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There goes my 3D virginity!

Old 07-29-2011, 10:31 PM
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NJSwede
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Talking There goes my 3D virginity!

I *finally* finished my Airfoilz Extra 300NX and since this was the first kit of any kind I've ever built, I had to take it for a spin right away. I chose a field with 3 ft tall grass for crash protection. And...

...SHE FLEW!!!! Straight as an arrow! Not a click of trim on anything!

I had all rates at 50% with 25% expo, but I could still make it do some crazy stuff! I even hovered for a few seconds.

Wow, this felt like the first time I had a successful flight with my Champ. Just a rush of adrenaline and euphoria! So completely different from anything I've flown before.

Still, I have a question:

I've noticed I pretty much had to steer it with the throttle. Full throttle, and it takes of like a rocket, pretty much straight up without me having to touch the elevator. Is this normal or is something out of trim? The build manual doesn't mention any down thrust, so I guess it's to be expected that it wants to climb like crazy when I throttle up. But since this is my first 3D-bird *AND* my first build, I wanted to make sure this is the way it should be. Any point in adding some down thrust or would that ruin the 3D capabilities?

But overall... MAN, this is absolutely amazing! So happy I picked this birdie up!
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Old 07-29-2011, 11:04 PM
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Old Fart
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Where's your CG Swede? - and do you do a 45 degree upline check on it?
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Old 07-29-2011, 11:19 PM
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Yeah, sounds like CG may be too far forward. Should fly inverted with very little to zero down elevator.
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Old 07-29-2011, 11:38 PM
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Originally Posted by Old Fart View Post
Where's your CG Swede? - and do you do a 45 degree upline check on it?
Did I do a... WHAT?

I'm clearly out of my league here...

The manual recommended 3.5" -- 4" behind the leading edge, so I put it at 3.5" since I figured a nose heavy plane would be easier to handle. I'll move the battery backwards a tad tomorrow.

You think what's causing it to pitch upwards at high RPM is that it's nose heavy?

With a little bit of luck Jim, the designer himself, will be at the field tomorrow so I can ask him. We happen to be members of the same club.
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Old 07-29-2011, 11:46 PM
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Originally Posted by NJSwede View Post
Did I do a... WHAT?

I'm clearly out of my league here...

The manual recommended 3.5" -- 4" behind the leading edge, so I put it at 3.5" since I figured a nose heavy plane would be easier to handle. I'll move the battery backwards a tad tomorrow.

You think that's what's causing it to pitch upwards at high RPM is that it's nose heavy?

With a little bit of luck Jim, the designer himself, will be at the field tomorrow so I can ask him. We happen to be members of the same club.
Hi with a 3d Plane is all about how you want to fly your plane, If you want to fly slow and Hover the plane, dont give the plane any down thrust, and a Back position CG is better for hovering, but it wont fly fast very well, because it will be a little tail heavy, but you need that for hovering, if you want to fly Aerobatics, move the CG forwards more and add about 3 degrees of down thrust, this will mess up the hovering ability, but it will fly better level and fast, your Planes set up and how you want to fly will determine where the CG is to be at and down thrust given.
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Old 07-29-2011, 11:54 PM
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Thanks Chellie! What I'm reading between the lines is that I should experiment with different settings and that there's really no right or wrong.

Oh, BTW, it was a bear to land. If I let go of the throttle, the nose dropped like a led balloon. I guess that means nose heavy, huh?
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Old 07-29-2011, 11:58 PM
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Originally Posted by NJSwede View Post
Thanks Chellie! What I'm reading between the lines is that I should experiment with different settings and that there's really no right or wrong.

Oh, BTW, it was a bear to land. If I let go of the throttle, the nose dropped like a led balloon. I guess that means nose heavy, huh?
yes it sounds to be nose heavy, just move the CG to find the sweet spot, a little at a time, for your type of flying, also add a little down thrust for stability, start at about 3 degrees, that will be about the thickness of a washer on the top of the motor mount, on both sides on the top to move the prop shaft down. try different amounts of down thrust to find the sweet spot, normally no right or left thrust is needed on a 3D plane, but that could vary from plane to plane.
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Old 07-30-2011, 12:31 AM
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Originally Posted by JetPlaneFlyer View Post
Yeah, sounds like CG may be too far forward. Should fly inverted with very little to zero down elevator.
Nose heaviness is causing it to pitch up at high throttle? Sounds almost counter-intuitive! Please enlighten me!
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Old 07-30-2011, 12:39 AM
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I was taught this a long time ago..

Fly across the field (left to right, right to left - whatever works for you best - I generally go into the wind)

Climb at a 45 degree angle, roll the plane inverted and hold it to maintain the 45 degree "upline"

Have to input lots of down elevator - shift CG rearward

Plane increases the angle (wants to go vertical?) shift CG forward.

MUCH easier than checking from level flight.

Jeff

Originally Posted by NJSwede View Post
Did I do a... WHAT?

I'm clearly out of my league here...

The manual recommended 3.5" -- 4" behind the leading edge, so I put it at 3.5" since I figured a nose heavy plane would be easier to handle. I'll move the battery backwards a tad tomorrow.

You think what's causing it to pitch upwards at high RPM is that it's nose heavy?

With a little bit of luck Jim, the designer himself, will be at the field tomorrow so I can ask him. We happen to be members of the same club.
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Old 07-30-2011, 01:15 AM
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Thanks Jeff! I'll definitely give that a shot at the field tomorrow!
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Old 07-30-2011, 01:23 AM
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Not a problem sir. I _might_ get to fly slope on Sunday, if I get a few more boxes unpacked. Damn but I hate moving.....
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Old 07-30-2011, 01:31 AM
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Originally Posted by NJSwede View Post
Nose heaviness is causing it to pitch up at high throttle? Sounds almost counter-intuitive! Please enlighten me!
lack of Down Thrust is causing the plane to pitch up at higher speeds, if you want to fly slow, then no down thrust for hovering and slow flight, with higher speeds you need down thrust to load the wing and make the plane more stable in flight.

Last edited by CHELLIE; 07-30-2011 at 02:02 AM.
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Old 07-30-2011, 01:58 AM
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Originally Posted by NJSwede View Post
Nose heaviness is causing it to pitch up at high throttle? Sounds almost counter-intuitive! Please enlighten me!
Yup
First, balance the model properly. Then, say you add 20% of the weight of the model as a piece of lead in the nose of the airplane and try to fly it.

That nose is going to drop like a rock, so you've got to hold up elevator to make it fly. Probably a lot of up elevator.

So, if you're flying at 30 MPH, with the proper amount of up elevator, it might fly OK. But now, go up to 60 MPH, and that up elevator is going to push the tail of the plane down, causing the model to pitch up.

And just as bad, slowing the model down to 20 MPH for landing is going to cause the nose to drop like a rock, diving toward the ground, making it difficult to land the thing.
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Old 07-30-2011, 02:15 AM
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Thanks Dennis! That makes perfect sense.

Of course I couldn't keep myself from custom decorating her in Swedish colors...

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Old 07-30-2011, 03:00 AM
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Looks nice Swede and I see you bought your motor from Jeff getting a package from him Sat. myself.
I have the Airfoil edge and before I learned on it to much "kinda hints of crashes" it was a great flier now it is on the heavy side. I had to play with mine also to get it the way I wanted it to fly. After I found the spot for the battery I marked it with a felt marker.
Like it was pointed out to learn hovering I moved it back some and put another mark. This way depending on how I wanted to fly I put the battery on the mark to the front for more sport aerobatic and to the back mark to practice hovering which is still not my strong point, but it gave me a reference to go by each time when I flew.
Have fun they are nice flying planes.
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Old 07-30-2011, 03:49 AM
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Originally Posted by gramps2161 View Post
Looks nice Swede and I see you bought your motor from Jeff getting a package from him Sat. myself.
I have the Airfoil edge and before I learned on it to much "kinda hints of crashes" it was a great flier now it is on the heavy side. I had to play with mine also to get it the way I wanted it to fly. After I found the spot for the battery I marked it with a felt marker.
Like it was pointed out to learn hovering I moved it back some and put another mark. This way depending on how I wanted to fly I put the battery on the mark to the front for more sport aerobatic and to the back mark to practice hovering which is still not my strong point, but it gave me a reference to go by each time when I flew.
Have fun they are nice flying planes.
Thanks for the tips, Gramps! Any idea what the difference between the two positions was in inches (or fractions thereof, maybe)?
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Old 07-30-2011, 09:02 AM
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NJ,

CG position is often a quite personal thing and it's usually impossible to find a position that's perfect for every aspect of flight.. but it certainly sounds like you are way nose heavy right now. On my aerobatic models I've usually found that zero or very close to zero down thrust is required once I get the CG nailed. Apparent requirement for lots of downthrust is sometimes an indication of CG too far forward. A bit of right thrust is usually a good idea though, about 2-3 deg.


I tend to just fly inverted horizontally rather than 45 deg up to do my check, but the principal is exactly the same. A vertical dive should also indicate if your CG is right; for an aerobatic model if it continued vertical hands off then CG is good, if it pulls out toward the canopy it's nose heavy, toward the belly it's tail heavy. Knife edge is another manouvre that is sensitive to CG position, nose heavy pulls toward canopy, tail heavy toward the belly, but most planes have a slight natural pull toward the belly in KE in any case so a bit of rudder to elevator mix is often required.

Personally I dont change CG location for different types of flying, once I get the plane set up I like to stick with it.

Steve
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Old 07-30-2011, 12:55 PM
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Originally Posted by NJSwede View Post
Thanks for the tips, Gramps! Any idea what the difference between the two positions was in inches (or fractions thereof, maybe)?
It is not much maybe 3/8 of a inch difference, you will have to figure this one out with your plane.

Jetplaneflyer pointed out a good point it is a personal preference on how you want to setup the CG. On other models I don't play with the CG this plane I did move it as a shift in the CG creates a different flight character, and made hovering a little easier as others have pointed out a little tail heavy makes it easier to learn to hover.

So play around with it till you find your sweet spot for flying.
John
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Old 07-30-2011, 04:29 PM
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Originally Posted by JetPlaneFlyer View Post
NJ,

I tend to just fly inverted horizontally rather than 45 deg up to do my check, but the principal is exactly the same. A vertical dive should also indicate if your CG is right;
Steve
I've tried this, works well

Question, how would a flat bottom or semi-symmetrical wing affect the cg check when flying inverted or in a dive??
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Old 07-30-2011, 06:39 PM
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Originally Posted by kyleservicetech View Post
I've tried this, works well

Question, how would a flat bottom or semi-symmetrical wing affect the cg check when flying inverted or in a dive??
The Airfoilz has a fully symmetrical wing, so it's not an issue.

I moved the battery about an inch back. It flew much better. Unfortunately I had a prop strike on my second landing which messed up the motor mount (on closer examination, it looks like I skimped on the epoxy...)
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Old 07-31-2011, 11:00 PM
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Took it out again today. This time I moved the battery as far back as I could and taped $0.25 to the tail. That did the trick! Now I can fly it hands off on 1/2 -- 2/3 throttle and only use slight down elevator to keep it level on full throttle. I thought I measured the CG the first time, but I must have messed up royally...

So now she flies like a sports plane with bigger control throws. Now what? How do I fly 3D? Can you give me the 2 minute rundown?
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Old 07-31-2011, 11:33 PM
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Originally Posted by NJSwede View Post
So now she flies like a sports plane with bigger control throws. Now what? How do I fly 3D? Can you give me the 2 minute rundown?
No, but seriously... I can do loops, rolls, inverted flight, hammerheads and that kind of stuff until the cows come home. What's the next thing I should try?
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Old 08-01-2011, 12:01 AM
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Originally Posted by NJSwede View Post
No, but seriously... I can do loops, rolls, inverted flight, hammerheads and that kind of stuff until the cows come home. What's the next thing I should try?
Knife Edge, Rolling Harrier I Know you can do it

[media]http://www.youtube.com/watch?v=BMJHCZ71kMc[/media]

[media]http://www.youtube.com/watch?v=CT3tc1-tXfU[/media]
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Old 08-01-2011, 12:23 AM
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Im sure people cheat when doing rolling harrier....they make it look so easy! :P
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Old 08-01-2011, 12:50 AM
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Originally Posted by Crumpet46 View Post
Im sure people cheat when doing rolling harrier....they make it look so easy! :P
I know... I can do a knife edge with my PZ T28D (with full throttle and ton of rudder), but rolling harriers is like dancing and I have a horrible sense of rhythm... We'll see. As some of the Wattflyers may have noticed, I love challenges and I NEVER give up, so this will be a fun one!
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