TWF Gurus - Pitcheron + elevator = CROW? - RC Groups
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Jul 09, 2007, 01:41 PM
BillO's Avatar

TWF Gurus - Pitcheron + elevator = CROW?

I'm thinking about building my first twisty wing plane, and I had this idea for how to slow it down for landing. Suppose you had 3 servos, 2 for the wings like a pitcheron, and 1 for the elevator like a wingeron.

You fly it normally like a wingeron. When it comes time to land, you flip a switch and activate the CROW function. Now the wings pitch up and the elevator compensates when you move the throttle stick. This would be easy to do with my Eclipse 7.

Am I crazy? Could this work? Has anyone tried it? Thanks!

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Jul 09, 2007, 02:17 PM
AKA - The "Flywheel"
StevenatorLTFO's Avatar
I want to see video when you try this
Jul 09, 2007, 02:49 PM
NY Slope Dog
Wind Junkie's Avatar
That's not going to work. The plane will just pivot or rise depending on how much "elevator compensation" you program with that "crow" mix.

What you really need is to make that wing dirty like a real crow program does. That means articulating the wing TE to give it some camber or reflex.

You just can't have your cake and eat it too. Sorry.
Jul 09, 2007, 03:07 PM
Registered User
Sleedo's Avatar
All that would do is skew the fuse through the air, might slow it down a little. I would like to see an airbrake arrangement like a jet fighter where a flap is deployed from the sides of the fuse. Or go with a Winchdoc canopy brake.
Jul 09, 2007, 03:16 PM
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slopemeno's Avatar dont need it. Most twist-wing planes are not that hard to land once you get the pattern down. A canopy brake might make it easier though.
Jul 09, 2007, 04:25 PM
Hutch's Avatar
It would definitely make the plane more dirty, but you would really have to tweak that mix pretty cleanly to avoid having to compensate instantly on approach. It may not work in a linear fashion, might have to be an instant on/off switch. If stopping her on a dime on the spot every time is really important...there is always Harley's Flap-Mo device.

Buuuuuut, after buying & fitting that second hi-torque servo in there why not just keep it a nice clean pitcheron?

who wonders what kind of fun project Bill is planning on getting into.
Jul 09, 2007, 04:40 PM
Fun ain't cheap!
droydx's Avatar
I did it with a Snipe years ago and it was not very effective. I mixed up wing with down elevator, and it took a long time to dial it in, for what it achieved. I wouldn't mess with it now, like Slopmeno says, just practice a long pattern from down low on the slope and bleed the speed off back up to your LZ.
"Go like Hell, don't let up"
Jul 09, 2007, 04:43 PM
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jofo1's Avatar
The only way I can see doing this effectively is to build a conventional flap into the pitcheron wing, only use for crow. j
Jul 09, 2007, 04:48 PM
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jofo1's Avatar
or go flaperon and a camber change friendly foil...????
Jul 09, 2007, 05:08 PM
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slopemeno's Avatar
I was flying my Shredder this weekend (love that plane, btw) and it was actually pretty easy to land. I have to fly down about half the height of Tick Pt (so, about 200-250 feet) and climb back up the face and enter the pattern.

Lately I've been doing a tight a 360 before climbing back up, and the plane comes back up quite slowly. People who fly lower slopes might want to give this a shot if you cant pop-n-drop.

I had a semi-scale 3 meter ASW-19 that used a hatch that was about 3" x 6" behind the canopy as a speed brake, and it wasnt super-effective. The trick to using it was to open it early and leave it open. As the speed bled off so did the brakes effectiveness, unfortunately.
Jul 09, 2007, 05:13 PM
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winchdoc's Avatar
I built a Xica with that feature. Never flew it, but depending on what mix you had, you could concievably skew the fuselage in flight, to give it the appearance of changing pitch. Mixed the other way, It would be easy to blank out and stall both the wing and stab with high angles of attack, and high delta between the two.

I always thought it would be cool to do a cobra manuver and use the fuse skew to accentuate it. Couldn't think of any really practical use for the feature, (other than it's a wild idea) so I converted the Xica back to wingeron.

You'll never see flaps or spoilers on any of my TWF. To me, the compelling beauty of TWF is the simple wings, no hinges, no plug-ins no clevis. Neat and clean.

I like having a canopy brake, or the Kestrel speed brake. They are not enough to stop a plane dead in it's tracks, but they DO slow down with the brakes. I'll build another Xica with the split rudder speed brake.

Jul 09, 2007, 06:13 PM
BillO's Avatar
All right, thanks you guys. I had a feeling I would have seen it by now if it really worked. But it didn't hurt to ask.

On the pop'n'drop technique, can a pitcheron execute the turn at the top without stalling the wing? Usually I'm pulling a bit of up elevator right at the end, then crank the ailerons hard over to turn it back into the wind. This could stall the low wing pretty easily, no?

Jul 09, 2007, 06:28 PM
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slopemeno's Avatar
Not a problem with my Shredder, which is a pitcheron. I'll let you fly it Bill, its very easy to fly. You CAN tip stall it (which results in a turn opposite of what youre feeding in) but thats more likely to happen in a scratching situation.
Jul 09, 2007, 09:18 PM
Fun ain't cheap!
droydx's Avatar
On the hard turn back to slope for a pop and drop....yes some do stall and some don't.
I have a Rotor that does not enjoy sharp hard turns....Snipe - no likey either.
My old Shrike and Samruai's were much more forgiving. So the basic design isn't the problem.
Jul 10, 2007, 04:47 PM
Knowledge increases life's FOV
Sled Driver's Avatar
Bill – here are a couple more thoughts for you based on my limited experience:

TWF’s are kind of like wives/girlfriends, they are all kind of the same, but they do have some significantly different characteristics… so, choosing wisely is important (more on choosing a first TWF below). Different handling characteristics are chief among the differences, since they do not necessarily respond to the same to the same inputs and techniques you have used in the past with others. For example, if you are used to landing by bringing the plane in high behind a big hill and using flaps or spoilers to bring the plane down, then you are going to have to learn a new landing technique or two. Fortunately, the landing techniques are not difficult to master and work well for other planes, e.g., sleds.

TWF fly the same as other slope planes with wing control surfaces, but since they do not have articulated control surfaces they tend to be much cleaner and lower drag machines. Remember, drag is the great evil, but low drag has consequences during landing. For a first TWF, I would suggest a wing with a more moderate airfoil, e.g., a DS4 (very similar an RG-15), RG-15, or S6062, that has nice stall characteristics, rather than an airfoil that is thin. I like the DS4, it is faster than the S6062, is theoretically faster than the RG-15, and has pleasant stall characteristics like the RG-15. After you have landing a TWF down, then put on a set of wings with a 7.5% thick, 0.7% camber airfoil. Keep the plane light weight and clean – the light weight will make landing easier (slower) and the clean will keep it stroking in big air at a lighter weight.

I do not know if Brian McLean has announced it yet, but I suspect that his Vector II design will be an excellent first TWF with its 2-meter’ish span, S6062 airfoil wing, rudder, and full-flying articulated stab.

There are two landing techniques that I use. I fly on big hills and typically in good to outrageous lift. The technique that I use on Eagle Butte, which has a nice top landing area, is to bring plane relatively low (around telephone pole height), pretty close to me (50 yards), and fast. I simply turn the plane around into the wind and drive it to the dirt (just a left hand TD landing approach). Driving the plane to ground is important. You need to keep some speed on the plane, but it does not have to speared in. How much speed you need to keep is determined by the weight, span, airfoil, etc. But, you need to keep the nose down and plane moving – a little turbulence can dump a TWF plane being flown too slowly on wing and TWF’s generally do not take cartwheeling or hitting on a wing well.

The other landing technique I use is to land the plane on the face of the hill at Kiona Butte or the shoulder of Chandler Butte is to bring the plane up the face of the hill close to it, turn plane parallel to the ridge line and near the crest to kill a little more energy, point the plane down hill, and drive it to the dirt while close to the ground. I’ve heard some folks call this technique the plop and drop, . This technique frequently requires a number of approaches to get the feel of. I would suggest that you intentionally shoot a number of approaches, say six, before you even think about setting the plane down. Your first couple will be kind of high and scattered, but you will surprised how much better your third and fourth approaches will be.

If you have to come in high and land on top of your hill (why someone would have to do so, I don’t know, but if you have to), you can use the technique I learned from Ken Stuhr. Drive you plane behind the hill and S-turn back and forth behind the hill until you are at landing altitude. Just make sure that you don’t allow the plane to get blown too far behind the hill when you are S-turning back and forth behind the hill. After watching Ken do it with a Xica, I had to try the technique. It works, but it takes a lot more skill to plop the plane at your feet.

58 posts left...
Last edited by Sled Driver; Jul 10, 2007 at 09:34 PM.