Spa3d inverted flight

Spa3d inverted flight
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Spa3d inverted flight - 7/11/2003 6:00:03 AM

psk560

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Ok, I've built my second 89% spa3d. I love these things but the last one broke it's back a couple (20) times. I kept re-bending it back and it flew fine. The leo heli engine just wasn't reliable enough. Now, i've got a tt 42 on it and that seems ok on the power side. Still brand new engine so I haven't revved it up yet. My question.

1. inverted the thing heads for the clouds. I have to hold back on the stick to keep it from going up. Is this an aileron angle problem?

Thanks for your time.

craig

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Experiment - 7/11/2003 6:45:43 AM

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Scotch tape (it's plastic!) a one ounce fishing weight to the front and see what happens.

Maybe the wing creates lift while inverted. I'd like to see the spa3d wing design in a wind tunnel to see what is going on under there. It looks to me, with the opening on the underside, like the air would travel smoother across the top side (unencumbered) than the bottom side (turbulance at the opening) and create negative lift in normal flight, which would require nose up attitude for level upright flight. If that's the case, up elevator in inverted flight would make sense to keep it from gaining altitude.

But then what do I know?

I can only guess, and experiment. No formal education in areo or fluid dynamics.

Maybe someone with some brains will chime in.
I know one thing, they are easier for me to crash if they stay close to the ground.

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Spa3d inverted flight - 7/11/2003 6:52:43 AM

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[QUOTE]

1. inverted the thing heads for the clouds. I have to hold back on the stick to keep it from going up. Is this an aileron angle problem? [/QUOTE]

hmm, A plane that climbs when inverted. Very odd, i'll agree. But, with my dumb thumbs, i think its awesome! I wish all my planes had that tendency. Sure would make inverted less scary, especially for newbies. If you get in a dive, let off the elevator, and up it goes.

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Spa3d inverted flight - 7/11/2003 9:06:08 AM

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I believe that its due to its tail heavy nature. From reading other posts from tattoo, it seems like this plane defies the rules because it flies better with a further aft CG.

With most planes, you can test the balance point by rolling inverted. If it needs down elevator, add nose weight. Could this be the case?

This is only my belief. could be wrong...probably is...but what they hey. nobody knows why this plane does what it does.

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test. sorry - 7/11/2003 5:13:47 PM

psk560

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Just wanted to see if this will work.

craig

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Spa3d inverted flight - 7/11/2003 8:32:10 PM

Tattoo

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quote:

I can only guess, and experiment. No formal education in areo or fluid dynamics

Me either!!! It would be interesting to hear from a educated aerodynamic engineer...because guess what?...mine does it to!

However, I'm with Chris...I LOVE it!!! While inverted I have to conciuosly hold down (up) to keep it level, and any signs of trouble and I just let go. Also...in this condition, sevaral clicks about idle and I get the most perfect natural inverted harrier, and I can just crawl around inverted with very little elevator input...it's almost like cheating and makes me look a LOT better than I really am...but I sure aint telling nobody...

!!!

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Spa3d inverted flight - 7/11/2003 8:52:59 PM

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Maybe I'm missing something...
The SPA3D flies the way it does because it is tail heavy (at least in part). Because of this, it needs down elevator to maintain level flight . Inverted, this becomes up elevator so the plane goes up. Is it more complicated than this?

Ross

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Spa3d inverted flight - 7/11/2003 9:45:53 PM

psk560

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On my old spa3d (RIP

) I moved a lot of weight up front. SO much that it made it very hard to fly without power because I'd run out of elevator. It still did it. I thought it could be the aileron alignment with the fuse. I'm going to move them around some and see what happens.

craig

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Spa3d inverted flight - 7/11/2003 9:48:01 PM

SeacretsOceanCity

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I have the same problem.Well maybe not a problem because I know how it will act inverted. The first thing someone said to me while putting around at a few clicks above idle(ARE YOU TAIL HEAVY) I gunned into a hover and said no,but I think its the case.
My QHOR tail on take off comes right up instantly as soon as I nail it. The SPA3D takes much more speed before the elevator is effective ( tail comes up).Or maybe its a combination of tail heavy
and location of the landing gear. to far forward of the CG.

I Dont know??I will experiment monday with both its the only thing I can come up with. Any one else??????

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Spa3d inverted flight - 7/11/2003 9:51:29 PM

Tattoo

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I'm actully thinking along the same lines as Ross but just slightly different. My Ailerons are set parallel to the fuselage (err to the slightly reflexed) and in normal flight my elevator is trimmed straight away. However, the normal flight neutral position of the ailerons are actually slightly up in relationship to the very slight natural AOA of the wing...therefore...when inverted...they become flaps, giving the extra lift.

As for take off roll on these planes, we've found it to be directly related to the AOA of the airplane as it sits on the ground. The more level is sits (short mains long tail wire) the longer the take off roll, and the more nose high it sits (long mains short tail wire) the shorter the take off. Our planes (almost identical) were taking off in approx 30-40 feet. Then Kraut switched his main gear to 5/32" music wire and made them like stork legs

...and his plane was sitting way nose high. He was off the ground in less than 10 feet.

< Message edited by Tattoo-RCU -- Jul 11 2003 4:59PM >

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Spa3d inverted flight - 7/11/2003 10:01:18 PM

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This answers a few questions I had. I built a 34x34" version powered by a 40LA. It acted extremely tail heavy! Combine that with some massive control throws and,,, well I kept it off the ground for about 45 seconds and kept it out of the trees.

I couldn't keep up with this thing. About 30 seconds into it I managed enough upward motion to try to trim it. Trim it?? I threw all the down trim in it in 1 quick move. It did help but, I still ended up boinkin' it in. My CG is about 7" from the LE. Am I to far back??

Also, I didn't have the profile fuse on it. Could that have made a difference?

BTW psk560, I used the 5/32" wire as instructed in mine and with about 70 degrees of throw in the ailerons (to much for me!) it seems like I got around 3, or more, rolls per second!!!

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Spa3d inverted flight - 7/11/2003 10:02:03 PM

SeacretsOceanCity

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I had my Rons set parallel to fuse and had the 6 inch CG I took off and would climb with anything above idle.I landed moved the Rons into a flap position 1/2 inch below fuse this helped not to use so much down trim on elevator What is happening here??.It flew better.

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Spa3d inverted flight - 7/11/2003 10:20:45 PM

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If a plane climbs when inverted, that tail heavy and I am yet to see or hear of a spa3d that is not, so its normal.. have fun

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asymmetrical - 7/11/2003 11:18:18 PM

rlt55

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It was kind of weird. I seemed to have been over-controlling every time I tried to fly inverted.

But then last Sunday, I flipped over inverted and didn't touch anything but the throttle.
It was going nose up until I backed off the power. It flew just fine and was stable as long as I used very small (next to none) rudder or aileron inputs. Pulling the stick back a tad (bringing the nose down) allowed it to go a little faster.

When you look at the QHOR and SPA3D wings, you know right away they are very asymmetrical and there is no way they are going to act anything like a symmetrical wing, when flying inverted.

The fun move to exit inverted, is to center the stick and add power.
My SPA3D will climb and arc back into upright flight, making a 180 direction change while gaining altitude. (upside down, 1/2 an outside loop?).
I don't try this too close to the ground if it's windy, but I've done it as a panic escape a few times when I ended up inverted too close to the weeds!
I just add power fast and push the nose up gently..

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Spa3d inverted flight - 7/12/2003 12:38:09 AM

SeacretsOceanCity

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I wonder If I unscrew the wing and slide it back an inch or two. anyone tried it yet????

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Spa3d inverted flight - 7/12/2003 2:37:25 AM

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[QUOTE]I wonder If I unscrew the wing and slide it back an inch or two. anyone tried it yet????[/QUOTE]

I've been wondering about that to. When I installed my wing I jammed it hard against the motor mount because doing it that way made a nice rounded leading edge. Now I wonder if I should have left it in line with the mount.

I put a .70 4-stroke on mine and had to move everything way back to get it to balance. My servos touch the rudder with my battery just in front of them.

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Spa3d inverted flight - 7/12/2003 2:41:52 AM

psk560

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i bet a 4 stroke is awesome fun on a spa3d.

Any pics?

craig

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