Bernie-
You're right on this. A model like you are describing here would indeed maintain the same bank but it would fall off into a spiral dive and change it's heading as it spirals down. The steepness would be determined by, I believe, the degree of bank and the resultant lift vector being aimed off to one side. It wouldn't just sideslip into the ground while pointing in the original direction. If it was shaped such that there was no roll resulting from other factors then it would keep the same bank angle all the way to the ground. I've had models built like you describe and they fly pretty much just as you're saying. But the spiral they fall into thanks to that bank is a product of side slipping.

Actually you can get spirals like this even with lots of dihedral. I've seen more than one free flight model where the fin area was too large and the center of gravity was too far back and it made the model spirally unstable. The model would fall off into a spiral dive and it would either keep the same size or, more usually, it would tighten the spiral into a vertical death dive and matchsticks would be the final outcome. And I'm talking about free flight models with LOTS of dihedral. But this is an extreme case. I thought you might appreciate the fact that you can have gobs of dihedral and still have a spirally neutral or unstable model. And trust me, it's a sad, sad sight to see a big 60 powered old timer with all that wood and silk bite Mother Earth like this.........

On that other "pigeon" model with the 45 degree dihedral the reason the fuselage would drop is because our lift is out in the center of the one wing rather than at the CG. If you stuck enough wingtip weight on it then it WOULD fly straight ahead if we didn't look at the drag of the fuselage... or if the lump of Plasticene was big enough to match the fuselage's drag........

Ya know, at this point I'm not sure if we aren't agreeing but in different words. Or is there still something that we can use to keep this thread going.......... :spinnyeye