[hpv-boats] hpv-boats Digest, Vol 55, Issue 2

[David Adrian]

Sorry to react so late to Rick's propeller advices.
For my aquatic vehicles I tested the props sold through Hobbycity, the master
airscrew 15x10 and the 18x12. 12 being the maximal pitch they sell. Obviously
they lack pitch if you keep the same gear.

As I definitely needed more pitch I wanted to try the 15x25 Bolly, but it seems
that Bolly have stopped somme of its works. The 15x25 prop is only sold by 30
pieces.
I am still looking for one, if one of you get one and could kindly sell it to
me, I would be the happiest.

David
www.velosub.com


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 Today's Topics:

    1. Re: Propellers (Rick Willoughby)


 ----------------------------------------------------------------------

 Message: 1
 Date: Sun, 5 Jul 2009 18:08:56 +1000
 From: Rick Willoughby <rickwill at bigpond.net.au>
 Subject: Re: [hpv-boats] Propellers
 To: HPV Boat <hpv-boats at bikelist.org>
 Message-ID: <89DFF61F-8C2E-4141-9D4A-49FAADCEF1B8 at bigpond.net.au>
 Content-Type: text/plain; charset="US-ASCII"; delsp=yes; format=flowed

 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




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 End of hpv-boats Digest, Vol 55, Issue 2
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