Twin stabs: has it been tried?

Has anyone every tried using two stabs with elevators stacked one of top of another!? Imagine wing mounted on the engine center line and two stabs in the back: one 2 inches above the thrust line and one 2 inches below. This should theoretically increase effective tail volume plus defeat the flap blanking effect on the tail on down manuver.
Sounds like a win-win proposition.

Seems to me that when giving up control the lower elevator would throw turbulance into the upper elevator/stab and vice versa on the down control.

Can't see it working very well, but I'm not an engineer

>Seems to me that when giving up control the lower elevator
>would throw turbulance into the upper elevator/stab and vice
>versa on the down control.

Not unless you place them far apart! 4 inches apart in my example. Let's take a 2 inch elevator. At a 30 degree deflection, the distance from the tip of the elavator to the other stab would still be 3 inches!

Here's another thought I have in support of this idea:

Physics of inteference between parallel stabs is sorta like airplanes flying in the ground effect: interference becomes noticable only when the plane is within half a wingspan away from the ground. If we translate this fact to my scenario, at 4 inches apart, the stabs can have a span of 8 inches and still have ZERO interferance with each other. That's an equivalent of a 16 inch single stab!

Do it. Let us know what you think.

There is something like that on the Vickers Vimy Bomber.

http://www.airandspacemagazine.com/asm/web/site/QTVR/VimyObj.html

Must be some reason why the idea didn't catch fire...

Cy.

Distinctive, but draggy. Currell

>Distinctive, but draggy. Currell

Hmmmm, not all bad, Currell. We've gone to lower aspect ratio tails to move the center of drag aft during maneuver to help stability and corner exit. The drag from the bi-stab would be even greater and maybe even tell us whether the whole idea of draggy tails is valid or just a little hyper aerodynamic conceit.

Ted

I agree w/Howard, Steven. Give it a try and tell us how it works.

Ted, Howard

According to Ty in post #7 the twin stabs didn't work on full size aircraft in 1917 so it was abandoned. I'm not sure how it might work on one of our tethered models though. I keep trying to build something that isn't tail heavy so two stabs/elevators is the last thing I need!

Jim Pollock

The drag from the bi-stab would be even greater and maybe even tell us whether the whole idea of draggy tails is valid or just a little
hyper aerodynamic conceit.
>

Sure, go ahead. But the easier way to get more drag, stab wise, is simply to make a longer/wider/thicker monostab (now there's a term).

Again, admittedly, it does look cool. After Walker and his B-17, perhaps anything is possible, stunt wise. So, take any one of several WW 1 twin engined bombers with the "bi-tail", and go for it.

Also tried on the ficticious "Reindeer" commercial passenger liner from the old Jimmy Stewart film, "No Highway in the Sky".

He was an engineer who found a fatigue problem with this unusual aircraft. No one would believe it was unsafe. To prevent it from flying, he yanked the LG lever - retracting the gear while said aircraft was still on the ground.

"It just folded up and sat right down!"

Jimmy Stewart? Please! The Neville Shute film! The film of the same name from his book "No Highway". Neville Shute was an aircraft engineer who left the industry and became an extremely successful author, usually with an authentic technical bias. Other books were "On the Beach" and "Trustee from the Toolroom". Shute was the stressman on the frame calcs for the R100 airship, with Barnes Wallis as chief designer, at Vickers. When a lad, my mother had a friend in the Arthur Rank organisation who got us tickets for the Press Shows of various films. No Highway was one of these. What a thrill. E&OE.

LAST EDITED ON Jul-31-03 AT 00:35 AM (CDT)
 
>There is something like that on the Vickers Vimy Bomber.
>
>http://www.airandspacemagazine.com/asm/web/site/QTVR/VimyObj.html
>
>Must be some reason why the idea didn't catch fire...
>
>
>
>Cy.

What I like about the website is the picture and the use of Quicktime software, where you can use your mouse on the picture and are able to get up to 360 degree views of the plane.
Also notice the word 'EXPERIMENTAL" painted on side of aircraft.

Jaco:D

>Has anyone every tried using two stabs with elevators
>stacked one of top of another!? Imagine wing mounted on the
>engine center line and two stabs in the back: one 2 inches
>above the thrust line and one 2 inches below. This should
>theoretically increase effective tail volume plus defeat the
>flap blanking effect on the tail on down manuver.
>Sounds like a win-win proposition.
>
>Steven Yampolsky

I have three words: 1) Why? 2) Weight. 3) Drag!

Why? The single stab seems to be working quite well. I don't see a flap blanking effect on the tail on down maneuvers now. Even if there were one that was bothersome, a stab inline with the wing would solve that. However, if there were one, (back to that argument) then on the twin stab half would be blanked out with "up" control and the other half would be blanked out with "down" control. It would seem to defeat its own purpose in this argument.

Weight. With most planes we are trying to keep the tail as light as possible. Simce there has to be some interaction, two horizontal tail surfaces will not equal the efficiency of a single surface with the equivilent area. So we will have to make it larger. Then we have to double the linkages and put in a more complex mechanism. And where do we put it? In the very back that we are trying to keep light.

Drag. With less efficiency and more area we are adding more aerodynamic drag. But there will also be a more complex mechanism which means more internal (mechanical) drag on the controls.

Now, are there really any arguments on the plus side? (other than doing something "different" which may be reason enough for those who like to do things different. Hey. There was a Tri-plane at each of the last two Nats. They were "different".)

The German Halberstadt tried this, It didn't work. The Brits tried it, it didn't work. That was in 1917. Hint, it still doesn't work in this century.
The air gets compressed between the two stabs like ground affect and the resulting drag and turbulence causes stability problems. Just the opposite of what they were attempting.
Now two rudders looks better.

I ain't no kind of math wizz, but I do know that simply halving a typical elevator and putting one above the other would not give the same effect as the single elevator, but the linkage would not have to be complex, and the weight would not have to get out of hand. The linkage could simply be a wire going from one to the other...no doubling reguired. Just like the alerons linkage for WWI biplane ....not difficult and very little extra weight. I am also unsure if there would be that significant of a blanking effect. With dual, smaller elevators, set wider apart? How would one effect the other? When a biplane goes hard up or down, does one wing blank out the other? Also, could not the extra tail weight be adjusted by simply shortening the tail moment? I think this is a project that could be a lot of fun to experiment with in a 1/2A format. May get a killer corner devil out of it! Go for it...could be a lot of fun.

Ty,

I guess the Human race is doomed to repeat every mistake made in the past. It seems if one generation passes then almost all the knowledge they gained regarding what work's and doesn't is lost and doomed for a repeat attempt.

Yep, some genes are just too tight.

Steven,

Last one I saw was on a Reindeer in the Movie "No Highway In the Sky" with Jimmy Stewart. There was a structural problem and the whole tails kept breaking off the Reindeers.

We don't want that kind of problem on our stunters!

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"Nothing so needs reforming as other people's habits." -Mark Twain

Steve,

Yes it has been tried. A friend of mine Mark fechner Built a twin tail. He had a Double Whatiz kit of Riely Wooten`s and he built them as one plane. So it had a very long wing and rudders top and bottom with stabs and elevators top and bottom. It flew vey well.Had a fox 35 black head,Combat special. He built this in the 1960`s.Look cool too.

Although I was not at Muncie, I heard that someone was there with a TRI-PLANE that was in fact equipped with twin elevators of some sort. It also had two engines.
Truth or rumor? If true, anyone see it fly?
Bob Z

>Although I was not at Muncie, I heard that someone was there
>with a TRI-PLANE that was in fact equipped with twin
>elevators of some sort. It also had two engines.
>Truth or rumor? If true, anyone see it fly?
>Bob Z

Yup, same flyer who had the Fokker Tri-Plane last year. This was a take-off on the Wright Bi-plane (now tri-plane) but flying the "wrong way" (tail last). He (I wish I could remember his name) likes Tri-planes and builds/flies only tri-planes.

He doesn't spend a lot of time on construction and admits it. He would rather fly. They are cute, and do stunt OK, but even he would admit they are not a real "serious" attempt at building a stunter. (They are an attempt in building a tri-plane that stunts.)

Now, some people will miss their bottoms on occasion and get away with it. Doing this with a tri-plane can be a bit more difficult, as he later demonstrated. Missing a bottom in an outside maneuver resulted in an impact between the top wing and terra firma (very firm-uh) that reduced it to a monowing and a half during an official flight.

Not to be deterred, he got out his back up ship for his next official attempt. Oh, yes, this one, too, had three wings.

(As an aside, did you ever see anyone lug their car battery to the flight line and use it for their starter battery?)

A car battery - what is he starting? A Wright Cyclone?

I believe I know who you mean - a fellow by the name of Summer (or Sumner). Nice guy - he showed up at our contest with a really interesting triplane - the center wing appeared about twice the size of the other two. It really flew rather well. He also flew a tri-plane one year at Brodak's.
I heard he had a really BIG tri-plane at Muncie in 2002.

Bob Z

LAST EDITED ON Jul-31-03 AT 11:50 AM (CDT)
 
>>Although I was not at Muncie, I heard that someone was there
>>with a TRI-PLANE that was in fact equipped with twin
>>elevators of some sort. It also had two engines.
>>Truth or rumor? If true, anyone see it fly?
>>Bob Z
>
>Yup, same flyer who had the Fokker Tri-Plane last year.
>This was a take-off on the Wright Bi-plane (now tri-plane)
>but flying the "wrong way" (tail last). He (I wish I could
>remember his name) likes Tri-planes and builds/flies only
>tri-planes.

James Sumner, I beleive. Had a lot of interesting inputs for the pilot's meeting, too.

>He doesn't spend a lot of time on construction and admits
>it. He would rather fly. They are cute, and do stunt OK,
>but even he would admit they are not a real "serious"
>attempt at building a stunter. (They are an attempt in
>building a tri-plane that stunts.)
>

All of them have flown at least pretty well. Early in the week he did a great save over on circle one. He lost an engine, or engines, inverted, and he started walking off to the side. We all thought he was going to land it inverted on the grass. Instead, he used the fact that the *ground sloped away to give him more airspace to flip it over upright*. He was well below pavement level, but he had plenty of room over the local terrain. This was one of the more impressive examples of presence of mind that I have ever seen.

My gut impression is that Mr Sumner doesn't limit himself with conventional thinking, and in this case it was brilliant.

> My gut impression is that Mr Sumner doesn't limit
>himself with conventional thinking, and in this case it was
>brilliant.
>
> Brett

I think the guy is "out there", but in a very cooooll way. Excentric but kind of brilliant. Non linear. He seems like a real nice guy too.

I thought it was funny how one guy wanted every one to clear their planes out of the pits before he flew.

Great running Tandem Saitos. Very cool sound.

Not to forget the Capellis XC-12 which had to have been one of the last biplane-tailed airplanes built. That's the one that was in the movie "Flying Tigers" and a few other great old Republic movies.
Bare

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