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Old Oct 02, 2010, 08:54 PM
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alucard0822's Avatar
Pennsylvania
Joined Jun 2010
895 Posts
Your Extra300 wings look pretty much like mine, symmetrical until about 4" from the tip, then a slight flattening on the top, being a newer model it may have been formed a bit differently, others with earlier models look a bit more pronounced. You are right in that it seemed like people got the 300 when they first came out, liked them a lot, managed most IMAC aerobatics, some 3D, and spins, the honeymoon lasted for a couple months, then almost universally complained that they were not good at 3D, and that the wing tips were defective or "upside down", and the plane was practically unfliable.

I am far from an engineer or "full scale" pilot, but have a general grasp on aerodynamics, basically an airfoil develops pressure under the flatter side, being air flows slower across a straight edge and builds slight pressure, and a slight vaccum on a curved surface because of faster airflow over it. if both the top and bottom are symetrically curved, then there is a net of 0 lift unless the airfoil's angle of attack is changed, angling up in front slows the air underneath it, and speeds it above it, generating lift. Once the airflow over the wing slows and or produces enough turbulence to slow the air above the wing it stops generating lift and stalls. Different parts of the wing can stall at different speeds and angles, one of the issues with flapperons is that in slowing the air under the wing more than normal, there is increased lift, but then once the air over the wing can't keep up, it stalls, and at a higher speed than it would if the ailerons remained flat. At a higher angle of attack, or high alpha, it is even more pronounced, and the flaps will stall if you don't keep the speed up, being there is a lot of drag, it takes a lot of power to do this.

One thing that is done to keep increased lift at low speeds, but prevent the tips from stalling is crow, or having 4 flaperons, the inner flaps are down, increasing lift, the outer ailerons are up, slowing the air above the wings, that reduces the stall speed, and makes the wing tips stall after the inner flap portion does, losing lift, but maintaining control, this also has a ton of drag, and will bleed off speed quickly. For this reason, the tips being inverted could actually cause the wing tips to stall at a slightly slower speed than the inner portion of the wings making it a hair bit less prone to tip stalling, being air above the wings flows a bit slower than it would if the wings were completely symetrical. One of the "issues" with the 300 is that it is more stable, and easier to control in an inverted harrier, PROOF that the "inverted" wing is a defect, thing is this is true with most any plane, when upright at post stall speeds, there is a ton of turbulence coming off the top of the body and wings that hits the rudder, inverted, the rudder bites clean air, and has much better control and stability. Thing is even if this theory holds up, the wings don't have a huge difference in the airfoil shape top to bottom, and the difference in stall speed could be only a fraction of a MPH, it would have to be a lot more pronounced before it would do much at very slow speeds.

What it would seem would be more noticeable is dipping the wing opposite rudder control. When the rudder yaws the plane, the opposite side wing is angled into the flight path, with a plane that has dihedral, or a semi-symmetrical or flat bottomed airfoil, airflow pushes up from under the wing with the greater angle of attack, and rolls the plane with the rudder, basically yaw-roll coupling. With a symetrical airfoil, and straight wings, the rudder doesn't really change the roll much if any at all, or shouldn't, with the extra, and an "inverted" tip, it should dip the wing as angle of attack is increased with the rudder, the airspeed is much faster, and it would take only a small ammount of difference in airfoil shape to roll the plane, however at least mine doesn't do this, there is almost no roll at all with rudder input. Compared to slow speed flight where it takes a lot of surface movement to impart control, at high speeds it takes very little, if there was indeed a problem with the wing shape, it should be more apparent at higher speeds, and mostly with rudder input, in my case it isn't.
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Old Oct 03, 2010, 01:06 AM
Play tetris with my english
DaxFX's Avatar
Puerto Rico, San Juan
Joined May 2008
2,301 Posts
Quote:
Originally Posted by lightspeeddud View Post
also another note:

if anybody has the micro parkzone sukhoi it also has the upside down wing foil if you look closely
can you post a picture please.
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Old Oct 03, 2010, 09:02 AM
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SubManEric's Avatar
Joined Mar 2010
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Quote:
Originally Posted by alucard0822 View Post
Your Extra300 wings look pretty much like mine, symmetrical until about 4" from the tip, then a slight flattening on the top, being a newer model it may have been formed a bit differently, others with earlier models look a bit more pronounced. You are right in that it seemed like people got the 300 when they first came out, liked them a lot, managed most IMAC aerobatics, some 3D, and spins, the honeymoon lasted for a couple months, then almost universally complained that they were not good at 3D, and that the wing tips were defective or "upside down", and the plane was practically unfliable.

I am far from an engineer or "full scale" pilot, but have a general grasp on aerodynamics, basically an airfoil develops pressure under the flatter side, being air flows slower across a straight edge and builds slight pressure, and a slight vaccum on a curved surface because of faster airflow over it. if both the top and bottom are symetrically curved, then there is a net of 0 lift unless the airfoil's angle of attack is changed, angling up in front slows the air underneath it, and speeds it above it, generating lift. Once the airflow over the wing slows and or produces enough turbulence to slow the air above the wing it stops generating lift and stalls. Different parts of the wing can stall at different speeds and angles, one of the issues with flapperons is that in slowing the air under the wing more than normal, there is increased lift, but then once the air over the wing can't keep up, it stalls, and at a higher speed than it would if the ailerons remained flat. At a higher angle of attack, or high alpha, it is even more pronounced, and the flaps will stall if you don't keep the speed up, being there is a lot of drag, it takes a lot of power to do this.

One thing that is done to keep increased lift at low speeds, but prevent the tips from stalling is crow, or having 4 flaperons, the inner flaps are down, increasing lift, the outer ailerons are up, slowing the air above the wings, that reduces the stall speed, and makes the wing tips stall after the inner flap portion does, losing lift, but maintaining control, this also has a ton of drag, and will bleed off speed quickly. For this reason, the tips being inverted could actually cause the wing tips to stall at a slightly slower speed than the inner portion of the wings making it a hair bit less prone to tip stalling, being air above the wings flows a bit slower than it would if the wings were completely symetrical. One of the "issues" with the 300 is that it is more stable, and easier to control in an inverted harrier, PROOF that the "inverted" wing is a defect, thing is this is true with most any plane, when upright at post stall speeds, there is a ton of turbulence coming off the top of the body and wings that hits the rudder, inverted, the rudder bites clean air, and has much better control and stability. Thing is even if this theory holds up, the wings don't have a huge difference in the airfoil shape top to bottom, and the difference in stall speed could be only a fraction of a MPH, it would have to be a lot more pronounced before it would do much at very slow speeds.

What it would seem would be more noticeable is dipping the wing opposite rudder control. When the rudder yaws the plane, the opposite side wing is angled into the flight path, with a plane that has dihedral, or a semi-symmetrical or flat bottomed airfoil, airflow pushes up from under the wing with the greater angle of attack, and rolls the plane with the rudder, basically yaw-roll coupling. With a symetrical airfoil, and straight wings, the rudder doesn't really change the roll much if any at all, or shouldn't, with the extra, and an "inverted" tip, it should dip the wing as angle of attack is increased with the rudder, the airspeed is much faster, and it would take only a small ammount of difference in airfoil shape to roll the plane, however at least mine doesn't do this, there is almost no roll at all with rudder input. Compared to slow speed flight where it takes a lot of surface movement to impart control, at high speeds it takes very little, if there was indeed a problem with the wing shape, it should be more apparent at higher speeds, and mostly with rudder input, in my case it isn't.
Alucard, I applaud your efforts to help a fellow pilot understand what is going on. A couple of things to clarify what you wrote.

Although a lot of folks ascribe to the hi/lo pressure caused by acceleration/deceleration of air as an explanation for lift, it is kind of wrong. A better way to think of it is by what physically is happening to cause the upward force - lift. Air changes velocity (think direction, although there is a speed component, too). The wing camber forces air down, the reaction force up is lift. Mathematically, it becomes mass flow rate times change in velocity(direction). This is classic fluid mechanics. It is also the reason you have to brace pipes with elbows - the change in direction causes a reaction force in the opposite direction.

Think of a ceiling fan. How much air does it shove straight down? Quite a bit. A wing or a propeller works the same way.

A "flat bottomed" wing has significant camber when straight and level. A symmetrical wing needs a positive angle of attack to redirect air down. That is how it achieves camber.

So why is air redirected down? When flowing along a curved surface, each air molecule would like to travel in a straight line if we think of the air flowing past a wing. It's a Newton thing. When it tries to do that a couple of things happen. Shear forces created by adjacent molecules will redirect it - think flowstream lines. Also, when the molecule tries to separate from the surface you get fewer molecules per volume downstream - think lower pressure that tries to suck the molecules back to the curved wing surface. When that can no longer happen at high angle of attack, flow separation occurs and the wing stalls.

Flaps increase both lift and drag. Because the camber is increased significantly, air is shoved more sharply down - greater change in direction. For a given velocity, lift INCREASES and stall speed DECREASES. The critical angle of attack (for a stall) DECREASES - this is the price of increased camber - it is harder to keep flow attached in the manner described. This is why you see airliners deploy lots of flap for landing - slow the plane down and give the slowest landing speed. The extra drag requires more thrust to fly at a given speed. For takeoff the flaps are deployed to a smaller angle permitting greater acceleration due to less drag, but the increased camber decreases stall speed, getting the plane airborne quicker than without flaps. It is a compromise.

Tip stalling. This gets tricky. Think of the tapered wing as more than one wing. Near the wing root you have a larger chord, so the change of direction happens less abruptly. Near the wing tip you have the same change in direction in less distance (chord) - a quicker change. Everything else being equal, separation will occur first where the most abrupt change occurs - at the tips. This is why highly aerobatic planes have tapered wings. It makes autorotation easier to achieve.

(I choose to write it this way instead of putting gobbeldy-gook about Reynold's Numbers which really don't explain what the heck is happening.)

This is why planes are designed with flaps near the root, not the tip, and why flaperons increase the risk of tip stalling at low speeds. With the flaps near the wing root, the plane will tend to stall at the wing root before the wingtips, making it easier to control.

Crow does not increase the likelihood of tip stalling. That is why spoilerons are used instead of flaperons outboard with flaps inboard. However, that tip section has a different camber shoving air somewhat up. Less overall lift there, but greater critical angle of attack. More drag. Flaps inboard make up for the overall loss of lift.

You also mentioned yaw-roll coupling. This is a bit of a black art, but has less to do with wing section shape than dihedral. It has to do with the angle of attack the wing sees. For knife edge performance it gets very complicated. Gyroscopic precession, pitch factor, slipstream, center of gravity, fuselage shape, rudder location, wing placement, etc. all play.

Back to the EXTRA 300. Yes, there is less camber at the wingtips than at the root. It will tip stall. Fly it slow with respect. Surface area has a lot to do with lift production when flying slow, and we are talking about laminar flow as well, which changes some things a bit. That is why I don't think the effect is large in the flight regime where I operate.

Hope this helps. Probably clear as mud.
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Old Oct 21, 2010, 08:39 PM
NTX Helidillos
tonkajeep34's Avatar
USA, TX, McKinney
Joined Sep 2009
1,530 Posts
Anyone mounted a GoPro camera on their extra?

The glue that holds the clear plastic on my canopy is coming loose so i was thinking of taking it off and mounting the gopro where the pilot is... then getting a new canopy for regular flights.

Thoughts? not sure the magnet would be strong enough...
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Old Oct 21, 2010, 11:02 PM
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United States, KS, Overland Park
Joined Jan 2010
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I gotta admit. I turned it back into the LHS because the one I got had some issues, but damn that thing could fly. I think I may have to get a new chistmas present for myself. I keep thinking about the one flight I had with it and the perfect KE it would do.
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Old Oct 23, 2010, 09:05 PM
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Originally Posted by Wookster View Post
I gotta admit. I turned it back into the LHS because the one I got had some issues, but damn that thing could fly. I think I may have to get a new chistmas present for myself. I keep thinking about the one flight I had with it and the perfect KE it would do.
Rescue the EXTRA!
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Old Oct 25, 2010, 08:41 PM
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Wendell, NC
Joined Jun 2010
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Tired of that OTHER extra 300 thread. Had 2 great packs through at the first day of my new club. My wings are so called "flat" and it had good slow speed flight. Landed in 50 feet, probably more like 30. All I know is that I touched down right bear the taxi way and was still able to taxi it in.

Where are you guys getting your 11x7 or 12x6 props? I want to start doing some 3D with it, which do you guys prefer?
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Old Oct 25, 2010, 08:46 PM
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United States, CA, Calabasas
Joined Apr 2010
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Originally Posted by lazor 22 View Post
Tired of that OTHER extra 300 thread. Had 2 great packs through at the first day of my new club. My wings are so called "flat" and it had good slow speed flight. Landed in 50 feet, probably more like 30. All I know is that I touched down right bear the taxi way and was still able to taxi it in.

Where are you guys getting your 11x7 or 12x6 props? I want to start doing some 3D with it, which do you guys prefer?
I got a 12x6 APC prop at my LHS for about $3. Works great. As far as 3D goes, not so much with this bird. A few folks have been partially successful (losifanatic is one example). It's great for precision stuff though.
Enjoy!
Josh
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Old Oct 25, 2010, 08:56 PM
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Wendell, NC
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Yea, I know it's not the best 3D out there, but I wanted to give it a shot. I'm probably gonna end up gutting it into a Electrifly Reactor Bipe (awesomeness) and wanted to give it a shot before I did. My LHS closed down this past week so no more local buying, unless I wanna drive 45 minutes to the next one.
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Old Oct 25, 2010, 08:57 PM
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Joined May 2008
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so where did everyone go?

they couldnt have all sold their extra's
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Old Oct 25, 2010, 09:01 PM
T-28C, Extra 300, Beast UMX
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United States, CA, San Diego
Joined Jul 2009
529 Posts
Haven't had good flying weather for a couple weeks (very wierd for San Diego), but I put several batteries through it just before the rain moved in - hope to fly again soon as well as maiden my new fun scale PZ T-28 Trojan when it is completed later this week.
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Old Oct 26, 2010, 03:54 AM
WHAT U LOOKIN AT!
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Penrith, NSW, Australia
Joined Dec 2005
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Originally Posted by lightspeeddud View Post
so where did everyone go?

they couldnt have all sold their extra's
alot of early byers have sold theirs...moved on i guess

on another note I heated my wings and made the swell on top, then sanded them into an airfoil...i like it better! feels more stable...I do put the battery slightly forward too!
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Old Oct 26, 2010, 07:53 AM
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USA, AZ, Surprise
Joined Apr 2010
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I do put the battery slightly forward too!
Everybody puts the battery forward it seems... not me. I've been moving mine further and further back, and the plane has become a lot easier to knife edge.
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Old Oct 26, 2010, 07:59 AM
WHAT U LOOKIN AT!
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Penrith, NSW, Australia
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hmm ok..I have no trouble at all with KE
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Old Oct 26, 2010, 09:44 AM
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Puerto Rico, San Juan
Joined May 2008
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mine is hanging in the wall since i buy it. when i first order this plane like some other i was thinking on a slow 3d flyer. for flying in my baseball park in front of home. after I placed the ordered and start reading revews I realize that this was an aerobatic and pattern flyer. so i need big area. i buy another plane a 3d HAWK from HK. this one is an exellent 3d for 30 bucks. I am not telling that i dont liked i love the look of the plane and i have view lots of video of exellent performance on this bird. i just need a bigger area as soon i flew her for the first time and known how handles then i will fly in my small field.

I love this video:
New Parkzone Extra 300 Doing some Harriers and slow tail first landings (3 min 47 sec)
.

now. any1 here have spoileron, aileron, A.Break setup. my futaba 7C have an option called Air Break. that raise up to 100% the spoilerons and -50% elevator. any1 have try this for slow it down for landing. slowing down I mean with throttle aplied, I know if you glide with no power with flaperon will stall even more.

any input on using, flaperons, spilerons etc...
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