Sizing an empennage (unconvetional) 2

[gibran_alves]

hello everyone!

I have a doubt about sizing empennage, not the convetional ones, but, for example, a H or a butterfly ones.

My doubt is: according to the authors that I read, you can use the same procedure used to estimate a convetional one, but if I find a area, example for a H empennage with 1 square meter, should I use 1 square meter on both sides or I must to split the area in two parts 0.5 square meters for each side (in this case a vertical empennage)?

thanks for reading

 

[rb1957]

ok, I'll add some words that help me understand your question.

You're talking about a plane with a double Vertical stabilizer, presumably (but not necessarily) mounted at the ends of the Horizontal stabilizer.

You're asking do these vertical tails Need to be symmetric about the horizontal plane.

I think the answer depends on the data you used to determine the size of the tail. I'd've thought that such available data assumed a symmetric installation (as being the most common and intuitive). If you deviate from this assumption, then you'll change (to some degree or another) the aerodynamic coefficients you used to determine your area.

Can you figure this out ? I'd've thought so ... using one of the many CFD programs out there.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[3DDave]

It's mainly the total projected side area that is stabilizing in yaw, but there are inefficiencies in dividing up the area based on the additional number of edges where air can leak from the higher pressure side to the lower pressure side as well as asymmetric airflow from the fuselage and horizontal stab, if using paired vertical rudders.

I have seen more cases where the area has been too little and bits are added on later than seems like were somehow too large and got cut down.

When one sees the BV-141 (Blohm & Voss BV 141) it's clear that a slavish attention to symmetry isn't always required, but attention to the overall design is.

 

[WKTaylor]

A sketch/drawing, photo, etc of Your configuration would be helpful for clarity.

In the for-what-its-worth category... FAA AC23-9 EVALUATION OF FLIGHT LOADS ON SMALL AIRPLANES WITH T, V, +, OR Y EMPENNAGE CONFIGURATIONS

OHHH.... late addition... in the for-what-its-worth category... NASA-CR-195496 Aircraft Empennage Structural Detail Design

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[rb1957]

"cases where the area has been too little and bits are added on later" ... like a Beech 1900D ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[gibran_alves]

Hello people!

My itention is to size a V-type and H empennage, just to simmulate on OpenVsp, to make a simple comparison between empennages.

And yes is a symmetric, and to find the area I'm going to use a volume coefficient for horizontal and vertical tais.

And my question is: First of all Should I find the area of both empennage; and after this Do I split it in small(vertical, case of H empennages) empenages, example - I want to make three vertical empennages, I must take the area that I find and split in three equal parts; or I find the value of area, and I must to make three vertical empennages of the area I find?

 

[3DDave]

The clear answer is - try it both ways.

 

[rb1957]

Maybe a design book like Raymer or Torenbeek would help. Maybe the olde Hoerner (s?) books ... Fluid Dynamic Lift and Fluid Dynamic Drag ?

With a conventional tail, tail volume is obvious. For an H tail ...
1) are the two 1/2 areas as effective as a whole one ? IDK, but
2) I know one advantage of an H tail is than the vertical tails act as end plates on the horizontal tail, improving its effectiveness (so reducing the horizontal tail size required).

For a V tail, is it "just" projected areas ?


"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[WKTaylor]

I am a bit surprised that the Long-list of references listed in AC23-9 were of no use...

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov