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moriarty
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*lets On Tailplane?

Fri Nov 23, 2012 10:02 pm

As I understand it, winglets/sharklets is not only about saving fuel but also a matter of design (fashion?).

But why isn't there any similar devices on the tailplane of aircrafts? If I would make a guess it¨s because it wouldn't make that big of a difference. Even on large wings the effect of *lets is small. Smaller area -> even smaller effect, not justifying the extra cost/weight. Or?

I personally think winglets, sharlets and by all means raked wingtips add much to the attitude of an aircraft, and makes them even more interesting and appealing to look at. They fascinate me. Hence, my thought.

edit: hmm. totally forgot about the 1900D, but that would be the exception that defines the rule, sort of

[Edited 2012-11-23 14:04:34]
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Stitch
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RE: *lets On Tailplane?

Sat Nov 24, 2012 12:57 am

Quoting moriarty (Thread starter):
As I understand it, winglets/sharklets is not only about saving fuel but also a matter of design (fashion?).

The only reason winglets exist is because it improves fuel burn. Aesthetics or fashion has nothing to do with it.  
 
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Starlionblue
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RE: *lets On Tailplane?

Sat Nov 24, 2012 3:20 am

Quoting moriarty (Thread starter):
But why isn't there any similar devices on the tailplane of aircrafts? If I would make a guess it¨s because it wouldn't make that big of a difference. Even on large wings the effect of *lets is small. Smaller area -> even smaller effect, not justifying the extra cost/weight. Or?

Yes, but also if more tailplane span is needed, all you have to do is make the tailplane bigger since there is no span restriction. Winglets would be a costly and heavy way to do so for very little benefit. Many winglets are an alternative to wider wingspan. For example Airbus would probably have given the 380 a bigger wingspan if it hadn't been for the 80x80 meter rule.

Quoting moriarty (Thread starter):
edit: hmm. totally forgot about the 1900D, but that would be the exception that defines the rule, sort of

AFAIK the 1900D fins on the tailplane are not winglets at all and do not perform a drag reducing function. They serve to increase longitudinal stability.
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RE: *lets On Tailplane?

Sat Nov 24, 2012 6:46 am

Quoting moriarty (Thread starter):
But why isn't there any similar devices on the tailplane of aircrafts?

It's not worth it. You don't want the tailplane to be creating much lift, because it is generally downward which is counterproductive. As such the vortices will not be especially strong on the tailplane.

But, it should be noted that the horizontal stabilizer on a T-tail actually does act similarly to a wing fence. The endplate effect does make the vertical tail somewhat more effective.

Quoting starlionblue (Reply 2):
AFAIK the 1900D fins on the tailplane are not winglets at all and do not perform a drag reducing function. They serve to increase longitudinal stability

   It also has a pair of ventral fins.
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KELPkid
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RE: *lets On Tailplane?

Sat Nov 24, 2012 7:56 am

Quoting starlionblue (Reply 2):
AFAIK the 1900D fins on the tailplane are not winglets at all and do not perform a drag reducing function. They serve to increase longitudinal stability.

And allowed Beechcraft to use a King Air 350 tail on the 1900D   (well, with modification-being the extra vertical surfaces).
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RE: *lets On Tailplane?

Sat Nov 24, 2012 6:45 pm

Quoting moriarty (Thread starter):
As I understand it, winglets/sharklets is not only about saving fuel but also a matter of design (fashion?).

There is a little bit of history behind that, but nobody does winglets for aesthetics anymore. Fuel is just too pricey. You only put them on if you need them today.

Quoting moriarty (Thread starter):
But why isn't there any similar devices on the tailplane of aircrafts?

Aerodynamically, you're always better off to increase span than to add winglets. So you only do winglets when you have a span limit or you're retrofittting (winglets don't add as much load to the primary structure as a span extension). For a tail you "never" have a span restriction so you just make it as wide as it should be and don't worry about winglets.

Tom.
 
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moriarty
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RE: *lets On Tailplane?

Mon Nov 26, 2012 5:18 pm

Thanks for the input. Pretty much what I thought.

One thing I still ponder about is the aesthetics aspect. If that was not something that was taken into account why all the different variations of winglets? Now even Airbus does sharklets with the XWB, yet 380 has their old design. Boeing goes for the raked wing tips for the 787. I guess this is off topic under the current subject and that it has been widely discussed elsewhere.

Quoting tdscanuck (Reply 5):
Aerodynamically, you're always better off to increase span than to add winglets. So you only do winglets when you have a span limit or you're retrofittting (winglets don't add as much load to the primary structure as a span extension). For a tail you "never" have a span restriction so you just make it as wide as it should be and don't worry about winglets.

That makes sense I guess. So for the tailplane case, it's a matter of designing it well enough to minimize drag. This whole question popped up when I saw a beautiful pic with vortexes visible from both wing tips and tailplane, not exactly these pics but something similar:


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RE: *lets On Tailplane?

Mon Nov 26, 2012 6:08 pm

Quoting moriarty (Reply 6):
Now even Airbus does sharklets with the XWB, yet 380 has their old design. Boeing goes for the raked wing tips for the 787. I guess this is off topic under the current subject and that it has been widely discussed elsewhere.

As I mentioned before, the A380 is span limited to 80 meters, but ideally the wingspan should be greater. Airbus had to go with the greatest possible wingspan and tack a vertical wingtip device on it. In this case the ideal one was the fence type. If they hadn't had the span limitation they would have used something else.

787 is not span limited to 80 meters so they can use raked wingtips. If memory serves there are patent issues as well.
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RE: *lets On Tailplane?

Mon Nov 26, 2012 6:12 pm

Quoting moriarty (Reply 6):
If that was not something that was taken into account why all the different variations of winglets?

The aesthetic appeal is because of the function. Years ago, they were just funny things on the wingtips. Eventually as people began to learn what they were for, and with the increasing fuel prices and environmental movement airlines (and Aviation Partners themselves) used them for marketing purposes as well in the context of "We have winglets because we want to be efficient and environmentally friendly." That's how they got their appeal to passengers who began to associate them with modern, efficient airliners.

Variation in wingtip device types and design is based on the constraints of a given aircraft and technological advances.

Quoting moriarty (Reply 6):
Boeing goes for the raked wing tips for the 787.

Raked wingtips are better aerodynamically but they add span and also lift which may make them unsuitable for retrofit applications.
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RE: *lets On Tailplane?

Mon Nov 26, 2012 6:22 pm

Sorry for being very ignorant here but what's a *let, in the title of the thread? "Starlet"?
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RE: *lets On Tailplane?

Mon Nov 26, 2012 7:02 pm

Quoting AirframeAS (Reply 9):
Sorry for being very ignorant here but what's a *let, in the title of the thread? "Starlet"?

A "place-holder" for more than one name, describing similar things, that end in "-let". e.g. "winglet", "sharklet", somethinglet". etc?
 
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RE: *lets On Tailplane?

Mon Nov 26, 2012 8:12 pm

Quoting moriarty (Reply 6):
One thing I still ponder about is the aesthetics aspect. If that was not something that was taken into account why all the different variations of winglets?

The analysis of wingtip devices is relatively difficult. Early wingtip treatments were as complicated as the OEM's could analyze with any hope of getting a good result at the time...that's why the early stuff was just fences. The full huge blended winglet is a major design undertaking and really easy to get wrong. It wasn't until about 20 years ago that they really figured out how to do it right.

Quoting moriarty (Reply 6):
This whole question popped up when I saw a beautiful pic with vortexes visible from both wing tips and tailplane, not exactly these pics but something similar:

As long as a surface is producing lift, it will generate a vortex. The presence or absence of a vortex doesn't change with wingtip devices. The strength and distribution of vorticity do change with a properly designed wingtip treatment.

Tom.
 
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RE: *lets On Tailplane?

Mon Nov 26, 2012 10:03 pm

Quoting KELPkid (Reply 4):
And allowed Beechcraft to use a King Air 350 tail on the 1900D

Thank you, KELPkid!! You've answered a nagging question I'd always forgotten to seek the answer for...for decades.  
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moriarty
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RE: *lets On Tailplane?

Tue Nov 27, 2012 3:46 pm

Thank you for the answers. The span issue for the A380 I completely undestand. And as pointed out, the 1900D tailplane has little to do with fuel economics but more to get appropriate tail area when reusing a tail from another design. That's cool to know actually.

Sorry for the * in the title but I honestly didn't know what to put there. Being a programmer I just used what came to my mind   But yes. insert whatever you want instead of the *. I should have written sharlets/winglets/raked wing tips instead. Or something like that.

Great to get so many good and serious answers to a, more or less, pointless question  
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RE: *lets On Tailplane?

Wed Nov 28, 2012 3:16 am

Quoting AirframeAS (Reply 9):
Sorry for being very ignorant here but what's a *let, in the title of the thread?



On the B1900D tail, they are 'toilets', seen clearly here:

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Photo © Michael Fritz



Also, on B1900D, as described to me by a CMA pilot, there are 'delta fins' (aft bottom) and 'stabilons' (aft sides). This is a good view of all the fins from below:

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Photo © Kevin Wachter






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RE: *lets On Tailplane?

Wed Nov 28, 2012 6:35 am

Quoting starlionblue (Reply 2):
AFAIK the 1900D fins on the tailplane are not winglets at all and do not perform a drag reducing function. They serve to increase longitudinal stability.

They increase directional stability, not longitudinal.

Quoting KELPkid (Reply 4):
And allowed Beechcraft to use a King Air 350 tail on the 1900D   (well, with modification-being the extra vertical surfaces).

The 1900 and 1900C use a King Air 200C aft fuselage and tail. The additional horizontal surfaces increase longitudinal stability. When the 1900D was developed (by adding a horizontal plug to the fuselage), dual ventral fins were added, replacing the single centerline ventral fin. They 1900D ventral fins are different than the ventral fins used on the Beech 1300 and the 350ER MP:

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Photo © Mark Kwiatkowski


Raisbeck Dual Aft Body Strakes:

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Photo © Joost de Wit


1900C and 1900D:

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Photo © Trevor Nelson
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Photo © Szabo Gabor



Horizontal tails in cruise are usually only lightly loaded, so fancy tips won't help much. However, the Diamond DA-42 does have anhedral tips on the horizontal tail:

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Photo © AirSpeed
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Photo © Trevor Thornton



[Edited 2012-11-27 22:38:12]
 
KELPkid
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RE: *lets On Tailplane?

Thu Nov 29, 2012 9:21 pm

Quoting Western727 (Reply 12):
Thank you, KELPkid!! You've answered a nagging question I'd always forgotten to seek the answer for...for decades.

No prob. Although I was, in spirit, correct, my facts were a little muddled (it is actually a King Air 200 tail!)  ...

Quoting dlednicer (Reply 15):
The 1900 and 1900C use a King Air 200C aft fuselage and tail.
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RE: *lets On Tailplane?

Wed Dec 12, 2012 1:10 am

I wonder if *lets work on over the wing turboprops (i.e. Q400)?
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RE: *lets On Tailplane?

Wed Dec 12, 2012 1:13 am

Quoting bjorn14 (Reply 17):
I wonder if *lets work on over the wing turboprops (i.e. Q400)?

Sure. Why not? There are high wing prop planes with winglets. For example the Tecnam P2006T.
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RE: *lets On Tailplane?

Wed Dec 12, 2012 5:31 am

Well I'm not sure why everyone seems to like winglets, I certainly don't. The wing fences are better, and the small winglets on the 744/A330/A340 are OK too, but the bigger things look wrong to me.
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RE: *lets On Tailplane?

Wed Dec 12, 2012 6:09 am

Quoting dlednicer (Reply 15):
They increase directional stability, not longitudinal.

What is the difference?

Quoting Aesma (Reply 19):
Well I'm not sure why everyone seems to like winglets, I certainly don't.

Well, yes, but...you're wrong.   Winglets are awesome. They even make the A320 series look attractive, which is a thing to achieve.
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RE: *lets On Tailplane?

Wed Dec 12, 2012 12:19 pm

Quoting DocLightning (Reply 20):
Quoting dlednicer (Reply 15):
They increase directional stability, not longitudinal.

What is the difference?

My terminology mistake there. The devices increase stability around the yaw axis (goes vertically through the aircraft), not the longitudinal (roll) axis (goes horizontally through the aircraft from nose to tail).
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dlednicer
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RE: *lets On Tailplane?

Wed Dec 12, 2012 6:15 pm

Quoting DocLightning (Reply 20):
Quoting dlednicer (Reply 15):
They increase directional stability, not longitudinal.

What is the difference?

Directional stability is about the vertical axis and longitudinal stability is about the lateral axis:

 
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RE: *lets On Tailplane?

Wed Dec 12, 2012 6:59 pm

Quoting DocLightning (Reply 20):
Well, yes, but...you're wrong. Winglets are awesome. They even make the A320 series look attractive, which is a thing to achieve.

I like natural looking things and the winglets as an afterthought are certainly not that. Some sailplanes have wings that taper up and those are awesome, they look like bird wings.
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