Visual Aircraft Center of Gravity Calculator (beta version)

[Ex-jazz]

Hi

Due my hobby flight sim project, I found a use for the tool with what I can measure, calculate / estimate the plane stability characteres from plane drawings.

I just like to get to same ballpark, not exact real life figures. Close enough is enough.

Screen shot (240k)
http://www.mediafire.com/imageview.php?quickkey=njzrt4kmke0&thumb=5

User can design own plane or 'read' the dimension from actual drawing (backround picture).
User adjust the wing and stabilizator vertex positions and run the script.

More about plane stability blaa blaa and two online calculators:
http://adamone.rchomepage.com/index5.htm
http://www.geistware.com/rcmodeling/cg_super_calc.htm

Sample .blend+script with packed FW190A8 picture (366k)
http://www.mediafire.com/?qykvnmgywmu

This requires a Blender 3D 2.48a installation
http://www.blender.org/download/get-blender/

This is a beta version

ReadMe
#
#Visual Aircraft Center of Gravity Calculator (0.1b) by Xjazz
#
#This script calculate t the plane Neutral Point (NP) location from to the wing & stabilizator dimensions.
#
#This is tested with Aircraft_Center of Gravity Calculator by Dean A. Scott
#http://www.geistware.com/rcmodeling/cg_super_calc.htm
#--------------------------------------------------------------------------
#
#Usage
#Adjust in EDIT MODE the wing & stabilizator size, aspect ratio and also distance to each another.
# Get back to the OBJECT MODE and run the script.
#--------------------------------------------------------------------------
#
#Markers:
#Black cross - MAC position
#White square - AC position
#Blue Square - NP position
#
#The tail-arm, Vbar, and NP % MAC values can find from console.
#
#Things to do
#- On screen texts for the figures... somehow.
#- UI for few values

Probably there are ready solutions already for this.

[Stoney]

Very impressive.

[Ex-jazz]

Thanks

Working with next version

Here is a picture from 0.2beta with 'semi-automatic' menu data update.


You adjust the wing/stabilizator and click the menu-window and figures will update.

[BaDkaRmA158Th]

Bump, ya'll gotta check this out.

[SmokinLoon]

Niiiiice.

I wonder how this will compare... with... oh nevermind.

Nice tool!   

[Ex-jazz]

Hi

Thanks to the Tuxer in www.opendimension.org (Finnish blender forum) for the good advice about script-link feature.

The menu problem is solved 

WIP screen shot


User can move and scale the menu in 3Dview.

To do
- Finish the CG pointer code with intent CG position or to actual CG position function.
- Check, check and check the output figures.

Limitations
As you can see from picture, this script is working only with rectangular shapes.

???
Are there available any similar applications for the flying model planes?
 

[Stoney]

A couple of observations:

1)  When computing the reference wing area, you include the portions of the wing covered by the fuselage, and include the area at the wingtips that is "missing" due to camfered or rounded tips.  That way, your wing span measurement isn't short (10.38 m computed vs. 10.51 m in real life) and your wing area isn't low (15.81 m^3 vs. 18.3 m^3).

2)  Same thing for the horizontal stab as in #1

[Ex-jazz]

You are right, Stoney

Calculator works best with pure rectangular and trapezoid wing shapes, because calculator is using only a four measuring points.
The round shapes requires some best guesstimate. I tested few ideas for the rounded wingtip area calculation, with actual span length...

That 18.3m2 figure must be a wing gross-area, since the wing net-area is that ~15.9m2.

[Stoney]

Just extend the two wing and horizontal stab sections through the fuselage and make each poly touch the opposite side.  Have the polygon at the wing tip cover over the rounded off section, to at least make sure the wing span is accurate.  At the root, do the opposite, with the reference wing polygon inside of any wing root fairings, which you've already done. 

Wing area formula for this application is:

Sref= b X Cavg

Where:

Sref = Wing reference area

b = Wing span

Cavg = Average Chord

You can also derive the wing area through span and aspect ratio.  The point is, you may want to bounce your calculated dimensions off known values for these aircraft, or your results could potentially be imprecise.

[Ex-jazz]

Hi Stoney

Thank you for your hint.

I could calculated the fuselage area between the wings from the wing root vertex coordinates.

First public beta


User can give in EDIT-mode a intent static marginal % to the green text field in calculator and see the result on plane.

OR

User can move in OBJECT-mode the CG-marker on plane and read the actual position % from the calculator.

NOTE! This is still beta version.

The actual calculator .blend file. This requires a Blend 3D 2.48a installation from www.blender.org:
http://www.mediafire.com/?sharekey=2585963c345f514f4012e8015643d9c835ffb5519d3574eb

[Ex-jazz]

Just one more time for the Stoney

I added a function, which calculate the rounded wingtip area as a circle segment and take that to the total wing area calculation.

The horizontal line near wingtip is a reader-object, with what you can adjust the circle segment size. No better visual for that.


Anyhow the figures are pretty close even with given drawing 

FW 190F-8

[Stoney]

Very nice!  And your figures for span and area are both within +1% of listed.  That's a great approximation for this sort of tool.  This is a very nice tool you've put together, especially for doing comparisons between different aircraft.