V tail versus Conventional tail

[John Armstrong 2]

As a novice flyer I am interested in the pros and cons of V tail versus a conventional rudder/elevator tail. Are there different techniques employed to fly planes with V tails?

[ken anderson.]

hello john......wellcome from me.....a new can of worms you may have opened(different opinions)...i dont know all the right/wrong reasons......but i know a few 'glider' pilots who say the a conventional tail is better for aerobatic performance....

 

ken anderson ne..1 ......can of worms dept..

 

Edited By ken anderson. on 27/12/2011 19:02:24

[Phil 9]

is there any advantage of a V tail?

[Biggles' Elder Brother - Moderator]

I've only ever flown one V-tail model. In my experience they are no more difficult to fly than conventional models - but then I fly mode 2 so have the rudder and elevator on separate sticks - I don't know if they are any more of a challenge if you fly say mode 1. But I suspect not.

 

They are certainly more complex to set up as you have to get the mix right so that you can get pure rudder or pure elevator movement.

 

Aerodynamically they are viewed in some circles as being slight inferior to a conventional arrangement in that if you stall the tail you can lose both rudder and elevator control simultaineously. In a conventional arrangement a stalled elevator still generally leaves you with rudder control. This can be significant in spin recovery.

 

BEB

[Devon Flyer]

There is supposed to be less drag with a V tail compared to a cruciform tail; there being only 2 surfaces instead of, effectively, 3. This is why they are favoured on high speed slope racers.

(That's what I've always been led to believe, anyway.)

[Vecchio Austriaco]

A V tail is lighter than a conventional cross or t-tail - so this could give an advantage at design stage of an aeroplane. I used to fly gliders with V-tail - also without aileron - in this case the V-tail is following the commands better than a conventional tail.

Also you have the advantage to see what your plane is - should you be the only one with a V-tail in the sky. This sounds silly - but if you get a nice thermal it is really a challenge to see what is yours - especially if you together with many others... VA historic department

[Tom Wright 2]

Hi John

As a novice flyer I would suggest you stick to a conventional tail set up and try V tails as you become more experienced .

[John Armstrong 2]

WOW, 15 mins in and already 5 posts with words of wisdom!! As a newcommer to the forum thank you all very much.

 

I should at this point say that I have put the cart before the horse as I have already just purchased a set of plans for a V tail electric glider, an Apollo. As I currently bungee and thermal a Gentle Lady I wanted a new build project. I thought a V tail and electric option would be something new to try.

[Tim Hooper]

John,

 

I'm not an expert, but I've had a couple of v-tailed models and never had any problem whilst flying. I can see the arguments about not being quite so efficient as a conventional tail, as each half of the V is a bit of a compromise between being a fin and a horizontal surface - but unless you're an afficiando in search of the ultimate, then I can't see any real downside.

 

The only thing I would stress however, is that the ruddervators are just that - a mix of rudder and elevator. There's many a modeller (well, me to be exact) who has happily programmed them as elevons only to find that directional control is reversed!

 

tim

[Tim Mackey]

I find that rudder effect is not as strong on V tails as it is on most T tails.

.......most likely for the reasons already given earlier.

As Tim says, be sure to set them up correctly.

 

The easiest way to do this - I find - is to view the model from the rear, twist the fuselage so that one tailplane half is vertical with the tip uppermost. Now, rudder right command should move the surface to the right, and viccky verky.

Now, twist the model around again so the the other half is vertical as stated, and repeat. Again, the relevant surface should follow the command direction.

Edited By Tim Mackey on 27/12/2011 19:37:06

[Frank Skilbeck]

I have a couple of V tailed gliders and the rudder function isn't as powerful as a conventional rudder can have some unwanted pitch effects when applied, but that could be because I haven't got the mix ratio correct.

 

As for spin recovery, my V Tailed Mini Blade is very reluctant to come out of a spin once you've managed to get it to spin in the 1st place, I only did it once and won't try and repeat it

[Steve Houghton 1]

I have both too. If you're someone who like me, likes to uses rudder for aerobatic manoeuvres, the cross tail is better, otherwise I find there's no real difference.

[Simon Chaddock]

One further point to consider is potential ground damage.

A conventional low set tailplane can be easily damaged in a plane with a low slung fuselage.

In this respect a "V" tail is better although a "T" arrangement is better still.

[Martin Harris - Moderator]

I used to fly a V tailed glider - the Schempp-Hirth SHK - which felt essentially the same as any other glider to fly. There were no limitations on spinning that I can recall.

 

I understood that the main reasons they'd designed it (and it's predecessor, the Standard Austria) with the V tail were, as Simon says, to avoid the situation where a low set tail could catch in a crop or long grass and get damaged in an outlanding and for drag reduction due to reducing the number of tip vortices or drag producing junctions in the case of a T tail.

 

The main disadvantage of the T tail was felt to be in the leverage exerted by the weight of the tailplane on the fin base area causing damage to the fuselage in a ground loop. However, the T tail seemed to very quickly become the convention so it seems that either these theories were false or the simpler mechanics and/or arguably better aesthetics won out.

 

BEB - I'm rather interested in your tail stalling scenario - I know better than to question its validity but I can't think off hand how you stall a tail other than in a deep stall situation which would be typical of a T tail - how would this arise?

Edited By Martin Harris on 28/12/2011 01:21:25

[Martin Harris - Moderator]

Feel free to delete this post!!!

 

Edited By Martin Harris on 28/12/2011 01:22:08

[Mark B]

The reduced drag theory has multiple sides, yes there's only two surfaces but partially disregarded is the fact that they are slightly greater in area than the three separate surfaces in what has become a conventional tail layout, ie a t tail. Control is reduced when using full throws with V tails as if you have full elevator in, only half rudder can be applied, also causing a reduction in elevator applied. The advantage with V tail use on models is the clearance for the main surfaces when flying from long grass.

[Mark B]

During a spin the fin and rudder can be partially blanketed by the tailplane on low or mid tail aircraft. This does not occur with T tail aircraft and has therefore led to wide use of this tail setup on full size gliders due to the large quantity of time they spend near the stall and turning. All V tail aircraft are more difficult to get out of a fully developed spin not because of blanketing as this is nil on V tail aircraft, but due to the lesser quantity of movement available to exit the manuever, ie mixed elevator and rudder. This is easily rectified by moving the CoG foward until the aircraft will not spin, or by increasing the surface area of the tailplane and fin, ie both surfaces on the V tail setup.

 

Many slope soaring speed and combat models use V tails without rudder control. This is simple to do, only requiring a split in the elevator control rod to go to separate surfaces.

[Mark B]

The term stall seems to have been confused. A wing stall and tail stall are very different including symptoms and effect.

 

A wing stall is where the wing exceeds an angle to the airflow, generally 12-14 degrees, speed has no effect on this stall.

 

A tail stall is similar in terms of the angles but is usually because the control surface is stalled - on models anyway. Easy fix, reduce movement or increase control surface area.

 

With mid and low tails the fin and rudder can be partially blanketed during a deep stall. Mid and T tails also blanket the fin and rudder but only in an inverted stall situation. V tails do not have any blanketing effects as both controls are combined on the same surfaces, the only problem during stalls and spins is the reduced movement when combining rudder and elevator as mentioned above.

 

A few things to think about are the pro's and con's of inverted V tails and Y tails, neither are very common on full size aircraft, and even rarer on models.

[Erfolg]

It seems we are all agreed, that from practical experience both types of tail arrangements work pretty much the same.

 

I am not sure that I agree that the "V" tail has a more complicated set up. I have used push rods and snakes for actuation. That is two snakes and two servos. I find that snakes are easier. The one difficulty I have is to actuate the elevators. I use ball links, with bent torque rod type actuation horns, with the ball soldered on. There may be easier methods that accommodate the angles that the horn goes through. My method is not for the beginner, that has not installed ordinary torque type systems.

 

With respect to controlling the "V" tail, in this era a computer radio is the obvious solution. All mixes are there.

 

There is possibly a theoretical aerodynamic advantage with a "V" tail. In that the interference drag at the tailplane junction, is limited to the two surfaces at one location. Whereas there two at the elevator fin junction and an additional one at the fin body junction.

 

It has been argued that the tailplane area of the "V" tail is less. All my models have very similar areas to the combined fin and tailplane areas combined.

 

The "V" tail does seem a little better than a conventional tail when it comes to damage from very heavy arrivals. It certainly beats a "T" tail, which will often damage the tail boom in a glider or the base of the fin with a sports model.

[John Armstrong 2]

Can I thank everyone for their responses to this thread. I have learnt a lot as I knew I would. My build with a V tail now holds no fear for me. Especially as Mrs Christmas has also allowed me to upgrade my very old 2 chan Tx to a new Hitec Optic 6 2.4Ghz

[Mark B]

I have the original apollo article somewhere. A 2002 issue it came out as a free plan. It was a good read including info about soaring i believe. It might be worth getting your hands on if you can.