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From: rmiller@ccvaxa.UUCP
Newsgroups: net.auto
Subject: Re: Orphaned Response - (nf)
Message-ID: <4900040@ccvaxa.UUCP>
Date: Wed, 11-Apr-84 18:14:00 EST
Article-I.D.: ccvaxa.4900040
Posted: Wed Apr 11 18:14:00 1984
Date-Received: Tue, 24-Apr-84 07:24:03 EST
References: <325@hou2h.UUCP>
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Nf-ID: #R:hou2h:-32500:ccvaxa:4900040:37777777600:1164
Nf-From: ccvaxa!rmiller    Apr 11 17:14:00 1984

#R:hou2h:-32500:ccvaxa:4900040:37777777600:1164
ccvaxa!rmiller    Apr 11 17:14:00 1984

quantitative tests on sailplanes (very high performance gliders if you
must) have shown that bugs on the wings can knock as much as 20-30% off
of the glide ratio. nominally, we are talking about things that glide (in
smooth air) at 40:1 and drop to 32-35:1 (typical) with a "standard"
collection of junk on the wings. (typical powered airplanes come in at
from 5:1 up to 15:1 BTW).

note that these wings (actually the entire aircraft) are designed to
maintain LAMINAR flow. there are extremely few powered aircraft (or
cars) that meet that requirement, but it's a benchmark. a laminar
surface that becomes turbulent due to {bugs, dents, rain gutters, rain,
discontinuities in shape (read that as a notch back roof!), etc} may
actually be WORSE than a mildly turbulent surface due to something called
a laminar separation bubble (please refer to a real aerodynamicist for
an explanation) and destructive interference of air flow elsewhere on
the surface.

the distinctions are important. overall, clean surfaces are likely
better, but you have to be really pushing the design to the limit to get
any useful advantage (other than a psychological one) from washing.