[PSUBS-MAILIST] props

[hank pronk via Personal_Submersibles]

Alan,
This is for maneuvering thrusters on Gamma
Hank --------------------------------------------
On Sun, 12/14/14, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Subject: Re: [PSUBS-MAILIST] props
 To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
 Received: Sunday, December 14, 2014, 8:34 PM
 
 I
 thought Gamma had an internal motor.Or
 is this for something else?You could
 run a propeller fore & aft of the motor, &
 the brushless
 motors I'm looking at have provision for
 that.But you
 would need two shaft seals & have that additional
 friction.It would
 make it more complicated bolting the motor can
 together.If you had
 the propeller that was back the front, trailing, then the
 flowcreated by
 the forward propeller might help compensate for the
 inefficienciesof the
 propeller for reversing.A lot of
 the thruster manufacturers ( of which there aren't many
 ) publicizethe
 forward & reverse thrust. That might be interesting
 reading.Alan
     
    From: hank pronk via
 Personal_Submersibles
 <personal_submersibles at psubs.org>
  To: Personal
 Submersibles General Discussion
 <personal_submersibles at psubs.org> 
 
 Sent: Monday,
 December 15, 2014 2:09 PM
  Subject: Re:
 [PSUBS-MAILIST] props
    
 
 Alan,
 Another
 idea, make a thruster with a prop at each end of the motor,
 what do you think?
 Hank--------------------------------------------
 On Sun, 12/14/14, hank pronk via
 Personal_Submersibles <personal_submersibles at psubs.org>
 wrote:
 
  Subject: Re:
 [PSUBS-MAILIST] props
  To: "Personal
 Submersibles General Discussion" <personal_submersibles at psubs.org>
  Received: Sunday, December 14, 2014, 8:04
 PM
  
  
 
 Alan,
  Maybe it is better to make a prop
 that works in
  both directions.  I can
 afford to loose efficiency, that is
  better
 than mounting two thrusters in my case.
 
 Hank--------------------------------------------
  On Sun, 12/14/14, Alan James via
  Personal_Submersibles <personal_submersibles at psubs.org>
  wrote:
  
  
 Subject: Re:
  [PSUBS-MAILIST] props
   To: "Personal
 
 Submersibles General Discussion" <personal_submersibles at psubs.org>
   Received: Sunday, December 14, 2014, 7:04
  PM
   
  
 Hi
  
  Hank,I guess
   you would be getting the same
  thrust in both directions,
  
 butyou would
   be doubling the pitch of the
 propeller by
  doubling up, &
   there maybe a lot
   of
 turbulance between the propellers.There
 
 are
   propeller calculators that take a
  number of input variables
  
 like hp, revs,
  boat size,intended
   speed, diameter of the
 
 propeller & pitch. You leave one
  
 input
  out & it calculatesthat for
   you. You
  could call the two
 propellers one (add the two
   pitches
 together) & see what diameter
   it
 calculates for you at a given pitch &
 
 play around
   till you get the most
  efficientdiameter /
   pitch
 combination; then
  use the diameter but
 halve the
   pitch.I
  
 don't think I made a lot of sense, but if
  you go down
   that path I
 will explain a bit
  better.However
   given that submarines
 
 operate better with bigger diameter,
  
 lower
  pitch propellersit
  
 probably isn't a
  good idea going to two
 smaller higher
  
  pitched
 propellers.Alan
       
 
     From: hank pronk via
  
  Personal_Submersibles
  
 <personal_submersibles at psubs.org>
   
   To:
  
 personal_submersibles at psubs.org
  
    Sent: Monday, December
  
  15, 2014 10:38 AM
    Subject:
   [PSUBS-MAILIST]
 props
     
  
   Hi All,
   If I build a
  thruster
   with an extra long
 shaft, then put
  two props on back to
   back, one prop
  reversed. 
 Will the thruster perform equally
   in both
 directions?
   Hank
  
 
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