[PSUBS-MAILIST] props

[Alan James via Personal_Submersibles]

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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