegham Lauriot-Prevost present a new wingsail design: http://www.sailingscuttlebutt.com/2017/04/07/wingsail/

 

[Doug Lord]

Reefble 360 degree Wingsail

Thanks, Manfred-very interesting!

 

[upchurchmr]

Very interesting.
Any other details would be very much appreciated.

It does look like a development system (they said so in the article).
As such it looks like a significant reduction in sail area compared to a typical rig.
Which is appropriate for development.

There is always a question as to the relative performance (when they get finished).

 

[redreuben]

Electrickery and salt water aren't a good combination, besides, I like pulling strings. Looks good though, the second "mast" was something I looked at for the split rig idea, I thought it would be too hard to engineer, looks like I was wrong !

 

[Konstanty]

I'm worried about wrinkles in the hypertension side.

 

[upchurchmr]

What is a "hypertension side"?

 

[Konstanty]

What is a "hypertension side"?

This is windward side of wing sail. Look at drawing in attachment. There all with wrinkles should be OK.

 

[bjn]

I don't believe their claim of twice the aerodynamic efficiency.
A sail of the same aspect ratio should not be far from its performance.

 

[redreuben]

Bjn,
Agree.

 

[Tanton]

tantonyachtdesign.blogspot.com Search: From JR to Elia.
Also on Boatdesign.net Tanton at the Design Gallery.

 

[Manfred.pech]

I don't believe their claim of twice the aerodynamic efficiency.
A sail of the same aspect ratio should not be far from its performance.

Yes, I miss the experiments or tests which prooved the assumtion.

 

[Ilan Voyager]

VPLP do know their job. And their credits are impressive, they have designed more successful and innovative boats than any other NA office in the world in the history of yachting.
It's simply the most advanced NA and engineering office of sail boats in the world. It's a big office now and they have always been very innovative, with a very scientific approach and data acquisition since more than 30 years.
In the team there are top notch engineers in a lot of domains and they have a very vast web of consultants, independent and institutions. And they have access to very powerful tools for extremely complex calculations, plus wing tunnels and hydro. We are very far of the classic NA, compare more with aviation...
Marc Van Peteghem is now very implied in sustainable development, new bio composites and so on.

So the presentation of the sail is not dream, but a thing seriously designed. It's the prototype for the wings of a 88 m maxi trimaran yacht. You should read the wiki and I can tell you it's only part of their work...
https://en.wikipedia.org/wiki/VPLP_design

http://vplp.fr/en/informations-en/news-en.html

 

[John Perry]

I don't believe their claim of twice the aerodynamic efficiency.
A sail of the same aspect ratio should not be far from its performance.

I think it is possible. I am assuming that by 'efficiency' they mean lift to drag ratio.

If you do an internet search for 'forces on sails' or 'sail lift coefficient' you will probably find a wikipedia article with plots of lift and drag coefficient. The caption refers to a 'hypothetical sail', and there is also a plot relating to wind tunnel tests carried out by Gustave Eiffel in the early part of the last centuary. From this, information, albeit ancient and limited information, it would seem that the best lift to drag ratio for conventional sails is around 8:1. Doubling that would mean 16:1. Lift and drag data for aerofoils that are not a single sheet is far more widely available and better verified than that for 'soft' sails and it is well known that lift to drag ratios can exceed 16:1.

I think the lift coefficient at which the sail or wing is operating is also relevant. Wing sails have an advantage over 'soft' sails at low lift coefficient partly because the drag of the standing rigging and mast is present at all lift coefficients and partly because soft sails loose their shape at low angle of attack. At higher lift coefficient induced drag increases for both sails and wings, presumably reducing the advantage of a wing.

As it happens, over the past few weeks I have written my own software for predicting the performance of sailing boats. My main purpose in this is to compare performance with various configurations of lifting hydrofoil and for that purpose I dont think I need highly refined rig data, I just need a reasonably representative set of data that I can use with alternative hull and foil arrangements to estimate comparative performance. There is still a lot I would like to do on this, but I have got as far as producing one set of polar plots of boat speed for a trimaran with and without lifting hydrofoils. The rig data I have used is based on the data from wikipedia but I would like to see some better substantiated data with details of the rig it was measured on and the measurement method - the note on Wikipedia that the data is for a 'hypothetical sail' of unspecified type and size does not inspire confidence. So, can anyone here point me to lift and drag data for real rigs with 'soft' sails? Or for that matter CFD results. I know that CFD work is being done in this field but I guess it is commercially motivated so we probably dont get to see the results.

 

[Manfred.pech]

I think it is possible. I am assuming that by 'efficiency' they mean lift to drag ratio.

If you do an internet search for 'forces on sails' or 'sail lift coefficient' you will probably find a wikipedia article with plots of lift and drag coefficient. The caption refers to a 'hypothetical sail', and there is also a plot relating to wind tunnel tests carried out by Gustave Eiffel in the early part of the last centuary. From this, information, albeit ancient and limited information, it would seem that the best lift to drag ratio for conventional sails is around 8:1. Doubling that would mean 16:1. Lift and drag data for aerofoils that are not a single sheet is far more widely available and better verified than that for 'soft' sails and it is well known that lift to drag ratios can exceed 16:1.

I think the lift coefficient at which the sail or wing is operating is also relevant. Wing sails have an advantage over 'soft' sails at low lift coefficient partly because the drag of the standing rigging and mast is present at all lift coefficients and partly because they loose their shape at low angle of attack. At higher lift coefficient induced drag increases for both sails and wings, presumably reducing the advantage of a wing.

As it happens, over the past few weeks I have written my own software for predicting the performance of sailing boats. My main purpose in this is to compare performance with various configurations of lifting hydrofoil and for that purpose I dont think I need highly refined rig data, I just need a reasonably representative set of data that I can use with alternative hull and foil arrangements to estimate comparative performance. There is still a lot I would like to do on this, but I have got as far as producing one set of polar plots of boat speed for a trimaran with and without lifting hydrofoils. The rig data I have used is based on the data from wikipedia but I would like to see some better substantiated data with details of the rig it was measured on and the measurement method - the note on Wikipedia that the data is for a 'hypothetical sail' of unspecified type and size does not inspire confidence. So, can anyone here point me to lift and drag data for real rigs with 'soft' sails? Or for that matter CFD results. I know that CFD work is being done in this field but I guess it is commercially motivated so we probably dont get to see the results.

Thank you John for your explanation. Have you seen this: http://www.boatdesign.net/forums/sailboats/lift-drag-coefficients-sails-foils-1253.html and http://www.boatdesign.net/forums/sailboats/windsurf-sail-lift-drag-vs-alpha-25992.html ?

 

[Ilan Voyager]

The difference of efficiency is easily explainable.The wing, which can rotate on 360 degrees an important point, is a high lift configuration composed of 2 wings with a variable slot, or if you prefer a main wing with a flap. It's similar to the high lift devices found on a Boeing.
You can camber the wing as you want and insure with the slot an energetic ventilation of all the extrados side, plus an optimal orientation of the whole wlng to the apparent wind. The profiles are specially designed for the task, including the vibrating surface of the cloth which has very interesting effects on the drag.

Add the facts that the wing is rectangular, without the losses of a triangular sail. Add that the profiles are good all along the wing with the right twist, and that the wing works in a clean air flow as there are no cables nor spreaders. And last but not the least there are also 2 extremities plates.

Plus some work in wind tunnel and simulations on a big fast computer, you can determine the optimized set of configurations of the variables; total camber, slot opening and final orientation to the apparent wind and you make it automatic. In fact you create a configuration map like in the EPROM of a computer injection metering on an engine but happily that can simply be done with a mechanical system.
All that has been done before on the Class C catamarans and Amrica's Cup. The difference is that the VPLP wing is reefable.

The efficiency coefficient of 2 is rather conservative.