Message-Id: <ab8e35eb01021004a011@[132.177.128.6]>
Date: Thu, 16 Mar 1995 15:14:36 -0500
To: baidarka@imagelan.com
From: prl@hopper.unh.edu (paul labrie)
Subject: Re: Traditional Paddles new thoughts
George replied:
>Usefulness of a paddle (or sail, or airplane wing, or
>parachute) is as much (or more) a function of shape than of area.
>
>All the interesting stuff happens along the edge. Traditional paddles
>have a lot of edge. And Aleut paddles had very interesting edges.
>
I admit I've only half-followed this paddling thread ( I wish I
could just do boats instead of work!!) but I would second that this "edge
business" is the essence of the discussion. In the past 20 years I have
been involved in hang-gliding, soaring (mostly crewing), aircraft modeling,
small-craft sailing (including some exploration of ice boating) and, yes,
even made two parachute jumps (which I'll never willfully do again,
BTW...). In each of these "different" sports the common denominator was
"aspect ratio"; all things being equal a wing/sail with a "higher aspect
ratio" (i.e. long and slim) was considered more efficient than its lower
aspect ratio counterparts (short stubby wings/sails) (remember, we were
only after two things; speed and/or distance!). Indeed most of the
important stuff (read: "lift") happened along the edge. The implication, of
course, is that there is good benefit in creating "more edge", all things
being equal...If you look at the evolution of hang-gliders you'll see a
very nice progression from the early, billowy, low-aspect ratio/high drag
Rogallo wings to the leaner modern craft. There are, of course, valid
reasons for having low aspect ratio wings/sails -- the reasons involve
power/safety more than speed -- for example, a lower-aspect ratio sail
might be found on a large workboat used to dredge oysters. Us sporting folk
weren't very interested in these reasons, however...
A hard and fast statement: high-aspect wings/sails are often found
coupled to light, low-drag, low-volume hulls/fuselages whereas low-aspect
ratio wings/sails are typically found on heavier, high volume (higher drag)
hulls/fuselages. A good rule in aircraft construction is to "build light &
fair" & I expect this has great relevance to baidarka construction. Seems
to me that any discussion of paddle efficiency also has to include what
boat the paddle is driving (apologies if this has been mentioned before).
The two, in my experience, are hopelessly intertwined. (Didn't some of the
heavier paddlers bemoan the fact that they found quill paddles to be
frustrating to use? -- is this why kayak builders used body-based
measurements? -- seems to me that a heavier paddler needs a larger-volume
boat and a correspondingly larger paddle)
Question: A good friend of mine owns a sailplane (an LS-4) and uses
it in soaring contests and some cross-country flights here in NH. The wing
has a "turbulator", essentially a narrow cloth tape arranged in a zig-zag
fashion just a few inches aft along the bottom leading edge of the wing.
This "intentional roughness", in an otherwise glass-smooth skin, was
installed to break up laminar flow, as I recall. Is there any equivalent
to this roughness along the edges of traditional paddles that have been
collected???
Finally, a request: "lifting body" paddles suggest different
paddling techniques than I'm used to (I'm a crude paddler, I admit). I
remember that someone had addressed this in an earlier post which I have
since lost (I remember something about "slicing" a Greenland blade through
the water i.e. using lift rather than drag...) could someone email it to
me? Thanks.
- paul -
paul r. labrie paul.r.labrie@unh.edu
university of new hampshire ---------------------
telecom center voice 603.862.3684
durham, nh 03824 fax 603.862.4545