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crazy roll

Old 06-26-2011, 10:18 PM
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spitncobra
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Default crazy roll

I have an extra 300 and a couple of other planes over the years that has this problem.I need the fix.When you give full up the plane goes nuutttzzzz floping around like you threw it out of the car any ideas would be appreciated Spitncobra
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Old 06-26-2011, 10:23 PM
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Default RE: crazy roll

It's a combination of a radially tapered wing, too much up elevator and maybe too high a total weight and thus a higher than ideal wing loading.

And you're not alone. There's more posts around here about "bad habits" from Extras than about any other design.

The first solution is to avoid giving full elevator input for super tight loops. Second is to experiment with outboard loacted turbulators to aid in delaying the almost built in tip stalls due to the high taper ratio.

It's a fine line between weight, airfoil and stall charactaristics on such planes. We want 3D capability and to be able to do multiple snap Lomchevoks on demand but we don't want the wing tips to stall on a super slow dragged out landing approach. I got news for yaz. You can't have both. One or the other has to suffer. Folks that value the easy snaps and 3D performance have to learn to ease the model in during the landing approach with small control inputs so as not to induce a sudden and radical wing twist from the aileron motions and the typical tip stall that goes with it. With such planes you need to just "breath" on the sticks during slow flight such as landings. You also need to learn to use just the right amount of elevator input to achieve tight but stall and snap roll freel loops. Yes, it's THAT sort of design. It does not suffer folks that jam the sticks around like it's a video game.
Old 06-27-2011, 05:24 AM
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rmh
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Default RE: crazy roll

The funny side of this, is that a scale Extra , not some cobbled up so called POS 3D varient, is a extremely easy to fly design
The usual problem is that the RTF models are usually grossly overweight and that,coupled with extreme throws and typical aft cg (most are tailheavy out of the box) provides the unsuspecting purchaser with a model totally unlike the one he was really after.
The CAP 232 -from years back suffered the same fate - The rash of kits available were almost always extremely overweight and tailheavy.
the moniker "Snappin Cap " was assigned to it and the experts all solmnly noted that " Caps snapped."
As a sidenote consider this
Many smallish scale aerobatic models of say 400 square inches -had a typical weight of 4 pounds
(ugh!)
a good modern electric powered model -same size- weighs in at 2 pounds.or less
Does anyone think these examples fly the same ?
Old 06-27-2011, 04:08 PM
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Default RE: crazy roll

The easiest of the reasons to correct is reducing the elevator throw.
Old 06-27-2011, 04:47 PM
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rmh
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Default RE: crazy roll

The elevator throw simply reveals the basic problem
overweight
Old 06-27-2011, 08:51 PM
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Default RE: crazy roll

I gotta go with Dick's thinking. It sums the issue up nicely.

I'd far rather start with too light a model that had an airfoil which resists stalling and then work at adding stall strips or other "tricks" to make the model snap the way I want it than to start with an overweight model with a poor airfoil choice and try to tame the bad stall habit.
Old 06-28-2011, 12:41 PM
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Default RE: crazy roll

Thanks guys all is well we also discovered along with it all we had set it up with the wrong CG making it extremely tail heavy
big oooppppssss
Old 06-29-2011, 04:35 AM
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Default RE: crazy roll

Excellent! Instead of accepting the dismissal of the naysayers, you actually did some checking and diagnosis! I expect you'll find the plane like most Extras - agile, aerobatic, and as stable as you set it up.

My applause!

Happy flying,
Dave Olson
Old 06-29-2011, 05:09 AM
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Default RE: crazy roll

absolutely-
good aerobatic setups are THE easiest of models to fly.
The have to be ,in order to get predictable results when performing maneuvers.
I have handed the tx to absolutely novice fliers ,and allowed them (supervised of course) to fly competition aerobatic stuff - 33% - 42% models
The comments are always that the planes are easier to fly than the trainers they are flying.
The reason being, the models go smoothly where they are pointed .
Many trainers are badly setup, making control, slow or erratic,unresponsive.

getting the weight /balance/control parameters correct on scale aerobatic designs, makes them possycats to fly
If you want scaled models which typically are hard to setup - try speed designs or some military designs .
These were never intended to be docile thru a wide speed range - where the aerobatic designs ,on the other hand must be able to perform.
Old 06-29-2011, 10:17 AM
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spitncobra
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Default RE: crazy roll

Could someone explain turbulator. thank you guys you saved my plane and mostly my nerves.Your advice also stopped my knees
from knocking together each flight.
Old 06-29-2011, 10:28 AM
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rmh
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Default RE: crazy roll


ORIGINAL: spitncobra

Could someone explain turbulator. thank you guys you saved my plane and mostly my nerves.Your advice also stopped my knees
from knocking together each flight.
Read the Wilkapedia explanation for some of the more involved stuff. Basically Turbulator(s) are pieces or strips of material that tries to prevent the air from smoothly "sticking" to a surface.
The "why" of needing this done -depends on the plane -the speed etc..
On our models - really of no need - we are simply flying stuf too small and too slow. Some will say it is needed -
I could never proove it was needed.
Old 06-29-2011, 01:06 PM
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Jezmo
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Default RE: crazy roll


ORIGINAL: rmh

absolutely-
good aerobatic setups are THE easiest of models to fly.
The have to be ,in order to get predictable results when performing maneuvers.
I have handed the tx to absolutely novice fliers ,and allowed them (supervised of course) to fly competition aerobatic stuff - 33% - 42% models
The comments are always that the planes are easier to fly than the trainers they are flying.
The reason being, the models go smoothly where they are pointed .
Many trainers are badly setup, making control, slow or erratic,unresponsive.

getting the weight /balance/control parameters correct on scale aerobatic designs, makes them possycats to fly
If you want scaled models which typically are hard to setup - try speed designs or some military designs .
These were never intended to be docile thru a wide speed range - where the aerobatic designs ,on the other hand must be able to perform.
Now we're on the same page. My 50cc AeroWorks Extra 260 is so easy to fly I sometimes think a brain-dead idiot could fly it. As you said, I've handed the radio to fairly inexperienced pilots who commented on how well it flew. Even with tapered wings the stalls are a non event. It simply slows down and as you pull back on the stick will eventually start falling pretty much straight down (aka an elevator or sometimes called a parachute) without so much as dropping a wing. Incredibly gentle stall transition.
Old 06-29-2011, 11:13 PM
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spitncobra
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Default RE: crazy roll

Thanks again guys I do appreciate your info Rico
Old 07-09-2011, 05:45 PM
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mithrandir
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Default RE: crazy roll

"Turbulators" as they were applied to RC Sailpolanes way back in the day were simply edged irregularities added to the airfoil to force the boundary layer to transition from Laminar to turbulant.

RC sailplanes (Back then) flew at speeds that were very low reynolds numbers... an Rn of less than say 100,000 ish (That would be about a 10 inch cord at 15 mph) were prone to persistant laminar flow... and the bad part is that a laminar boundary layer seperates more easily than a turbulant boundary layer...

There are also devices called "VG's" or Vortex generators... you see'em alot on full size aircraft... the F86 has'em on the bottom of the stab ahead of the elevator...

VG's basically add energy into the boundary layer so it is less likely to seperate... also you will see'em in "S" shaped inlet ducts to turbofan engines.. (L10-11 I think)

generally speaking, turbulators and VG's are bandaids to fix a problem.

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