Crab claw sails evolving to rectangular shape

Discussion in 'Sailboats' started by gonzo, Nov 28, 2020.

  1. Will Gilmore
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    Will Gilmore Senior Member

    THE NEW RIG http://www.flyinglateen.com/the-new-rig.html
    upload_2021-1-12_3-5-12.png
    Note the lower spar. Boom or yard?
    More of an Oceanic Lateen.
    They could simplify it more by tacking down the tack to the bow and get rid of the fore leg. Probably get better air flow too. Although, those split leg masts look like they would interrupt air flow plenty.

    Have we settled on a definition for crab claw yet?
     
  2. BobBill
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    BobBill Senior Member

    Someone suggested Marchaj never really "did" his game and that does make for curious thought. His subject grasp is amazing.
     
  3. BobBill
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    BobBill Senior Member

    I just recalled I forgot to mention here earlier that this rig is the one which convinced me that my adding stays to my outrigger, per suggestions herein taken, would not demand outlandish downwind sailing...
     
  4. BobBill
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    BobBill Senior Member

    Gaff or lateen?
    One, the lateen has spars that cross the stubby on one tack or the other, save the one shown above, gaff spars do not, which is the MO rig - and then there is the one above, a lateen, to me.
     

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  5. sharpii2
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    sharpii2 Senior Member

    I would call it a lateen as well.

    This is because the yard extends all the way down to the foot of the sail.

    If it extended mostly to the foot of the sail, I would call it a setee.

    But if it extended halfway down or less, I would have to call it a gaff.
     
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  6. BobBill
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    BobBill Senior Member


    Yes, I agree with your reasoning...but am so used to seeing this as a gaff as it hinges at the boom-spar and stubby.

    Perhaps classifying "ad hoc" sail design is always going to be a bit ambiguous...habit/beholder/user sort of thing. Just a point of view.
     
  7. BobBill
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    BobBill Senior Member

    Gonzo-msg...Really? Be fun, avec WI fromage! But, Gonz, me-thinks you right! Not enough brew, even in WI, and those dodgers know how to quaff.

    Had idea to change current arrangement to Wishbone...but Marchaj, got me to reverse that one.

    Works for me, beer or not!
     
  8. CT249
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    CT249 Senior Member

    Is it? The paper showing wind tunnel results includes a Marchaj quote claiming that rating rules and racing rules favoured, or required, bermudan rigs. But that's simply untrue. The development-rule Skiffs, Moths, windsurfers, most offshore multis, most shorthanded racers, cruisers, small cats, speed record machines and other craft do not normally sail under rules that require bermudan rigs. You could throw a crab claw rig on a windsurfer (they did, it failed), a beach cat, a skiffa So Marchaj is wrong, and wrong on something that is so fundamental and so obvious that his grasp of the subject can seem to be pretty dodgy from some angles.
     
  9. BobBill
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    BobBill Senior Member

    CT I understand and amen, but to me he shows some grasp of topic...enough to do the math...! But, I am not so smart either.
     
  10. BobBill
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    BobBill Senior Member

    The other "thing" that is curious, is the idea that if he did not understand the topic, why do the books? A Dick and Jane primer is quite an endeavor, so one must wonder...
     
  11. sharpii2
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    sharpii2 Senior Member

    Perhaps he confused greater maximum lift with greater lift/drag efficiency. The two are different.

    Greater lift comes with the plane deploying maximum flaps. But it's engines had better be near full throttle.

    Once it reaches its assigned altitude, the plane retracts the flaps, and then the higher lift/drag efficiency comes in.

    Less lift, so the plane has to fly faster. But even far less drag, so the plane can reach its destination with the amount of fuel it has.

    Since racing requires a lot of upwind sailing, lift/drag efficiency is of primary importance. So the trianguloid Bermuda rig, with its AR relatively high, and it's CE relatively low, shines in this department.

    The crab claw has its CE relatively high, when it is peaked up, but relatively low when it is peaked down. And, as far as I know, there are no reef points.

    It appears that the masts on most of these can be canted fore and aft. At least on one of them, an Indonesian one, the sail is peaked up when sailing down wind. And peaked down when sailing upwind. As the mast is forward on this canoe (a double outrigger) this makes sense. When peaked up, the CE of the sail moves forward, which provides relatively good down wind sailing manners. By peaking the sail down, the CE of its trianguloid shape moves aft, providing good upwind manners.

    Also, on a narrow hull multi hull, speed is no longer limited by the boat's wave length, like with a more traditional monohull. Maybe this is the reason reefing never seems to have been a thing with these rigs. When the wind blows harder, the boat simply goes faster. At least to a point.

    It seems that if the size of the rig is kept within reason (a relatively low S/D ratio), this could work quite well.

    One canoe I read about carried two such rigs. One was trianguloid and the other was rectanguloid. One was stored on the cross-beams while the other was in use. I guess that was one form of reefing.

    I suppose that this rig type, permanently peaked up on a stationary mast, might be of use if the sail area was going to be quite limited, and the sail was of secondary concern. The high CE of this "V" shape would catch more wind than a Bermuda rig's inverted "V" shape would.

    Also, the boom would be well out of the way.

    I have seen a "V" shaped sail used on an expedition kayak, but it seemed designed for only down wind work.
     
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  12. sharpii2
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    sharpii2 Senior Member

    With some embarrassment, I found out that the canoe I mentioned was Balinese, not Indonesian.

    Also, the larger or smaller sail was stored on boom crutches, not on the cross-beams.

    While further reading, I learned that the rig peaked upward automatically.

    The way this works is that only the yard is connected to the mast, and it has a sheet line of its own.

    The front end of the yard is either tethered or stuffed into the open bow, so it can move only fore or aft.

    The front end of the boom is either directly connected to the front end of the yard, or is indirectly connected to it by the open luff of the rectanguloid sail.

    When sailing upwind, the yard sheet is held firm, so only the boom can move. It is always kept to the Lee of the mast, so it can swing out freely. This is the sole way of getting a sheeting angle when sailing up wind.

    When it's time to sail off wind, the yard sheet is eased, so the aft end of the yard can swing to leeward. But the front end cannot, because it is trapped in the open bow, or is limited by a tether. But it can move fore and aft. And so it moves aft. This peaks the aft end of the yard higher, and moves the CE of the sail forward, where one might want it for downwind sailing.

    Changing tacks requires sailing dead down wind, then letting the yard and boom pivot around the front of the mast. The two sheet lines are then used to haul them aft after that. Now the canoe can turn upwind on its new tack.

    As for reefing, the boom is simply allowed to sing further down wind than the yard, causing it to act as much as a kite as it does as a sail.

    Not bad for stone-age technology.

    PS. The sails were proportionately larger than I said in my previous post. About 15 sm for about 600 kg of canoe.
     
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  13. BobBill
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    BobBill Senior Member

    Can you cite the reference?

    Gonzo...it is a gaff, according to basic reference in the Anarchy Front Page Vid on rigs and so on.
     
  14. BobBill
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    BobBill Senior Member

    Sharpii, you mention "reading"--can you cite the reference? This swab is looking for Balinese shunter rig...just curious.
     

  15. gggGuest
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    gggGuest ...

    Marchaj was pretty smart within the limitations of what was known then. I think you need to be a bit wary of a quote of what he said, it could be very selective indeed. If the context was limited to offshore boats with lids, as it often was for his writing, then there is more of a case for it. I have a vague recollection that on crab claws he was talking in the context of what a working seaman might require from his rig, and not about what might be the most effective for getting round a race course.
     
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