[hpv-boats] Propellers

[Rick Willoughby]

Ken
I have been travelling.  I did email directly but not sure if you got  
it.

The best prop is designed to suit the application.  You need to know  
what power you can produce and what speed you will achieve with that  
power. If you have a hull in mind then the speed v power can be  
worked out.  The best way to determine your power output is to do a  
test on a recumbent machine at a gym.

Typical value of cadence is 70rpm and prop speed is 300rpm.  The  
300rpm works well for a suitable prop.

JavaProp is quite good for designing a prop.  You need to set the  
Options to suit water and select a suitable foil.  You need to select  
a foil.  The E193 at Re# 100,000 and 1 degree AoA is OK.   The design  
process is iterative.  You need to achieve adequate strength while  
aiming for the highest efficiency.

If you can weld then the easiest way to make a nice prop is to use  
stainless steel flat bar.  I have a procedure for this.

The Bolly boat prop is OK for an easily driven hull.  Will not be as  
good as you can make to suit but still good for most applications.

Rick


Greetings All,

It's time for me to do a little research on propellers and such.  I was
looking at Rich W's. boat here:
http://www.rickwill.bigpondhosting.com/V11J_Dec_2008.jpg   and I  
noticed a
wide and steeply pitched prop.  I'm sure that this is a very efficient
setup, so are there plans/drawings for this prop?  How wide is it,  
and at
what pitch?  Are there props for sale?  If I have to make my own, what
materials would I use, wood, fiberglass, or...?

On a related thread what rpms do these generally run at, and what  
cadence is
typical for the pedaling?

Thanks a lot,

Ken


Rick Willoughby
rickwill at bigpond.net.au
03 9796 2415
0419 104 821