Human-powered hull design

Discussion in 'Boat Design' started by CBTerry, Jan 6, 2019.

  1. CBTerry
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    CBTerry Junior Member

    I am building a plug for an Outrigger Canoe fiberglass mold and wanting a little help regarding designing the main hull. Because form stability is not relevant with the Outrigger, I guess the only two parameters are the overall length which will be 16 foot oh, and how much displacement I need. That figure is 500 lb. So if I am wanting a set of stations at one foot intervals that I could cut the plywood shapes from, how best should I go about the hull shape, underwater that is? I and not trying to set World Records or anything. Is there a program that is not too crazy difficult to learn nor too expensive or would I be better served to have a naval architect type bang away at his program for the entire 10 minutes it would probably take to generate the stations at 1 foot intervals or two foot intervals if that seems better. Thank you in advance
     
    Last edited: Jan 6, 2019
  2. DCockey
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    DCockey Senior Member

    What construction method and materials? That can be a major influence on hull shape. Semi-circular cross section will have the minimum surface area for a given volume but are not easy to build in sheet plywood or similar. Then there is the distribution of volume along the length. Someone will probably respond and talk about something called prismatic coefficient which relates to how much volume is in the center vs the ends. Another consideration is the number of passengers and where they will be located in order to have sufficient space for them.
     
  3. rwatson
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    rwatson Senior Member

    D Cockey has said it all.
    All racing shells, native outrigger canoes etc have as close to circular sections as they can get. Make it double ended for minimum drag like all Kayaks, and that is all there is to it.

    D Cockings mention of weight distribution will be critical for 16 feet, so you need to plan if you are steering in the stern, 2 or 3 people.
     
  4. CBTerry
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    CBTerry Junior Member

    I apologize for not being more precise. I plan on making a mold so I will hopefully be popping them out in polyester resin and fiberglass. I understand that a semicircle has the lowest wetted surface area but I guess I was more concerned with the taper. I was just going to eyeball it after taking some crude measurements from an ocean kayak but I thought that using a computer to generate stations might actually be quicker. It will be a single person vessel. My inclination from what I have read is that I would be best off to have the center of mass/occupant about a third of the way back from the Bow, the trailing Edge being more important. Does that jibe with your thoughts? Again, I am not going after the last percentage points in efficiency but just wanting to get a smooth paddling hull form. It will be geared towards distance paddling and voyaging in protected Waters.
     
  5. CBTerry
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    CBTerry Junior Member

    I built a Rudder for my sailboat using a NACA profile 0 0 1 3. Given that I am not after the last percentage point of efficiency, Is there a general formula (similar to a NACA profile) with which I could generate my own stations with a bit of paper and a pencil, and a bottle of wine? I always find such calculations easier with a bottle of wine, dry Chardonnay.... or a robust Cabernet if it is especially tedious work.
     
  6. DCockey
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    DCockey Senior Member

    Much too far forward for a boat. Sounds like advice for an object moving through the air or water, not on the surface creating waves.
     
  7. DCockey
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    DCockey Senior Member

    Symmetric or close to symmetric would be good.

    500 lbs total displacement sounds high for a single person vessel. What is you estimate of the weight without the occupant? What is the weigh of the occupant?

    Will this be a commercial product? How will the mold be made - strip planking?

    16 foot hull with parabolic waterline and semi-circular submerged cross-sections will have a waterline beam of 18.5" and a prismatic coefficient of 0.41. Probably should be more volume towards the ends which would result in narrow beam. How much beam is needed for the occupant? If the displacement is less than 500 lbs the boat would be narrower. Perhaps a flatter cross-section shape is needed.
     
  8. CBTerry
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    CBTerry Junior Member

    Yes I was confusing the two. I don't play in this sandbox very often so I jumble some of the theory up when I do.
     
  9. upchurchmr
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    upchurchmr Senior Member

    Copy a real one.
    Inventing something without lots of experience is a sure way to wasting your time and money.
    500# is way too heavy.
    Something weighing less than 100# is more realistic. And much more desirable.
    Add in a 150# guy and 10# of goodies would give 260#displacement
    DCockey's numbers are pretty good for the initial displacement.

    I suggest you do a strip planked hull and test before making a mold.
    You need to make sure anyone will want the boat before committing to the expense of the mold.

    Have fun and report back please!
     
  10. CBTerry
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    CBTerry Junior Member

    I have a prototype out of plywood already just to get some of the characteristics right. I'm confident that as long as I have the displacement and a reasonably low coefficient of drag that everything else will fall into place. There will be some quite unique qualities about this which will be The Driver of sales, but that I don't wish to discuss in a public forum at this time.
    500 is total displacement and is right where I want it. There are some things about this vessel that are not germane but that required this weightt. Patents have not been applied for yet . sorry for the misspelling using voice to text. Voice wreck ignition
     
  11. DCockey
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    DCockey Senior Member

    Write down how the boat will be used. How important is top speed in a sprint? How important is sustained cruising speed? Flat water or waves? If waves how big?

    Write down the "requirements". Note which ones are absolute must have without any changes, which ones are important but could be modified, and which would be nice to have.

    Work out the lightest payload and heaviest payloads including occupants.
     
    rwatson likes this.
  12. CBTerry
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    CBTerry Junior Member

    When you say copy a real one I do not understand. If there is nothing I am familiar with which has no regards for form stability and a 500 lb total displacement, Layton, and 16 foot in length. I looked at an ocean kayak but it was a little bit too thin For the displacement that I wanted. I thought there would be some general Notions about such an Endeavor kind of similar to NACA profiles
     
  13. DCockey
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    DCockey Senior Member

    I was suspecting something like that. Good luck.
     
  14. CBTerry
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    CBTerry Junior Member

    I edited the original post to include that it would ba voyaging craft used in relatively protected Waters. So Flat Water to a foot of chop at the most
     

  15. CBTerry
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    CBTerry Junior Member

    Well I came up with the same maximum beam last week so I seem to be on the right track. Any suggestions on how to come up with the stations?
     
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