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Flying Stab
I see there are "some" planes using a full flying stab. Is there enough benefit to make this worthwhile? I intend to build one of the older Insite models as an entry level plane. If this is worthwhile I thought I might make the modification. What is being used for linkage to operate the stab. Thanks!
Ken |
Ken, while I have not flown any power planes with a flying stab, I have flown a number of high end sailplanes with flying stabs and normal elevators and honestly could not tell any significant difference. In theory a flying stab is less drag which is good for a sailplane but not nessisarily so on an aerobatic model.
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The problem with the full flying stab is the servo has to be very strong, so it's also heavy, but this is not really a problem for most, the other thing is it has to be well set up to take the most advantage of the servo torque/resolution, as if it is not well set up, it can have some inconsistencies with centering in flight, particularly, I don't think it worth the hassle and the airplanes fly either the same or worse, I only flew the Bi-Side from a friend on F3A, but own some 3D planes with the full flying stab where it has been good for some maneuver and really bad for level flight.
Regards |
It sounds like the full flying stab is sort of a "gimmick" to sell an airplane. I messed around trying to mock one up one time many years ago with mixed results (never actually flew it). Since starting this post and doing a bit more research I think I'll pass on the idea. I was just looking for someone with practical experience. I think the FFS has it's place, just not on a F3A airframe.
Ken |
I have an all moving stab on my biplane and recently converted my monoplane to the same arrangement. My experience is that overall it is a lighter set up than a dual servo system or a single servo DEPS. I believe it is easier to build than a conventional stab (no elevators to cut and hinge) and and is easier to trim. No need to adjust the stab to remove elevator trim. I have the pivot point at 24% MAC and the servo torque is 7.5 kg-cm on the biplane and 8.8 kg cm on the monoplane. Difference is what servo would fit rather than a need for more torque. Seems to work fine. Certainly wouldn't claim any aerodynamic benefit, but easier to build and for trimming than the conventional stab IMHO. Bill
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Do you have a photo or drawing of the linkage? Part of the draw to the FFS was not having to adjust the stab to center the elevators. It is "self adjusting";)
Ken |
A friend has always been using flying stabs on his F3A designs, I have seen them fly and there does not seem to be any problem with it. With the right placement of the pivot axis and mass balancing, this is actually much easier on the servo.
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Originally Posted by kenh3497
(Post 11870921)
It sounds like the full flying stab is sort of a "gimmick" to sell an airplane. I messed around trying to mock one up one time many years ago with mixed results (never actually flew it). Since starting this post and doing a bit more research I think I'll pass on the idea. I was just looking for someone with practical experience. I think the FFS has it's place, just not on a F3A airframe.
Ken Ken EDIT: Found this site if you need/want to desigh from scratch http://www.ultimate-jets.net/blogs/f...ols-on-rc-jets While it is for "jets" the principals should be the same for any airframe. |
https://www.facebook.com/photo.php?f...type=1&theater
this is the plane I was talking about, the guy one of the Slovak top 3 flyers and I have seen the plane fly - impressive despite the somewhat unorthodox looks and building technology. |
Originally Posted by David Kyjovsky
(Post 11871843)
https://www.facebook.com/photo.php?f...type=1&theater
this is the plane I was talking about, the guy one of the Slovak top 3 flyers and I have seen the plane fly - impressive despite the somewhat unorthodox looks and building technology. |
I am flying the Biside, for me there is no difference between the flying stab and a convencional elevator.
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5 Attachment(s)
Ken,
There is no drawing as such. I sort of made it up as I went along. Have done a rough sketch plus a few pics that should give you the idea. Essentially a normal 7/16 carbon stab tube fitted at 24% MAC. The carrier bearing is two bushes in an aluminium tube glued in the fuse. There is an aluminium cross rod fixed in the right stab that passes through the fuse and goes in to a stab adjustor. The end of the rod is reduced and notched. The stab adjustor is used to align the two stab halves and the notch engages the top grubscrew to retain the stab halves. The servo is mounted in a hatch under the leading edge of the stab. A carbon tube slides over the cross rod and a 4-40 threaded rod is bent around the tube and goes down to the servo clevis. No complicated linkages and no slop. The carbon tube protrudes outside the fuse by about 5 mm and acts as a spacer to maintain clearance between the stab root and the fuse. PM me if you want any more info. http://www.rcuniverse.com/forum/atta...mentid=2027539http://www.rcuniverse.com/forum/atta...mentid=2027547http://www.rcuniverse.com/forum/atta...mentid=2027549http://www.rcuniverse.com/forum/atta...mentid=2027552http://www.rcuniverse.com/forum/atta...mentid=2027534 |
Thanks for the photos and drawing CW. It's becoming a bit clearer now that I've read through your description a couple of times! Sounds like a simple solution. From what I can find it seems having the pivot at the correct spot in the stab is the most critical thing. How many degrees of travel are you using? From the slot in the fuse, it looks like about 10ish total.
I mentioned using an Insite as an entry level airframe. I should also say it will not be in a 2X2 size. I'm thinking about a 65ish inch wingspan 'cause that's the equipment I have on hand. This will get me started and if I like it will move up in a year or so. Ken |
I'm going to start off by saying I absolutely have no clue what I'm talking about. So use that as a guide as I try to convince you that I know what I'm talking about and that you should listen to me.
Or better that you should be cautious before putting anything I say into practice. If you are building a plane that does not need very large control throws AND minimum drag actually matters then a flying stabilizer should be considered but not necessarily implemented. If you are building a plane that may need to medium to medium-large throw and you're flying for fun or fun competition (not serious competition) where you don't care if you always lose then you may want to consider a full flying stabilizer. If you are building something that needs more control throw than that then forget it. I can't see that you'll be able to 3D a plane using a full flying stabilizer but as I said, I have no idea what I'm talking about so it may be very well possible but I think you will need the fixed portion to at lease get some air directed at the deflected portion of the control to make it work at all at least in very low speed maneuvers and maybe in all maneuvers. I'd be very interested to see how they work. If I had the right micro stuff handy I'd probably try to whip something together in a weekend after pondering it a couple weeks but I don't have anything at all except maybe a couple servo but they're probably to big and I don't have any receivers that small and no motors or escs and I'm not really interested enough to buy it. But I don't mind if you do. :) |
Originally Posted by CafeenMan
(Post 11872327)
I'm going to start off by saying I absolutely have no clue what I'm talking about. So use that as a guide as I try to convince you that I know what I'm talking about and that you should listen to me.
Me Too Or better that you should be cautious before putting anything I say into practice. Another "Me Too" If you are building a plane that does not need very large control throws AND minimum drag actually matters then a flying stabilizer should be considered but not necessarily implemented. My intention If you are building a plane that may need to medium to medium-large throw and you're flying for fun or fun competition (not serious competition) where you don't care if you always lose then you may want to consider a full flying stabilizer. A large consideration and I lose all the time anyway so why change things up now:confused:;):D If you are building something that needs more control throw than that then forget it. I can't see that you'll be able to 3D a plane using a full flying stabilizer but as I said, I have no idea what I'm talking about so it may be very well possible but I think you will need the fixed portion to at lease get some air directed at the deflected portion of the control to make it work at all at least in very low speed maneuvers and maybe in all maneuvers. No 3D for this guy. I can barely fly straight and level:D Besides, why would you WANT to 3D a pattern plane:confused::confused::confused: I'd be very interested to see how they work. If I had the right micro stuff handy I'd probably try to whip something together in a weekend after pondering it a couple weeks but I don't have anything at all except maybe a couple servo but they're probably to big and I don't have any receivers that small and no motors or escs and I'm not really interested enough to buy it. But I don't mind if you do. :) Ken |
Ken
Stab deflections are Normal 5degrees, spin 10 degrees and snap 4 degrees. Personal preference is the main driver. Feels no different than a normal elevator set up. At least to me! |
Originally Posted by CW
(Post 11872754)
Ken
Stab deflections are Normal 5degrees, spin 10 degrees and snap 4 degrees. Personal preference is the main driver. Feels no different than a normal elevator set up. At least to me! Thanks CW! I've been doing a little looking and the BJ Craft Nuance 70 uses a FFS. It has what appears to be a conventional control horn sticking out of one stab half. No "fancy" linkage at all. I still like the idea of getting the linkage inside the fuse. Ken |
Having a flown a BJ craft BiSide for most of this year, which is several hundred flights, I can say I have been impressed with the feel. I don't know that it is better or worse, but seems to be smoother and have a more linear feel (which is should). Properly setup, you shouldn't need a lot of torque for a servo as it is balanced. Using the new Futaba HV brushless servos the the trim didn't even change over the course of the time I've flown it. Now that we have servos capable of truly finding center, building a full flying stab is no longer a problem. Myself and most of the guys that have been flying the Biside's have noticed that we end up using similar deflections, 8-10 degrees for most flying and more for spins and less for snaps. The bottom line is that it works, and it lasts and I know myself and others have commented that they like the feel, I wont say it is a major advantage, but I wouldn't call it a disadvantage either.
Arch |
One nice advantage is that it you do not use Expo for the elevator. This also adds to the nice linear and smooth feel.
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Originally Posted by David Kyjovsky
(Post 11871843)
https://www.facebook.com/photo.php?f...type=1&theater
this is the plane I was talking about, the guy one of the Slovak top 3 flyers and I have seen the plane fly - impressive despite the somewhat unorthodox looks and building technology. Never could get this link to work. Tried it on my PC and Chromebook. Not a big deal so don't worry about it:D |
It sounds like the FFS is a good thing. (thinking out loud here...) I wonder how long before somebody tries a full flying wing panel?????? Just think of all the possibilities. It might fly like the control line ships with the right mixing!!
OK.... Back to the FFS discussion. I can see where SLOP FREE linkage is an absolute necessity. And a good centering servo. Ken |
Originally Posted by kenh3497
(Post 11873879)
It sounds like the FFS is a good thing. (thinking out loud here...) I wonder how long before somebody tries a full flying wing panel?????? Ken
The pivot tube (wing tube) would need to be moved from its typical position around the CG to the more aerodynamically practical AC (25%MAC by convention). It would take considerable amount of mass to statically balance each panel so beware. The result would be a heavier model (by quite a bit) |
I was sent some info from the Classic forum. The "Flying Fork" from the 70's returns. It looks like a very viable thing to use. Definitely something to think about.
http://www.rcuniverse.com/forum/clas...r-cut-kit.html Ken |
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