What is the advantages of a V-tail over a t-tail?

[Mat]

What about the upsidedown rudders with upsidedown v-tails?

[Sparky Paul]

An inverted vee-tail usually has the surfaces mounted on a single boom, which places the surfaces in peril when close to the ground.
The inverted style with the surfaces on booms keeps them out of harm's way.
As for the rudder action, there's no difference.
With the single boom, hold the boom level, and rotate the vee until one surface or the other points down.
Rudder is then set to move the trailing edge left for a left turn.
For the twin-boom style, rotate the vee until one surface points up, and set the rudder direction for a left turn.. trailing edge left..
This is the point which everyone trying vee-tails screws up the first time.

[raptor22]

V-tails are generally less effecient than t-tails or X-tails, especially when turning hard because any correcting force is deflected to either side as well as down, so elevator action causes more drag.

X tails follow behind, with t-tails being the lowest drag.

Unfortunately, the mroe effecient designs are also heavier and mroe expensive to produce.

--Alex

[BMatthews]

Technically it's a fine option.... until it's time to land.

[raptor22]

It is a fine option, but when it comes to really fast stuff such as dsing people are starting to notice measurable differences betweent he x-tail and v-tail designs.

--Alex

[chlee]

For a novice flyer, V-tails have an advantage: when I accidentally catch a wing tip or wing "elbow" on a clump of grass, the quick yaw causes the V-tail to rise upward, avoiding damage to the tail.

Chung

[davidleitch]

Hmmm

If you look at the competition F3J gliders (descriptive rather than normative theory) the last two seasons has seen a switch from from V tail to X tail. None are being produced with T tails. T tails are common in F5B (very fast gliding).

Not actually sure why the switch has ocurred, or why we don't see T tails in F3J gliders.

[skylark3f]

In straight and level flight, with the aircraft in trim, the V-tail is more efficient than the low mounted tailplane, the type found on a Cessna 172 for example. Not only is there less profile drag but also there is less induced drag because there are only two lots of tip vortices and two lots of interferences with the fuselage.
The problems arise in accelerated flight where it is possible in some manoeuvres for the movements of the rudder-vators to become restricted due to their combined effect. Large torsional forces are also induced on the fuselage: this can obviously be problematic.

The T-tail needs a stronger fin structure to deal with the flight loads but the advantage in this is that the fin is automatically fitted with a drag reducing end plate. 1:1 sailplanes use the T-tail as it prevents the horizontal stabiliser from being ripped off when landing in standing crops.

Jack

[Salto]

Not only is there less profile drag but also there is less induced drag because there are only two lots of tip vortices and two lots of interferences with the fuselage.
When producing a vertical lifting force, I count two sources of tip vortices for the conventional tail - same as the Vee. When producing a yawing lift force the conventional tail has only one source, as opposed to two on the Vee tail. So if looking at induced drag, the Vee would appear to be inferior to the conventional layout.

Regarding profile drag, for equal tail areas (the accepted rule for equivalence between Vee and conventional tails), any profile drag difference is going to be strongly influenced by the interference drag created where the various surfaces intersect. Intalled on a nice slender rear fuselage, the Vee tail would appear to win here, with only one near acute angle of intersection.

The problems arise in accelerated flight where it is possible in some manoeuvres for the movements of the rudder-vators to become restricted due to their combined effect. Are you arguing here that a Vee tail cannot reach the same Cl as a conventional tail due to restricted control surface movement?

Large torsional forces are also induced on the fuselage: this can obviously be problematic. Agreed, I think this is the primary reason the discuss launch people don't use Vee tails too often.

The T-tail needs a stronger fin structure to deal with the flight loads but the advantage in this is that the fin is automatically fitted with a drag reducing end plate. I wonder how effective this end plate is when there needs to be a large gap to allow for down elevator movement. I suspect that the complex interference drag created by this gap outways any advantage.

1:1 sailplanes use the T-tail as it prevents the horizontal stabiliser from being ripped off when landing in standing crops. I suspect this is the primary reason 1:1 sailplane designers use the Tee configuration. There is also the benefit of having the horizontal stab clear of wing downwash, even in high alpha maneouvres, but a Vee would also have an advantage here.

Weighing this all up, for low drag in trimmed flight the Vee would appear to be pretty good option. So I wonder why, as David points out, there is a trend in F3J away from Vee tails.

Graham.

[Sparky Paul]

"When producing a vertical lifting force, I count two sources of tip vortices for the conventional tail - same as the Vee. When producing a yawing lift force the conventional tail has only one source, as opposed to two on the Vee tail. So if looking at induced drag, the Vee would appear to be inferior to the conventional layout."
.
There's three on a conventional tail.. the fin tip and both stabilizer tips.
For an X-tail, theres the fin-fuselage junction and the horizontal junctions..
Only two of these for a vee-tail.
I've built a lot of vee-tails recently.
I find them easy to construct, attach and use.
The ground clearance in a sliding landing is superior to the conventional type.

[raptor22]

Are you arguing here that a Vee tail cannot reach the same Cl as a conventional tail due to restricted control surface movement?


I dunno what he is arguing, it is right that they can have less authority with higher drag. This is becuase half of the force is cancelled out by the other surface when up elevator is pulled, so much greater control movement is needed for a given amount of movement.

[Ollie]

The V-tail is harder to develop the design. If the designer wants to makes the Yaw or the Pitch responses it the area and including angle (two changes) for only Yaw (or Pitch) with making the other response.

For the T-tail or cross-tail, only the area with no including angle change is a brother for V-tail. I this is why V-tail designs are not finished well while fixed tests are not finished delevoping.

[skylark3f]

I agree with Sparky Paul on the issue of the fin. There has to be some interence with the fuselage and even though the fin generates no lift per se, it simply must induce interference/drag at the tip.

On the point concerning restricted control movements. It makes sense that will full elevator, the rudder movement is limited and vice versa. This makes spin recovery and exact science, whereas in most trainer type aircraft (i.e. those that fly with the trainer type attributes) one can just 'let go' of everything and it will recover itself.

On the subject of T-tails, if the elevator isn't full span but provides room enough for full rudder deflection, an efficient setup is the result. I agree with the reasons regarding the why the T-tail is chosen for sailplanes is for practical, not theoretical purposes, primarily and would like to add that it is indeed true that only at the stall, does the flow brake off and hit the tailplane.

However I would like to add, that with a user-name like 'Salto', I suspect that you are pretty o'fe with the nuances of V-tails and welcome any further comments on the section.

Regards,

Jack