Edge Vs Extra 260 (Straight LE Vs Swept LE)

[LJJ]

I'm doing a scratch build project..... I'd like to hear the differences you've seen between the Edge style wing and the extra.... Everything... precision, snaps, rolls, 3D, coupling.... the works.

I like the looks and roll handeling of mid wing monoplanes. (260, 300s, YAK, Edge) and that leaves me with few scale choices. There is also Wayne Handleys RAVEN.... It's his own fuselage design with a Zivko straight LE wing. I really like the looks of it, and want to hear some feedback on what would be expected of the flight envelope.

I should say I'll be flying IMAC with it, as well as frestyle. Attached are some drawings and pics to see the fuse and wing design
.

[dmichael]

I think that you'll find that the straight leading edge doesn't work as well for IMAC as a swept leading edge. Rolling manuevers suffer. As a matter of fact, I have noticed that two 40% designs that seem to really fly well, the Godgrey Extra and the Quique/3W Yak, seem to have an exaggerated leading edge sweep. I have wondered how much this modification contributes towards these two particular designs excellent flight characteristics.

If I'm not mistaken, the original Raven had a swept leading edge. Assuming I'm right, If I were building a model of the Raven, this is the wing I would use for IMAC.

Dave

[why_fly_high]

	Quote: Originally Posted by dmichael
	I think that you'll find that the straight leading edge doesn't work as well for IMAC as a swept leading edge. Rolling manuevers suffer. As a matter of fact, I have noticed that two 40% designs that seem to really fly well, the Godgrey Extra and the Quique/3W Yak, seem to have an exaggerated leading edge sweep. I have wondered how much this modification contributes towards these two particular designs excellent flight characteristics. If I'm not mistaken, the original Raven had a swept leading edge. Assuming I'm right, If I were building a model of the Raven, this is the wing I would use for IMAC. Dave

The RAven offers some interesting experiment opportunities. I am not convinced that the straight leading Edge is the only factor affecting the precision performance of model Edges.

The original wing did have a swept leading Edge. The Raven started life as a Rebel 2-300. Wood wings were failing so people started using different wings. It would be fun to do a Raven with 2 sets of wings. One with a straight leading edge for 3D and one with a swept leading edge for precision.

Dan

[LJJ]

	Quote: Originally Posted by why_fly_high
	The RAven offers some interesting experiment opportunities. I am not convinced that the straight leading Edge is the only factor affecting the precision performance of model Edges. The original wing did have a swept leading Edge. The Raven started life as a Rebel 2-300. Wood wings were failing so people started using different wings. It would be fun to do a Raven with 2 sets of wings. One with a straight leading edge for 3D and one with a swept leading edge for precision. Dan

Dan.... That same light bulb just went off in my head. I sent an e-mail off to Wayne H about drawings for the original wing. How cool would it be to IMAC with a set of precision wings, then do your freestyle stuff with the Straight LE wings. They seem to snap faster and do better walls/blenders and such. Since the Edge is the only plane I've flown with a flat LE, its hard to say if it's just the wings shape.... or other issues like ratios on the tail surfaces or fuselage moments. Any ideas?

[Uncle Brett]

It's funny you brought this subject up, I was just discussing this with a friend that designs model airplanes for a company called Wing Warrior. I asked him why my Edge 540 tumbles better than my Extra. He said it's because the Edge's wing is actually foward swept and the Extra's wing is straight. I said "dude, you gotta lay off the pipe", I mean any fool can see that the leading edge of the Extra is swept and the Edge is straight, right? He said it's all about the wing CORDS not the leading edge. If you draw a line from wing root to wing tip at the thickest part of the wing cord you'll see that the Edge's wing cord actually is foward swept and the Extra's wing cord is straight. Then he went on to explain all kinds of technical stuff on the how's & why's and the what happens if you do this & that and lost me pretty quickly. Anyway, I'm sure someone here on FG that knows aerodynamics can explain the how's and why's.

[LJJ]

Your example is correct... It is forward swept from the point of view of oncoming air at CL (Thickest part of airfoil.... causes a tip-root span flow at stall. I'm thinking that the "forward sweep" on an edge wing is what pulls the precision down.... makes the tip have less positive stability. (Good for some things) There is a difference in snap and High Alpha maneuvers though... Where the LE becomes the separation of the boundary layer.... That straight LE makes everything happen all at once, nice and clean. (Walls, Elevators, Etc) I think that also explains why the edge's generally have less wing rock.

NASA did some tests with High Alpha stuff with the X-29 project. It is a jet with forward swept wings.... Great stability at extreme AOA

I'm beginning to think that there is a plus to both styles.... and that 2 wings need to be built on the same fuse to see the real difference....

Waiting to see if Wayne has some drawings on a swept wing Raven, but I found a couple old pics, and you guys are right.... it was double tapered.... So now I'm excited that this may be the perfect airplane with 2 sets of wings....


Question to you Technical IMAC guys. The rules state scale is based on wingspan, and outlines must be within 10% of the plan view. So does that mean that I could lengthen the fuse by 9% relative to the overall length and still be "Legal"? Say 105" length at the true scale fuse length... and then add 10" to be 115" Still within 10% right?

Thanks...

[Jaybird]

If you built 2 sets of wings, it seems the Edge wing would also move the CG back, if installed in the same location. Mighty handy for 3D huh?

[LJJ]

You guys be thinkin' just like me.... In fact, it moves it back about 1.75". Pretty handy for mixing it up.

[LJJ]

Thanks for the help guys. I got some Rebel 2 300 drawings and redid the wing accordingly. Should be a great winter project. I'll do a build thread on here when I get started. It's gonna be pretty sweet!

Screen shot of drawings so far.

Thanks again!
-Levi

[BreadBowl]

What would be the aerodynamic repercussions if you moved the peak of the chord section progressively back so as to achieve the straight aerodynamic chordline?

[LJJ]

Do you mean on the edge wing? I thought about that.... it puts the CL at 15% at the root and 30% at the tip. If I'm not mistaken, the full scale edge is kind of like that with the Conical airfoil? (comment Dan?)

I'm not sure why we don't see that airfoil selection on any of our RC stuff. I've thought about trying it.... any one wlse have feedback on that?

By Conical I mean the LE is almost a half circle, with the thickest part shortly after it, then a straight line to the trailing edge.....

[BreadBowl]

Andreas Gietz did that when he first designed the 3M Extra (using the scale airfoil). My cousin did some testing on the design and remarked that the scale Extra airfoil, which is similar to the Edge, flew sluggish, and didn't snap well.

In reference to my post, to clarify, I was referring to the straight LE wing. I'd be very interested to see how that would turn out.

[KrisW]

I'm glad some people brought up the information concernign the actual sweeping forward of the airfoils highest point on the Edge. It's hard to describe until you draw it out on paper.

A couple of other things to consider. .

Swept leading edges on a flat wing act as a kind of pseudo-dihedral, helping the wing to self-level in stragith and level flight. It's a small thing, but it's there,and let's a tapered LE wing, such as on an Extra, or more blatantly on a Giles, enter and exit snaps more cleanly.

Second thing to consider. . The Edge models, as far as I have seen, use a non-dihedral wing, whereas the Extra's use a wing with a flat top, and dihedral'd bottom, giving aobut 1-1.25 degrees of average dihedral. This stabilizes in upright flight, and de-stabilizes in inverted flight, at normal flying speeds. . but in High-Alpha stalled flight (3D) actually makes inverted easier because of the airflow being held on the wing better and not stalling the center of the wing as badly, whereas in upright flight the air tends to flow toward the tips, causing more vortices and separation, and destabilizing the wing in the stalled environment (leading to wing rock).

My personal favorite is a "straight" wing, with no dihedral or anhedral, and the Extra style planform with a 1:2 LE-TE taper ratio, and approximate 2:1 root-tip ratio. Wing rock is minimized due to both upright and inverted flight being self-stabilized by the LE, the plane snaps very crisply and exits clean, and there is no difference in feel between normal speed upright or inverted flight.

THEN, we could go into the angles of the ailerons in a "flat" versus mildily dihedralled wing, and how it affects coupling and throw differential and how axial rolls actually are. . .

[Billa]

	Quote: Originally Posted by KrisW
	THEN, we could go into the angles of the ailerons in a "flat" versus mildily dihedralled wing, and how it affects coupling and throw differential and how axial rolls actually are. . .

Go on ...go on... I am all ears. And while you are at it, please shed some light on the fact that the CAP 232 is rock solid upright or inverted (high alpha) while using the same wing as the Extra, with exaggerated dihedral in some cases. I suspect it has something to do with the placement of the tail feathers.

[JoeAirPort]

	Quote: Originally Posted by KrisW
	I'm glad some people brought up the information concernign the actual sweeping forward of the airfoils highest point on the Edge. It's hard to describe until you draw it out on paper. A couple of other things to consider. . Swept leading edges on a flat wing act as a kind of pseudo-dihedral, helping the wing to self-level in stragith and level flight. It's a small thing, but it's there,and let's a tapered LE wing, such as on an Extra, or more blatantly on a Giles, enter and exit snaps more cleanly. Second thing to consider. . The Edge models, as far as I have seen, use a non-dihedral wing, whereas the Extra's use a wing with a flat top, and dihedral'd bottom, giving aobut 1-1.25 degrees of average dihedral. This stabilizes in upright flight, and de-stabilizes in inverted flight, at normal flying speeds. . but in High-Alpha stalled flight (3D) actually makes inverted easier because of the airflow being held on the wing better and not stalling the center of the wing as badly, whereas in upright flight the air tends to flow toward the tips, causing more vortices and separation, and destabilizing the wing in the stalled environment (leading to wing rock). My personal favorite is a "straight" wing, with no dihedral or anhedral, and the Extra style planform with a 1:2 LE-TE taper ratio, and approximate 2:1 root-tip ratio. Wing rock is minimized due to both upright and inverted flight being self-stabilized by the LE, the plane snaps very crisply and exits clean, and there is no difference in feel between normal speed upright or inverted flight. THEN, we could go into the angles of the ailerons in a "flat" versus mildily dihedralled wing, and how it affects coupling and throw differential and how axial rolls actually are. . .

DAM !!! Nice write up man. Really enjoyed reading that.

Joe