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Old Jan 05, 2013, 09:25 PM
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And funny thing is...the side arm launches are still identical. If thrown flat it goes flat. If thrown at 45 it climbs at 45...same as before, when it was nose heavy.
This is what you should expect if you didn't re-trim anything after adding the penny.

My takeaway at this point is that the dive test is more useful when the CG is way off. If the plane is really nose heavy, it's going to pull out quickly (assuming you've trimmed to hold level flight at "normal" speed). The closer to optimum the CG is, the less useful the test becomes as it's affected too much by whether you've trimmed for minimum sink or maximum distance. I'm also suspecting that as the plane speeds up in the dive other variables change, like the center of pressure, which will also affect the outcome. So like Daryl said, it isn't useful for optimizing.

It's not flying season here, but I look forward to fiddling around with all of this come spring.

Jim
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Old Jan 05, 2013, 10:17 PM
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United States, CA, San Jose
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I just can't believe how many planes I've had, that just plain fell out of the sky after a stall.
If I could go back in time (this would be before the internet even existed when I "left the hobby") well....shoot, across the board I'd do things differently...wouldn't have dated her/wouldn't have sold that car/would have....

Funny thing, though, despite this "information age" we live in, is that the "information" has less value than it did before. Most of what one reads is merely repeated from X, repeated from Y, repeated from Z...a virtual vomit-spew of (mis)information good/bad/indifferent.
Case in point is Wikipedia having a fake article repeated the world over as true fact. Just because you read something doesn't make it true.
Only true, personal experience and trial and error, and honest sharing...

shoot, I prolly should stop drunk-posting.
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Old Jan 05, 2013, 10:35 PM
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OH!!!
Totally forgot the inverted flight test!!!

That was the culmination of today's flying. It flew virtually identical upside down/right side up!!

Now it's time to do some color-differentiating to know whether upright or inverted!
Previously, it was clearly obvious when it was flying inverted based on HOW it was flying...now I have to go by sight alone.
For those unfamiliar, the Alula is a flying wing with a vertical tail, and is (visually) perfectly symmetrical upright/inverted.
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Old Jan 06, 2013, 08:44 AM
Red Merle ALES
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United States, Mt, Helena
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Hypothetical question

Hypothetical question.

Daryl Perkins and cityevader are going to fly their models together. Lucky guy that cityevader! They have the same model, same flight control movements, same camber settings, same weight etc... The only difference is that cityevader hadn't started this thread so his model was significantly nose heavier than Daryls. Daryl had ballasted his so that these two models are the exact same weight. So everything is the same but the balance location.

They both launch at the same time and cityevader follows Daryl, who wouldn't. At 400' AGL Daryl finds lift, so cityevader starts turning with him. They are flying in the exact same point in space in the same thermal.

We know that Daryl's model showed more of a reaction to the lift thus it made it easier for him on the ground to see what the atmosphere was doing. Thus without his help cityevader may had just flown right through that lift without ever noticing due to the nose heavier model.

But now that they are both in the lift will both models climb at the same rate?
Is the more neutrally balanced model going to out climb the nose heavier model?
Are there differences in the speed the model needs to be flown to obtain the same climb rate in the thermal?

Thanks
Curtis
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Old Jan 06, 2013, 09:14 AM
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Are either of the planes red?
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Old Jan 06, 2013, 09:45 AM
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The extra downward force on the tail must be countered by an increase in lift from the main wing. Both of which will come at a drag penalty.

For any given airspeed that means a bit more drag, hence higher sink rate.
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Old Jan 06, 2013, 11:34 AM
Ricky Windsock
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USA, FL, Sanford
Joined Nov 2008
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Quote:
Originally Posted by CloudyIFR View Post
Hypothetical question.
But now that they are both in the lift will both models climb at the same rate?
Is the more neutrally balanced model going to out climb the nose heavier model?
Are there differences in the speed the model needs to be flown to obtain the same climb rate in the thermal?

Thanks
Curtis
No they cant climb at the same rate because one is producing more drag than the other.
Neutral model will out-climb the nose heavy model.
At all speeds the nose heavy model will perform less efficiently due to more drag so will always be out-climbed by the neutral model.
Of course in practice ain't too many thumbs that will theoretically match DPs to test it out. This thread has certainly been informative and very worthwhile reading but I know that going out and flying a lot ensures we can fly thermals really well even when our models are not set up so perfectly.
Gordon
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Old Jan 08, 2013, 12:03 PM
Red Merle ALES
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I'm trying to make a point and thanks for sharing/playing along.

So, now cityevader has started this thread and learned a lot about balancing his glider using different methods that all get him to a similar balance point.
Now, if he were to fly against Daryl in the same scenario as post #229 it would come down to piloting skills, thermal turning skills, use of flight controls, experience etc....
Each flight control deflection is some sort of drag, albeit necessary to control a model.

So in all 233 wonderful posts the one thing I certainly agree with Gordy about is get the lead out, of the nose that is! Then go fly, fly and fly! Nothing will improve your skills more than flying in different types of weather and competing to learn from the others around you. What a wonderful hobby.

Curtis
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Old Jan 08, 2013, 05:38 PM
MrE
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Ah ha! One of those rare posts on RCG that no one could possibly disagree with.... at least IMHO
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Old Jan 26, 2013, 12:24 AM
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Australia, QLD, Townsville
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I know bugger all about glider set ups, so I would like to pose a question to you learned gents.
I have a dynamic S from durafly ( I know it's not the greatest for pure gliding ).
On my maiden I had to set up the elevator with about 2 degrees down trim . I'm happy with the way she flys and does pick up thermals well. at times I can soar around for 20 minutes without using the motor.
My point is, with elevator down trim . Why does it want to pull up in vertical dive?. I even have to put more down trim in to keep her diving to build up speed. I have played with the cofg, but all I do is upset my gliding ability.

By the way ,the dymanic is a V tail.

I'm new to the gliding scene, but The couple of gliders I have , really have me hooked.

I look at gliding like fishing. You are hunting for fish in snags and holes ,just like you are hunting for thermals in cloud holes , ground hotspots etc. Cheers.
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Old Jan 26, 2013, 11:24 AM
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Why does it want to pull up in vertical dive?
Self preservation.
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Old Jan 26, 2013, 11:37 AM
Herk
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Virginia USA
Joined Jun 2007
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Quote:
Originally Posted by medroller View Post
I know bugger all about glider set ups, so I would like to pose a question to you learned gents.
I have a dynamic S from durafly ( I know it's not the greatest for pure gliding ).
On my maiden I had to set up the elevator with about 2 degrees down trim . I'm happy with the way she flys and does pick up thermals well. at times I can soar around for 20 minutes without using the motor.
My point is, with elevator down trim . Why does it want to pull up in vertical dive?. I even have to put more down trim in to keep her diving to build up speed. I have played with the cofg, but all I do is upset my gliding ability.

By the way ,the dymanic is a V tail.

I'm new to the gliding scene, but The couple of gliders I have , really have me hooked.

I look at gliding like fishing. You are hunting for fish in snags and holes ,just like you are hunting for thermals in cloud holes , ground hotspots etc. Cheers.
What you describe is both normal and desirable. The why is somewhat complex, but it's mainly because of the interaction between the weight/CG which is pretty much constant and the aerodynamic forces which are proportional to speed squared. The slight down elevator at your ideal soaring trim and CG doesn't cause any problem and doesn't need fixed. It's normal too for higher speed flight to require more down trim in a well balanced sailplane.
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Old Jan 26, 2013, 02:00 PM
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the entire goal of a balanced plane is so that it WON'T require different trims for different speeds; that is an indication of an unbalanced plane, and it is NOT desirable to have it fly different all the time just because speeds are different (an unbalanced plane).

The slight bit of down trim may likely be due to the v-tail itself being at a "up-trim" angle...but regardless, for the time being, ignore any slight bits of trim (relative to the fixed portion of v-tail).

Try Gordy's method of giving continuously more up elevator until it's stalling, and if the nose suddenly drops, it's still nose heavy.
If you still don't like how it flies with the CG further back, try reducing throws, it does indeed help.
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Old Jan 26, 2013, 02:02 PM
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Quote:
Originally Posted by cityevader View Post
the entire goal of a balanced plane is so that it WON'T require different trims for different speeds; that is an indication of an unbalanced plane, and it is NOT desirable to have it fly different all the time just because speeds are different (an unbalanced plane).
If we agree that trim is what forces the wing to a given AoA, then the idea that you can glide (i.e. in steady state with load factor 1) at different airspeeds with the same trim doesn't make any sense. That is a fallacy.
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Old Jan 26, 2013, 02:26 PM
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actually, based on what I've learned from this thread as applied to my own planes, the AoA was always different because it was always changing with speedbecause the trim was off as a result of the imbalance, and was only good for whatever speed I decided to pick. Once balanced, the trim became nullified (for lack of a better phrase) in that I could fly fast or slow and it would still fly level (once I leveled it).

you CAN glide at different speeds with the same trim if it's balanced. It should go exactly where it is pointed.
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