Hmmm ... that number 50N looks proper. I see I clipboarded my drag number from cell before adding induced drag ... sorry for confusion. Fortunatelyy someone reads what I write  , thanx Howard.

Yes it is right, 2^2 (lift SQR)/pi/5.5(AR) ~=  0.25

means the drag on 0.5m^2 at 25 m/s will be (1.2/2) * 25^2 * 0.25 * 0.5 ~= 50N

Anyway, the speed loss in corner 0.2s is still less than speed loss in climbing

Hmmm ... that number 50N looks proper. I see I clipboarded my drag number from cell before adding induced drag ... sorry for confusion. Fortunatelyy someone reads what I write  , thanx Howard.

Yes it is right, 2^2 (lift SQR)/pi/5.5(AR) ~=  0.25

means the drag on 0.5m^2 at 25 m/s will be (1.2/2) * 25^2 * 0.25 * 0.5 ~= 50N

Anyway, the speed loss in corner 0.2s is still less than speed loss in climbing

If the model weighs ~60oz (1.7kg), then the airspeed loss would be ~6m/s, out of the original ~24-25 m/s. This isn't negligible.

I just don't seem to be seeing such a dramatic airspeed loss. Maybe I am not even making 10 foot corners though!

Here is some data from a flight last week where I think the airspeed and altimeter are nominally working. This is the wingover. The blue vertical line (at t=178 seconds) is where I think I hammer the plane (Nobler). The white trace is airspeed (mph-- right vertical axis for scale), the red is altitude (feet -left vertical axis for scale), and the purple is the power into the motor (kwatts--right vertical axis for scale).

A couple of caveats--I still feel a little uncertain about how well the sensors are working. For example the airspeed is indicating ~46mph level, while my lap times show ~54mph. The altimeter accuracy is something on the order of 4 feet. Also each tick is 0.1 second.

The max power into the motor coincides with minimum airspeed , which seems to occur a little before the top of the wingover. I wish the data was a little cleaner.

I need to go out and hammer some corners and use my video camera to synchronize when exactly the corner occurs!

My calculation was pretty crude.  I used the 5.25 sec/ lap cruise speed to calculate 52 N.  Induced drag would decrease as airspeed decreases.  It's proportional to the square of airspeed.  Also, this is a pretty dynamic case, and I only understand the static case.   

An interesting set of wing tips on the racing Mustang "Precious metal". Now what would happen if you mirror-imaged those tips so you had one up and one down on each side.

http://stunthanger.com/smf/index.php?topic=14690.msg133449#msg133449

John W

Hi Gang,
I went back to von Doenhoff...

George Aldrich's cousin, by the way

Aldrich's cousin? No kidding! Now that's some neat toy airplane trivia.
Did this come up in conversation with George the departed or what?

Drifting further afield from the thread's intent or interest.

Yes, back when he was alive.  On one of these fora I mentioned Abbott and Costello's airfoil book, as it's known in the trade.  Somebody came on and sternly corrected me regarding the author.  Then George piped up and mentioned the kinship.  Awhile later, I met a Roger von Doenhoff at work.  I asked him the obvious question: whether he was related to George Aldrich.  (When I met Curt Nixon, I similarly asked him if he was kin to Mojo.)  Roger didn't know George, but admitted to being Albert's nephew.  I put the two of them in touch. 

An interesting set of wing tips on the racing Mustang "Precious metal". Now what would happen if you mirror-imaged those tips so you had one up and one down on each side.

http://stunthanger.com/smf/index.php?topic=14690.msg133449#msg133449

John W

We tried this on a Coyote back in 95....it was a hog  in the wind.