FOILS = COOL!

  I'm a big fan of foiling, particularly the way the Windrider company has done it with their Rave trimaran. 

  A foil on each ama with trailing edges that determine up and downlift, and a foil at the bottom of the rudder.  The trailing edges of the ama foils are governed by comma-shaped wands that drag in the water.  As an ama goes lower, the wand drags deeper, angling the trailing edge down, increasing uplift.  As the ama goes higher, the wand drags less, leveling the trailing edge out, and eventually creating downlift.

   
    http://www.sailingbreezes.com/Sailing_Breezes_Current/Advertisers/Rave/rave_redefining.htm
    (see the Foil Systemsection)
    https://www.youtube.com/watch?v=CRTBYyNsmic
    (see video at 1:40 - 1:55 and at 3:30)

  Just about as simple as it gets, and at well under $10,000 for a used boat, amazingly cheap.

  I was inches away from getting a Rave when I decided to get an overgrown beach cat instead, for three reasons:

    - The Rave only lets me take one other person out.

    - I live in Maine, and there are lobster pot warps and buoys /everywhere/ in the warm weather (catching those at 20 knots would be ugly).

    - We've got a lot of rock shoals in our area, requiring a bit too much attention at foiling speeds.


  But if I didn't want to be able to take a few folks out with me, and lived somewhere else, that Rave would have been mine.  It would have saved me a lot of money, too.

  Would I consider a larger foiling craft if I lived in a location where the coast is basically a long line made of sand, without lobster traps?  Probably not.  I'd probably grab a used Rave for fast fun and then have a "slower" (15 - 20 knot) multihull for general use.

  But that's just me.  I'm ultra-cautious, and try hard to avoid anything that could go wrong and ruin my day (or worse). 

  Right now the harryproa has bascially a single point of bigtime failure: the mast.  Fortunately that's easy to design for, it's not dependent upon any small pieces of hardware, and even if it does go wrong, the mast is to leeward, so a failure there is not likely to induce injury or death.

  I'd have a tough time going cruising with a series of foils that add several more points of failure.  Catching a single foil on a log, shoal, or even a big plastic bag, could result in some foils up and some foils down, which could get ugly at speed.

  That said, I'd love to see it done on a 30' - 50' scale that doesn't involve millions of dollars.  A boat like that would be great to watch, and to sail, even if I weren't going to get one myself.


FOILS + HARRYPROA = ?

  I'm not sure the proa is an ideal platform for foiling. 

  Challenges with a foiling Harryproa:

    - Foils would have to work in two directions.  Getting a single-direction foil working is a challenge, but bidirectional?  That's a tall order.  You might be able to do kick-up rudder foils instead of just kick-up rudders, and then rotate them 180 degrees for each shunt, designing them to handle the loads would be interesting.  Plus there's still the windward hull.  Two foils there, lifting one and dropping the other for each shunt?  And if you don't do rudder foils, four foils on the leeward hull, with two down and two up on each shunt?  That's a lot of work, cost, and weight.

    - Double-ended design is non-optimal.  The proas are already challenged, when compared to cats and tris, when looking at their weight distribution and CLR.  For a cat or tri, just put the mast where you want it relative to the foils, make sure there's more weight in back than in front for level trim, and you're good.  For a proa you're going to be slightly unbalanced, and that's going to be much more noticeable on foils.

    - Weight and cost.  A series of foils, plus the structure needed for them, is going to add weight and expense.  If you really want foils, perhaps that's fine.  But it just goes against the smaller/simpler/lighter/faster/cheaper design ethos behind the harryproas.  You could probably make it happen, but might end up spending and weighing more than if you used a single-ended multihull.


  It seems to me that you might be happier with a trimaran, hopefully with an unstayed rig, than proa.  Or perhaps a biplane catamaran with twin unstayed rigs. 

  Both are tried-and-true platforms for foils, there are no worries about double-ended weight distribution and sailing loads, and the foils wouldn't have to handle working in two directions.  You'd also potentially be able to gybe on the foils without touching down.

        - Mike 

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