First I will ask a question, Is the Sparrow Hawk registered with an N-number
and does it have an Airworthiness Cert that it is a "glider"

14 CFR § 1.1 General definitions.
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Aircraft means a device that is used or intended to be used for flight
in the air.
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Glider means a heavier-than-air aircraft, that is supported in flight
by the dynamic reaction of the air against its lifting surfaces and
whose free flight does not depend principally on an engine.

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The Federal Aviation Regulations do not limit the definition of a
Glider to an aircraft operated solely under Part 91, 121 and/or 135:
it may be operated under Part 103 and still be a Glider. Aircraft
operated under Part 103 do not require Airworthiness Certificates.
While an insurance policy may have requirements that the towed vehicle
have an Airworthiness Certificate, the FAA does not require one in
order to consider the vehicle a "Glider."

Also, the Airworthiness Certificate issued for the vehicle I regularly
fly does not anywhere describe it as a Glider, or as anything else.
There isn't even a box on the certificate where one would enter that
kind of information.