Dagling) was a single-seat training glider produced in the 1930s by Fred Slingsby in Kirbymoorside, Yorkshire.

During the 1920s Alexander Lippisch designed a training glider with very low performance to introduce pilots gradually to full-blown gliding.

The plans for the modified Zögling made their way via the United States to the London Gliding Club and Reginald Foster Dagnall, whose RFD company put it into production as the RFD Primary.

Fred Slingsby took over construction in 1934 and production continued up to the outbreak of World War II.

The Primary should not be confused with the similar T.38 Grasshopper which was produced for the Air Training Corps in the 1950s.