V-tail sailplanes are more efficient, but are they harder to fly and more difficult to land?

From : Don Stackhouse

Not if they're designed right. No particular tail type has a monopoly on any particular type of handling characteristics, good OR bad. It's all in the details. V-tails do have a bit of a bad reputation, but that's primarily because a great many designers don't really understand V-tails, and don't design them correctly. The problem isn't the V-tails, it's the design flaws in SOME V-tailed models. What Joe Wurts says may have some merit if you're merely surveying existing models and tail designs, but it is not an inherent characteristic of any particular tail type, and in that sense his statement is an oversimplification.

Aerodynamically V-tails have some pros and some cons. Overall it seems to come out slightly in favor of the V-tail in most typical installations, but those aerodynamic margins tend to be very small at best. Aerodynamically, a given amount of tail authority and stability tends to cost nearly the same amount of drag regardless of the tail type. In general, the main reasons we use V-tails so much are primarily structural. They do a good job of staying clear of rocks and other obstacles on landing (like a T-tail), but keep their structural mass low (unlike a T-tail), so they minimize twisting and bending loads on the tail boom.

Joe Hahn and I personally have NO particular allegiance to any particular aircraft configuration. Contrary to what some folks might try to tell you, we are not on a crusade for V-tails, or any other particular design feature. We succeed ONLY by manufacturing models that FLY BETTER. PERIOD. We use whatever configuration does the best job of achieving that goal. For us to do any differently would require that we be intentionally stupid. Our kits use a variety of tail types, as determined by each model's individual mission requirements. It just so happens that for most typical R/C sailplanes, we've found that an upright V-tail does the best overall job. If some other type of tail did a better job in one of these designs, we would use it. The V-tails are on those particular DJ Aerotech kits ONLY because they were the best choice for those particular applications, including landing considerations.

As far as ease of landing is specifically concerned, there are MANY factors involved, and the tail aerodynamics, assuming that tail is reasonably well designed, are not really one of the bigger considerations. As I indicated above, it's possible to make a model of almost any configuration and layout behave well or badly on landing, depending on how the design is tuned.

On the Spectre 120, the original prototypes performed well in flight but had some inconsistent control response problems on final approach. After making adjustments in a LOT of different parameters, including tail design (where the main problem was not specifically because of the "V" configuration, although the way that problem manifested itself was different for a V than it would be with a conventional tail) but also including things like aileron design, tail moment, mass distribution, aileron/flap mix and crow setup, aileron differential, and a number of other things, we got an airplane that had exemplary handling in all flight modes including landing. We used some well-established conventional-tailed open models for comparison during flight testing, and the Spectre 120 was significantly easier to land than all of them. The subsequent performance of the Spectre 120 in competition also supports this. It is possible to make a V-tailed model that lands well.

Your question is an excellent one, and your efforts to get more information are a very smart move on your part. I'd recommend that you not rule out any particular tail type offhand, but that you do try to get some more details on the behavior of any specific type of model you're seriously considering spending your hard-earned money on. As I said above, ANY design configuration can be outstanding, or absolutely crummy, depending on how well the designer did their homework, and on how well the builder followed the instructions when assembling their kit.

Don Stackhouse
DJ Aerotech