quote:

ORIGINAL: Doug Cronkhite

SFGs are intended to provide more yaw lifting force I'd guess. The problem I see is that it isn't free. You lose yaw stability because of the proximity to the aerodynamic center of the airplane. Today's fuselages are big enough that I just don't see a need for the SFGs in the sizes most people are using. In order to get any real effective use out of the SFGs they'd have to be MUCH larger.

quote:

ORIGINAL: TonyF

No such thing as crabbing in a crosswind due to vertical fin area or amount of side area. The amount a model has to point in to the wind depends on what the crosswind component is compared to the airplanes speed. Slower airplane speed there is more angle, faster there is less. It's just a myth that more side area is bad in a crosswind.

quote:

ORIGINAL: TonyF

Yep, that's what I'm saying. The airplane has to be yaw stable, which means the tail wants to stay in the back. If it's not yaw stable, the tail will wander all around and it will look and feel terrible. When it's flying, the airplane only feels it's relative wind which is it's velocity through the air. It does not feel the crosswind, except when that crosswind might change, as in a gust or a wind shear at different altitudes. Then it will only feel it long enough to align itself with the relative wind, which is a very short time period. Every airplane that is yaw stable, and that should be every good pattern model, will react the same. Doesn't matter if it's a pencil fuse like a Typhoon or a Nuance.

Alpha is the term used to describe angle of attack. Beta is the term used to describe angle of yaw. If your model is yaw stable it is always trying to fly at zero beta. You can kind of test just how stable your model is in beta by doing a quick rudder pulse while it flies overhead. Just blip the rudder and let go. The model should yaw with the rudder pulse then after you let go return quickly to zero beta. A model that is lacking yaw stability will oscillate a few times before returning to zero beta. You'll see that as a tail wiggle, which in pattern is bad. Also, a model that is lacking yaw stability will be very hard to "point". It will be unreliable on where it is going when you come out of a maneuver. Probably what you didn't like about the Onas when you had one. Which is why when I went to the Contra on the Onas I added the triangles on the rudder and a ventral and now the stab fences. They make the model point better coming out of a maneuver.

In a crosswind, to draw a straight line on the ground, which is what we are doing when we fly a track parallel to the runway, the model must fly on a heading that is not parallel to the runway, but one that is pointed slightly in to the wind. The amount of that angle is determined only by the speed of the model in relation to the crosswind component. The faster the model, the less the angle between the model's heading and the ground track. The slower, the greater that angle must be. Nothing to do with fin area or total side area.

I'm sure in trying to keep it simple I've upset some aero engineer out there. I'm not an aero engineer, but I did stay at a Holiday Inn!

quote:

ORIGINAL: TonyF

I have the stab fences on my Onas now and they have really improved that model. I think they work even better then just making the fin bigger as they work in cleaner air then the fin does. I'm just about ready to start flying my Nuance with the Contra unit and I expect I will be adding them to it.