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Old Nov 25, 2008, 09:46 PM
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Happymcc Keith, One of many

Thank you Keith. This thread is loaded with great modelers like you who are looking for something different and unusual. Their aka's are scattered throughout RC Groups and they are the type of modelers who are hardcore and will always be working with flying machines. They have advanced into electric flight, clever control systems and most of the ones that I have met are also involved in inventive outside activity. I am grateful for all the input and also for the answers to the questions submitted by the viewers which overwhelmed my capability. Please keep the projects and knowledge coming!

Charles
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Old Nov 25, 2008, 10:14 PM
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Hey Charles

I am finishing a Long EZ like your white one right now . I took off the horrible color
scheme and am doing a Red White and Blue one . Will post when I get a pick .
I have several other projects to work on before I can get back to my one off
canard . To many planes and not enough time :P
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Old Nov 26, 2008, 06:02 AM
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Keith, Do you have the 55" light electric version? I have not seen any of those for sale in a long time.
Charles
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Old Nov 26, 2008, 06:27 AM
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Yep I have one of those .
I looked and asked and searched and found one from a collage student that
he started to build and lost interest . . I have had it for some time and have
searched the internet looking for color schemes and have had no luck . All
the schemes I could find are mostly white with a colored line here or there .
I was talking to a friend of mine a few weeks ago and he told me why they
are so bland . Pretty much all composite planes are mostly white because of the
Sun . The Sun heats up colors and that would damage the composite materials
that plane is made of . So I changed my strategy and I think I have come up
with something I like . I also want rudders . Have you thought about rudders at all ?
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Old Nov 26, 2008, 08:26 AM
Jets are for kids-of all ages
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Remember the rudders only move outward on each. Never inward. they are drag producers for the wing on the inside of a turn. Look at where they are placed. They are very effective out there on the tips of the real long ez, velocity, cozy, etc. Devise a spring and pull system, to make it operate that way, for max effectiveness.
Roger
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Old Nov 26, 2008, 10:02 AM
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The rudders on the full-scale VariEze (and presumably the other similar wingletted canards) move outwards for normal rudder action. Both can be deflected simultaneously to act as drag brakes, just push on both rudder pedals at the same time.

However, the rudders are not merely "drag brakes", they do develp normal lift forces that work just like a rudder on any other tailed aircraft. Because making lift also produces drag (i.e.: "induced drag"), deflecting the rudder on only one side does get that induced drag to help the process, but that only assists the rudder's lift-generated effects, it does not replace them.

One of the two rudders has an adjustable stop, allowing it to move inboard by as much as six degrees. This provides rudder trim. Note, in this case that one rudder can be moving inwards for a yaw command.

The other benefit of having a hard stop against inward movement is the effect it has on yaw stability. The vertical surfaces on a layout like this are not very far behind the C/G, and getting adequate yaw stability is a problem. Add to that the problem of "stick-fixed" vs. "stick-free" stability, and the issue becomes even more difficult.

On most manual controls, if the controls are not held firmly (i.e.: "stick-free"), the movable control surfaces are free to float with the airflow, and provide little or no stabilizing force. Essentially all of the stabilizing force has to come from the fins and other fixed surfaces, reducing the effective size of the tail. A bad yaw stability situation (due to the extremely short vertical tail moment arm) becomes even worse. By providing hard stops for the rudders to sit against changes this, so the plane acts like it is in "stick-fixed" mode all the time.

Because our servos are strong enough to prevent back-driving by the airflow, R/C models typically operate in "stick-fixed" mode even with the controls in neutral.

One benefit of the tip-mounted winglets as vertical surfaces, as opposed to a central fin with the same moment arm and area, is the enhanced spiral stability. Both winglets produce inward lift as they try to recover energy from the wing tip vortex. However, in a turn, the winglet on the outside of the turn has a higher airspeed than the one on the inside of the turn, so it develops more inward lift force. This yaws the plane towards the outside of the turn, which interacts with wing sweep and/or dihedral to try to roll the plane back to level flight.
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Old Nov 26, 2008, 11:58 AM
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Great discussion, Don, You must have been in touch with Mr. Rutan, one of my heroes to say the least. My Voyager has ailerons and elevator with a bit of UP aileron reflex. With a small amount of aileron movement, the rolls are sluggish but the model is such an attention getter in flight, I just do the pattern and make passes down the runway. It loops and flies inverted well. I save it for the deep blue skies on Sundays. We have a full scale Long EZ at our local county airport and on one of those special Sundays, it did the pattern several times doing touch and go landings. The climb out was steep like a jet liner. It just made my day especially since I seldom go to the airport.
Charles
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Old Nov 26, 2008, 12:51 PM
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Quote:
Originally Posted by canard addict
Great discussion, Don, You must have been in touch with Mr. Rutan...
Yup, a few times. Attended some of his seminars. Started building a full-scale VariEze back in the late 70's (project got stalled by several issues, by the time I had those resolved, my needs in an airplane had changed. However, I still have it out in the barn). Worked on the props for the Voyager round-the-world airplane. I also did some consulting for the guy in Cincinnati who built the 24 ft. span R/C model Voyager.

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My Voyager has ailerons and elevator with a bit of UP aileron reflex. With a small amount of aileron movement, the rolls are sluggish but the model is such an attention getter in flight, I just do the pattern and make passes down the runway.
You should not need the reflex, and in fact that reflex could be part of the explanation for the poor aileron response.
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Old Nov 26, 2008, 02:11 PM
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Hello guys

I can't always follow these discussions, as you know, but I found that one useful. Following on from Don's point about outward movement being more useful than inward movement in winglet rudders, what strikes me as a good idea is to set up rudder differential. With a centrally mounted servo driving both rudders, we push one side while pulling the other. So we need to arrange for more travel on the pulling side, which goes over top dead centre, than on the pushing side. Provided that the linkage is connected in front of the hinge at each rudder, pulling on the linkage will push that rudder outwards. Exactly what we want, yes? How does that sound?

Another question about winglet rudders and yaw control: is that why the Starship has rudders that lean inwards?

Am I making life too complicated here?

Nick
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Old Nov 26, 2008, 03:35 PM
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Hey
Thanks for the rudder info . I did not know about the outward only movement .
And I will keep inmind the 6% inward movement trim on one side .

Thank you
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Old Nov 26, 2008, 05:41 PM
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Don, What state of construction is your real Vari-eze? Has it been setting since the 70's? Did I read that right? I know it is quite a project, but you can't fly anymore econimical than one of those. If you just need to get from here ot there fast and cheap, it is the way to go. I'm a little too big (i.e. heavy) for one, but was going to buy the plans for the Cozy MK IV. I do have plans for a Bearhawk, Now there is a quick build kit for it. Never got the time to pursue beyond cutting wing rib templates. Post some pics here of some of your canard planes, model and otherwise.
Roger
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Old Nov 26, 2008, 10:42 PM
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Quote:
Originally Posted by nickchud
...Following on from Don's point about outward movement being more useful than inward movement in winglet rudders, what strikes me as a good idea is to set up rudder differential. With a centrally mounted servo driving both rudders, we push one side while pulling the other. So we need to arrange for more travel on the pulling side, which goes over top dead centre, than on the pushing side. Provided that the linkage is connected in front of the hinge at each rudder, pulling on the linkage will push that rudder outwards. Exactly what we want, yes? How does that sound?
More than one way to skin this particular cat, but that way is certainly one of them.

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Another question about winglet rudders and yaw control: is that why the Starship has rudders that lean inwards?
No.

I haven't talked with the enginers at Beech to confirm this (although back when Beech was developing the Starship, I did get to do some work with that project and knew some of their engineers on it), but it appears to be to counteract yaw-roll coupling.

The lift force on the winglet is located at the winglet's aerodynamic center ("AC", which is a little below the mid-span of the winglet, 25% aft of the leading edge of the mean aerodynamic chord, or "MAC"), and perpendicular to the span. If the winglet stood straight up and down, that force would pass above the level of the aircraft's C/G. Every time the rudder was deflected, the plane would yaw as commanded, but it would also roll in the opposite direction. By tilting the winglets inward, their lift vectors are angled slightly downwards, so that they are pointed at the aircraft's C/G instead of above it. This eliminates the rolling moment when the rudder is deflected.

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Am I making life too complicated here?
Maybe. However, keep in mind that the only truly "dumb" question is one that you should have asked, but didn't. The above question was a perfectly good one.
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Old Nov 26, 2008, 11:08 PM
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Quote:
Originally Posted by mullinspsm
Don, What state of construction is your real Vari-eze?
Still a long way from finished.

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Has it been setting since the 70's? Did I read that right?
Not quite. Early 80's.

I'd saved up the money for an engine, and I was planning to shop for one at the EAA Convention in Oshkosh. Then, just before the convention I came down with pneumonia (maybe from respiratory irritation from some exposure to methylene chloride fumes from a project at work, or maybe from the guy with the bad cough I was standing next to at the Dayton Air Fair the weekend before Oshkosh). The trip to Oshkosh got cancelled that year. Not too long after that, well, there was this girl, and a wedding and a down payment on a house that used up the money I'd saved for an engine. By the time I was in a position to start working on it again, I needed something with more than two seats, and I'd gotten interested in aerobatics (one of the things VariEzes are NOT good at, can't do snap maneuvers at all, and too clean, so they tend to pick up too much speed on the down lines). I'd also come to realize that the VariEze was designed for very long distance VFR travel, and that we rarely if ever got a thousand miles of VFR weather in Ohio. The VariEze just wasn't the right airplane for my needs anymore.

However, my VariEze was my first exposure to working with composites, and that initial exposure and the experience from other projects that followed has opened doors for me in my subsequent career that are far beyond anything I could have imagined at the time. That unfinished airplane sitting out in the barn profoundly changed the rest of my life.

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I know it is quite a project, but you can't fly anymore econimical than one of those.
Well, there are others that are as good or better, but the VariEze is certainly near the top of any efficiency list.

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If you just need to get from here to there fast and cheap, it is the way to go. I'm a little too big (i.e. heavy) for one, but was going to buy the plans for the Cozy MK IV. I do have plans for a Bearhawk, Now there is a quick build kit for it. Never got the time to pursue beyond cutting wing rib templates. ...
I have another airplane in the works, an original design. However, the time, money and effort required to start a model airplane company from scratch and then keep it alive forced my original design homebuilt onto the back burner, where it still is today.

I've done a fair amount of work with unusual arrangements both before and after that, right up to today, some of them canards, lots of flying wings, various other things.

I've learned quite a few things along the way, including some much deeper insights into both the pros and the cons of things like pusher props, winglets and canards. I'd have to say that all three of those have been grossly oversold by their more enthusiastic proponents, and they are nowhere near the panacea that some folks try to make them out to be. However, they do have their place, and in some cases they can be the best choice. It's important to objectively understand and evaluate the entire mission profile, and the way the various design concepts interact with it, then choose the concepts that do the best job of accomplishing the mission. Sometimes the best choice is a canard pusher with winglets, sometimes it isn't.
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Old Nov 27, 2008, 09:27 AM
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Don, I seemed to have forgotten that the vertical stabs on the Long EZ are like airfoils with the convex side turned toward the fuselage? Thanks for the working details and also for the personal touch.
Charles
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Old Nov 27, 2008, 10:34 AM
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Quote:
Originally Posted by canard addict
Don, I seemed to have forgotten that the vertical stabs on the Long EZ are like airfoils with the convex side turned toward the fuselage?...
Yes, winglets are much more than just fins stuck on the tips. They are small wings that lift inwards towards the fuselage (note, the little ones in front that stick downwards make lift outwards, away from the fuselage).

Lift is always the component of the total aerodynamic force that's perpendicular to the direction of the local airflow (NOT the chord line!). Because of the helix angle of the tip vortex, the local airflow direction at the wingtip is at an angle, which causes the lift vector on the winglet to be angled forwards. The amount of this depends on how strong the tip vortex is. At higher speeds, above the "crossover velocity", the forward component of the lift vector is not as much as the aft component of the winglet's own drag, and so the winglet makes a net loss.

However, at lower speeds, where the wing's induced drag and the strength of the tip vortex are greater, the forward component of the winglet's lift is more than its own drag, so it makes a small (typically very small) amount of thrust.

In general, the possible gains are slim, and you have to get everything, the winglet airfoils, twist, incidence angle, etc., just right to come out ahead on the deal. If you can make the winglets serve double-duty, such as replacing the vertical surfaces you would have to provide without them, then your chances are better. You've already "paid' for the winglets' parasite drag by eliminating something else.

However, if you don't get the winglet design correct, it's still possible for the winglets' own induced drag to exceed the drag they are recovering from the wing, resulting in a net loss even at low speeds. Good things happen for those who do their homework!
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