Slickest folder ever

Discussion in 'Multihulls' started by garydierking, Jan 14, 2012.

  1. Manfred.pech
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    Manfred.pech Senior Member

    Thank you hoytedow. I can understand "Verschiebung" but would normally say "Verdrängung" (of the water - Archimedes). Thanks, Manfred
     
  2. hoytedow
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    hoytedow Carbon Based Life Form

    Danke. Ich lerne hier heute.
     
  3. Manfred.pech
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    Manfred.pech Senior Member

    Me too, always. But am happy, that the times of Latin and Greek are over. It is more interesting here. Good night, just 12 o`clock here and cold below zero (Celsius). Thanks for kind help, Manfred.
     
  4. hoytedow
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    hoytedow Carbon Based Life Form

    Gute Nacht süße Träume.
     
  5. upchurchmr
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    upchurchmr Senior Member

    Frank,

    I haven't been able to see the new photos yet. Soon?

     
  6. DIY Tri Guy
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    DIY Tri Guy Junior Member

    I have (finally) been able to upload the photos of the new "replacement" hull for the boat in the video that originally got this thread started. And just yesterday I transplanted the folding aka-ama rig from the old hull. (If I knew how to add photos to this page, I'd include it here. But I'm pitifully low-tech. If I can't hammer it or saw it, it's too high-tech for me :) In any case, I can now give you the link to the photos on the most recent "new projects" page at my site. (See my previous post for details.)
    http://www.diy-tris.com/2012/8-okoume-hull.htm

    BTW, I'm now working on a 12' flat bottom mini-tri that will weigh under 100 lbs all up. It's got a 10' beam, but will fold down to just 47" -- so I can get it in the back of my minivan! I made some Dierking-style 8' ply amas for it that weigh just 7.5 lbs each. But that's a whole nother project page I'll need to post...
    Cheers - Frank
     
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  7. upchurchmr
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    upchurchmr Senior Member

    Frank,

    Can you give us a rundown on the differences in the new hull and what you like about it compared to the older boats?
    What is the overall beam of the boat - perhaps you mentioned it but ......
    Are you going to always have the boom of the Easy Up rig be angled up? You know I want more sail area and it looks like it would be an easy increase, if you ever make a new sail.
     
  8. DIY Tri Guy
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    DIY Tri Guy Junior Member

    Hi Marc - I made some comments on the DIY-Tris.com web site about the differences between the original double-ended hull and its "replacement" hull, which is similar to the hull on my older tri, No Commotion. The biggest problem with the double ender hull was that it was not directionally stable, it "hobby horsed" and it drew way too much water (about 9") for where I sail. So the new hull I just finished is a shallow V with a transom, which seems to be the best overall design for small tris.
    The folding ama rig was transplanted from the original hull with zero changes, since it worked perfectly. The E-Z-Up sail rig was also transplanted intact, with just a tightening of the downhaul, outhaul, and mast top attachment lines. That's because my homemade polytarp sail is prone to a bit of stretching.
    Re the angled boom, my original design was to have it a bit lower, and have the sail a bit larger (100 sf vs the current 90 sf). But my tarp was too small to make the 100 sf sail in the right shape, and 90 was all I could get. Ultimately I do plan to have a 100 sf sail professionally made, once I fully understand how this odd but amazingly effective design really works.
    I could be wrong, but this rig seems to point better than any sail I've ever used. More experimentation is planned -- with actual testing, not just speculation.
    - Frank
     
  9. rapscallion
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    rapscallion Senior Member

    Marchaj was impressed with the performance of the crabclaw sailshape. I wouldn't doubt the rig works very well. It may work even better if it was shaped more like a traditional crabclaw sail because the extended tips reduced the vortex at the tips of the sail. look up marchaj. Afterall, an hour in the library could save you a month in the garage :)
     
  10. upchurchmr
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    upchurchmr Senior Member

    I would appreciate an actual reference to Marchaj's discussion of the Crab Claw. He references his works pretty well but I can't find "crab claw" in either Sailing Theory and Practice - 1964 or Aero-hydrodynamics of Sailing 1990. I did page thru both books looking for an illustration but did not find one.

    Given that the big round spar at both tips would naturally be a large drag, by itself, the statement above doesn't make much sense to me. I've also never seen where having the "boom" angled up would help much - due to loss of area. Some of the crab claw rigs shown from the Pacific have the tack right down on the deck, this could reduce drag according to some of Marchaj's discussion, but the width of the area touching the deck is really small.

    All that said I have always heard the matra - Crab Claw Good! repeated many times, but it never seems to be demonstrated. Do you have any race results showing equal area where the crab claw wins over a typical dingy sloop rig? Is this suppose to be good upwind, reaching, or downwind - or all three?

    I would also like to see some objective benefits in performance with Franks sail, given that it has so many benefits in convenience for day sailing. Especially since I was thinking about putting one on a Kayak/trimaran.
     
  11. yipster
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    yipster designer

    Marchaj crab claw findings under chapter "the sail power of various rigs" page 152 to 167 in airo-hydrodynamics of sailing" (3rd edition) and later also, unchanged as I can make in "sail performane" techniques to maximise sail power but basicly same book.
    remains a bit of a riddle, many claim a windtunnel mistake as no live size crab claw outpowers any racing rig yet but have a look at thse polenesian kids racing ther model proas, these little crab claws fly !
     
  12. upchurchmr
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    upchurchmr Senior Member

    Yipster,

    Thanks, I only have the 2nd edition. My library around here is guaranteed to have nothing on sailing, especially if it was useful.

    Seems a lot of people "believe".

    Frank made his sail himself. I wonder what a "pro" sailmaker would suggest about shaping. Possibly nothing since it and crab claws are so uncommon in the Western world.
     
  13. DIY Tri Guy
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    DIY Tri Guy Junior Member

    The sail on my little boat is definitely not a crabclaw, though it bears a slight similarity to one. First, my sail has battens -- radial ones. Crab claws have no battens. Second, my sail has a pronounced roach. Crab claws don't have any roach, or are cut hollow.
    My sail is what I have come to call a "fan sail" -- the general shape being inspired by various Asian designs, and the construction loosely inspired by the batwing and sliding Gunter sail.
    In reality, it works perfectly "as is." If I were having a pro make one (and I probably will be), I would not change the cut one bit. I gave it a bit of luff curve and a bit less foot curve, trying to anticipate how much the C/F mast and the alum. boom would bend. Amazingly, I got it right on the first try. Hey, sometimes you just get lucky!
     
  14. yipster
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    yipster designer

    Try crab claw in the search btton above
    posted some pages of the chapter some time back
    think it was in the exellent sail airodynamics discussion
     

  15. DIY Tri Guy
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    DIY Tri Guy Junior Member

    Even though the sail on this boat is definitely not a crab claw (or maybe because it's not a crab claw) it pulls like crazy and goes upwind amazingly. Never had a sail that would point so close to the wind.
    - Frank
     
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