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Propeller RPM's on the prototypes

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Propeller RPM's on the prototypes

Postby roedj » Sat Sep 18, 2010 10:54 pm

I am wondering if anyone knows how fast, in RPM's, a typical propeller would turn on a prototype submarine. I realize it's a function of speed and design but what would be the range of RPM's.

I ask this because all the R/C subs I see have their propellers spinning so fast that they're just a blur. I can't believe that's prototypical but I really don't know.

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Re: Propeller RPM's on the prototypes

Postby Bigdave » Sun Sep 19, 2010 11:18 am

Not sure on the exact RPM but your main problem here is scale.
Lets say a 1/48 scale.
A full sized sub would be traveling 10 MPH a scale sub would be traveling 10/48 or .2 MPH which would look like it is barely moving. :shock:
So we tend to run (Not me of course) our boats faster to not be bored out of our goard!! :roll: :lol:
The props have to spin faster to do this. I think water density may have something to do with it as well. :?:
But I could be totally full of crapola on this. :mrgreen: BD.
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Re: Propeller RPM's on the prototypes

Postby chips » Fri Sep 24, 2010 12:43 am

The last two ships I served on in the USCG had a max speed of 18 knots, with the props turning at 300 srpm. These two sister ships were 210 feet long; Diesel powered with 3.32:1 reduction gears to the shafts (Diesel rpm around 1000 for 18 knots); crew of 70-75. On the other hand, I remember reading that the turbine powered unlimited hydroplanes are turning their props around 12,000 rpm through a 1:3 gear box; turbine is spinning around 4000 rpm.

To figure for scale wake you need to divide the prototype (full size) speed by the square root of the scale. That 10 mph of the full size sub becomes 1.4 mph for the model. The actuak sopeed over ground will be higher than an actual scale speed, but the model will look right as it moves through the water.
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