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Old 04-19-2016, 03:21 AM   #1
mclarkson
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Default Double Down - the double wing.

I saw a photo on another RC forum which intrigued me. I thought it was a cool-looking, unique design but, when I examined it more closely, I realized that it was two differently sized flying wings, sitting next to each other.

Still, inspiration will not be denied. I decided to try and build the plane I thought I saw. And … here we go.

//edit: I just found my initial outline sketch, maid in Photoshop:



Here are my super-detailed plans, complete with approximate measurements.


I started off by making a small cutout from some 1/4″ foam and tossing it around my basement to try and establish an approximate CG for the final plane.


Next, I spent some time transferring my sketch to the Rediboard / Dollar Tree foamboard I’m using for the project.






Here’s half of the plane’s basic form.


And two halves, glued together.

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Old 04-19-2016, 03:23 AM   #2
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Next, I glued airfoil-shaped ribs to the bottom skin of all wings.


Then I cut out a piece to serve as the shape of the fuselage side.


I made four of these, glued them in pairs and glued them to the wing. I added a wide 'floor' of thin balsa, and a CF spar.





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Old 04-19-2016, 03:24 AM   #3
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Fortunately, I had plenty of help with punching holes into foam.

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Old 04-19-2016, 03:26 AM   #4
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Gluing the upper skin on one of the wings.




The wings are nearly finished. Time to start filling in the blanks.


I created some ‘shoulder pieces’ to bridge the gap between the wing and the fuselage.


Everything skinned up. Time to make the hatch(es).






Time to get to work on the control surfaces.

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Old 04-19-2016, 04:40 AM   #5
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Love it At first glance I thought it might be a Horten Bros. design Then a X47B.
But no, it's a Mark design !

Very cool

Hawk
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Old 04-19-2016, 06:05 AM   #6
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Or is it just a very short coupled conventional wing and tail design? Either way it has an unusual look about it for sure.

But....No vertical stabiliser? That might be 'interesting'. Or is it that you just havent fitted it yet?

I think you might have a hard time with the CG too. With the motor way out at the back and no nose it's probably gonna come out very tail heavy.
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Old 04-19-2016, 08:44 AM   #7
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Indeed, I think CG will be a problem. I may end up packing an enormous battery up there to compensate.

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Old 04-19-2016, 08:46 AM   #8
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Time to get started on the control surfaces. First, I cut out some foamboard (sans paper) and glue a bamboo skewer to one end. The (hopefully) straightens and strengthens the wobbly foam, and creates a sort of 'bevel' to accommodate elevon movement.


Next, a layer of packing tape skin.


A half strip of fiber-reinforced tape serves as a hinge.

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Old 04-19-2016, 08:46 AM   #9
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Everything's almost done. Time for a preliminary weigh-in.


434 grams! Ouch!

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Old 04-19-2016, 10:33 AM   #10
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Interesting concept and build photos. Looking forward to the rest of the project!

Take care and thanks for posting at WattFlyer!!

Don
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Old 04-19-2016, 11:22 PM   #11
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Woot!







Guys, she's soooo tail heavy. I wound up with a 2200 3-cell and an 850 3-cell both jammed all the way up in the nose to get her flyable. But she did fly.

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Old 04-19-2016, 11:28 PM   #12
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It looks cool in the air though.

Take care and thanks for posting at WattFlyer!!

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Old 04-19-2016, 11:29 PM   #13
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very cool design!!!!sweeeeeet!

narrow is the place to land...wide is the space to crash....choose the narrow way!
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Old 04-20-2016, 04:18 AM   #14
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Thanks, guys. Here are a couple more shots. This one's from just before the flight.


And this one's the launch.


I'm thinking the way to go is to extend the nose a bit, so I can push the battery farther forward. I'd pull weight off the tail but it's all RediBoard with the paper off and a few bamboo skewers - not much there to remove.

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Old 04-20-2016, 05:45 AM   #15
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Ah... so there were verticals stabilisers going on after all! Did you add them after flight testing (they were still missing at the final weigh in I see).

You could solve the CG problem by transferring the motor to the nose?
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Old 04-20-2016, 07:25 AM   #16
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I added the v-stabs at the last minute before flight testing. I think I'll try cutting them down a bit.

I could move the motor to the nose but that would be cheating.


Here's the video of the maiden.
YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.

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Old 04-20-2016, 09:10 AM   #17
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I’m modding the nose to allow a more forward battery placement.

“Sketching” out some designs in foam and paper.


I’m liking the looks of this one.

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Old 04-20-2016, 08:24 PM   #18
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Is not the fact that is flies tail heavy suggesting that it is not actually a 'double' wing but a single wing with a large, close coupled, flat section tailplane?
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Old 04-20-2016, 08:36 PM   #19
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Um ... ... ... yes?

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Old 04-20-2016, 11:05 PM   #20
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Here are the finished pieces to extend the front of the fuselage.


In place in the side of the new, more bulbous, nose.

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Old 04-20-2016, 11:36 PM   #21
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Originally Posted by quorneng View Post
Is not the fact that is flies tail heavy suggesting that it is not actually a 'double' wing but a single wing with a large, close coupled, flat section tailplane?
And your point would be.....?

The "fact" as inferred here, that it is "tail heavy" due to it's suggested "tailplane" appearance........"single wing", does not define "tail heavy" just because it appears to be a "close coupled flat section" airfoil design....!

It certainly appears, to the viewer on this end, to be more of a custom "canard" design that has a C/G aft approx. 2/3rd's it's fuselage length......thus the "tail heavy" aspect.

Mark.........impressed with the design, and (be it a handful) without more forward weight/length.......it flies......!

Been following this build of yours only because it's outside (the wheel house) of what I come to appreciate from previous Basement RC models......Double Wing caught my attention as related to a "bi-plane" concept............

AMA 928214
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Old 04-21-2016, 01:15 AM   #22
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Alright, guys. I took it out today with the new, bullnose mod which allows me to push the battery forward another couple of inches. And it flew Fan--tastic!! One upside of having to use a relatively big 2200mAh battery is that it flew for 12 minutes and still had 60% charge left.



(It's also got about 1/4 of a paint job...)

And thanks for all the positive comments. I really appreciate them.

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Old 04-21-2016, 01:54 AM   #23
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I’m also quite satisfied that, at 7.5″ from the original nose, the CG is exactly where my little model predicted it would be.

Here, I’ve marked the CG, as derived from actually flying the plane, with a red line. I’ve marked the same spot on my little crude model. If you squint you can see that it falls just behind the spot I originally marked NH (nose heavy) and well in front of the spot marked TH? (tail heavy?).


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Old 04-21-2016, 02:17 AM   #24
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Nice Build and Flight Mark

I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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Old 04-21-2016, 04:26 AM   #25
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Thank you, ma'am. Nice to see you around.

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