On Wednesday, December 12, 2012 11:05:28 AM UTC-7, soartech wrote:
While discussing tailwheel weight I wondered why we need a tail dolly?

Why do most modern sailplanes have fixed tailwheels yet SGS gliders

have castering tailwheels. Shouldn't we have a caster instead?

Your basic question is valid. Back in the round engine days, some big taildraggers had lockable tail wheels which castered for taxiing and locked straight-ahead for takeoff.

One imagines a variation of this could work with gliders. If the cockpit is empty, weight on the tailwheel would make it caster. With a pilot in the cockpit, the lighter weight on the tailwheel locks it straight ahead. The castering shaft would just have a axial spring pushing the tail wheel down 5mm or so to lock it straight ahead. Basically it would be automatic with no input from the pilot.