[PSUBS-MAILIST] propeller size

[Alan via Personal_Submersibles]

Hank,
I am not sure but I think that would be OK. 
If you can measure the amps you are drawing & the speed your sub is
doing on the surface, you could make some conclusions from that, &
I think that is the only way to get some really good results. A bollard
test in a pool doesn't take in to consideration the forward movement of
the submarine, & there are also various effects from the sides of the test
pool & circulating currents. I will have to do this with my thrusters but it
is not perfect.
If you can test the amp draw & speed at both voltages then you can say
"Is the gain in speed worth the extra power draw on the battery!"
Are your propellers plastic? I don't think they are but as an aside, I have 
wondered whether the tips bend when you put an extra load on them. 
If say you are producing 100lb thrust, that thrust would be distributed across 
the propeller & surely they wouldn't work efficiently with too much load on them!
Alan



Sent from my iPad

> On 14/11/2017, at 2:37 PM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Hi All,
> Gamma has always run on a 24v 2 hp motor.  The 24v 2 hp motor is simply a 36v motor run on 24v with reduced rpm.  I am thinking about running the motor on 36v to increase surface speed.  This is very simple because the controller will also run on both voltages.  My question is, will the propeller still be sized correctly.  I am assuming the extra rpm is supported by the extra hp, or am I over simplifying it.
> Hank
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