I’ve always wondered this. Why do gliders use a T-style tail, as opposed to a V-tail ie a swallow tail design? I think it would represent a significant reduction in weight over a conventional empennage, not to mention, offering a reduction in drag.
The V-tail was a trend in glider design between the late Fifties and the early Sixties. High-performance gliders like the HKS-1, the Arlington Sisu 1A$^*$, the SB-5, the Standard Austria or the Schempp-Hirth SHK had them, as well as the aerobatic H-101 Salto.
However, eventually the T-tail became the preferred choice for these reasons:
- The endplate effect of the horizontal allows to make the vertical about 20% smaller.
- A T-tail will suffer the least damage in an outside landing.
- The effectiveness of a V-tail is lower for the same area, especially in damping.
- V-tails are not really better in terms of drag reduction.
$^*$ Added thanks to the helpful advice by Thomas Perry.