Subject: RE: : Re: [harryproa] Blog update and human power |
From: "'Jerry Barth' shredderf16@sbcglobal.net [harryproa]" |
Date: 6/17/2015, 10:22 AM |
To: <harryproa@yahoogroups.com.au> |
Reply-to: harryproa@yahoogroups.com.au |
Rick,
Is there a source of
pedal drive parts/drivetrains that you can suggest? I did find some full
boats by several different companies for sell, but what I’d like is
something that I can carry in checked baggage and fit it to some craft that I
build. I have a property in the USVI. Shipping to there is very
expensive, at least as far as big stuff like the completed pedal boats that are
sold online. What I’d like to do is carry the drive down there
myself, then mate it to something I make down there. Not looking for a
whole lot of speed/efficiency, just something that performs reasonably well for
exercise and fun.
Thanks,
Jerry Barth
From:
harryproa@yahoogroups.com.au [mailto:harryproa@yahoogroups.com.au]
Sent: Wednesday, June 17, 2015
5:09 AM
To: harryproa@yahoogroups.com.au
Subject: Re: : Re: [harryproa]
Blog update and human power
John
From a biomechanical perspective - Rowing with a rigger or sliding seat
has a lot of muscle groups involved. In calm conditions a trained rower
has a measured efficiency of 22%. That compares with 26% for a trained
cyclists. So aerobically, in calm conditions, the pedals deliver slightly
higher biomechanical efficiency. However in anaerobic conditions the
rower can do better because there are a lot of muscles involved and all can be
pushed into the anaerobic state. That means the rower will be able to
work at a slightly higher power level over 5 to 10 minutes. From there
the cyclist will do better. My boats are about the same speed over
2000m as a rowing shell with equivalently trained pilots.
From a propulsion perspective - Paddles matched to the boat and power
output of the rower will have slightly less efficiency than a similarly matched
propeller drive.
When conditions get a little choppy rowing tends to drop efficiency
because the motion of the oar is more difficult to control. With
pedalling it is a matter of just rolling legs over up to the point where the
prop begins ventilating.
With the first iteration of the pedal drive on the 8T catamaran to test
the concept, one cyclist could match what two rowers could achieve. There
is a brief note at the beginning of this video with regard to the pedal drives
in their final configuration:
You can see they are pulling away from lighter rowed boats.
Fundamentally the prop drive will have a slight advantage over rowing.
On the other hand a rowing system can be simpler to engineer to get
reliability. The boats that chose pedal drives this year left it quite
late to set up systems. None of them are what I regard as reliable.
I have supp! lied standard folding props, which are a bit small for the
size of boats they are pushing.
Rick
On 17/06/2015, at 5:58 PM, "jrwells2007@googlemail.com
[harryproa]" <harryproa@yahoogroups.com.au>
wrote:
Rick,
How does the power output of a peddle drive
compare with a sliding seat rower? I assume that comparisons have been made
between your peddle craft and a sculler.
One of the Farriers
used sweeps from the outriggers, not sliding seat and required 2 rowers.
Sliding seat and sculling could be devised.
Regards
John
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