CG estimate?

[IAD]

Could somebody do a quick CG calc. on this planform for me?
(Note that the red lines represent short LEXs that aren't installed yet.)

Thanks in advance..!


~Luke

[Sparky Paul]

30%

[IAD]

Thank you VERY much!

~Luke

[Sparky Paul]

Thank you VERY much!

~Luke
.
Well... you're welcome, but you might not like this next part.
With that much of the wing ahead of the m.a.c. including all the tip, the aeroelastic load on the structure in torsion will be large. As speed is increased, the outboard section is going to twist downward. This can result in either destructive flutter, as the structure pulls the deflection out and the airload forces it back down, or an uncontrolllable nose-down pitch, with the wingtips possibly meeting -below- the fuselage.
The forward swept wing requires additional care in structure to prevent either of these. :(
A foam-balsa covered wing would be more rigid in torsion. or add diagonal ribs/chordwise struts to rigidize the open structure you have.

[IAD]

I am very aware of that bit, I did my research, and I know I am tredding on fairly thin ice... :D I am going to add large sections sheeting to the top of the wing, so that I have about 50% of the area sheeted. The LE is solid 1/4", a technique I have used on other aircraft, which also helps a bit...

Lastly, as a very light (5 oz.) parkflyer, powered by an IPS motor (direct drive) I am just going to hope for the best. ;)


~Luke

[vintage1]

I'll add something else. Don't attempt to fly it in rudder/elevator. Fit ailerons or tailerons.

It will tend to roll out of turns badly I would say. You may need to couple rudder/ailerons to get any sensible contollability.

Still, why not experiment? Its the most fun there is IMHO.

[IAD]

I already flew a foam mockup, and it turned fine with just rudder/elevator... A full metric ton (;)) of dihedral makes it work just fine, it would seem.

(On the other hand, as a Fanfold ship, it was high-drag, so it was also totally underpowered.)

~Luke

P.S. Just curious (don't take this wrong, you are probably right about the rudder situtation) have you ever flown a SFW setup?

[davidfee]

I have flown FSW before... it was fun. Looked very unusual at the slope. I used ailerons.

-David

[IAD]

Oh, nice looking ship there...

~Luke

[BMatthews]

I....A full metric ton (;)) of dihedral makes it work just fine...

The dihedral will easily overpower the forward sweep effect. There's no firm numbers on equivalency but I have seen references to the idea that a 20 to 30 degree sweep angle is only equivalent to about 4 or 5 degrees of dihedral for yaw to roll coupling.

A unique looking model there IAD. Best of luck with the flight trials. But where does the motor go? It's obviously not a pusher and the forward canards look like they are right by where the motor would be.

[IAD]

Hehe... The motor goes on the top of the tail fin... Gives me 'blown controls' to boot. Look at the last post here: http://www.rcgroups.com/forums/showthread.php?p=2241762#post2241762

~Luke