All true.

  The drone is a great idea, and may be just about perfect for its intended function.

  However, it's essentially a deep draft ballasted monohull that can flatten out in big winds and then pop back up.

  Three issues with that configuration for a proa, though:

    - If that wing were caught broadside with a weird gust, a multihull could be in a world of hurt. 

    - The feathering mechanism won't always react in time when on the hook in a big storm.

    - Without the ability to reef, a failure of the mast bearing could be a failure for the whole boat.


  I'd trust the system more on a boat that can absorb a big gust by heeling, and which isn't going to sink if stuck in a knockdown position (sealed hatches and/or positive flotation).

  I'll bet it would be awesome on an Admiralty 30.

---

  For a wing sail, I'd feel much more comfortable with a reefable soft wing on a round mast that won't present feathering issues even if a bearing fails.

  Current favorites:

    http://soft-wing.ch/en/
    http://wharrambuilders.ning.com/group/junkrigged

  Neither one requires electronics, multiple panels, or other items that could get in the way of quickly dropping the sails.

        - Mike

 

Here are some boring technical sail and wing trivia.

The secret to a wing is that its shape accelerates the flow of wind over the low pressure side. It actually creates its own wind.....

Lets say the true wind speed is 10 knots, then the windspeed on the leeward side could easily be 12 knots, while the wind speed on the upwind side stays very close to 10 knots.

Using this principle very fast boats (low resistance) can sail directly downwind much faster than the true wind.  Ice boats do it all the time.  Interestingly the old square riggers can do the same thing, but the airflow is over the top and down the front of the sails creating lift in front of the sails as they sail downwind, airflow has to be maintained under the square sails too.

Sails with non rotating masts can only take advantage of the wing shape at specific angles and are often only about 1/3 -1/2 as efficient as a properly oriented wing.

In general, a properly oriented wing with half the surface area of a sail will produce twice the driving force in a much wider range of wind directions.  If the boat has high resistance though, the wing won't work going downwind. Can anyone say motor sail?  Heresy I know, but it works.....  All the engine has to do is overcome a little resistance and the boat will sail very well down wind, faster than the wind.

Here is the point, a wing with half the surface area of a sail will generate more drive than the sail (except at about 100˚ apparent wind) and always have less forces on the mast, so it can be lighter and weaker.  That isn't precisely true because the wings Center of Effort is higher so it has a higher moment, but it is close.

Talador