Re: [PSUBS-MAILIST] fairings drag vrs entrained mass

["Rick and Marcia" <empiricus@telus.net>]

Rick M . . .

 

I knew I had this in my files.

 

I think this will answer your question rather handily.  It's, um, a little involved.

 

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P = 0.005 V³∆^2/3

^{where . . .}

          ^{P = shaft horsepower}

        ^{V = speed in knots}

    ∆ = propelled displacement (or LBD/60 in long tons [2,240 lb.])

 

where

          L = length in feet

          B = beam in feet

        D = depth (or height) of hull in feet

 

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This deals mainly with entrainment, existing boat mass, etc.  For actual drag formulae of appendages, etc. go to the usual sources

 

 

Warm regards,

The other Rick

 

 

 

----- Original Message -----

From: rick miller

To: personal_submersibles@psubs.org

Sent: Sunday, November 27, 2005 6:03 PM

Subject: [PSUBS-MAILIST] fairings drag vrs entrained mass

hi guys

 

    Rethinking fairings and have a question. how much saving in hydrodynamic drag do i have to save to justify the the entrained mass that i will carry in traped water? especially with a speed of only 3.5 kts. diplacement about 6000 lbs

 

 

rick m