05-08-2013, 04:11 PM
I disagree with several of your statements, thrust varies with speed because drag forces have increased not prop angle. Prop angle changes very little at electric motor speeds so don't confuse the issue there.
uhm, it would help if you didn't confuse the issue.
I never talked about prop angle changing at electric motor speeds.
If you don't understand that forward speed decreases thrust particularly on low-pitch props, you don't get the whole propeller thing. I didn't ever say that top speed won't occur where thrust equals drag. I said that at speed your motor will not put out its rated thrust -- because the prop Angle of Attack (not the pitch) changes. So top speed will occur when drag is below the rated motor thrust.
Everything you said about efficiency is 100% correct. Matching the right motor and prop for the application is critical.
MinnKota motors and props are set up to be trollers... which is why they use those big, low-pitch props. They are great at holding a constant low speed in a variety of conditions.
But the question was about going faster in a canoe -- which are generally low-drag vessels.
For that application a smaller diameter, higher pitch prop would be very helpful.
Unfortunately such props are not readily available.
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uhm, it would help if you didn't confuse the issue.
I never talked about prop angle changing at electric motor speeds.
If you don't understand that forward speed decreases thrust particularly on low-pitch props, you don't get the whole propeller thing. I didn't ever say that top speed won't occur where thrust equals drag. I said that at speed your motor will not put out its rated thrust -- because the prop Angle of Attack (not the pitch) changes. So top speed will occur when drag is below the rated motor thrust.
Everything you said about efficiency is 100% correct. Matching the right motor and prop for the application is critical.
MinnKota motors and props are set up to be trollers... which is why they use those big, low-pitch props. They are great at holding a constant low speed in a variety of conditions.
But the question was about going faster in a canoe -- which are generally low-drag vessels.
For that application a smaller diameter, higher pitch prop would be very helpful.
Unfortunately such props are not readily available.
[signature]