Heres my next question (I know, I'm full of them).

How doess knife edge, effect top speed? In other words, are you better off holding close to knife edge around the course, or are you better off (speed wise) banking to a 45 degree angle in the straights.

My opinion is that straight and level flight is definately the fastest, however does all the aileron movement of 90 degrees for the turns and 45 degrees (to level) for the straights bleed off more speed than what you would have lost if you stayed in knife edge??

I'm not sure here. I probably stay banked more than I should, but not sure if the extra aileron movement is worth the gain (or loss) in speed.

For me I try to stay in the knife position and use elevator for heading corrections. I also fly with about 2 clicks of down trim,,, My reason for that is when I release the back pressure on the stick, the plane will drift out to where I need to be vise having to go back thru the center detent of the stick.

As for the speed, I don t think it will matter,,, at the knife or at a few degrees from,,, as long as the plane is properly balanced.

Sooooooo, the less amount of stick movement,,, the less induced drag and the Faster you GO



BV

Dave,

This is a really interesting question. In your previous thread, I noted that flying banked required the wing to fly at a higher coefficient of lift, which would increase induced drag. I still think this is true, but it occurred to me that something more important is probably happening as well, which is that some surfaces other than the wing start providing the lift. In particular, the side of the fuselage and the vertical stabilizer. These are lifting surfaces which are certain to produce much more induced drag than any decent wing, including one with ailerons deflected. I have not done a quantitative analysis, but I would bet that maximum speed ( straight & level ) would be achieved with no bank. This does not necessarily mean that flying the pylon course with zero bank is best, because a pilot that overshoots when coming out of the bank could end up flying a very nonoptimal trajectory, and come out worse than if he/she had stayed banked.

Hmmm....

banktoturn

And now you have one of the answers to why Dan Kane's Q-40 Pole Cat is soooooo fast.

The Pole Cat canopy and turtle deck go all the way back to the rudder, and the rear of the fuselage is taller than the so-called P-51 style planes. So it has more of a surface to provide stabilization when the plane is on its side.

The pattern and 3D (especially the profile) guys figured out that they need tall fuselages a while back.

Don,

It's interesting that there is a plane that seems to be using the fuselage/canopy shape to some advantage. It had occurred to me that you might want to build up as much of a lifting surface for knife edge flight as you could get away with, and fly the whole course on knife edge, using the elevator to steer. Apart from the inefficiency of supporting the plane's weight using something other than a real wing, it make sense, since the force in the turn is something like 10 or 20 times as much as required to keep the plane up. You could even put the elevator on the rudder channel, to make it more natural. I'm sure that the landing gear could be configured as a pretty decent lifting surface for the bottom ( or 'right' side of the plane, if you visualize it in knife edge flight ), and a prominent canopy, or even a fin-like surface behind the engine could provide lift on the top/left. Maybe a little balast in the left wing for stability, and you could roll it over right after takeoff and fly on your side.

banktoturn

Duane Gall (Hi DHG ) has reported that his Stinger tracks the turns really nicely. He is using wheel pants, which are allowed on planes that had them in real life. When I mentioned my theory about the turtle decks being advantageous, he connected the same principal to the wheel pants on the Stinger.

I started my Hughes H1-B project because I really believe that the height of a turtle decked fuselage can help.

When I had my RealFlight G2 server up and running, I got to watch Dave Norman and Mike Deneve fly. Both stay at a knife edge the whole time (almost) in the simulator. I practiced and practiced. I even practiced with Mode 1 which is actually quite handy for full time knife edge.

Then I went out and did it with the F3D/30. I had to use a fair amount of rudder. So I added a 1/4" piece of balsa from the canopy high point back to the fin. Less rudder was required, and the plane tracked better.

I could very well be wrong with this theory though. By increasing the height of the fuselage in the rear, you increase the wetted area. So the additional drag could nullify the added stability.

Don,

One of the reasons I thought "Mr. Smoothie" would be an ideal subject is that, with its tall, flat-sided nose section (upright engine, no cheeks) the fuselage would provide a good lifting surface in knife-edge flight. If only the prototype had had wheel pants, it'd be perfect!

The really good pilots seem to split the difference between a constant knife-edge and the traditional "bank and yank" flying style. They'll come up to about 89 degrees of bank for the turns, then gently and smoothly roll out just a few degrees -- say, to a 50- or 60-degree bank -- for the straightaways. They're not using a lot of aileron deflection, but neither are they relying entirely on the fuselage for lift in the straightaways.

Also, I would caution against focusing too much attention on the fuselage "airfoil" because you're not really using it much. If you go into a turn at 89 degrees of bank and pull "up" elevator, the turn (actually a half-loop in a horizontal plane) will launch the airplane slightly upwards as it comes out. This means that even with zero lift from the fuselage or the wing, the airplane will follow a long, shallow, ballistic arc rather than a perfectly level line.

At QM40 speeds, it may take the entire length of the straightaway before you notice the airplane beginning to settle towards terra firma. Therefore, the amount of lift you need -- and the amount of right rudder trim you need to generate that amount of lift from the fuselage -- will be barely noticeable.

If you want to test this theory, give Ed some rum and tell him you need to borrow one of his fuselages for a minute. Scrape off the "horizontal stabilizer" (no great loss; it was illegal anyway) ... muzzle-load the remains into a potato cannon ... stand at the starting line ... align the barrel to an elevation of 2 degrees and an azimuth toward Pylon #1 ... and fire! Q.E.D.!

Euclid of Ohio

Euclidian Master,

I'm still infatuated with the Mr. Smoothie. But the Cub's next on the roster.

I showed a bunch of Q-40 designs to Irwin Funderburk, and he actually picked out the Mr. Smoothie from the bunch. Yeah, it's too bad they were using retracts, instead of wheel pants. (BTW, I have a whole lot more designs drawn up than I've posted in the Q-40 forum )

I'm going to do the Cub without trying to get design approval first, but Mr. Smoothie is going to be submitted prior to implementation.

I tend to overbank on turns, so I come out lower than I came in. It may not be the best way to fly, but I feel like the plane slows down less. Since I learned to do the full time knife edge, I tend to use a little right rudder as I'm coming out of the turn to adjust the trajectory, then try to stay off of everything as much as possible.

Euclidian Space Cadet

Don,

If you rely on the side of the plane to generate lift, you would probably come out ahead by adding the extra area. If you observe that you need less rudder deflection, then the drag reduction that results is almost certainly less than the increase in drag resulting from the added wetted area.

It doesn't seem as though you could come out ahead by overbanking, if it requires you to generate extra lift to climb back up again, but I could be wrong.

DHG,

The idea of climbing in the turns, when you are using your most efficient lift generator ( the wing ), and then trying to generate zero lift on the straights, is really interesting. This could be the best of both worlds, since it would always allow you to generate lift with the lowest induced drag, and would also allow you to avoid the drag associated with deflecting the ailerons. You could get a rough idea of whether you are truly flying ballistic between the pylons by timing the flight between pylons, and estimating the amount that the plane drops during that time.

banktoturn