As best I can tell, the answer appears to be no. My ASW20 has one but
I don't think I have ever looked at it.

A review of the FAR's turns up the following "compass" or "direction
indicator" citations:

91.205 Powered civil aircraft with standard category U.S.
airworthiness certificates: Instrument and equipment requirements.

(a) General. Except as provided in paragraphs (c)(3) and (e) of this
section, no person may operate a powered civil aircraft with a
standard category U.S. airworthiness certificate in any operation
described in paragraphs (b) through (f) of this section unless that
aircraft contains the instruments and equipment specified in those
paragraphs (or FAA-approved equivalents) for that type of operation,
and those instruments and items of equipment are in operable
condition.

(b) Visual-flight rules (day). For VFR flight during the day, the
following instruments and equipment are required:
(1) Airspeed indicator.
(2) Altimeter.
(3) Magnetic direction indicator.

But this section applies to POWERED AIRCRAFT

---OR---

PART 23--AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND
COMMUTER CATEGORY AIRPLANES
Subpart F--Equipment
§ 23.1303 Flight and navigation instruments.
The following are the minimum required flight and navigation
instruments:
(a) An airspeed indicator.
(b) An altimeter.
(c) A direction indicator (nonstabilized magnetic compass).

But this will not apply you are not an AIRPLANE

So unless someone can come up with a reference to gliders or aircraft,
my vote is that the "direction indicator" is not required, unless
otherwise required by the manufacturer certification.

The FAR's are searchable online he

http://ecfr.gpoaccess.gov/cgi/t/text...4/14tab_02.tpl