Hello Hal

Once more unto the breach.......or something like that .

I quote >>But, first a couple of wonders> It is said that the retyreating blade articulates downwards, what causes that? <<

Simple, centripetal force. Advancing blade meets a faster airflow so its lift is greater than the centripetal force holding it down therefore it flaps up. The retreating blade meets a considerably lower airflow therefore its lift is less and centripetal force returns the blade to its original position ( flaps down ). Do not think that by saying the blade is flapping down that it goes below the horizontal. Flapping and coning can be fractions of a degree yet their effects are quite considerable. You say that your rotors spin virtually flat, they probably do but the amount it flaps is miniscule especially with a high rpm. As I said once before, you will not be able to see this flapping happening. The flapping could be as little as 1 degree but this is still enough to alter its angle of attack to alllow for lift disymmetry.

I have attached an image of my Huff&Puff in flight, you can quite clearly see it has a visible coning angle.

Quote >>There is no question that a blade can not change it's angle of attack to the plane of rotation, that angle is fixed. <<

Well, if the blade is flapping then its plane of rotation is changing, it has to. The axis of rotation doesn't change but the plane of rotation is constantly changing for a gyro in forward flight. I am not making this up honest !! I sit through lectures all about this stuff and watch demonstrations as well as have to study all sorts of books that explain it. The proof is that my own gyros fly and don't roll over like dead turkeys.

In USA, George Townson's book 'Autogiro, the windmill plane' gives a good description of what is going on. I ordered mine through Hannans Runway online. It also contains lots of great images and three views of all the Pitcairn and Kellet gyros.

Well, regardless of what exactly is going on up in that whirling maelstrom that is a gyro rotor, the fact is that it works. I am one of those poor unfortunate people that HAS to know how things work to sleep at night . First thing I did when i bought my first motorcycle was take it apart to see how it all worked !!

I will just happily agree to disagree with you on the aerodynamics and spend my time building those wonderful quick and dirty blades you designed.

>>stay out of that Channel on Holloween, the
skeletons of those 109 pilots will grab you, if you are not careful! <<

Do you have any idea how cold the channel is at halloween ?!
Who needs scary ghosts when you would have to be raving mad to go in the sea at that time of year.

Respectfully

Sean

P.S Angle of attack is also a different angle from root to tip on an autogyro in forward flight. You have a stall region near the hub ( high angle of attack) prgressing outward to a driving region and then on to the driven region at the tip which is at a low angle of attack relative to the root !!!!!!!! You may now shout 'HERETIC' and throw bottles of Budweiser at me.