Mustang Air to Air: The Sequel
/forum/topic/600984/4290

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futurshox
Registered: Feb 15, 2008
Total Posts: 2775
Country: United States

Talking of propellers, while I am sure most of us know why rolling shutter artifacts occur, here is a nice animated gif that really explains it well.







ELinder
Registered: Feb 14, 2010
Total Posts: 1070
Country: United States

That's a cool GIF, never seen it before.

So Jim, now you're adding fashion model to your CV?

Erich



Wrei
Registered: Aug 01, 2008
Total Posts: 2939
Country: United States

The original Jim...







stevezzzz
Registered: Aug 01, 2010
Total Posts: 4082
Country: United States

chas wrote:
kwbarnes wrote


Rules of thumb for propeller design...

" To the original poster. The term for the length of an airfoil is chord. I believe it is pronounced as cord. The length of an airfoil is the width of the wing, so, you would use wing chord to describe the width of a wing/propeller/rotor, at any point along it's length."



This last statement raises another question in my mind. Most wings are tapered, and as such, the chord as you define it constantly changes from wing root to wing tip. So is the chord of a tapered wing defined as a formula as opposed to a discrete unit measurement?


You can refer to the chord at a certain distance from the wing root, or calculate a mean chord.

The question of why wings are generally tapered is an interesting one. The answer, again, boils down to efficiency: aerodynamic efficiency as well as manufacturing efficiency. From the aerodynamic point of view, the best (most efficient) wing planform is a long, skinny ellipse; the worst is a short, fat rectangle. From a manufacturing point of view it's the exact opposite, at least when you're building in aluminum: it's so much easier to build a wing with a constant cross section (think Piper's 'Hershey Bar' wing) than one that varies at every span wise station and has curved leading and trailing edges (Spitfire!). Various compromises have been seen over the years, but the trade off is always there.

Why is a long, skinny ellipse the most efficient wing planform? It has to do with induced drag, the portion of overall drag that results not from 'friction' but from the very act of generating lift; you never get something for nothing, and induced drag is just the cost of doing business. Induced drag manifests itself as the energy that is lost to creating wingtip vortices, those horizontal tornadoes that spiral off the end of a wing. An elliptical wing 'fools' the air by minimizing the apparent size of the wingtips, as the chord at the tip approaches zero. All the various winglet designs are intended to either inhibit the formation of wingtip vortices or to minimize them by increasing the effective wingspan (and thus the aspect ratio).



MMcGrath
Registered: Apr 15, 2006
Total Posts: 2649
Country: United Kingdom

A bit on advanced rotor design:

https://en.m.wikipedia.org/wiki/BERP_rotor



JWilsonphoto
Registered: Jan 16, 2002
Total Posts: 19252
Country: United States

Much as I didn't want to let go of my pillows at 4:30 this morning, I was rewarded with some beautiful light. Pre-dawn shoot, daytime perspectives, annual report partners portraits on location, wrapping up with some dusk shots. Full day for an old photographer, but a good day!



kwbarnes
Registered: Jun 26, 2005
Total Posts: 286
Country: United States

chas wrote: (deleted)

This last statement raises another question in my mind. Most wings are tapered, and as such, the chord as you define it constantly changes from wing root to wing tip. So is the chord of a tapered wing defined as a formula as opposed to a discrete unit measurement?


It depends on how you are using the chord measurement. As a physical description the chord is a physical measurement. Omitting all other airfoil information a wing would be described by it's span, and chord (or chords (root, and tip), or it's span, and aspect ratio.

When designing the aircraft, or propeller/rotor. some calculations need to be done in relation to the wing/propeller/rotors airfoil, chord, and sweep angle. For a rectangular "Hershey bar" wing this is just a measurement. If the wing is tapered, and, or swept, then calculations are made to define a "mean chord", aerodynamic center, aspect ratio, and other essential measurements for the wing in question.






alawadhi
Registered: Feb 25, 2004
Total Posts: 417
Country: Bahrain

kwbarnes and Steve...

Thank you very much for explanations

As a result of what you both described, other than efficiency, is there anything to do with what dictates number of blades? For example, is 2-blade design more beneficial in high small high power fast planes and 6-blade design in cargo lifting? (as racing car VS cargo truck)



ELinder
Registered: Feb 14, 2010
Total Posts: 1070
Country: United States

As with any design, it depends on what you pick as your performance priority. What's most important to you, climb performance, cruise performance, noise, fuel effieiency, or are you trying to be a jack of all trades? Are there operational condition limitations, ground clearance issues, design to a specific lifetime or fatigue limit or budget limitation? Juggling any or all of these variables will change what you end up with, plus what the designers prefer or have experience with.

Erich



chas
Registered: Nov 04, 2003
Total Posts: 1820
Country: United States

kwbarnes and Steve,
Thank you for the details and insight of your explanations. Now I know why I failed out of engineering school!!

Chas



JWilsonphoto
Registered: Jan 16, 2002
Total Posts: 19252
Country: United States

Thought you might like this promo clip Lady Jo. Shot on the soon to be released Sony FS/5.......

https://pro.sony.com/bbsc/video/related-most_popular/video-FirstLookAtWhatThePXWFS5KCanDo/



futurshox
Registered: Feb 15, 2008
Total Posts: 2775
Country: United States

Very nice Jim! I watched the first couple of minutes; enough to see the camera is obviously pretty capable. I'll give it my full attention later on, I want to watch the rest when I can listen to it as well.


Now, I'm not one to blow my own trumpet, but I kind of want to share this with you all. Yesterday I had the great honor of being inducted into the Sport Air Racing League's Hall of Fame! Apparently hanging around and taking everyone's pictures over the last few years has been appreciated :-) The award was made for services to the sport of Cross Country Air Racing, and providing a visual record of planes and pilots.

I was (and am) delighted to receive this fabulous trophy - a hand made, life size Canon 400mm replica in turned wood. Today will be spent finding a suitable spot in the house to house this huge beast! It even weighs about the same as a real one, it balances in the hand very similarly to my own camera. Mike makes all the trophies, but his brother has a lathe and so Mike commissioned him to make the lens. I wish you could all see this for real; it's a work of art.



futurshox
Registered: Feb 15, 2008
Total Posts: 2775
Country: United States

Also, Pat Purcell has been busy... she was asking me a few weeks ago for a ton of pictures and one of me. Glenn kindly allowed me to send her one he took of me in Georgetown a while ago. We all turned up to the race to find Pat had made photo plaques of every racer who has ever earned year-end points. They're not all my photos, but most of them are. Now Mike has to find somewhere to put them all! ;-)



Jeff W.
Registered: Feb 09, 2008
Total Posts: 2444
Country: United States

Well done Jo. These folks are rightly recognizing the incredible work you've done on their behalf that promotes and documents their sport in ways that only terrific photography can. Congratulation young lady



JWilsonphoto
Registered: Jan 16, 2002
Total Posts: 19252
Country: United States

No Lady Jo, you are certainly not one to blow your own horn, even when it is greatly deserved So pleased to see all of your hard work and dedication to your racing folks get the recognition and appreciation that it deserves! Well done, seems, as I have long suspected, you are not just a treasure here........we're happy to share you!



Jan-Arie
Registered: Dec 24, 2005
Total Posts: 4092
Country: Netherlands

Well deserved Jo perseverance will last forever and is greatly appreciated.



futurshox
Registered: Feb 15, 2008
Total Posts: 2775
Country: United States

Thank you :-)
It was a fun day, for sure :-)



Tim Adams
Registered: Jan 01, 2004
Total Posts: 2887
Country: United States

John Muszala arrives in style in Berlin Express for the Heritage competition in Reno.



JWilsonphoto
Registered: Jan 16, 2002
Total Posts: 19252
Country: United States

An opportunity for the D810 to do what it does so well..................



JWilsonphoto
Registered: Jan 16, 2002
Total Posts: 19252
Country: United States

...................



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