My major concern with doing this is to enhance the flight characteristics of the plane not to trash what is a basically good design. The Sig SE is a good plane built as it comes out of the box, but being an engineer it is hard for me not to try to tweak it a bit. I know the knife edge performance is lacking and a lot of builders have added fin and rudder in order to improve it, others have used Side Force generators. It seems that the real issue is the amount of side area of the fuselage and short of increasing that everything is a stop gap measure. So I decided to approach it from that direction adding the cowl and a cooling duct to increase the side area of the fuselage, hopefully without a negative impact on the overall design. But I am not an aeronautical engineer and seek the input of others with both more knowledge and experience, as to what the changes I am thinking about will do to the performance. You said “Lateral stability is an odd creature. Too much is often worse than too little.” , and I am a bit aware of this, hence my question. I have included a bit more of the sketch,and one for the rudder, so you can see how the duct for the cooling adds to the side area behind the cowl, along with the added rudder area. The blue shows the fin and rudder as on the plans the red is the added area along with where it will be tapered.

I would rather feel stupid for asking questions about what may be a non issue, than to forge ahead without the input of others and trash the build of this plane.

“And how is it possible to overthink model airplanes? We're men. We're supposed to do stuff like that. And what better thing to do while in a conversation with the wife. Actually listening can ruin a man's ability to reason. (matter of fact, she's talking to me right now..”

Gee, I thought I was the only one to use airplanes as an escape while my wife was talking…


edit to add rudder picture