C.G. Formulas

[CloudyIFR]

http://adamone.rchomepage.com/cg_calc.htm

Does anyone know where I can obtain the formulas used for the above link?

I'm looking for a multi panel wing.

Sweep Distance at MAC (C) =
From Root Chord to MAC (d) =

Thanks
Curtis
Montana

[JetPlaneFlyer]

A similar online calculator with all the formulas listed can be found here: http://www.geistware.com/rcmodeling/cg_super_calc.htm

Steve

[CloudyIFR]

Thanks Steve,

But I'm looking for the formulas for a multi panel wing.

I think I have the Sweep Distance at MAC (C) figured out but I just can't get the distance from root chord to MAC figured out.

I also realize that in all actuallity the MAC really can't be measured out on the wing chord somewhere for a multi panel wing that has strange sweep angles, but for what I'm trying to achieve it's not an issue.

Curtis
"Sailplane Calc" Programmer
http://h1.ripway.com/cloudyifr/files.htm

[Derfy]

The MAC and MAC position for a multi-panelled wing can be worked out using moments of area.

For each panel, work out the area, the MAC length and the X (C) and Y (d) positions of the MAC leading edge. You can use the online calculators for this.

To calculate the MAC for a multi-panelled wing,

Wing MAC = [(MAC_1)*(Area_1)+(MAC_2)*(Area_2)+....(MAC_n)*(Are a_n)]/(Total Area)

Where n=number of panels and Total Area=sum of the panel areas.


For the MAC position the procedure is similar,

Wing X_MAC (C) = [(Offset_X1+X_MAC_1)*(Area_1)+(Offset_X2+X_MAC_2)*( Area_2)+....(Offset_Xn+X_MAC_n)*(Area_n)]/(Total Area)

Wing Y_MAC (d) = [(Offset_Y1+Y_MAC_1)*(Area_1)+(Offset_Y2+Y_MAC_2)*( Area_2)+....(Offset_Yn+Y_MAC_n)*(Area_n)]/(Total Area)

Where Offset=the offset of the panel root chord (X from the wing root chord leading edge and Y from the wing root chord)

I hope this all makes sense (it doesn't to me :D ).

P.S.

Don't you just hate typing in formulae, they most always turn out gobbledygook. :eek:

:cool:

[CloudyIFR]

Derfy,

Thanks, that helped a lot.

Curtis

[adam_one]

Ok guys, for those who are not so keen on math, the Sweep Distance at MAC (C) and the distance from Root Chord to MAC (d) have now been implemented at:

http://adamone.rchomepage.com/cg2_calc.htm


And for wings with more than 2 panels, you might check out following:
http://perso.orange.fr/scherrer/matthieu/english/mce.html
It accepts 5 panels.

:)

[CloudyIFR]

Adam One,

Thanks for that, would it be possible to obtain for the formula "d" for a two panel wing?

I've worked on an MS Excel Spreadsheet now for about 15 years and would like to add this to my graph.

Thanks
Curtis
Montana

[CloudyIFR]

Adam

Oh, and I must add what a wonderful piece of work you have accomplished!!!

Curtis

[adam_one]

Curtis,

First you calculate "d" for each panel:

d1 = panel span_1 (Y) * ((root chord_1 (A) - panel MAC_1) / (root chord_1 (A) - tip chord_1 (B)))

d2 = panel span_1 (Y) + panel span_2 (Y2) * ((tip chord_1 (B) - panel MAC_2) / (tip chord_1 (B) - tip chord_2 (B2)))

Then you calculate "d" of the wing:
d = ((panel area_1 * d1) + (panel area_2 * d2)) / (panel area_1 + panel area_2)

Cheers,
adam

[CloudyIFR]

GOT IT! Thanks

Once I'm convinced I have it plotted correctly I'll post the updated spreadsheet.

Thanks
Curtis
Montana

[CloudyIFR]

Updated version of Sailplane Calc available here:

http://h1.ripway.com/cloudyifr/files.htm

Curtis
Montana