V-tail

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skier

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I did a search and found some information of V-Tails, but I was wondering if anyone knew of anyplace to find out how the rudder and elevator controls are mixed such that there are only 2 movable surfaces on the tail?
 

wsimpso1

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The best advice on V-tails is DON'T. Yeah, they look neat, but by the time you get projected areas equal for tail volume, you have the same total wetted area. And then there is control authority and interference between the foils, which actually drives you to more wetted area than with a three surface tail...

There are a few places where they make sense. The Cirrus VLJ is one. No place to put a conventional vertical tail, what with the engine on centerline above the fuselage.

If you just want It, I hope someone can show you how they are mixed. Or visit a mechanic who specializes in Beechcraft...

Billski
 

skier

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I wasn't planning on adding one to my aircraft, I am just curious how they work. I thought about stopping by my local mechanic, but it's pretty uncommon for him to have a V-tail in his shop.
 

autoreply

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Assuming each tail is actuated by one push-pull bar and both rudder and elevator are two push-pull bars each, each tail surface is actuated by the "average" of the rudder and stick input. This is usually achieved by having some kind of "beam" that's halfway connected to the tail, on one end to the rudder and on the other side to the stick. Of course this can also be done by cables and all kinds of mixing are possible.

I should still have some pictures of the flaps/ailerons mixer in a Nimbus 3D which is a great system for it's simplicity, even though it has very complicated outputs. (Ailerons droop and rise with flaps, but with the flaps in the landing position the ailerons go all the way up again for better roll control)
 

Dan Thomas

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I did a search and found some information of V-Tails, but I was wondering if anyone knew of anyplace to find out how the rudder and elevator controls are mixed such that there are only 2 movable surfaces on the tail?
The Davis DA-series homebuilts all have the V-tail, and it works well. The mixer is an astoundingly simple device inside the tail. I have the blueprints somewhere. They have a diagram of the setup. If I can find a few minutes, I'll unroll them and post the diagram. Should be no copyright issues with that, is there? A small bit of one sheet; there's 110 square feet of blueprints for the thing.
The Bonanza's mixer is a bit more complicated but does the same thing.


Davis DA-2A:


Dan
 

Topaz

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...Should be no copyright issues with that, is there? A small bit of one sheet; ...
Nope. That'll fall under 'fair use' - you're illustrating a point in a discussion, and I can't see how it could be shown that posting that small portion of the plans could deprive the legitimate rights holders of income in any way. It's not like they sell kits or plans for just the mixer...
 

Inverted Vantage

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The Davis DA-series homebuilts all have the V-tail, and it works well. The mixer is an astoundingly simple device inside the tail. I have the blueprints somewhere. They have a diagram of the setup. If I can find a few minutes, I'll unroll them and post the diagram. Should be no copyright issues with that, is there? A small bit of one sheet; there's 110 square feet of blueprints for the thing.
The Bonanza's mixer is a bit more complicated but does the same thing.


Davis DA-2A:


Dan
Thank you Dan! I had this specific aircraft in mind when I was talking about low aspect ratio aircraft, just couldn't remember the name. Thank you! :)
 

Tom Nalevanko

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To counter some of the negative points above... Some advantages are: less interference drag due to one fewer control surface and one fewer control surface to build...
 

bmcj

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and less total surface area of tail surfaces
Not necessarily. Billski made that point about total area requirements. Just because they are dual-function doesn't excuse you from needing the requisite amount of vertical and horizontal projected area:

By the time you get projected areas equal for tail volume, you have the same total wetted area. And then there is control authority and interference between the foils, which actually drives you to more wetted area than with a three surface tail.
 

Topaz

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and less total surface area of tail surfaces
That one turns out to be a myth. To get equivalent stability, you end up enlarging the V-tails surfaces to the point where you have the same area as discrete vertical and horizontal tails.

The potential for interference drag reduction is real, but the results probably wouldn't be noticable for most light aircraft. The 'hunting' tendency, especially in turbulence, appears to be real as well, by all accounts. The things just don't want to keep the nose pointed the same way all the time. Mostly annoying, more than anything else.

I can see benefits from the construction simplicity and aesthetic standpoints only, and most of the former is sucked up in having to build a mixer for the control surfaces. Sure looks sexy, though...
 

Dan Thomas

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Something easier than unrolling all that blueprint to find the DA-2 mixer; Here's the mixer in the Personal Cruiser. Essentially the same idea as the DA-2's but using tubing instead of steel flat bar bent into shapes. In examining some of the pictures I think I have it figured out. The ruddervators have their bellcranks on their undersides so that the push-pull rods push to get up-elevator.




You are looking down into the tailcone, and aft. The mixer tips forward and back in those bearing blocks, and as it does the rudder cable attach points do not move because they're in line with the pivot. If you work the rudder pedals, the control stick rod does not move.

The rod that comes in from the bottom of the picture comes from the control stick, and if you pull back on the stick, that rod pushes on the mixer assembly and tips it back, pushing both of the ruddervator rods which push on the control surface bellcranks and both move upward. Up we go.

At the bottom you see the rudder pedal cables. Push left rudder, and the mixer rotates (it appears to be just tubing slid over another tube that is welded to the transverse pivot shaft in the bearing blocks) and the left ruddervator pushrod is pulled forward, angling the left ruddervator down, and the other rod pushes, angling the right side up. A left yaw is what we get. If we pull back and push left rudder at the same time, the left ruddervator won't move and the right one will move a lot, moving the tail down and to the right, a left climbing turn.

Elegant, yes? And definitely sexy, as topaz points out.

Dan
 

skier

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Wow, thanks for that picture. It really clears up what is going on. I must admit thats a really nice piece of engineering right there.
 

Inverted Vantage

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But what are the construction benefits offered? And what is this "hunting" tendency; is there a video of it or a detailed pilot report?
 

K-Rigg

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v tails tend to be more capable of recovering from a stall then a conventional tail. thats what i have read at least.
 
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