Wind Tunnel Measurements of the Performance of Canoe Sails From Oceania

01 October 2018     Editor    9 Comments.

Crab Claw Tests

GALLERY | Click images to enlarge

In what is no doubt the longest headline ever at Proafile, The Journal of the Polynesian Society has published a paper by Anne di Piazza, Erik Pearthree and Francois Paille on their wind tunnel research results. Apparently inspired by C. A. Marchaj and his wind tunnel testing of various rigs of working sail, including the “crab claw”, the new study expands the range to a wide variety of Pacific rigs:

The primary objectives of this paper are twofold: (i) to test different traditional Pacific rigs in a wind tunnel, rank their relative performance, and compare these results with other studies, in particular Marchaj’s “crab claw”; and (ii) to question developmental implications of such results and consider whether the geographic distribution of the various rigs could shed some light on the history of settlement within Oceania.

Much thanks to G. Baron for the submission!

 Rigs  Research

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  • Remember the German windtunnel tests by the fellow whose name I forget right now, who refuted many of Marchaj’s results?  I still have his test results saved, which he posted to the old Yahoo Proa-file forum.

    2018-10-09 07:53 | by Wade Tarzia

  • Be nice to have some understanding she’s on the utility of these rigs, the wind tunnel tests are interesting (especially regarding further development) but possibly a bit limiting when it comes to understanding why some of these plans had such longevity.

    2018-10-11 18:41 | by Guido

  • Locale wind conditions, typical use of the boat (what courses sailed for trade/visiting, what fish chased, etc.) , what materials (lengths, strengths) locally available, and of course local buildability/repairability and kindness toward available sail materials—Asian countries sometimes suffered when being brought into a global economy—adoption of factory fertilizers for crops enslaved farmers to global prices, adoption of outboard motors (etc.), similarly.  These would be some of the factors I would first posit as arguing for longevity of plans.  The notion of “tradition” goes without saying, though traditions show both remarkably longevity in the face of Western colonization and in many cases remarkable delicacy (susceptibility to destruction). One might wonder to what extent a rebellion against Western encroachment helped some of these traditional plans survive, where there was energy left for cultural pride.  These designs now so often figure in cultural revival/pride projects, and perhaps cannot always be layed on the shoulders of point-origins—galvanizing figures such as Herb Kane and Ben Finney for Hokulea—but there also must have remained other kinds of forces to keep things alive—perhaps in some cases the geographic backwaters—Mau Pialuig and Satawal come to mind, although he was asked to join revival education rather than having put himself forward, but there could have been no Mau without a Satawal to have produced and sustained him into this period.

    2018-10-12 09:33 | by Wade Tarzia

  • That the Ninigo and Massim sails perform so like an air plane wing and thus so well seems really logical, but I’m surprised with the crab-claw from Santa Cruz, and it matches quite well Marchaj results !
    One caveat to the analysis is that the wind gradient in real conditions is what makes sail twist important, and this have been left out of the study.

    2018-10-20 14:45 | by Joan Pons

  • Aloha, Of course the closer winded that the prescribed Rig with long frontal-node best attained friction-free lift coefficient will produce the results for Developing a more Kindlier Apparent Wind Penetrator, with More Smooth and Consistent Performance Numbers.
    The higher aspect-ratio rectangular profile is the superior projected area for power-n-trust for such windward-ability, as opposed to the general practice of Triangle Design and Construct Sailing-Rigs- with the three corners coming to points, this is the cause for useless turbulence, and the counter-productivity of that which produces “Air-Brakes” with the triangulated sail plan.
    When one gets the Rig Right, this formula can be applied to any “platform”!  Of course Light-Weight/Balanced-Rig, along with Ultra-Strong Build will be the Continued Success Stories to Pull The Apparent; and Go! Swifter/Safer/Simpler Faster than the Wind. Keep Pulling The Apparent, and Be At-One-ment with The “Pulse” of The Wind and The Waves- Enjoy The Sweet Effortless “Glide”.  aloha nui jais’iruka

    2018-11-19 13:29 | by DolFunHeart

  • I am just curious to see the smoke trails off the Santa Cruz type Vaka Taumako Crab Claw.  What’s happening up at and between the “horns”?  Is some sort of whirlwind generated that has some negative or positive effect?  This type of wave piercing fundamental log shape with windward planing and piercing, foil-like ama with all human accommodations above an organized sea wave top is so cool, it looks like it must be remarkably comfortable, like it just has to do the most important thing, drive a partially submerged log to weather, at an angle through a swell that would stand you off a lee shore, get you home on long close reaches in the most sea kindly manor to keep the rest of the contraption together and not blow out all the natural cordage connections by exceptional close winded ness slamming you into a wave train.  The entire concept blows my mind, the “reverse hiking” where the crew sits to leeward during the day to help the ama to plane, clever as the day is long!

    2018-12-16 23:27 | by Paul Berry

  • Paul Berry—I remember we talked about this at the Yahoo proafile forum.  The most interesting idea I recall was the possibility that the pointy tips of the “true crabclaw sail” might generate vortexes that could have some positive effect. 

    I wondered if the extreme curve in the sail leech would provide extra stretch (as a fabric curve tightens, it pulls on the weave from tack to leech—no doubt exploited by lingerie engineers) to induce some flattening of the sail.

    I have half a mind to make scale model of the sail, start the video camera, and sift talcum powder in front of a fan to see at least what the air is doing—though someone out there is crying “Reynolds number scaling!”

    2018-12-17 09:06 | by Wade Tarzia