Good Page and New Innovations

Good Page and New Innovations

Post by Hamilton Richards J » Sun, 23 Aug 1998 04:00:00



Quote:

> ....  I also have
> ideas about redesigning the current oar to make it more efficient by
> keeping the blade perpendicular to the boat at all times, but I don't
> yet have the resources to do the extensive research and development that
> the ME4016 crew did.  

> This picture is from their page and proves that (in theory) my new oar
> design would be much better:

Hmmm.... that picture doesn't show that "keeping the blade perpendicular
to the boat at all times" would improve its efficiency. There's an
implicit assumption that maximizing force maximizes efficiency, but
efficiency is about minimizing wasted work (i.e., energy), not about
maximizing force.

Not only do the diagram, and the accompanying discussion, omit any mention
of work, they fail to take the hydrodynamics of the blade into account,
and assume that during the drive the blade remains essentially stationary
relative to the water. That's not so, of course-- the puddle is ample
evidence of slippage. To the extent that the rower's effort accelerates
water backwards, rather than accelerating the boat forwards, that effort
is wasted.

As we have learned from the recent thread on "the mechanics of the blade",
the blade is actually most efficient near the catch and finish, when its
lift minimizes slippage and hence wasted work. If that analysis is correct
(and this former mechanical engineer found it persuasive), keeping the
blade perpendicular to the boat would minimize lift, maximize slippage,
and maximize **inefficiency**.

--Ham Richards

------------------------------------------------------------------
Hamilton Richards Jr.            Department of Computer Sciences
Senior Lecturer                  Mail Code C0500
512-471-9525                     The University of Texas at Austin
SHC 434                          Austin, Texas 78712-1188
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Good Page and New Innovations

Post by John C. Sundqvis » Sun, 23 Aug 1998 04:00:00

Quote:

> Hello All,
>         http://www.vt.edu:10021/eng/mech/tidwell/me4016/index.html

>         The above page is a really good site about redesigning the rigger to
> make it more efficient, lighter, and easier to adjust.  I also have
> ideas about redesigning the current oar to make it more efficient by
> keeping the blade perpendicular to the boat at all times, but I don't
> yet have the resources to do the extensive research and development that
> the ME4016 crew did.

> This picture is from their page and proves that (in theory) my new oar
> design would be much better:

> Goodbye for now,
>         Douglas KN Fullerton
>         CDT CPL Fullerton
>         D-3, '01
>         USCC
>         West Point, NY

>     ---------------------------------------------------------------
>  [Image]

In theory, there is no differance between theory and practice. In
practice, it is different.  Without a well designed experiment and some
stain gage readings, it is nothing more than speculation.