Aerodynamics Discuss the concepts of aerodynamics here

advantage to "profiling" round tubing

Old 11-15-2010, 01:58 AM
  #1  
hillbillynamedpossum
Rode the short bus
Thread Starter
 
hillbillynamedpossum's Avatar
 
Join Date: Aug 2009
Location: West Plains MO USA
Posts: 721
Default advantage to "profiling" round tubing

Im working on my AP platform and Im figuring on using schedule 20 3/4" pipe for the fuse. There will be some pipe catching the wind. (Thinking of making the landing gear out of pipe too)

Any way is there a way to calculate drag on lets say a 1" round tube flying thru the air, versus a 1.25" thick NACA 0018. The NACA 0018 profile would have more frontal area, but should have less drag.


Id like to have some real numbers on an element about 12" wide, but I have no idea how to calculate it.


Possum
hillbillynamedpossum is offline  
Old 11-15-2010, 06:27 AM
  #2  
Wildflyer
Past President of PSSF
 
Wildflyer's Avatar
 
Join Date: Sep 2009
Location: Lacey WA, 1 mile E of Mushroom Corner
Posts: 2,013
Default

I think I saw that a round would have about 3 times the drag as an airfoil of the same thickness.

I hope you have better schedule 20 pipe than I had one time, It was quite cold out but not freezing, I dropped a piece of sch 20 pvc pipe on the sidewalk, and it shattered!

Good luck, I have just started AP, and have not gotten a good picture of my house yet.
Wildflyer is offline  
Old 12-10-2010, 10:09 PM
  #3  
JetPlaneFlyer
Super Contributor
 
JetPlaneFlyer's Avatar
 
Join Date: Mar 2009
Location: Aberdeen, Scotland
Posts: 6,120
Default

Possum,

Coefficient of drag (Cd) for various shapes can be found here: http://www.princeton.edu/~asmits/Bicycle_web/blunt.html

It does depend on Re number but assuming a Re of about 50,000 then a cylinder has a Cd of about 1.1 and an 'airfoil' streamline body has a Cd of around 0.1 So the cylinder has nearly 11x the drag of a streamline body of the same frontal area.

Allowing for your difference in 'thickness' (1" vs. 1.25") then the cylinder would have about 9x more drag... Quite a big difference!

You can work out actual drag force with the drag equation:
http://en.wikipedia.org/wiki/Drag_equation
JetPlaneFlyer is offline  
Old 12-11-2010, 06:48 AM
  #4  
Wildflyer
Past President of PSSF
 
Wildflyer's Avatar
 
Join Date: Sep 2009
Location: Lacey WA, 1 mile E of Mushroom Corner
Posts: 2,013
Default

Thanks for the better information, I will have to study that page as soon as I can, obviously what I heard was way off base.
Wildflyer is offline  
Old 12-11-2010, 02:36 PM
  #5  
idealhobbies
Super Contributor
 
idealhobbies's Avatar
 
Join Date: Dec 2007
Location: Milford, Delaware
Posts: 1,564
Default

Socrates - "I know nothing except the fact of my ignorance."

Jetplaneflyer, you just dumbfounded me first thing in the morning. Wow!
idealhobbies is offline  
Old 12-11-2010, 04:56 PM
  #6  
hillbillynamedpossum
Rode the short bus
Thread Starter
 
hillbillynamedpossum's Avatar
 
Join Date: Aug 2009
Location: West Plains MO USA
Posts: 721
Default

Thank you JPF. I do truely delive that the Scotts are the worlds best engineers. Now if yall could just overcome that cheap-skate cast you would be the greatest nation on earth! Perhaps you already are.


Possum
hillbillynamedpossum is offline  
Old 12-11-2010, 05:34 PM
  #7  
radialarm
Crash Test Clown!!!
 
radialarm's Avatar
 
Join Date: Sep 2009
Location: Boyd, TX
Posts: 299
Default

Remember the "flying hole" paper airplane? Use thin wall 4" for the fuselage. Let the air flow right through. You could buildup the leading edge inside to form a circular airfoil.

I'm trying to be a clown, but it might work.
radialarm is offline  
Old 12-11-2010, 05:54 PM
  #8  
JetPlaneFlyer
Super Contributor
 
JetPlaneFlyer's Avatar
 
Join Date: Mar 2009
Location: Aberdeen, Scotland
Posts: 6,120
Default

Originally Posted by hillbillynamedpossum View Post
Thank you JPF. I do truely delive that the Scotts are the worlds best engineers. Now if yall could just overcome that cheap-skate cast you would be the greatest nation on earth! Perhaps you already are.


Possum
Thanks.. but I'm not Scottish I'm English but moved north chasing work, met a Scottish girl, married and now i'm stuck here.. No complaints, it's a nice place apart from the weather.

The numbers I quotes were assuming the cylinder was 'broadside' to the airflow.. Numbers would be much different if the airflow was along the axis if the cylinder.

Good luck with your model anyway!

steve
JetPlaneFlyer is offline  
Old 12-12-2010, 07:04 PM
  #9  
radialarm
Crash Test Clown!!!
 
radialarm's Avatar
 
Join Date: Sep 2009
Location: Boyd, TX
Posts: 299
Default

Here's a good example:


I guess jet engines killed this off.
radialarm is offline  
Old 12-12-2010, 07:54 PM
  #10  
hillbillynamedpossum
Rode the short bus
Thread Starter
 
hillbillynamedpossum's Avatar
 
Join Date: Aug 2009
Location: West Plains MO USA
Posts: 721
Default

That just proves "There is nothing new under the sun" The craft is just basically a ducted fan. I think it bears a good resemblance to a sabre, given some imagination. I dont have the means to try building something like that, but it would be pretty cool.

possum
hillbillynamedpossum is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Sky Sharkster
Scratch and Kit Built Aircraft
9
01-08-2013 01:46 PM
Sky Sharkster
Vintage and old timer models
4
05-10-2008 01:14 AM
Demetrius
Airplanes - Electric For Sale & WTB
2
03-30-2007 05:30 AM
papamac
Motors and Speed Controllers for sale & WTB
0
10-02-2005 06:29 PM
papamac
Motors and Speed Controllers for sale & WTB
0
10-02-2005 06:27 PM

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Quick Reply: advantage to "profiling" round tubing


Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.

Page generated in 0.10513 seconds with 15 queries