Tacking Proa (for lack of a better term)

Discussion in 'Multihulls' started by Owly, Nov 27, 2020.

  1. Robert Biegler
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    Robert Biegler Junior Member

    At this point, I have trouble visualising what you have in mind. If you are still discussing a tacking outrigger, than sometimes the foil will be to lee and need to push up, sometimes to weather and need to pull down. If you always want a foil to lee, and you want to tack instead of shunt, you need a foil on either side. Then a catamaran or trimaran would seem most logical, or a triscaph, like the later incarnations of Loisiers 3000: . If you need the boat to go alongside somewhere, then the cat seems most practical.

    If you are willing to let the foil pull down on one tack, then you might be thinking of a foil adjusted by a mechanical sensor, like the wand on the Rave Windrider or the little waterski ahead of the foil as on the Hobie Trifoiler;

    There used to be a kit for that, the K-Wing Sailing System for kayaks. The only trace I can find of it now is one low resolution picture in a primer on kayak sailing: Kayarchy - sailing rigs for kayaks & canoes https://www.kayarchy.co.uk/html/01equipment/014sailingkayaks.htm The reviewer is unenthusiastic, but it is not clear whether that opinion is based on experience or theory.

    There was also the Blue Arrow challenger for the America's Cup that pretended to be a monohull by replacing the outer hulls with adjustable inverted T-foils: [​IMG]
     
  2. Owly
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    Owly Senior Member

    I didn't express myself very clearly..... This is purely a flight of fancy speculating on what one might do. It's probably pretty impractical to to build an outrigger on one side, and a foil on the other, but it would allow you to fly the outrigger on each tack using the foil with minimal risk of capsize. The Blue Arrow shown makes more sense, dispensing with the outriggers altogether.........but depending on foils completely, it would be pretty unstable unless it's moving all the time. I've personally zero interest in racing, but it's useful to be able to make speed at times.

    With an outrigger on one side and a foil on the other in a tacking proa, the foil would have to provide lift when it was on the lee side, and would be the only thing keeping the boat upright unless you were hiking out on the other side. You could allow (would want) the outrigger to fly. The foil could be automatically controlled by the attitude of the boat as sensed by a linkage with a pendulum weight. On the other tack, the outrigger would function like the outrigger on an Atlantic proa, but you could use the foil pull down on what is now the windward side, lifting the outrigger out of the water. The outrigger would be installed in such a way that at a level attitude it would be just clear of the water. The whole idea is to have the outrigger flying virtually all the time on both tacks, only being in the water at slow speeds and at rest. The outrigger is mainly "insurance" in case the foil pops out of the water when the foil is on the lee side. It also allows you to sail in thin water.....hiking out on one tack.
    The only reason for not having a foil on each side is drag. You'd probably want to pull up the windward foil.
    A simple gravity pendulum linkage might not do a good job for auto control. It might call for a gyro to do a good job.... another level of complexity. Imagine a small gyro operating a trim tab.. similar to how a wind vane steering system works but keeping the boat level... you would use the force of the water passing by to amplify the force of the gyro and control the foil. It could be controlled by hand....perhaps with a trim wheel. The faster you went, the less angle of attack would be needed. An interesting toy to play with.
    ** The water ski on the boat in the Utube is interesting.... it inherently wants to stay on the surface

    I'm wondering what you can do with foils to make them inherently stable at least with reference to the water surface. an angled foil projecting above the water surface could be made to maintain depth more or less when pulling providing lifting force. The deeper it goes, the more foil area is submerged, but that doesn't work the other way when you are pulling down.
    H.W.
     
  3. Robert Biegler
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    Robert Biegler Junior Member

    My guess is they needed a RIB to get Blue Arrow started up. Or you could make the hull just wide enough, and perhaps the foils just voluminous enough, that the boat doesn't fall over at rest. That seems to be the approach taken by Gerald Holtom when he designed Foiler 21 in the mid 70s
    [​IMG]

    Mounting them high enough that a few degrees of heel gets the windward foil out of the water solves that problem without moving parts.


    A pendulum would be sensitive not only to roll, but also changes in course. A gyroscope would try to keep the boat level, which is fine if the water is flat, but will cause trouble when it is not. I would prefer to follow the water surface.

    That waterski is one solution. The wand used to control a trailing edge flap in the Moth dinghy class, and the Windrider Rave is another:


    If you want to achieve the same without moving parts, and you know that your foil only has to provide lift, I know of three features you can use, singly or in combination:
    1) Increase lifting area as the foil is pushed down, either by inclining the foil (as you mentioned), or by mounting additional foils higher up (see ladderfoil).
    2) Let the tip of the foil be closer to vertical than the root. Then if some of the angle of attack comes from leeway, the more the foil comes put of the water, the larger a proportion of the total area is in the vertical(ish) tip, and the total force from the foil will be more horizontal. You can see that angled tip at 1:24 in this video of Hydroptere:
    3) Use washout on an inclined foil. Twist the foil so that angle of attack near the tip is less than near the root. Then lift increases even more as the foil is pushed down than it would from the increase of area alone.

    Look at the lower strut on the windward foil of Foiler 21. If you made that large enough and angled it appropriately, you could use that to prevent a foil from pulling down too deeply.

    Some of what you're thinking about is explained at greater length in the Amateur Yacht Research Society's October 1970 publication "Sailing Hydrofoils", available for free at Booklets – Amateur Yacht Research Society https://www.ayrs.org/booklets/ More up to date work is in Catalyst. Have a look at the index: Index to Catalyst Nos 1-19 – Amateur Yacht Research Society https://www.ayrs.org/catalysts/catalyst-index/
     
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  4. BobBill
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    BobBill Senior Member

    A boat (proa) is either a shunter or a tacker. Besides, each has its rationale, so who really cares?
     
  5. BobBill
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    BobBill Senior Member

    "Ninja" is now-defunct SA small tacker in a box. Slicker'n seagull poop, but no money to spread the rig.
     
  6. BobBill
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    BobBill Senior Member

    White designed "the dragonfly" as a "tacking proa." Proa, used to refer to "boat."
    Then there is the venerable Warren Seaman design, "Malibu Outrigger, MO," which Alter used to creat his once and certainly still ubiquitous Hobiecats. The last pic is a MO using scrapped Hobie hulls, scrapped surfer/thin 6061T spars, hook and loop and soon to be foam outrigger.
    Ease of used was intent, though for some not so easy...I needed tacker, so came Gnarly...last pic.
    Missed this, and, if input has bearing, sorry I missed this thread. 1origDragonfly.gif MIorigMO_1.JPG
     

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  7. BobBill
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    BobBill Senior Member

    Link for the slickest of all...Ninja from SA but had to fold
    (intende)(i...money...came/stored in a wheeled box...simple, fast and fun.

     
    Last edited: Mar 1, 2021
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  8. BobBill
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    BobBill Senior Member

    I did forget one thing, pragmatic or practicability...a foam rig with a jet engine may be swift, but not practical.
    Ninja, is all a sailing rig needs and goes into a box...besides.
    Seems we forget, too easily, boats need storing etc, much less rigging and it's elements should complement it.
     
  9. waynemarlow
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    waynemarlow Senior Member

    So why did the beach cats take over, there were other early examples of the likes of the Ninja and yet the cats proliferated or was that just a Hobby brand thing?
     
  10. Russell Brown
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    Russell Brown Senior Member

    I had a fantastic ride on the Chris White single outrigger. Super fast and powerful. One advantage over the beach cat is ergonomics. One sits higher with feet in a footwell mostly.
     
  11. BobBill
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    BobBill Senior Member

    Wayne, who really knows? Was easy rigging, simple sail, (no boards), easy mooring (beach) trailer, easy capsize-recovery, fun kid-rig. Remember 14s were first and were HI, then CA boat, most non harbot adverts, MO's ruled Malibu, until ugly CA Malibu-money real estate killed the beach sailing club??? Now they worry over slides and fires, not a few pot-stoked surfing MO crews. Boat was a class rig; all wood, and a few originals still sail.

    Russ Brown, Thanks.
    Did not know White's boat was produced, never really viewed pic of a Dragonfly outrigger sailing; only big tris.


    Thanks, good to know. Looks on paper to be one slick and easy and well done 16 footer and could be crafted in garaqge...A might more boat than a Hobiecat-16, or the flimsy Alcort Hulu rig.

    Later MOs like mine have small cockpits for feet, self draining like Sunfish holes...

    FWIW, it it my belief the Ninja would have been a hit here...but that is me...only thing rig lacks is paddle-space...space adjacent to main hull to use paddle...and small cockpit for feet... easy to do (dos),
     
    Last edited: Mar 2, 2021
  12. BobBill
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    BobBill Senior Member

    BTW, you want extreme outrigger, look up "Crossbow." A huge machine.Oor its sister ship. Built mostly of wood for speed but was really unwieldy and never really did much, either one.
     
    Last edited: Mar 8, 2021
  13. Doug Halsey
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    Doug Halsey Senior Member

    Is this your idea of not doing much???
    500MetreSailingRecords.jpg
     
  14. BobBill
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    BobBill Senior Member

    "Re did not do much," ...based on couple facts, "Crossbow and Crossbow II were not same rig, as I recall. Did not mean to twistanyoine's shorts...just an observation with poor word choices...and seems neither met expectations, either until wrecked or refitted.

    Also, Owly...OP said, at later point, "it all depends what you want."

    OK, tacker vs shunter...to me is simple...tacking means: shove tiller, maybe grab sheets to move boom/sail, expect winward, leeward to maybe switch side balance etc, and go....simple; and can do all inside OAL of hull...but cannot do is some harbors, harbor inlets, and have to motor ingress etc.

    Either means "gets it done," but simple is best but sometimes not discovered 'til tried and may not be able to revert...but can recraft later.
     
    Last edited: Mar 8, 2021

  15. Russell Brown
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    Russell Brown Senior Member

    The single outrigger makes a lot more sense than a proa in small sizes. Being able to tack easily and the simplicity (one rudder) make them more popular. Gary Dierking would agree and he is responsible for more single outriggers than anyone, I'll bet.
     
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