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JSJ
4 Posts |
 Posted - 06/19/2004 : 12:00:20 AM
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Do you know of any planes that are flying successfully without vertical stabilizers?
Since no real birds have vertical stabs, I have always longed to build a plane without any. The potential payoff is lower drag, and therefore better efficiency. The cost is in putting some sort of active control loop on board to stabilize the yaw in normal flight and to induce yaw in special maneuvers.
Before I start designing this, I'd like to hear about any stab-less aircraft that have already been attempted. Please describe or provide pointers to any you know about.
(I know about Vtails; they don't count as being stab-less. ) |
Edited by - JSJ on 06/19/2004 12:05:56 AM |
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Jeff_Newcum
7 Posts |
Posted - 06/21/2004 : 2:01:19 PM
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Someone in our club flies one.
More information can be found here. |
Edited by - Jeff_Newcum on 06/21/2004 2:06:19 PM |
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kiesling
45 Posts |
Posted - 06/21/2004 : 4:22:45 PM
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Helmut's model is missing the horizontal stab.
The only models I've seen with no vertical stab have been flying wings - and they fly better with a vertical tail.
I don't think that eliminating the vertical fin is going to be worth the effort. It doesn't add that much drag and there are probably other areas that can be improved to give the same amount of drag reduction.
Tom |
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Anker
83 Posts |
Posted - 06/22/2004 : 1:32:02 PM
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If you watch birds flying, the best is sea gulls sloping off a ship, you can see that they constantly twist their tails. The tail doesn't just go up and down it also twists and moves side to side. By doing this they in effect have a vertical stab when they need one.
Anker |
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JSJ
4 Posts |
Posted - 06/22/2004 : 2:50:49 PM
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| Yes, I have often noticed this and I have thought about how to use the idea. It's clear that you could get a force vector in any direction you wanted just by rotating the tail feathers, but I worry that there may be transitions from one setpoint to another that might be ill-defined. For example, if you view the force vector from the rear along a line that is parallel to direction of flight, then a setpoint would be any position in the 2-D plane within a radius of neutral. Trajectories in this space from one side to 180 degrees opposite would be wildly ill-conditioned if the trajectory went close to zero; depending on which side of zero your control inputs went, the rotation might be sharply clockwise or sharply counterclockwise. Have you ever pondered what to do about this? |
Edited by - JSJ on 06/22/2004 2:53:05 PM |
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JSJ
4 Posts |
Posted - 06/22/2004 : 3:14:14 PM
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quote:
Originally posted by kiesling
The only models I've seen with no vertical stab have been flying wings - and they fly better with a vertical tail.
What is the symptom? Do they "wander" and oscillate in yaw? Are they hard to control on launch?
If I could fix either of those problems without adding a tail, wouldn't everyone be happy about it? Sticking a tail on a flying wing kind of defeats the whole premise!
jsj
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kiesling
45 Posts |
Posted - 06/22/2004 : 5:23:18 PM
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Not quite sure how to describe the symptom, but I think the best description is that they slide down the span of the wing during a turn. From what I remember, even during level flight they wander in yaw.
I think that using an active control system to control yaw will likely be more draggy than the use of a vertical fin. If you were to say use the ailerons or some kind of spoiler system to control yaw, I suspect you'll find that it is considerably more draggy then using a vertical fin.
I'm sure that there are some aeronautical engineers (Mark?) out there that have a better perspective on this.
Tom |
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JSJ
4 Posts |
Posted - 06/22/2004 : 7:48:40 PM
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You are thinking of more clunky control surfaces than I am. When I watch birds, I see them using just a couple of feathers at the extreme wing tips for a second to affect the yaw, and then they fold them back up and streamline them again. I haven't built this yet, but it appears that birds use the maximum yaw moment they can produce with the minimum drag. And, of course, it appears to be worth it.
jsj
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lincoln
49 Posts |
Posted - 09/21/2004 : 11:01:19 PM
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Horten flying wings used no vertical surfaces, and some could make coordinated turns without using their yaw drag controls, because of the weird lift distribution. They were swept, and had lots of twist so the tips were pushing down a little. No adverse yaw. Al Bowers has a neat paper or two about this, maybe it's at Nurflugel.com. Horten style wing has relatively poor span efficiency but good ratio of structural weight to induced drag, as it can have a longer span for the same root bending moment. My impression from Al's papers and other places is that this would make a pretty good single point machine (i.e. designed for cruising speed) and maybe not such a good glider, but the Horten 3 was among the best in the world for its time. (Just before WW2, I guess I can't just say "the war" and have anyone know what I mean, particularly since I'm too young to say that.) A big Horten style wing would be awfully fun.
P.S. You can't use aileron differential on most flying wings (possible exception of Marske and other slight forward sweep types) as the ailerons also provide elevator inputs.
Lincoln Ross |
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Eliminating the vertical stabilizer
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