Subject: Re: [baidarka] Lift and Drag
From: Will Samson (willsamson@yahoo.co.uk)
Date: Thu Oct 07 2004 - 12:00:05 EDT
What I haven't heard anybody give, yet, is an exact, agreed definition of
'lift' and 'drag'.
Having googled these words along with 'foil' there's loads of semi-intuitive
stuff about them, but no clear definition.
One that I did come across, though, was a diagram of a foil in a flow.
There was an arrow labelled "resultant hydrodynamic force" which was
resolved into two perpendicular components - "lift", and "drag". "Lift was
the component at right angles to the direction of flow (or travel, depending
on how you look at it) and drag was parallel to the direction of flow.
Now that makes sense to me - there's a force on the foil, and it acts in a
particular direction. If that direction is mostly at right angles to the
direction of flow, then "lift" exceeds "drag". If it is parallel to the
direction of flow, then "drag" exceeds lift.
If anybody's got a more precise definition, I'd be glad to hear it. Please
don't hold back because there's a bit of math there - I can cope with that,
as can many of us on the list.
Unless we agree on what terms mean, we'll be arguing until the cows come
home.
Bill Samson
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