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Student Design, critique?

Discussion in 'Yacht Renderings & Plans' started by vling, Oct 6, 2009.

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  1. CODOG

    CODOG Senior Member

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    We are so off the wall it doesn't really matter, but his maximum beam isn't affecting his centre of buoyancy. His maximum waterline beam may be however, and looking at the drawings I'd say its almost exactly between the two mid masts, almost directly above the centre of bulb...looking at his hull form under the waterline, I'd say the LCB is close to maximum beam at waterline. The waterline plane is almost aerofoil shape, hard to see at first.
    Still, wrong shaped hull whichever way you crack it, but I see scope to improve it hydrodynamics wise and keep the main thrust of the concept.
    Looks like it was done in Rhino or similar ? Can the OP measure the volume below waterline and see where the centroid is relative to the masts / bulb ?
  2. Henning

    Henning Senior Member

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    If you want to compare it to an airfoil, it's flying backwards. The bow is to the right and a reversed wave piercing type. The stern is the bit with the overhang.
  3. vling

    vling New Member

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    I think we are on the same page as far as relationship between beam and CP.
    I've attached an image of approximate WP's of the current design (rev v2e), and an earlier version (rev g) to help clear things up. Rudder is something that still needs to go in, I'll have roughed in soon.
    Welp, it seems like the main message here is to get rid of the reversed bow, so I'll grab the clipper bow from the earlier version to try it out. What do you think about the pinched bow and stern as in Rev. G?

    Thanks again for the advice!

    Attached Files:

  4. CODOG

    CODOG Senior Member

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    Yup, I sussed that from the first post....the OP's reference to a Trireme and the direction the sails were facing sort of helped.
  5. Henning

    Henning Senior Member

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    Still, once she lays on her side with the rail down, and with her shape, she will definitely go rail down when pressed to weather, her maximum beam and bouyancy will shift aft, and even shift aft of her longitudinal center of mass, so she's going to try to drive the bow under.
  6. PropBet

    PropBet Senior Member

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    Is Everything!
    While it looks fun on paper, might I recommend a few points of reading which may help in regarding to the overall design and functional seaworthiness once in the water. (if you end up going that route with this or any other design)

    Hydrodynamic Modeling Of Sailing Yachts - Harries / Abt / Hochkirch
    Manual Of Yacht And Boat Sailing And Architecture - Kemp
    Principles of yacht design - Larsson, Eliasson

    Enjoy-
  7. Garry Hartshorn

    Garry Hartshorn Senior Member

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    Also worth a read is

    "Seaworthiness the forgotten factor" by C.A. Marchaj
    "Aero-Hydrodynamics of sailing" by C.A. Marchaj
    "Skene's elements of yacht design" by Francis S. Kinney ( out of print )
  8. vling

    vling New Member

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    I read a bit from Principles of Yacht Design, aside from the paragraph long equations and enough graphs to make a baby wombat cry, I think I got an idea of how wrong my hull was. Also read some more from Understanding Boat Design by Ted Brewer.

    Here is the latest revision. I got the hull better balanced this time, and got rid of the reversed bow. The flare at the top is less drastic now. Would a double ended hull be possible for a boat this size? I couldn't find much info on double ended hulls this large.

    CODOG - This is being done in Alias studio. I'm sure there's a way to measure volume but I don't know how (still learning the program).

    Attached Files:

  9. vling

    vling New Member

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    Syracuse V2Q progress shots.

    Attached Files:

  10. PropBet

    PropBet Senior Member

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    Looking better.
    Add proper keep / bulb, chop off the extended keel on the aft, and you'll pick up a another 2 or 3 knots by reducing drag and how much of the boat you are pulling through the water.
  11. Henning

    Henning Senior Member

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    Well, we've gone from Star Wars to Civil War, but now you have a much more functional design...
  12. vling

    vling New Member

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    Tough love as always Henning. :p Thanks.

    Here is the latest, I ditched the Dynarig. Added a keel and rudder. Do you think the jibs are raked too steeply?

    Also, everyone is catching the tapered mainsail battens as a Chinese visual cue, although the sails are not a Chinese design functionally.

    Using horizontal battens, to me isn't as aesthetically pleasing. I need to find an excuse to use the tapered battens. Also I'm not sure, but would the tapered battens cause problems with the sail's airfoil shape?

    Attached Files:

    Last edited: Oct 20, 2009
  13. 84far

    84far Senior Member

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    vling, i think u should go back to your original idea and make it work, there's no reason why it cant. u might have to modify the bow and stern slightly (reduce length). your last 2 designs are nice, but they are a bit mainstream. comments?

    far
  14. Henning

    Henning Senior Member

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    The thing is, the laws of physics regulate hull design, not the whims of design.
  15. Henning

    Henning Senior Member

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    The battens are not a deal killer and do look good IMO. Once you move the mast forward some to where it belongs, the jibs will be at a better angle. (take the square surface of all the sails and then find the median longitudinal point of area, that should be just aft of the center of longitudinal effort. You are now far aft). You also don't have a provision for an overlapping headsail such as a Genoa to take advantage of slot/venturii effect in lighter airs.
  16. 84far

    84far Senior Member

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    Henning, wheres the faith ;) ? vling can i modify your first drawing and get back to u? hate to see a good idea go to waste.

    far
  17. Henning

    Henning Senior Member

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    LOL. I'd just turn around the pilot house and sails and run it the other direction, she'd do just fine that way.:D :p
  18. Marmot

    Marmot Senior Member

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    Post #13 showed a beautiful piece of art. It kind of went downhill from there.
  19. vling

    vling New Member

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    84 Far - Sure give it a try.

    Marmot - Thanks. That was the aesthetic I had in mind first, although functionality came in to ruin the party :p. I tried to retain some of the feeling of it in the final version though.

    Henning - Why won't overlapping headsails work in this situation?
  20. Marmot

    Marmot Senior Member

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    Execute that esthetic in SS and/or glass, find a gallery, and you might be able to finance your education. Seriously, that design would make a beautiful work of sculpture.