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Hand powered boat propellor? Answered

I am trying to build a boat for a physics project, and i wanted to try building one that used a propellor instead of the usual paddlewheel or oars that other students have used.  I bought a 2-blade trolling propellor from Walmart, and i plan on attaching it to a crankshaft via a 4:1 belt drive ratio (so with every rotation of the crankshaft, the propellor spins 4 times). Two people will be turning the crankshaft , and the boat itself is stocky with a flat bottom and pointed end.
Is this even possible, and will it actually get the boat to move at a reasonable speed? ("Reasonable" meaning rowboat-ish speed) 

I included a quick sketch of what im talking about, and a picture of the blueprints to the civil war submarine that I got the idea from, just for proof of concept. 



Best Answer 6 years ago

Do some math.
a.) Find out what the output of the original trolling motor was, and its top speed.
b.) Find out what the rated output of two students' arms is - less than the legs.
This will allow you to get some idea - assuming that your crank/gear is enough to get the prop to the same speed in water.
Build it, test it, repeat experiment using whips on students..........


6 years ago

A propeller for low speed RPM is a vastly different configuration ie-shape
then your Walmart 2-blade.



6 years ago

It will "work", but how well will depend on the propeller - the size and pitch of the blades needs to match the intended speed of rotation and size of the boat.


Answer 6 years ago

Human output around 1/2 hp for a while depending on your fitness. perhaps a little less for arms

Prop I guess will need to have big blades and a slow rotation for best use of power. I could be wrong and gearing may be a better answer with a more standard prop.

As Stevs says do the maths