Horten Xc - The ultimate hang glider-part 2 - Page 5 - RC Groups
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Feb 25, 2012, 05:27 PM
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Vernon Hunt's Avatar
Kent,

Yes! That looks fabulous! The glider is a good convenient size as well... hhmmmm.

Vern
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Feb 26, 2012, 05:58 PM
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Knoll53's Avatar

Maiden


For the first flight, I set the CG too far forward by about 1/4" and I'm glad I did. In later test flights I moved the CG to the aft with fascinating and hair raising results. I'll think that I'll run with the forward CG for a while until I get control issues dialed in. Bloopers to follow.

The horsy is from Iceland. Very mellow. Mostly shaved for our climate. Riders suggested that my sinister looking plane might spook normal horses.

Kent

HXc maiden (1 min 36 sec)
Feb 26, 2012, 06:13 PM
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Knoll53's Avatar

Bungee break


It's hard to tell from the video, but one of the 2 bungee strands breaks at full pull, comes back and smacks my hand. This is no way to start a flight.

Kent

Bungee break (0 min 24 sec)
Feb 26, 2012, 06:23 PM
Deniable plausibility
Shedofdread's Avatar
Good to see it in the air! Looks really smart Btw, where was the flying site? Thought you'd have thrown it off the hill...?
Feb 26, 2012, 07:02 PM
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ohmite's Avatar
Kent,
She looks great in the air, looks like it hangs together very well during those low altitude pulls. How did your skid hold up? Ready to head to the hill now?
Congratulations!
Regards,
-Eric
Feb 26, 2012, 07:18 PM
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nmasters's Avatar
Looks like you had a rough day, Kent. The glider looked OK though
Feb 26, 2012, 08:00 PM
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Knoll53's Avatar
Glad you enjoyed it lads. It was a fun and challenging day.

As far as Horten maiden flights go, this was good news. I explored the aft regions of the CG envelope and lived to talk about. A little worse for wear, but it's only new once. Pitch control was do-able but turn response was...interesting. Still would like to spend more time trying different combinations of CG placement and elevon programing. Today, the inner elevons were slaved to both the elevator and ailerons. This may not be the best for turn response. There was a flat spot in turn response for most of the flights and when at the most aft CG, there were flat spots all over the place. I'll hobble together a new bungee for the next effort. Launch heights were weak today. Fine for test flights.

I'll continue to learn here on the flats before venturing out to the rugged terrain of Big Sur. One tumble. off of launch, landed me in a tree, which happily broke my fall, so no damage. Hate to think what would have happened in Big Sur with the same tumble. Once I'm at 100% on the flats, I'll head out to the mountain for some thermal hunting. Can't wait.

Skid saw some action and performed well. I'll build more of those. It's hard to see, but I got a nice hop off of the skid on the last "bungee break" video.

This flying site is a recreation area in the old Fort Ord firing range. Now a MRA. It would have been safer to maiden at the beach, but I refuse to get sand in my pull/pull system. Now that I've got some air time, this plane will never see the beach. Well.... never say never. There IS some iceplant at the beach that could serve as a LZ.

BTW, I ended up flying at 14.1 oz./s.f. It's no gentle trainer.

Kent
Feb 27, 2012, 04:15 PM
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Tijgerhaai's Avatar
However,

congrats for the maiden flight. I would use the ailerons not devided in two parts. Only if you want to use it as a drag side rudder. In all other cases a serious mixing could show better results.

and put the cg more forward....

Regards

Lothar
Feb 27, 2012, 04:46 PM
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Knoll53's Avatar
Quote:
Originally Posted by Tijgerhaai
I would use the ailerons not devided in two parts. Only if you want to use it as a drag side rudder. In all other cases a serious mixing could show better results.
and put the cg more forward....
Thank you. This was the direction I was heading and it is good to read it stated so clearly.

I am fitting demountable lead trim ballast in the nose, so I'll have a choice to move the CG back, but I will no doubt never do so.

During the first flights shown on the maiden video, the CG was the most forward. Although I had good movement at the control surfaces, I noticed that that elevator response was "sluggish" and required full throws just get the nose up enough for a landing. It is this sluggish response that prompted me to move the CG back. I paid dearly for that move. I got some gray hair that day.

I'll remove elevon mixing for aileron and increase the mixing for elevator. I'll explore the forward range of CG next time.

I'll experiment with the inner elevon as a drag rudder. See sketch. Happily, I have a new Hitec Aurora 9 Tx so mixing options are only limited by my imagination.

Kent
Feb 27, 2012, 04:53 PM
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miniphase's Avatar
Good stuff Kent, she looks to have a long flat glide. Also enjoyed the 'incidental' k9 and equine reportage. Hopefully you can find a way to protect the pull-pull system from sand ingress and get her on that superb coastal site of yours!
Feb 27, 2012, 05:22 PM
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Knoll53's Avatar
Quote:
Originally Posted by miniphase
. Hopefully you can find a way to protect the pull-pull system from sand ingress and get her on that superb coastal site of yours!
I am itching to do so. Only at the slope can you get some real airtime to tweak the settings. The hill with the iceplant is little more than a bump, so I'll have to wait for the killer slope winds.

Should be fun.

Kent
Feb 28, 2012, 01:02 AM
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andrecillo76's Avatar
Hi Kent,

congratulations for the maiden . As Lothar wrote, that wing looks too shaky and its CG was for sure aft. How or where did you get the value for the maiden?

I am not really a friend of splitting elevons into smaller pieces or making them short, because they lose functionality and a well designed Horten does not really need a drag ruder. Just look at all the late argentinian Hortens. None had small elevons and we can be confident that Reimer had collected enough experience until then. Even the older IV, which had three controls per side, had quiet large surfaces. In total, this corresponds to the experience I have made. If you make them too short, you end up using too large deflections, reducing maneuverability and increasing stall speed. You also risk tumbling due to a flow separation on the bottom side of the control surface. From a practical point of view, you need to use two servos more, which cost money and add up weight. Also regarding failure it makes no sense, as the chance of servo-failure is twice as high without having increased much controllability. And all these drawbacks for a weak drag ruder, which the wing should not need at all? If I were you I would just use those elevons together and forget about them in your next Horten


You made a great job building that beautiful wing! I guess you have now space and time for the RFA Manatee

Regards,

Andrés
Last edited by andrecillo76; Feb 28, 2012 at 07:28 AM.
Feb 28, 2012, 10:44 AM
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Knoll53's Avatar
Thanks Andrés. I now understand what you mean by flow separation on the bottom of the airfoil. This is due to too large of an elevon deflection. Large control surfaces ( chord and spanwise length) will combat that sort of separation (and tumble).

You can bet, the CG is moving forward. I have stuffed as much lead as will fit in the tiny space available in front of the servos. If I need more, I'll replace the LE strip with lead at the nose. My next test flights will be at the beach, which will allow much more air time. During 1st Flying Day, there were also other flights that had a more aft CG than the ones shown in the video.

The original CG was from the original Nurflügel (Ranis program) output that I got from IG Horten member contribution. That file is attached.

If I understand you correctly, having the split elevon act as one would be the best approach for both elevator AND aileron, no drag rudder required. I will try it, along with any other combination I can dream up, including the drag rudder. I'll attempt to fully test each approach with a dedicated video for each. I've yet to try the crow function with the split elevons.

I've always noticed that flying in ridge lift, such as at the beach, makes any plane perform better. Not just apparent glide ratio, but less bad habits, like tip stalls. The true test is slow thermalling flight without ridge lift. If it doesn't tip stall, spin and tumble, I'm happy.

This should be an interesting test bed for me.

Maybe for next test flight I should provide a live video link to your cell phone.

Kent
Last edited by Knoll53; Feb 28, 2012 at 09:29 PM.
Mar 02, 2012, 09:22 PM
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Flight testing - Day 2


The CG has been moved forward as compared to Day 1. Short little launches just to get a feel. The video includes every flight from today. The good, the bad and the scary. It's all there.

This flying site is TOO SMALL for this bird. I'm always dodging a tree or something. Hardly any room to just let it fly. Still learned a lot about this ship today. There is enough elevator throw to stall a slow landing, which is followed by a tip stall and cartwheel. So the CG could potentially move even farther forward and still have elevator control. Although adverse yaw did occur, a little up elevator solves it.

At 14oz./s.f., it moves beautifully through the air and with a hour on the slopes to learn turns, I'll be in the groove.

Turn your sound down for the video.

Edit: I almost forgot. The crow did next to nothing. Not only did not slow the glider much, but it seemed to improve the glide. My guess is that the inner elevons dropping down did something very good for the lift distribution. I've got a glider that has "legs" without glide path control. This should be fun.

Kent

Horten Xc Flight Testing - Day 2 (6 min 56 sec)
Last edited by Knoll53; Mar 03, 2012 at 12:26 AM.
Mar 03, 2012, 12:59 AM
internet gadfly
nmasters's Avatar
Nice flight. As long as you can recover from the stalls the CG isn't too far aft but you're directional stability will benefit from moving it forward. If, when you're satisfied that the directional stability is good enough, you still have stalls you can improve the recovery with a stall delaying device in front of the elevon. It's not scale but it could make the plane more docile.

--Norm


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