A moderately high AR plank flying wing - Page 3 - RC Groups
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Feb 10, 2017, 09:44 PM
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EdSoars's Avatar
Looks a lot like a Frigate Bird, a soarer of the highest degree. NOT a Catastrophe, not even an apostrophe.

ed

oops. I meant this to go to Kent's Catastrophe thread! sorry!
Last edited by EdSoars; Feb 11, 2017 at 07:23 PM.
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Feb 10, 2017, 10:06 PM
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Carolynne's Avatar
Hi Kent,

The Calliope has a calculated AR using the span squared over area method, of 16.1.

Your design looks very neat too and should look amazing if you are going to stretch it further. I am almost tempted to halt work on the Calliope and watch how yours flies first!

I have been working on my little beastie, getting fillets and the canopy fitting properly and adjusting contours here and there ( this is the sculptural bit that I really like). The wiring is now installed in the wing and the aileron linkages are the subject of my current pondering. Then I get to close the wings, remove the control surfaces and then play with all those fiddly bits that come before painting and covering.

Carolyn
Feb 10, 2017, 10:30 PM
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Knoll53's Avatar
I hope you keep nibbling away at the Calliope Carolyn. From where I stand, you are almost done. It will probably take me at least 4 months to get mine in the air. I'm looking for an easy project to try a molded fuse, so this could be a good candidate.
Feb 11, 2017, 01:05 PM
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Knoll53's Avatar
BTW, I just did a quick calc. based on your initial sketch and dimensions and using the same formula got an aspect ratio for the Calliope of 14.5. I do like the lines of your highly tapered wing.
Feb 11, 2017, 11:49 PM
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Carolynne's Avatar
Hi Kent,

So, I didn't have to go and do all those calculations after all??

Actually though, in order to give you real numbers I did have to go back to basics. You see the dimensioned sketch was a very early poke at the idea. Since then and subsequent to a little examination in the fluid dynamics models, things have changed a bit. So, in fact the aspect ratio of 16.1:1 is correct.

Similarly, the taper ratio used for the bulk of the wing is very moderate compared with a lot of thermal aircraft.

Good luck with your model

Carolyn
Feb 12, 2017, 10:02 AM
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Knoll53's Avatar
That explains it. From the shop photos it looks more like 16:1 than 14:1.
Feb 22, 2017, 03:41 AM
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Carolynne's Avatar
A little bit more progress.

I am generally happy with the overall shape of things so far, but now, having cut out control surfaces and organised linkages etc, its time to get all those fiddly bits to fit just so. Time also to shape leading edges and get nice sharp trailing edges happening. While I think about funky colour schemes, I'll also have a try at making a spinner to match the nose contours.

Carolyn
Feb 22, 2017, 08:04 AM
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EdSoars's Avatar
Question; Carolynne, why did you stop the ailerons so far inboard of the tips? I'd have thought that since they are for roll only and have a near zero pitching input, you would want the most roll moment arm for the deflected area.

The bird is shaping up beautifully...

Ed
Feb 22, 2017, 09:54 AM
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Knoll53's Avatar
Ed, did you see post #16 in response to post #15 which was a very similar question?
Feb 22, 2017, 07:01 PM
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EdSoars's Avatar
Whoops. Yes, of course. Thanks Kent.
ed
Feb 22, 2017, 09:16 PM
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Carolynne's Avatar
A little more detail on the aileron thing:

Firstly Ed, and I hate to contradict you, but I am sure that the ailerons will indeed have a pitching moment. The reasons that I say that are: Klaus's wing which uses the same airfoils and almost the same planform as the outer section of the Calliope wing, and uses outboard elevons for control, has a very 'snappy' pitch response. Also, having played with differential aileron movement to get a straight and axial roll component on the Taborca, the Little Plank, and also the Anara Nuovo canard, I found that in all cases significant differential produced a pitch component that quickly became 'ugly'. So, using lots of differential to minimise adverse yaw wasn't going to make me happy.

Because the Calliope is supposed to be a best L/D kind of aeroplane, I also wanted to minimise the drag when using ailerons and so I didn't want to be waving large amounts of rudder around all the time. Hence by sacrificing a little roll power by restricting the ailerons inboard and so limiting their drag moment, I was hoping to limit the amount of rudder required to produce a balanced turn.

Also, I am using a hoerner tip which has a helical surface on its underside which opposes the tip vortex. I've used these tips in the past and not only do they look neat but they are quiet at speed. In this case, the other neat thing that they do is present a different aspect depending on the yaw angle, and so I am hoping that they will contribute a little to the yaw stability of the aeroplane. With this in mind, I really didn't want that whole tip vortex system being interrupted every time I deflected the ailerons, potentially producing unexpected nasties near the stall when the tip vortex is strongest.

There are other reasons why I took this choice but I shan't bore you with them here.

best regards

Carolyn
Feb 22, 2017, 09:47 PM
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EdSoars's Avatar
Always happy to read constructive contradiction! Planks are non-intuitive for sure. I had not been thinking about differential producing up elevator effect. Of course!

So "contradict" me more about that rudder in a balanced turn: if you want to reduce the amount of rudder input, why was the rudder moment so short? Weight control?

And I do realize that effective design is a combination of successful compromises. And you won't ever bore me with wing design talk. I'm getting more and more as you move along on this.

Back to the shop...

ed
Feb 22, 2017, 09:51 PM
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Knoll53's Avatar
Quote:
Originally Posted by Carolynne
Firstly Ed, and I hate to contradict you,
When two people agree all the time, at least one of them is not thinking.
It's a discussion.........without it, we wouldn't have a forum.
I like to start a discussion with "I disagree with everything you said ".
Feb 22, 2017, 10:48 PM
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Carolynne's Avatar
Hi Ed,

Actually, the rudder moment is not that short. It looks that way mostly because of the way the root of the wing stretches aft. The fin is quite large and as you can see the rudder is of quite a reasonable area too. The fluid dynamics said that this should be more than adequate for yaw stability, so Im prepared to at least try it!

For drag reduction, I would like to move a large rudder through as small an angle as possible as infrequently as possible...... Hopefully the aileron setup will allow this.

On another note, you probably noticed it, but let me bring to your attention that the leading edge of the fin 'grows' out of the fuselage just ahead of the elevators. My thought behind this was to create a compression where there is normally wholesale flow separation. This might, if I am very lucky, reduce drag further.....

Kent, I noted your comment and in an effort to please you, from now on I shall remember to disagree with you loudly and often!!!

Carolyn
Feb 27, 2017, 07:44 AM
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Hi Carolynne.. Just found this thread. You have excelled, great subject well thought out.. Here are a few points to ponder. As a camber change is more effective than an incidence change, maybe the fin could have had more chord at the top. Might not look so sexy tho !
I recall the Hortens did some work on wrong way differential to correct a pitch change in turns.. looks like you are finding similar things.
Also, have you read any of the Pioneer stuff, some good ideas hidden away in there.
Anyways, I look forward to the results Good Kuch


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