Pardon the stupid question: Are the control surfaces included in measurements?

Absolutely!

Curtis
Montana

So are you saying that the elevons would be considered part and parcel with the chord of the wing at the tip? Even though the elevons usually don't go full span? Isn't that going to cause the calculator to overstate the wing area? And isn't it going to cause the calculator to move the CG back too far?

Originally Posted by ombudsman

So are you saying that the elevons would be considered part and parcel with the chord of the wing at the tip? Even though the elevons usually don't go full span? Isn't that going to cause the calculator to overstate the wing area? And isn't it going to cause the calculator to move the CG back too far?

This is just a simplistic geometry calculator. Since it only dose one trapezoid you can't accurately model the usual cut up trailing edge. Control surfaces are part of the wing and affect the aerodynamic center whether they are deflected or not. By leaving the elevons out of the stability calculation you have created a model that is slightly less stable than the real plane will be so, although leaving the elevons out of the calculation is technically wrong, the error that is introduced is conservative and therefor acceptable. Kinda

--Norm

Originally Posted by nmasters

This is just a simplistic geometry calculator. Since it only dose one trapezoid you can't accurately model the usual cut up trailing edge. Control surfaces are part of the wing and affect the aerodynamic center whether they are deflected or not. By leaving the elevons out of the stability calculation you have created a model that is slightly less stable than the real plane will be so, although leaving the elevons out of the calculation is technically wrong, the error that is introduced is conservative and therefor acceptable. Kinda

--Norm

Thanks. I'm considerably out of my depth here.
Dave

Originally Posted by ombudsman

So are you saying that the elevons would be considered part and parcel with the chord of the wing at the tip? Even though the elevons usually don't go full span? Isn't that going to cause the calculator to overstate the wing area? And isn't it going to cause the calculator to move the CG back too far?

No. The elevons are part of the wing, and help generate lift. The fact that they change the camber locally to change the lift distribution left and right, or fore and aft, doesn't keep them from being part of the wing.

That´s great! I was looking for this thread!

I am building a kind of Lee´s Assassin wing, with a different profile and now, I´m just waiting for the servos arrives from Hobbycity. The battery, a 3s 1.3 I already have, and my worries are about finding the correct CG.

My wing is 40" wing span and 9" = root

I´m using a Emax CF2812 with a 7x6 and 3S 1.3

Can I use this program, correct? Any Ideas?

Thank you all,
Luis

I'm in the process of building my first wing:

50" wingspan $ store foam board with a 13" cord, 12" sweep & 7" tip:
http://fwcg.3dzone.dk/?wing_span=50&...ow_mac_lines=0

I'm wonder how much reflex to put into the elevons to begin with. I know there should be some, but what's the rule of thumb here?

Thanks,

Originally Posted by creapyd

I'm in the process of building my first wing:

50" wingspan $ store foam board with a 13" cord, 12" sweep & 7" tip:
http://fwcg.3dzone.dk/?wing_span=50&...ow_mac_lines=0

I'm wonder how much reflex to put into the elevons to begin with. I know there should be some, but what's the rule of thumb here?

Thanks,

I usually use as starting point the bottom of the elevon in line with the bottom of the wing and then two clicks of trim up.

Originally Posted by z80

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.

When I was using ie7 I can see the wing image and it's working for me for the last 2 years, but now i'm using ie8 and the wing image is disappear, some help please.

Just a quick question, can this do COG for forward swept wings?

Originally Posted by adamtlk

I discovered, the hard way, that for good low speed handling and performance a rough finish is better than a smooth, glossy one!
(...)
So rather eluctantly, I ripped off the nice glossy cover, and lo-and -behold, I had my old wing again! Searching literature on wind tunnel tests at low Re Numbers, I discovered that this was in fact a well established fact for some airfoils tested with different surface roughnesses.
But CG-calculator is a good starting point anyway.

What about your nice glossy cover with some turbulator love?

blatant AD but useful information:

If your wing is more complex than z80's calculator can handle, give http://wingcgcalc.bruder.com.br/ a try.

The calculator uses this wing.
Is this really the best wing for a flying wing? I would think this wing is more usefull:


can someone explain me why you guys chose for the first wing?

thx

EDIT:
I made a wing in autocad:


i would like to order this one but i dont have any idea it will be good...
the weight of the plane will be 2.6kg and 62".
(all the values are in cm but you have to /100 and x3)

Its a matter of taste, actually.

your first wing (straight leading edge) is more used in 3D models. That wing have no sweep and the tip chord is smaller than the root chord.

Your second wing have some sweep (exactly sweep =rootchord - tipchord).

Your third wing have tipchord smaller than root chord and greater sweep.

My calculator cant draw exactly your third wing, but a aproximation of it because of the tip chord not aligned with the Y axis of your drawing.