New Products Flash Sale
Thread Tools
This thread is privately moderated by z80, who may elect to delete unwanted replies.
Aug 27, 2012, 09:26 PM
Registered User
carr52's Avatar
Quote:
Originally Posted by z80 View Post
I wrote a little CG calculator for flying wings. If you have a HTML 5 browser supporting the canvas object you will get a little image of the wing too.

http://fwcg.3dzone.dk

Bug reports and suggestions are very welcome.
This thing is awesome. So I just put the full wing span?
Sign up now
to remove ads between posts
Sep 05, 2012, 10:50 PM
Registered User
rimshotcopter's Avatar
question please, what are MAC lines and what do they illustrate?

Thank you.
Last edited by rimshotcopter; Sep 05, 2012 at 10:58 PM.
Sep 05, 2012, 11:11 PM
Registered User
carr52's Avatar
Kinda wondering that myself. The mac lines look interesting but thats it for me.
Mean aerodynamic chord. Heck I don't know.

Tom
Sep 05, 2012, 11:17 PM
Envies his own avatar
rockyabq's Avatar
The MAC lines stand for Mean Aerodynamic Chord. They are used to determine the average (mean) chord of the wing. If the wing is rectangular (no sweep and no taper from root to tip), the MAC is the same as the geometric chord. When there's constant sweep and/or constant taper involved, the MAC can be geographically "calculated" by extensions of the root chord and tip chord and the intersection of diagonal lines from one to the other. If the wing is ellipsoid or of varying taper, the process of determining where the MAC is located is more complicated.

Does this make sense?
Sep 05, 2012, 11:19 PM
Registered User
carr52's Avatar
Man I was just guessing. I don't understand yet but give me time. I'll learn.

Tom
Sep 05, 2012, 11:21 PM
Registered User
rimshotcopter's Avatar
Thank you, makes sensor but now that I have the name (Mean Aerodynamic Chord), I can do more research.
Sep 06, 2012, 12:57 AM
Envies his own avatar
rockyabq's Avatar
http://en.wikipedia.org/wiki/Chord_%...odynamic_chord
Sep 30, 2012, 09:53 PM
Registered User
rpm3's Avatar

Flying Wing CG


When using the wing CG calculator.....do you include the elevons in the measurements?

I apologize if this has been answered...couldn't find it in the posts.......
Thanks
Ralph Matile
Sep 30, 2012, 10:07 PM
Registered User
rimshotcopter's Avatar
Quote:
Originally Posted by rpm3 View Post
When using the wing CG calculator.....do you include the elevons in the measurements?

I apologize if this has been answered...couldn't find it in the posts.......
Thanks
Ralph Matile
This was shared with me: https://www.rcgroups.com/forums/show...postcount=1589

I am not sure about this calculator but it would seem correct to include the elevons.
Sep 30, 2012, 10:59 PM
Registered User
rpm3's Avatar

Thanks rimshot!


thanks...I thought I hadn't, but rechecked and had included them in the measurements.....I'm a few weeks away from a test flight at the pace i am going (SLOW)....looking forward to trying this hacked pico....if i keep it as light as i think....its going to have "way enough" power....
Ralph Matile
Nov 21, 2012, 03:19 AM
Registered User
justeyfly's Avatar
This is what I do I dived the Main wing by 5 like 10 /5= 2 then I add that on to the center wing works every time :+J
Nov 22, 2012, 03:59 AM
Registered User
can someone please help me to calculate the centre of gravity of this wing, though its given in this plan i need to show workings on how i calculated it.

Here is the plan:

http://fadmuker.co.uk/html/meat_eater_plan.html
Nov 22, 2012, 08:01 AM
The original Flying Pigs Sqd.
Up&Away's Avatar
I found this the easiest CG calculator for a flying wing. It's a simple Excel file, and shows you the formula as well as has a working formula in the spreadsheet. Just enter the measurements (either in centimeters or inches, but don't mix!) as indicated.
Nov 29, 2012, 11:48 PM
Envies his own avatar
rockyabq's Avatar

CG determination for a delta-winged plane


To determine the proper center of gravity for a delta-winged plane, you must first figure out the length of the Mean Aerodynamic Chord (MAC). This is accomplished using the geometric method:

1. Determine the length of the root chord. That's the front-to-back length of the center of the wing. On the Meat Eater, there's a small cut-out for the motor. I'd just ignore that.

2. Determine the length of the tip chord. That's the front-to-back length of the tip the wing. On the Meat Eater, there's an extension at the wing tip that's rounded in the front and swept back to a point at the rear. It's pretty small, so I'd just ignore that too.

3. Draw a line forward from the front of the root chord line that's the same length as the tip chord.

4. Draw a line rearward from the rear of the root chord line that's the same length as the tip chord.

5. Draw a line forward from the front of the tip chord line that's the same length as the root chord.

6. Draw a line rearward from the rear of the tip chord line that's the same length as the root chord.

7. Connect the ends of those extended lines diagonally.

8. The two lines will cross somewhere near the center of the wing. This location is the MAC.

9. Measure the distance from the leading edge to the trailing edge at that point, and you'll have the length of the MAC.

10. Multiply that length by 0.80, and that will be the center of gravity location as measured from the trailing edge (which is usually easier than measuring from the leading edge).

That should give you a good, rock-stable starting point for your maiden flight. Make sure you have lots of "up" elevon travel available--particularly if the airfoil does not have built-in reflex. Your elevons will have to provide the reflex by themselves. If the elevons seem ineffective and/or the plane requires lots of forward stick to fly level inverted, nudge the center of gravity rearward, but do so a little at a time. Each time you move it rearward (by adjusting the battery rearward, or by removing nose weight, or by adding weight to the rear of the plane), you should find you need less reflex in the elevons to fly level when the plane is upright.

The example pictured below is for a plane called a Meat-Eater. While it's not a "perfect" delta, the cut-off nose and the tips are small enough that I think their differences are negligible.

--Rocky
Last edited by rockyabq; Nov 29, 2012 at 11:53 PM.
Dec 05, 2012, 07:36 PM
clark ross

delta cg


i have been locating the cg on a delta using the the flying wing formula
they always turn out nose heavy. what am i doing wrong?
cr73


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
flying wing cg ?'s mscj Foamies (Kits) 1 Mar 03, 2003 10:53 PM
Flying wing CG with shortened span MSB Foamies (Kits) 2 Jul 28, 2002 08:23 PM
Flying Wing CG Choppa Nutta Power Systems 8 Apr 17, 2002 12:45 PM
Flying Wing CG Paul Susbauer Parkflyers 2 Jan 29, 2002 02:31 PM
Flying wing CG Anders Power Systems 4 Oct 05, 2001 05:39 AM