Help with design
 

Hi Friends,

I´m designing a F3A plane that is supose to have all settings to 0º degree and wing paralell to stab, but the stab will have an angle of 120° negative like Curare has. Could will think this design will fly? What do you think about this project? Any coments apreciate please.
Please post your coments.

Thanks
Gaiotto

RE: Help with design
 

Using 0-degrees incidence on the wing will force the airframe to fly in a tailheavy condition. This will hurt performance of an F3A airframe. I'm assuming that on the stab you mean to put anhedral in it. If this is the case you can accomplish the same effect by lowering the stab height relative to the wing, but anhedral sure does look cool. That one is a matter of prefernce really. Will it fly? Yes... but then again you can get a sheet of paper to fly, it's a matter of what kind of performance you're willing to accept. The argument between 0-0 setups on the wing and stab versus positive-incidence setups will rage on as long as pattern exists. In my opinion the positive incidence airframes have a more "locked-on" feel, and they definitely snap better because the CG can be moved forward.

RE: Help with design
 

Not really, it'll force the model to fly in a very near neutral pitch stability point but this is how F3A models have been set up for decades and is the best way to do it. Any desired SMALL amount of pitch stability can then be trimmed in using a smidgeon of up trim and a small shift of the CG to a point marginally forward of the aircraft's neutral point. Granted this isn't the way that normal sport models and especially trainers should be set up but it's entirely normal for aerobatic models. In many cases the modern 3D models are actually purposely set up with the CG BEHIND the neutral point and the stability issues are tolerated to gain more ability with the post stalled 3D maneuvers. It makes for a busy workload if you're flying "normally" but if done within reason it's tolerable.

Gaiotto, the anhedral in the stabilizer on the Curare was not put in there just for looks. Shifting the stabilizer like this has been done on other models and in the articles explaining why it was always done for a reason that was often related to knife edge performance or some other aspect where a correction was required. The builder choosing to put in anhedral as a "repair" rather than rebuild the whole fuselage So if you WANT to use anhedral then you should really be looking at where the optimum point for the vertical center of the stabilizer should be and then shifting the root mount point up so that the effective vertical location is correct.

I'm not an F3A flyer myself but I've seen references to other pattern flying issues where these days it's more common to just build the model to the best design parameters that are known and then if there's any minor issues with knife edge or vertical lines or whatever then you use the programming mixes to fine tune rather than cutting into the model to add anhedral or other fixes.

RE: Help with design
 

I'm not going to get into a big argument, because everyone feels differently on the matter. Let's just agree to disagree. I fly pattern, and the best flying aircraft I have ever flown were running .5 - .75 degrees positive on the wing, and 0 - .25 positive on the horizontal stab. Like I said before, it's just a matter of the level of performance that is acceptable to the pilot.

RE: Help with design
 

Ok thanks guys,

All this coments hel me a lot.

Gaiotto