Gents, direction stability.
Normally there is a lot of posts about the horizontal stability.
Asymmetrical airfoils? Most people are not even finished with that!
But now the direction stability? Do we think it is just making a windshield with a barn door??
Gents, to check the direction stability I have my personal wind tunnel vision!
When an airplane is in the air, pointing exact vertical to the earth with one wing and has no speed, it will fall in a stall.
The first correcting force to get back the flight direction and speed starts on this important moment.
The total side surfaces and the distance of these to the CG is important for this force. The force to give the plane the normal flight direction again is ; dynamic pressure (difference) x surfaces x distance to the CG.
(Before you react, Yes of course also air friction of the wings and shape of the fuselage etc, etc, but this is my method to give me an idea without difficult wind tunnel activities and/or calculations and I do not use swept back wings and forget for a while the dihedral.)
THE PICTURES
Picture 1 Backside of one of the Taurusses.
I did glue cardboard on the backside. The weight is now the equivalent for the side surfaces. But??? It has two main wheels. So double cardboard on the wheel.
The piano wire (heat threatened steel, yes I have it !!!) of nose leg I did made a little wider and to compensate I removed the cylinder head. The Wester Taurus did have a piece of the shaft because it will fly with an exhaust.
Picture 2 balancing on the lineal (knife edge rule?) !!!
On the pictures I did note the distances in mm because the ratio is important not the value to compare. The both Taurusses have the calculated dimensions so the surface of the noses are the same.
Distance to CG op Flite Taurus is 59, Wester Taurus is 48.
The effective side surface of the Top Flite Taurus is about 15 % more .
So the “right direction regenerating force” of the Top Flite Taurus will be 40 % more.
In simple words, the Taurus is one big weather vane and we all know, I think it also gives the problems to start a spin with the thick wings. The wind vane is also the background of my special landing gear, to make it possible to turn on the ground with higher wind speeds.
Picture 3 Because I did not see the TE of the rudder on the crate picture I have to “test fly” with this part of the plane. To give myself an indication what is the effect in a stalled situation I add a piece of (calculated ) surface. The direction stability in total stalled situation is now 30 % less than the op Flite Taurus instead of 40 %.
Picture 4 When Ed did design the op Flite Taurus after his first contest Taurus he probably knew the direction stability was more than enough. With this added surface the stabilities are nearly the same. Later we see they did shorten the Top Flite fuselage without enlarging the rudder. Voila proved.
Now picture 5, a drawing and that’s an interesting picture.
The total side surface of my Wester Surface is small (+/- 15 % less than the Top Flite Taurus) and has a much better shape so, to generate lift during four point and slow roll I need a lot of down force of the fin and rudder.
It is very important to use the most effective and RIGHT TAPERED combination we can design and Ed did know that of course.
Look to the pictures.
TOP: Taurus fin is narrow (on top) and the rudder wide. We see this on all the taurussen!
Of course not on the Orion, with his frise ailerons and high positioned thrustline!!!
I did make mirror image of the fin and rudder, see the green airfoil. With maximum deflection it looks like a highly cambered airfoil with a positive AOA. That’s all right.
BOTTOM: This is what is happening when we enlarge the fin!!!!
We need the AOA of the fuselage to generate lift but an enlarged fin is behaving like a highly cambered airfoil in negative AOA, result drag. So that is not good!!!
”
One big doghouse! So you make a tialdragger from a Taurus!" Ed would have say I think
The pictures shows us also something about downwash, (this is up wash for the rudder and fin I the pictures).
A2 > A1 for the Taurus fin and rudder, so airspeed V1>V2 and Daniel Bernoulli tells us: P static A2 > P static A1.
Result of this pressure difference is upwash (normally downwash when looking to wings). The difference is more in practice, look to the light blue arrows.
(We can explain downwash also with Newton but that’s another story).
Down wash of the bottom situation? That kind of “wind tunnel vision” I do not have.
CONCLUSION
My method is not high tech, but Ed did not have the equipment for that either I think.
The position of the neutral point of the side surfaces during slow roll or four point roll will be nearly on position as shown on the drawing (not as the pictures!!!) and will do, I do not expect any problem. I always can enlarge the rudder a little to give a better result.
Interesting will be the way the spin will be “start”, but also “stop”. I think it is better controllable than with the Top Flite Taurus.
And Duane your post 251, I think you did forget my post 220, page 9.
ORIGINAL: Taurus Flyer
Next but also most important fact is the story.
The evolution of the Taurus in the Crate of Africa to the Taurus II of Kingaltair does have on this moment.
For me it is clear that there is a 100 % relationship between these two Taurusses, but that is not so important, when speaking about the evolution. There could be two fuselages In the story also, same design, but we know Ed could change every part of a plane without leaving behind visible indications.
That is not strange to me. I can do it myself. Look to my Taurus it was blue in the beginning, and one time the fuselage was in two parts after a low pass inverted deadstick.
Cees
Cees