Wing-drive

Are you saying that a fully rigged wing sail, left free to pivot has 10% of the drag of just a mast and rigging?

I find that just a bit hard to believe.

 

Hi Ari,
I have several Wing-Drive designs for Catamarans and Monohull.
Kjell

 

Scaled models of these 2 boats were tested in wind tunnel to compare the drag of the bare rig and the Wing-Drive in neutral position. The Wing-Drive has 10% les drag then the bare rig.

 

Oh, ok. A wing drive rig of half the height has 90% of the drag of a bare rig. That's more like it. Thanks for clearing that up.

 

The wing dimensions of the Wing-Drive is calculated to give the same driving force as the Standard rig.

 

Very interesting. At what wind speed? How much more area does the wing system have?

 

The Wing-Drive wing area is smaller than the sail area. The wings are more efficient than cloth sail and can handle stronger wind speed and are much safer as no crew has to reef or take down sails in stormy weather.

 

To equal the force of 500sq ft of soft sail, how much area would a wing sail rig need?

 

If you can tell me what drive force you have at X wind speed and X apparent wind angle I can give you an answer.

 

Wait a minute, you said that the wing was sized to give the same drive as the soft rig. If the wing has the same drive force as the soft sail, I just wanted to know at what wind speed you did the calculation.

Just for the sake of having some numbers:

in 20 feet per second apparent wind:
Working Sail (500 sq/ft) 480 pounds
Downwind (w/spinnaker) 1250 pounds
Apparent wind range 30 - 120 degrees

 

You must be a little more precise Do you means that you have a drive force of 480 pounds with 20 feet/sec apparent wind speed at 30 degree apparent wind angle?

 

Yes, 480 pounds force at 20 FPS with apparent wind angle of 30 degrees to the boat, more like 15 degrees to the sail.

But you don't need that information to answer my question.

I asked how much more area the wing had than a soft sail rig.

You said that the wing sail has less area for the same force.

To put in another way; Given a catamaran with 500sq.ft sail area, how big would the wing sail be to power the boat with the same performance?

 

I seem to remember seeng it stated that the best C Class rigs have around threetimes the lift/drag ratio of a soft sail. Bearing in mind that it doesn't seem unreasonable that you could have a wing sail with half the heeling moment of a conventional rig of the same power that also has 10% less drag when weathercocking dead to wind.

The fly in the ointment is the unsteadiness of the wind. With very varying gust, every downdraft, every bit of drag from a different direction will produce many times the drag of a pole mast until the mast gets back head to wind. In addition is more than possible for the wind at the top of the mast to be say 5 degrees different in direction to the wind at the bottom. So given a turbulent stormy see, although the theoretical drag of the wing mast would be less than that of the taller pole mast, its rather likely that the actual drag experienced would be more.

 

If you give me the dimensions and the weight of your catamaran I will calculate the size of the Wing-Drive that will fit your boat.
The wing with the same area as the sail is more efficient.

That is not the important question with the WING-DRIVE. The Wing-Drive is not a wing sail. It is a new wind propulsion system the only thing it has commune with sail system is that is converting the wind into propulsion power. The advantages are many. By dividing the wing area between two wings it is possible to reduce the height of the rig and eliminate the capsizing risk. It can safety be handled of non skilled sailor as there are no ropes attached to the boat and no sail to take down in stormy weather, The apparent wind angle is set with a single handle from the cockpit or inside the boat.

 

Here you are:

LOA = 37'1"
Beam = 21'5"
Draft = 3'9"
Displacement = 16,000 pounds
Main = 520 ft^2
Jib = 340 ft^2
Total area = 860 ft^2

What size Wing Drive?