Terry wrote:
the best glide speed of a warrior is quoted as 73 kts. but best glide
should
be at best lift /drag ratio...

It is.


which I recall is at about 4 degree angle of attack.

Who told you this? CFI? POH? Seems awful low to me; I've never seen an
AOA quote for Vbg for a GA aircraft.


But this must be a function of weight.

The airspeed is, not the AOA.


So my questions are what weight is the 73 kts based on?

Best lift over drag as you suggest.


My flying school actually rounds it off to 75kts, regardless of weight.

Stupid. Fly 73, not 75 - if you can't fly 73, you need practise. There are
numerous rules of thumb, to get it accurately, scale by sqrt(weight) /
sqrt(gross) - ensure you use CAS, not IAS.

Hope this helps,

Hilton