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Author Topic: How much is drag of Airplane and lines in level flight?  (Read 8337 times)

Online Peter Germann

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How much is drag of Airplane and lines in level flight?
« on: December 29, 2016, 07:04:21 AM »
When entering typical F2B numbers into “Line Rake Analysis” on http://nclra.org/Programs/LineRake.php

Weight: 61.7 oz (1750 Gr.)
Wingspan: 60 in (152 mm)
Line dia.: 0.015 in (0.39 mm)
Number of lines: 2
Lines length: 66.4 ft. (20.25 m)
Wing area: 700 sq. in (45 sq.dm)
Lap time: 5.3 sec

For a Coefficient of Parasitic Drag of 0.01, the program returns:

Line sweep angle: 1.73°
Line sweep: 0.908 in (23 mm)
Total System drag: 0.73 pounds (328 Gr.)
Line Drag: 0.34 pounds (153 Gr.)
A/C Drag: 0.39 pounds (175 Gr.)

As “Line Rake Analysis” is published by the National Control Line Racing Association, my question is whether the data returned is relevant for F2B type airplanes?

Peter Germann

Offline Brett Buck

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Re: How much is drag of Airplane and lines in level flight?
« Reply #1 on: December 29, 2016, 11:19:53 AM »
When entering typical F2B numbers into “Line Rake Analysis” on http://nclra.org/Programs/LineRake.php

Weight: 61.7 oz (1750 Gr.)
Wingspan: 60 in (152 mm)
Line dia.: 0.015 in (0.39 mm)
Number of lines: 2
Lines length: 66.4 ft. (20.25 m)
Wing area: 700 sq. in (45 sq.dm)
Lap time: 5.3 sec

For a Coefficient of Parasitic Drag of 0.01, the program returns:

Line sweep angle: 1.73°
Line sweep: 0.908 in (23 mm)
Total System drag: 0.73 pounds (328 Gr.)
Line Drag: 0.34 pounds (153 Gr.)
A/C Drag: 0.39 pounds (175 Gr.)

As “Line Rake Analysis” is published by the National Control Line Racing Association, my question is whether the data returned is relevant for F2B type airplanes?



   That appears to be quite a bit too low. I think I got something around 1.8-2.0 lb of total drag in level flight. The line drag might be about right. Randy did a similar calculation that (as I recall) came up with something similar but I can't find my notes, and I never saw his. I will dig around for my data.

     Brett

Online Peter Germann

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Re: How much is drag of Airplane and lines in level flight?
« Reply #2 on: December 30, 2016, 05:45:15 AM »
Forgot to mention that level in-flight power-in of the motor is 425 Watts, wich comes to approx. 340 Watts power-out.
Peter Germann

Offline Brett Buck

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Re: How much is drag of Airplane and lines in level flight?
« Reply #3 on: December 30, 2016, 02:09:36 PM »
Forgot to mention that level in-flight power-in of the motor is 425 Watts, wich comes to approx. 340 Watts power-out.

     340 watts is about .46 HP, which is definitely in the ballpark of the shaft horsepower run for IC airplanes. Figure 60% prop efficiency, and you get about .276 drag HP, or about 152 ft-lb/sec. At 80 fps, that's about 1.9 lb of drag, if I did my sums correctly. That is all very close to what we have gotten over the years. Assuming lower efficiency (entirely possible) yields lower drag, of course.

   We know the shaft HP very well from many experiments, but what would be very helpful would be to actually measure the drag or in-flight thrust at speed. The best way I can figure is to run the engine, with the baseline setup and the correct static rpm, in a wind tunnel or in the back of a pickup moving at 60 mph or so, and measure the thrust. With the same setup, You could also get the thrust with a constant needle setting over a variety of speeds, which would be the most useful model airplane engineering test I can envision for many reasons. I have been subtly suggesting this test to Frank Williams for about 15 years, since I found out he had a wind tunnel, but so far he hasn't bit.

    I suppose an enterprising electric guy could mount his motor on load cells and then fly it, while logging the data.  I would be hesitant to do that on an IC engine because of the possibility of it shaking apart, and there's generally no way to log anything.

    It would be more difficult to set up a similar test with an airplane, both because you would have to carefully adjust the AoA to give you exactly the right weight, and you can't model the effects of the lines. The latter is probably adequately modeled by LINE II.

      Brett

Offline Tim Wescott

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Re: How much is drag of Airplane and lines in level flight?
« Reply #4 on: December 30, 2016, 02:15:45 PM »
I have been subtly suggesting this test to Frank Williams for about 15 years, since I found out he had a wind tunnel, but so far he hasn't bit.

One might be able to do the measurement on a spinning arm setup.  It'd take more work to do the measurement and calibrate out any errors, but far less work to build the gizmo.  For just one measurement it may work out as being the sensible approach.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Howard Rush

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Re: How much is drag of Airplane and lines in level flight?
« Reply #5 on: December 30, 2016, 08:52:52 PM »
The best way I can figure is to run the engine, with the baseline setup and the correct static rpm, in a wind tunnel or in the back of a pickup moving at 60 mph or so, and measure the thrust.

Or sticking up from the Miata now in Bay 4 of the garage at JCT Manor.
The Jive Combat Team
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Offline Brett Buck

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Re: How much is drag of Airplane and lines in level flight?
« Reply #6 on: December 30, 2016, 09:09:40 PM »
Or sticking up from the Miata now in Bay 4 of the garage at JCT Manor.

  Miata?  Not another hippy-mobile?  Are you slipping?

    Brett

Offline BillLee

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Re: How much is drag of Airplane and lines in level flight?
« Reply #7 on: December 31, 2016, 12:27:53 PM »
The Line Rake program on the NCLRA web site is based on the work of Pete Soule. The actual algorithm is shown on the website so that anyone who has REAL knowledge (not me) could comment. So far, nobody has.

I would welcome any constructive input.

Bill Lee
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Offline Ted Fancher

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Re: How much is drag of Airplane and lines in level flight?
« Reply #8 on: December 31, 2016, 01:18:21 PM »
  Miata?  Not another hippy-mobile?  Are you slipping?

    Brett

I didn't even know they made an electrical Miata.  How many AAAs does it take?

Offline Brett Buck

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Re: How much is drag of Airplane and lines in level flight?
« Reply #9 on: December 31, 2016, 02:07:29 PM »
The Line Rake program on the NCLRA web site is based on the work of Pete Soule. The actual algorithm is shown on the website so that anyone who has REAL knowledge (not me) could comment. So far, nobody has.

I would welcome any constructive input.

Bill Lee

  LINEII is the same or closely-related algorithm. It has been extensively discussed in the past. There's an impressive engineering paper on it somewhere but I couldn't find it the last time I checked.

   There some nomographs published that I think were based on an earlier, less correct, analysis and test.

    Brett

Offline BillLee

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Re: How much is drag of Airplane and lines in level flight?
« Reply #10 on: January 01, 2017, 03:40:03 PM »
Where would I get access to LINEII, Brett?
Bill Lee
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Offline Brett Buck

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Re: How much is drag of Airplane and lines in level flight?
« Reply #11 on: January 01, 2017, 04:04:48 PM »
Where would I get access to LINEII, Brett?

   I would get in touch with Bob Reeves, who ported it to a new version, LINEIII.

     Brett

Offline Howard Rush

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Re: How much is drag of Airplane and lines in level flight?
« Reply #12 on: January 02, 2017, 12:19:00 AM »
  Miata?  Not another hippy-mobile?  Are you slipping?

The Miata is useful for aeronautical experiments.  Chris Cox and I calibrated an anemometer with it, attracting chicks in the process.  I'm not making this up.
The Jive Combat Team
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Offline Howard Rush

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Re: How much is drag of Airplane and lines in level flight?
« Reply #13 on: January 02, 2017, 12:21:14 AM »
Where would I get access to LINEII, Brett?

http://www.tulsacl.com/Linelll.html  I think the document comes along in the zip file.
The Jive Combat Team
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Offline Howard Rush

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Re: How much is drag of Airplane and lines in level flight?
« Reply #14 on: January 02, 2017, 12:26:36 AM »
I didn't even know they made an electrical Miata.  How many AAAs does it take?

Chuck Rudner's kid converted one to electric.  It was coincidentally electric blue.

My Miata is traditionally powered.  Bay 4 of the JCT Manor garage does have an electric car charging station, though.  I'm not making any of this up.

The Jive Combat Team
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Offline BillLee

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Re: How much is drag of Airplane and lines in level flight?
« Reply #15 on: January 02, 2017, 05:01:10 AM »
http://www.tulsacl.com/Linelll.html  I think the document comes along in the zip file.
Thanks, Howard, I found that, but unfortunately it is not accessible to those not running Windoze of some sort. Maybe not even those Windoze users that have "upgraded" to 8 or 10!

I have the documents from Pete, Pete was helpful in writing the Line Rake program on the NCLRA website, I just need someone to give me some idea if it is grossly wrong and why.

I would really like to have a "LineIV" or some-such that ran via the 'net so EVERYBODY could use it.
Bill Lee
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Online Peter Germann

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Re: How much is drag of Airplane and lines in level flight?
« Reply #16 on: January 02, 2017, 05:40:58 AM »
Thanks, Howard, I found that, but unfortunately it is not accessible to those not running Windoze of some sort. Maybe not even those Windoze users that have "upgraded" to 8 or 10!
I am sorry to confirm that I am unable to install/run Line III on my fairly up-to-date windows 10 system.

Meanwhile. Dr. Dieter Siebenmann (involved in aerodynamics of Picard's round-the-world fullsize electric airplane and indoor F1 modeller) has agreed to look into the data I've published above, trying to come-up with a number for the typical drag of an F2B model.
Peter Germann

Offline Igor Burger

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Re: How much is drag of Airplane and lines in level flight?
« Reply #17 on: January 02, 2017, 08:18:04 AM »
As “Line Rake Analysis” is published by the National Control Line Racing Association, my question is whether the data returned is relevant for F2B type airplanes?

Depends what you mean "relevant". Are you speaking about lines angle at model? Or line rake to properly adjust model to circle part? That program, as well as LineXX as well as Peter Soule calculations are done for racers without fuselage influence - means if you think about rock on lines it will work, also you can estimate some wing influence etc, but without fuselage data (motor offser, fusleage area, its distribution, rudder size and offset) such program cannot tell anything about line rake.

BTW - my program estimates Max Bee level flight drag to something at aproximatey 6 Newtons (including lines drag)

Online Peter Germann

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Re: How much is drag of Airplane and lines in level flight?
« Reply #18 on: January 02, 2017, 09:26:13 AM »
Depends what you mean "relevant".
I am referring to the aerodynamic drag of a typical 1'800 Gram F2B fixed gear airplane travelling at 25 m/sec in level flight. I wish to find this value in order to learn more about in-flight motor thrust and roll inducing torque.
Peter Germann

Offline Brett Buck

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Re: How much is drag of Airplane and lines in level flight?
« Reply #19 on: January 02, 2017, 11:51:54 AM »
Depends what you mean "relevant". Are you speaking about lines angle at model? Or line rake to properly adjust model to circle part? That program, as well as LineXX as well as Peter Soule calculations are done for racers without fuselage influence - means if you think about rock on lines it will work, also you can estimate some wing influence etc, but without fuselage data (motor offser, fusleage area, its distribution, rudder size and offset) such program cannot tell anything about line rake.

BTW - my program estimates Max Bee level flight drag to something at aproximatey 6 Newtons (including lines drag)

   The calculation assumes centrifugal force only, as otherwise, there is no way to calculate it from only the speed and the line dimensions.

   Since you have an independent estimate of the drag, you should be able to use that and the shaft power to estimate the prop efficiency - what did you get? 1.35 lb (6 newtons) implies a prop efficiency in the low-mid 40% range, which is in the range of believable.

    Brett

Offline Igor Burger

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Re: How much is drag of Airplane and lines in level flight?
« Reply #20 on: January 02, 2017, 12:36:11 PM »
   The calculation assumes centrifugal force only, as otherwise, there is no way to calculate it from only the speed and the line dimensions.

Exact calculation will need also wing span, because lines are connected proximately 700mm from CG, so the drag and centrifugal force cannot be calculated from the same diameter ... question is if it that difference make sense :- ))

   Since you have an independent estimate of the drag, you should be able to use that and the shaft power to estimate the prop efficiency - what did you get? 1.35 lb (6 newtons) implies a prop efficiency in the low-mid 40% range, which is in the range of believable.


Depends on prop, the better the prop, the worse efficiency, for example my 11" prop needs 1900mAh for 5 minutes and my 12" prop needs 2100mAh. It of for pattern flying, but does not matter, the difference will be still there. So let's assume the level flight will take the same amount of mAh for level flight but 6 instead of 5 minutes. That cab be.

So the current is  19A vs 21A at 22.2V. It makes power 422W vs 466W. The drag is 6N so the power at 22m/s is 132W, So the efficiency is 31% vs 28%. :- )))

so the moral is, we should fly smaller props, we will have better efficiency :- ))))))))))))))))  ... or? :- P

Online Peter Germann

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Re: How much is drag of Airplane and lines in level flight? Initial findings
« Reply #21 on: January 05, 2017, 07:53:46 AM »
Attempting to find resilient data on in-flight drag of F2B model aircraft, me and Wolfgang Nieuwkamp have recently inquired with NCLRA (Line Rake Analysis), Helmut Schenk (Prop Calc, Germany) and Dieter Siebenmann, Swiss aerodynamics scientist.

The following data describing a typical F2B model has been submitted, asking for drag in level flight at 5.2 sec laptime:

Wing Span: 60 in
Wing Area: 700 sq.in
Wing Airfoil: NACA 018 (modif)
Wing Thickness: 2.75 in
Wing Chord:12 in

Empennage Span: 25 in
Empennage Area: 150 sq.in
Empennage Airfoil: NACA 009 (modif)
Empennage Thickness: 0.8 in
Empennage Chord: 6 in

Weight: 64 oz
Line length: 67 ft
Line dia: 0.015 in
Number of lines: 2
Lap time / Speed: 5.2 sec / 25 m/sec

Propeller: APC 12 x 6
RPM: 9’500

Results are:

NCLRA, as per Line Rake Analysis*: Airplane drag of 184 Grams or (0.41 lb) + 162 Grams (0.36 lb) lines drag.

NCLRA, as per above specs: pending

Helmut Schenk (Prop Calc): Prop Calc returns in-flight propeller thrust at 25 m/sec to be 5.2 N (520 Gr / 1.15 lb). This comes to 358 Gr (0.78 lb) thrust/drag for the airplane, with lines drag of 162 Gr.
 
Dieter Siebenmann: Airplane drag 350 Grams (0.77 lb) Comes to total drag of 515 Gr  (1.14lb) lb with lines drag of 162 Gr.  at 1.2° AoA.

Conclusions

Without really knowing, we suspect that “Line Rake Analysis” uses speed aircraft specs to calculate drag. If so, someone qualified might wish to suggest changes of the published algorithms, thus making the very helpful program useable for stunt airplanes, too.

As the two sources PopCalc and Siebenmann independent from each other have come to almost identical findings we will use the value of 520 Gramm / 5.2 N total drag/thrust as typical for doing a bit of further studies on the moments having effect on 60 in size stunters.

Peter Germann & Wolfgang Nieuwkamp
Peter Germann

Offline Igor Burger

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Re: How much is drag of Airplane and lines in level flight?
« Reply #22 on: January 05, 2017, 08:16:30 AM »
So if you take real airfoil with flap hingeline on whole span, plus drag of fuselage and landing gears, you are at number which I told you on begin: 6N :- ))

Online Peter Germann

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Re: How much is drag of Airplane and lines in level flight?
« Reply #23 on: January 05, 2017, 09:27:56 AM »
So if you take real airfoil with flap hingeline on whole span, plus drag of fuselage and landing gears, you are at number which I told you on begin: 6N :- ))
Which is most probably why I never came closer than miles away from you class of flying, dear Igor...
By the way, what does you program say about in-level flight torque?
Peter Germann

Offline Igor Burger

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Re: How much is drag of Airplane and lines in level flight?
« Reply #24 on: January 05, 2017, 09:35:57 AM »
Thnaks Peter, however you highly probably fly better stunt then Dieter, so may be it is not related too much :- ))) 

Well ... may be you have to ask question with little more words ... the shaft torque is easy, since we know current and KV of motor, we can easily calculate it ( = current / Kv - in proper units), but it is opposed by wing torque and depending on trim also CG to LO torque, but sum is 0 so answer is easy ... nothing :- ))) ... but you probably wanted know something else, so try to write more what you mean :- ))

Online Peter Germann

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Re: How much is drag of Airplane and lines in level flight?
« Reply #25 on: January 05, 2017, 09:57:48 AM »
Well, you know Dieter was quite busy doing aerodynamics for Solar Impulse so I assume he could not find the time for possibly equal important C/L matters. As the Picard flyer is now going to a museum I might be able to talk Dieter into a change of his focus...

The point about resulting torque in (level) flight is that I would like to find out how much torque induced roll moment, if any, needs to be compensated by which measures such as trim tabs, twisted flaps, tip weight, vertical (battery) c.c. position and such.
Peter Germann

Offline Igor Burger

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Re: How much is drag of Airplane and lines in level flight?
« Reply #26 on: January 05, 2017, 10:34:41 AM »
Shaft torque is clear, speaking about your inliner, also CG torque is clear and equal to 0, so the rest is wing torque, here I see problem, because I do not know easy way how to figure it up. Then there is small amount which will not be covered by wing and that must be solved by tweeked flaps. I would say it is tiny value, but fun starts when models changes speed, nose up or when timer accelerates, simply when prop comes to slippage when induced drag on prop tips causes high shaft load (you can see it as current peaks = torque peeks), that is what we must solve more than static conditions in level, because that is what affects model quality and it is even more complicated and I affraid it is impossible without measuring in real conditions. So looks like it will be object of trimming also in this century  :- )) ... at least on its begin

Offline Air Ministry .

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Re: How much is drag of Airplane and lines in level flight?
« Reply #27 on: January 05, 2017, 09:57:15 PM »
Theres some French /? term , like Wind Resistance thats is closer in visualiseation to the ' action ' than the rudimentary term " DRAG " .

Aside ,



it has LEVEL in there, somewhere .

Offline phil c

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Re: How much is drag of Airplane and lines in level flight?
« Reply #28 on: January 08, 2017, 08:51:22 PM »
If you are going to start trying to analyze the lift/drag in maneuvers don't forget that the airfoils(wing and stab) dramatically change shape during a maneuver.  I haven't been able to find enough information on the effect(NACA wasn't much interested in that detail in the 1940's), but it would appear that the shape of the C/L curve changes quite a bit.  As the plane maneuvers both the AOA of the plane and the wing increase roughly equal amounts. The fuselage angle is easy to see, but the flap changes the camber/AOA of the wing at least as much.
phil Cartier


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