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Old Jan 24, 2011, 10:28 AM
lets go sailplaneing
seaspb's Avatar
long beach, ca
Joined Nov 2008
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f3f reflex use

During the drop in (first leg or two) I use reflex then switch to neutral. Should I keep in reflex or start with neutral and keep it there. We race coastal and inland sites. I think switching camber is far more critical at the inland slopes.
Thanks in advance.
Sam
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Old Jan 24, 2011, 11:08 AM
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Riverside, California, United States
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Hey Sam,

"keep in reflex"

B
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Old Jan 24, 2011, 12:47 PM
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reflex will depend on your wing section.
some b models have very slight under camber, so a 32nd of an inch or so will suffice, but that depends on the model and wing section.
j
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Old Jan 24, 2011, 03:23 PM
Phil.T-tailer
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Quote:
Originally Posted by ceres-syd View Post
reflex will depend on your wing section.
j
+1
some go faster with reflex, some dont, and some are slower
if yours goes faster with reflex, then suggest keep it in for the whole flight (but not the turns!)

Phil.
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Old Jan 24, 2011, 03:48 PM
In F3J size does matter!
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Israel
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Optimal camber setting is a function of the lift coefficient (Cl) your airfoil is producing.
Diving in, your Cl is very low so reflex is required to reduce the drag.
On the straight, Cl is low so reflex is still a very good idea.
In the turns, the Cl is high, so no reflex or even a small amount of positive camber will be required to reduce the drag. The optimal amount depends on your flying style and how hard you pull on the stick.
If you "bank and yank" to produce a very high Cl you will need quite a bit of positive camber.
If you prefer a wide turn with a relatively small amount of elevator, a small amount of camber, if any, will be required.
A good idea is to set up a constant amount of reflex right from the start of the dive and to keep it on all the time.
Use "Snap flap" to set the right amount of camber that suites your flying style and try to find something you’re comfortable with.
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Old Jan 24, 2011, 03:49 PM
In F3J size does matter!
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Old Jan 24, 2011, 07:13 PM
lets go sailplaneing
seaspb's Avatar
long beach, ca
Joined Nov 2008
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I've snap flap mixed in.
Flying style, well I'm still developing that. I better keep a log of how I set my plane up and how I like it. to keep the guess work out of it. I've done this with my thermal flying, don't know why I hadn't thought of doing the same with f3f. Thanks for the info.
Sam
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Old Jan 24, 2011, 07:22 PM
Detail Freak
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For that Extreme, you probably want a little reflex when you are racing.
You might set up a flight phase with 1mm, and another with 2mm, and see what you like best.
You have to add snap flap though, if you run reflex, the same amount of reflex you add.

G/L,
Target
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Old Jan 25, 2011, 06:20 AM
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The reflex that I had on my extreme was approx the width of the trailing edge plus a fraction.
I did a very low 36 with it.
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Old Jan 25, 2011, 08:47 AM
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Quote:
Originally Posted by roydor View Post
Optimal camber setting is a function of the lift coefficient (Cl) your airfoil is producing.
and Cx

Quote:
Originally Posted by roydor
Diving in, your Cl is very low so reflex is required to reduce the drag.
Diving in, you don't care about Cl, you want the smallest Cx, so you set the camber for it to drag the least: it can be with or without Reflex depending on the airfoil, there is no general rule.

Quote:
Originally Posted by roydor
On the straight, Cl is low so reflex is still a very good idea.
on the straight, you want to drag the least with enough lift: it can be with or without Reflex depending on the airfoil, there is no general rule.


Quote:
Originally Posted by roydor
In the turns, the Cl is high, so no reflex or even a small amount of positive camber will be required to reduce the drag. The optimal amount depends on your flying style and how hard you pull on the stick.
no, it doesn't, if it does, your glider is centered to far back, and snap flap can't be properly tuned. when you tune your snap-flap, it has to be on "every" elevator travel: it usually ends up with a curve between flap and elevator.

Quote:
Originally Posted by roydor
If you "bank and yank" to produce a very high Cl you will need quite a bit of positive camber.
If you prefer a wide turn with a relatively small amount of elevator, a small amount of camber, if any, will be required.
A good idea is to set up a constant amount of reflex right from the start of the dive and to keep it on all the time.
Use "Snap flap" to set the right amount of camber that suites your flying style and try to find something you’re comfortable with.
the global idea is to keep Cx low in every point of the trajectory, to do so, you have to work on camber, but there is no general rule: experiment is the way to go.

all the more, reflex can also produce instability on some cases (stability on others...)

have fun!!

Cedric,
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Old Jan 26, 2011, 09:24 AM
Detail Freak
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Ced,
Be nice now....

I agree that the strategy for best performance is likely very different between F3J and F3F, but, I myself am on a campaign to be well liked here (I need to actively persue that!).
Please be respectful of others.

If my post is misplaced, and I'm reading in something that isn't there, my apologies, and please, please, disregard.

Kind Regards,
Target
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Old Jan 26, 2011, 11:29 AM
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Quote:
Originally Posted by target View Post
Ced,
Be nice now....

I agree that the strategy for best performance is likely very different between F3J and F3F, but, I myself am on a campaign to be well liked here (I need to actively persue that!).
Please be respectful of others.

If my post is misplaced, and I'm reading in something that isn't there, my apologies, and please, please, disregard.

Kind Regards,
Target
sorry if it sounds nasty, that wasn't my point

"general rules" scares me, because if applied, they often lead to wrong tuning, and the pilot doesn't understand why its glider doesn't work.

it is a bit like:
"- how much snap flap to use?
- 4mm!
- me too
- so it bumps out the turns!
- no, it's like I've put the handbrake on..."
everybody will have noticed that the 2 guys didn't talk about the elevator deflection related to the flap...

one thing is sure about camber:
- when you set more camber, the Cxmin usually goes up in Cl
- when you set less camber, the Cxmin usually goes down in Cl

so about Reflex, if in straight, you fly under the Cl of Cxmin, you have to put reflex (old RG14 for exemple).

if you fly at the Cl of Cxmin, you keep the airfoil.

if you fly above the Cl of Cxmin, you have to put flaps; usually in turns (load increases), but also if you are too heavy.

Cedric,
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Old Jan 26, 2011, 05:10 PM
I'm your huckleberry
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experimentation has always worked best for me with regards to reflex and camber. My old Acacia and Sting seemed to love reflex, especially in strong lift conditions. My Ceres on the other hand did not seem to benefit at all from reflex. Airfoil seems to me to be a big factor. I always had snap flap activated when using reflex, so pulling turns were not affected by the reflex. I don't know a lot about the science so I will stop here. JMO!!

Bob
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Old Jan 27, 2011, 02:33 AM
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Leicestershire
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I always found it hard to notice the difference. But that's probably me. BUT the one thing I noticed with all models is that in very turbulent conditions, the reflex always seemed to damp the model a little bit and calm it down through the straight. Anyone else found this? And why (Ced? Happy New Year btw mate!)

Z
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Old Jan 27, 2011, 06:43 AM
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Standard ceres run no reflex.
Ceres lift and Cyril I run around 1/16th of an inch.
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