My Small Bluewater Trimaran

Discussion in 'Boat Design' started by Prismatic, Jan 26, 2014.

  1. Mr Efficiency
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    Mr Efficiency Senior Member

    I'd be rather less concerned about roll period, than the business of getting from A to B, the department in which your creation seems seriously "challenged" :p , which is a nice way of saying it looks like a complete slug. :eek:
     
  2. Prismatic
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    Prismatic Junior Member

    Here is my design goal
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    I can't see your platform moving at anything greater than 3-4 knots, speed through the water. Tide going the wrong way, you could be down to 1-2 knots, speed over ground.
     
  4. Prismatic
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    Prismatic Junior Member

    Thanks...I'll see soon...my main focus was stability. I could always go with a larger hp propulsion system for speed. I will post youtube vids of the sea trial in the GOM soon...Mr. E are you a gambling man?
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    :eek: Are you the John Edward of boatdesign.net ? :eek: I was in fact a professional gambler for many years !
     
  6. Prismatic
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    Prismatic Junior Member

    By no means! But I am positive I could do more than 3-4kn with a trolling motor :D
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    I think of you'd used elongated diamond shapes, rather than triangles, the thing may have moved through the water a little better, but it is hard to imagine the overall concept superceding the orthodoxy that has evolved to where it now stands. Yours is more revolution than evolution.
     
  8. Guillaume C.
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    Guillaume C. Junior Member

    Seriously, I don't want to be rude but this project is ridiculous, you will only loose time and money out of this, possibly more if you try to go offshore.
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    Every cloud has a silver lining, this could be adapted as a FAD (fish attraction device). Nice confined space for small fish to hide from predators.
     
  10. Guillaume C.
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    Guillaume C. Junior Member

    Hehe, good one, I did not see that possibility!
     
  11. messabout
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    messabout Senior Member

    Groper; Your post @36 stated that WSA is a high speed major influence while form drag was a lower speed influence. Did you not state that in revese order?

    I notice that no one challenged that statement and I am ready to learn of my possible mistaken belief that WSA is predominently a low speed detriment. Skin "friction" is a near linear function with respect to speed while form drag is more nearly an exponential function. ????
     
  12. groper
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    groper Senior Member

    Nope, I believe what I said was accurate... wave drag is the issue for low speeds upto hump speed. From there, wave drag starts to drop off whilst the friction drag is proportional to the speed squared...
     
  13. frank smith
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    frank smith Senior Member

    I remember flipping a tricycle when I was a kid. The shapes and rapid changes in speed will cause it tilt rather quickly , then you have to consider the rapid change in Disp. of the pods, as the weight shifts around. You might want to add a gyro stabilizer.

    Three bows is a good idea.
     
  14. messabout
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    messabout Senior Member

    Groper, I suspect that we are thinking of substantially different speed realms. I am thinking of very small S/L ratios for the likes of Kayaks or small sailing boats.

    I believe that there are some threads elsewhere on the forum where this subject has been thoroughly thrashed.

    Please excuse the temporary derail.
     

  15. groper
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    groper Senior Member

    Well it totally depends on the context of the discussion... if your discussing kayaks then all of them (the ones ive seen) already have very low wave drag because of their inherent long slender shapes which is ideal for minimum wave drag anyway- therefore, the WSA is important for improving/maintaining minimum total drag...

    When discussing small sailing boats however, this could be very different and the wave drag could be a large component of the resistance as sailing boats vary wildly from slow keeled fat cats to lightweight planing dingies.

    In either case, the friction drag from WSA is not linear. It increases exponentially as its proportional to the speed squared - which clarifies what you asked about.

    I see a big problem with this design in question here, from wave drag... i beleive its going to be huge and compounded with negative interference from the 3 hulls. All hulls are very short and fat at the waterline, blunt entry angle, huge immersed transoms, all in close proximity to one another. In fact, i cant think of a worse combination of design ratios to produce a higher drag configuration than this one!

    It also has a very high waterplane area as most of the displacement is carried up near the waterplane with the volume distribution of the pyramids... thus its response in a seaway will follow the sea surface closely.

    Not trying to be negative, im all for innovation, just calling what im seeing...
     
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