Airspeed between inboard wing tip and outboard wing tip

[Lanny Shorts]

Would one of you Boeing engineers or rocket scientist or math major compute the following for those of us who majored in history, business or political science the following. Line length 75'; plus 2' from body to andle, plus 6" leadouts for a total length of 77' 6"". For simplicity just say 78' from center of circle, point A, airspeed to point B,the wing tip of the inboard wing, airspeed to center line of fuselage point C with a 30" inboard wing, and the airspeed to point D, the out board wing tip of a 30" out board wing panel.  This would be using a lap time of say 5.6 seconds.
So airspeed: Pont A to B: Point A to C: and finally, Point A to D.  Or, has there ever been a computation of this already been done before.Thanks, Lanny

[Howard Rush]

Lines are too long. You’re disqualified.

[Dennis Toth]

Lanny,
For the line length numbers you posted at 5.6 lap time: inboard tips speed at 78' is 59.7mph; Center of fuse at 80.5' is 61.6 mph; outboard tip at 83' is 63.6 mph. Difference inboard tip to outboard tip is 3.9 mph.

Best,    DennisT

[Steve Berry]

Lines are too long. You’re disqualified.

 

Steve

[Dennis Toth]

Lanny,
Here is a little spreadsheet for Excel that you can play with. The cells in RED are calculation cell do not change them, Black cells are input. There is a section at the end for electric battery pack cals if you fly electric.

Have fun.   DennisT

[Howard Rush]

Speed is proportional to circle radius, so the ratio of speeds of any pair of those points is the ratio of distances from the center of the circle of that pair.  This doesn't count wind.

Post 40 of https://stunthanger.com/smf/stunt-design/unequal-semi-span-wings/ has some stuff on wing asymmetry and line length.

[Kees Roos]

Would one of you Boeing engineers or rocket scientist or math major compute the following for those of us who majored in history, business or political science the following. Line length 75'; plus 2' from body to andle, plus 6" leadouts for a total length of 77' 6"". For simplicity just say 78' from center of circle, point A, airspeed to point B,the wing tip of the inboard wing, airspeed to center line of fuselage point C with a 30" inboard wing, and the airspeed to point D, the out board wing tip of a 30" out board wing panel.  This would be using a lap time of say 5.6 seconds.
So airspeed: Pont A to B: Point A to C: and finally, Point A to D.  Or, has there ever been a computation of this already been done before.Thanks, Lanny

airspeed = radius of circle * angular velocity
angular velocity = 2 * pi / laptime

So, airspeed  point B : 78' * 2 * 3.1416 / 5.6 = 87.5157 ft/ sec
As you can see 2 * 3.1416 / 5.6 = 1.1220 is a constant,
So, airspeed at arbitrary radius R  = 1.122 * R

[Air Ministry .]

UM ,

call the lines 65 foot .
call the span 5 foot.
So thats 60 inches . which is a twelth of a foot . which is 12 inches . Nothing to do with legs .

So , the SPAN is one thirteenth of the line length , I think . Then you have Pies and things , but Percentages ( % ) will do .

SO , half the spans a 26th . Tho It'd be more conveniant at 25 % , in your head .But its not A 25th is 4 % , so there we are .

One Tips 4 % faster , the other 4 % slower . maybe . Say 55 mph .  1 % would be .55 mph , X 4 =2.2 mph ( as its actually a 26th , call it 2 mph )

Therefore , about 4 mph variation inboard tip to outboard .
Like the lines half way out'd be at 27 1/2 mph .

SO , if you calculated 62 1/2 speed , 65 speed , and 671/2 speed , youd be spot on , for 65 foot lines .
6 foot span on 70 foot lines'd be differant .

ACTUALLY , the differance is why 20 mm / 3/4 inch longer inboard balances things up , some how .

           too much coffeee will give you a headache . But how much is too much . 

[L0U CRANE]

I'm curious: why the interest only in speed?

Lift and Drag forces calculate using speed squared. These forces vary, increasing steadily along the span from inboard to outboard. Speed value at the tips only relates to those precise locations.

Speed is found from the circumference of the filght circle and the time per lap. Circumference   is diameter (two times radius) times Pi. What radius to use? Inboard tip? Outboard tip? Fuselage centerline? Something else?

Do you include overhang from handle and leadouts? Add for your flying arm length?  I use a convenient swag: add for leadouts, flier's arm - about 2 feet - to line length. That isn't critical - a reasonable approximation.

What to calculate? Cube the inner and outer radii. Average them. The cube root of their average is where Lift and Drag forces are (theoretically) equal left and right. You started with the "tip" locations and now you have the calculated mid-span radius.

 At that location Lift and Drag "are" equal and have no 'arm' to cause yaw or roll. I put the fuse centerline there.

Combined with a LINEXXX location for leadouts (by sweep angle from CG). things should be pretty close to right.

And, BTW, this aproach does support "longer inner wing" thinking, with a plausibke basis.

[john e. holliday]

Now I know why I fly for fun.  My thinking is the speed the plane is happiest at is what try for with out a stop watch until the plane is happy and I am happy.   Same with using tach to adjust speed for the laps on level flight.  Of course you don't use the tach first thing until engine has reached operating temperature.

[Howard Rush]

The cube root of their average is where Lift and Drag forces are (theoretically) equal left and right.

Yes, but what's the physical significance of that?  What counts is where the lift and drag moments balance.  Not the summation of each piece of lift or drag on either side of the balance point, but the summation of each piece of lift or drag times its distance from the balance point. 

Then you have an All American.  The "miracle of tip weight", as Brett calls it, also needs to be considered, as does the actual lift distribution. 

[Crist Rigotti]

Yes, but what's the physical significance of that?  What counts is where the lift and drag moments balance.  Not the summation of each piece of lift or drag on either side of the balance point, but the summation of each piece of lift or drag times its distance from the balance point. 

Then you have an All American.  The "miracle of tip weight", as Brett calls it, also needs to be considered, as does the actual lift distribution.

Howard check your PM.

[Gerald Arana]

Speed is proportional to circle radius, so the ratio of speeds of any pair of those points is the ratio of distances from the center of the circle of that pair.  This doesn't count wind.

Post 40 of https://stunthanger.com/smf/stunt-design/unequal-semi-span-wings/ has some stuff on wing asymmetry and line length.

Wait a minute Howard............are you talking ground speed or air speed?! 

Jerry

[Lauri Malila]

Speed is proportional to circle radius, so the ratio of speeds of any pair of those points is the ratio of distances from the center of the circle of that pair.  This doesn't count wind.

Post 40 of https://stunthanger.com/smf/stunt-design/unequal-semi-span-wings/ has some stuff on wing asymmetry and line length.

..and a fun fact; the difference between distance travelled during one lap, between inner- and outer tips, is always the same, regardless of line length. With 1m wingspan, it's always 6,28m.

[Brett Buck]

..and a fun fact; the difference between distance travelled during one lap, between inner- and outer tips, is always the same, regardless of line length. With 1m wingspan, it's always 6,28m.

6.28???  Where do you pull these numbers from, out of the air? Handed down from an oracle?  In any case, the state of Indiana thinks it should be 6.4.

    Brett

[Lauri Malila]

Is pi different in Indiana?

[Howard Rush]

Is pi different in Indiana?

Almost.  See Wikipedia for “Indiana Pi Bill”. 

Disclosure:  I am an ethnic Hoosier.

[john e. holliday]

All this stuff just now makes me think of the question, " when a commercial jet is flying between cities and the stewerdess walks to the front of the plane is she moving faster than the plane"?

[Brett Buck]

Almost.  See Wikipedia for “Indiana Pi Bill”. 

Disclosure:  I am an ethnic Hoosier.

  To be fair, it wasn't really about pi - because the guy proposing it was insistent that the area of a circle had nothing to do with its diameter! Which is arguably nuttier than trying to legislate a transcendental number.

     Brett

[Brett Buck]

All this stuff just now makes me think of the question, " when a commercial jet is flying between cities and the stewerdess walks to the front of the plane is she moving faster than the plane"?

  Yes.

    Brett

[Lanny Shorts]

I found my answer. 65' lines + 2'6', shoulder to handle, + 6" lead outs = 68" to inboard wing tip. I'm flying equal 30" wing panels.
Therefore 68'+ 60"=73' to outboard wing tip. Inboard wing tip "d" 136'x3.14 (pi)="C", 427.04 ft. Outboard tip "d" 146'x3.14 (pi)="C",
458.44 ft.  Lap time is 5.6 sec.  Inboard tip travels 76.25 ft./sec. = 51.98 mph. Outboard tip travels 81.86 ft./sec.=53.90 mph.  So,
that doggone 2 mph difference  has brought about a science in outboard wing panel lengths, flap sizes, and wing tip weights.  "d" is the diameter  to the wing tips; "C" is the circumference.  Lanny