design methods...and questions

Discussion in 'Boat Design' started by Redsky, Jul 9, 2006.

  1. Redsky
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    Redsky Senior Member

    the one question i have is would a 3/4" -1" boat form model..not nessairly high in details, be of enough size to indacate inherent problem? or would 1.5"-1' be better. ?
  2. marshmat
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    marshmat Senior Member

    Depends what kind of problems you're looking for. Is the model intended for tank testing? If so, the test has to match Froude number and at least approximate the right Reynolds number regime. This is a lot easier to do with a big model, even though the model is then more expensive. Or is the model being built to visualize the shape of panels, the fit of structural members, etc? Or just to see how the hull looks? How complicated is the design?
  3. artemis
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    artemis Steamboater

    Weston Farmer (and many others from his time) used the 3/4" = 1' scale. It simplified construction (1/16" = 1") and the scale allowed easy conversion/multipliers to full size. He describes the construction, etc. process as well as a simple towing/testing device in his book "From My Old Boat Shop".
  4. Redsky
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    Redsky Senior Member

    the hull insent that unusuall really, longship /knarr basicly
    however the drawing im working on is a bit taller than a single rowing deck hull so the need for outriggers is a possabilty, and i wanted a scale weight displacement check , also fine tuneing of base hull frame shape as needed.
    mutch easier to correct a scale model than a full size boat after its finished.
    properly for any boat/ship to be built sutch a model should be constructed to check agianst design? something that floats i the first place with proper machienery block weights fixed where they occur in said design?
    nothing worse to my mind that something that is in reality when floating that in inherently off balence due to design error. or other not so obvious on paper problems. pretty mutch everything in general detail Marshmat not trying to win races with it but if it dosent sit well in the water in the first place then something need work. and it may be that all the calculations in the world may say its correct but nothings wrong except like say like the drivetrain is subtly out of position or something like that and it just throws a wrench on how it sits in the water= harder to handle boat right?
  5. jehardiman
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    jehardiman Senior Member

    Models cannot be used to check stability, the effects of n dimensional scaling get in the way. Most tank testing models are captive for just this reason, and free RC models are a very special case only used for maneuvering checks and unrealistically weighted to get the moment coefficents correct.

  6. Redsky
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    Redsky Senior Member

    sorry i dident mean to imply that a model takes place of good calculations for stability in the first place..itd just iv seen way to many boats that the arraingment of the interior of the boat dident look like it worked very well or once it sitting on the water just looked unhappy or wrong, its like parking a nordic tug next to a bayliner ya know. one really looke like it belongs on the water.......this boat here has a lot of influence on what im working on i like the design a lot but that paticular hull im leery of due to the fact it looks like she has been on the rocks and fanged by her own anchor it looks like rather vividly to me, additionally its not designed to sail either.
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