Hello,

Hope everyone had a great new years day. We got in some good flying this morning until it started to rain again.

Stek79,

I don’t remember the details of the Dirty Birdy or others of that type from that time. I want to say about 1 or 2 degrees was the usual? Joe Bridi planes are still available at www.bridiairplanes.com

Gearup,

All you write in post #56 makes sense. No doubt lots of gradients and integrals and fancy math to actually figure spiral slipstream local velocities. My guess is that the spiral doesn’t really vary so much with prop diameter, pitch, or rpm, but more with power? A wing in flight not only makes downwash but some forward wash too. In reaction to drag, the air gets dragged along a bit. Basically a prop is a wing flying sideways to make lift forward. So basically the drag from lift production is what drags the air into a spiral as it is accelerated rearward through the prop. Faster airspeed straightens the flow but more power must be transmitted to fly faster. So the spiral might even increase with speed? My guess is since the rotation is comparatively slow, the wing probably doesn’t straighten it out much??

Happy New Year

Multiflyer