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Old Nov 13, 2008, 06:34 PM
Half scale electric builder
Joined Jan 2008
13 Posts
Knife edge square loop

The guys in my rc club in the UK are having a massive fall-out about whether a square loop can be done in knife edge. Watching some of the 4D footage on youtube would it seem that is is possible. Can anyone enlighten me (and my club) as to whether this move is possible.....this being a vertical square loop, in knife edge.....so knife edge along, snap 90 to go straight up, snap 90 to travel back in knife edge, and then the fun one - snap 90 to dive down and another snap 90 to pull back into the starting knife edge position.

Please help, its now a heated debate.

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Old Nov 13, 2008, 06:43 PM
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mattk0's Avatar
United States, MN, Apple Valley
Joined Jan 2004
2,118 Posts
Hmmm. Intriguing question. I honestly don't see any issue with the first 3/4 of the loop, but doing a 'quick' 90 while going down and pulling back into starting position would snap-out on every plane I've flown. Maybe more knowledgable physics/modeler members can speak up.

[edit] I would think a lot depends on the model too. It seems the lighter foam planes would have more potential of making that last corner 'snappy' as opposed to a larger/heavier planes.
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Last edited by mattk0; Nov 13, 2008 at 08:26 PM.
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Old Nov 13, 2008, 06:48 PM
Xpress..'s Avatar
United States, CA, Alpine
Joined Oct 2007
21,323 Posts
Yes, it's entirely possible, if you have the guts to perform the last leg, and the height to. You will have to get your timings right with the throttle, and having a trimmed out model on knife edge for it to look clean. I know several variations of a knife edge loop are done with smaller indoor foamies, but they fly on knife edge as well as they do fly on the wing(s).
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Old Nov 13, 2008, 06:51 PM
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theKM's Avatar
central PA.
Joined Sep 2004
20,712 Posts
possible, but most planes don't have the yaw authority to keep the corners tight.
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Old Nov 13, 2008, 07:45 PM
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Neil Morse's Avatar
San Francisco, CA, USA
Joined Jul 1999
6,154 Posts
My RC Factory Yak will do it, although the last turn really takes a lot of nerve to pull off. So far, I have only attempted this at a comfortable altitude. I decided to try it after seeing the great 90 degree flat rudder turns that this model will do, both upright and inverted. It has less side slip coupling than any model I've flown. The only thing I'm not sure I understand about your description of the square KE loop is the term "snap" to describe the 90 degree turns. I just do 90 degree turns in KE with rudder only. This is not a "snap." If you're talking about some kind of snap roll at the four corners, then that's something different that I don't quite understand.

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