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Old Jan 21, 2013, 01:38 PM
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Malaysia, Selangor, Kajang
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Dunne D.8 - Rubber Powered

Hot on the heels of my rubber powered flying wing project I'm starting another flying wing. Also peanut size. This time properly scale. It's the Dunne D.8.

When talking about flying wings most talk about the Horten brothers or Alexander Lippisch or Jack Northrop but the true pioneer was J.W. Dunne. Dunne evolved his flying wing design from his interest on flight stability. He eliminated control surfaces until the very minimum necessary for stable flight and found that the minimum configuration was the wing itself.

I first came across Dunne when I saw a picture of the Burgress-Dunne seaplane. It was a seaplane. It was a biplane. It was a flying wing! I was intrigued. Since then I began collecting pictures of these strange flying wing biplanes any time I come across one on the internet. And I began reading up on Dunne.

Dunne's flying wing was actually Britain's first military heavier than air aircraft. He built several gliders for the army (RAF didn't yet exist) until his budget was cut when the army decided to concentrate funding on airships and blimps. His first successful plane was built outside the army as a commercial venture.

One interesting aspect of Dunne's wings was how the controls work. Instead of using an elevon mixing mechanism Dunne simply connected one stick to each elevon directly. The pilot therefore had two control sticks, one in each hand, and had to do the elevon mixing manually. Pulling both sticks = up elevator while moving the sticks in opposite direction gives roll control.

I've just begun drafting the plans for the D.8. Hope to finish the plans by the end of the week so that I can begin construction next weekend. Completed the top wing and the fuse. The landing gear/skid is very complicated. The bottom wings is basically the same as the top minus the root rib.
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Old Jan 21, 2013, 02:11 PM
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And here's a link to the CG calculation:

http://fwcg.3dzone.dk/?wing_span=14....ow_mac_lines=0

The CG ends up roughly where the engine is. Which is smart of Dunne since it means he can test different engines without affecting the CG much.

In my experience with mid mounted motors, having the prop near the CG makes the plane insensitive to thrust line. For free flight this is a drawback because it removes one method of trimming.
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Old Jan 21, 2013, 03:44 PM
I don't like your altitude
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Absolutely brilliant choice!Always liked these,will be following.Lot of rigging,how are you going to treat it?
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Old Jan 21, 2013, 04:27 PM
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Don't know if you've seen this:

http://www.outerzone.co.uk/plan_details.asp?ID=1237

BTW, your Peanut rubber 'wing thread was a classic IMO.


Tony
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Old Jan 21, 2013, 07:29 PM
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Yeah, the rigging looks challenging. I'll do as much as I can. It won't be perfect scale. For example, I had to modify the rear of the fuse to take into account the fact that I'll need to install a removable plug to hold the prop. I'll probably be doing most of the rigging on the wings and the really obvious ones holding the landing skid in place. But I'm not sure if I'll be doing the stays on the bottom of the wing.

Frankly it's not the rigging that scares me. It's the spoked wheels that looks more intimidating. I'm planning on scratchbuilding them using cotton thread as the spokes. Saw a video on Youtube that shows a technique to do small spoked wheels that looks doable:

spoked wheels for peck polymers pietenpol (1 min 48 sec)
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Old Jan 22, 2013, 05:34 AM
I don't like your altitude
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Joined Sep 2011
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Wow,that's delicate work,good result though.
You don't fancy a bigger version for r/c when you've sorted this?I'll have to do a search,see what's out their.
Stuart
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Old Jan 22, 2013, 11:54 AM
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John Sizer has done a full scale drawing of the Dunne and it is available through Sams models in the UK

John
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Old Jan 22, 2013, 01:44 PM
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Quote:
Originally Posted by sp250 View Post
John Sizer has done a full scale drawing of the Dunne and it is available through Sams models in the UK
The site says it's a D.10 which is interesting because I've never seen pictures of the D.10. Apparently it's a version of the D.8 with shorter wingspan.
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Old Jan 22, 2013, 02:22 PM
I don't like your altitude
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http://www.ctie.monash.edu/hargrave/wings_home.html
This is a link from the last post on the "older..." thread.if you follow the links there's a pic of the burgess version of the 10,adapted to a float plane.Be warned- you may be gone a while,some good stuff on the site,and links to more
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Old Jan 22, 2013, 03:10 PM
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Some progress. Thought I could finish the landing gear tonight but problems with the wings caused me to pause to think.

The problem is that the root of the top wing has this weird droop called a bustle. Looks like it acts as a permanently deployed flap. Originally I thought I could build the wing flat and then set up a jig to hold the twist while I covered it but the bustle makes that impossible. Maybe I could still build it flat minus the middle three ribs and then install the ribs later when setting it up in the jig. The bottom wings could certainly be built flat.

Anyway, just managed to do the bottom wing. Marked the location of the interplane struts on the top wing. And also drew the jig that will be used to make the spoked wheels.

Upon closer look at different drawings I suddenly realized that what I originally thought were stays to keep the wing tips rigid were in fact control horns for the elevons. The real elevons also had ribs that didn't align with the ribs in the wings. The 3-view I originally based my plans on had the elevon ribs aligned with the wing ribs. So I'm keeping mine aligned for ease of construction. Which means I'll have to install the control horns in a slightly non-scale location otherwise it wouldn't be sitting on a rib which doesn't make sense.

So here's a screenshot of my updated plans so far. Once I've got the landing gear done I'll upload it as a PDF.
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Old Jan 22, 2013, 03:17 PM
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Quote:
Originally Posted by Stupot46 View Post
http://www.ctie.monash.edu/hargrave/wings_home.html
This is a link from the last post on the "older..." thread.if you follow the links there's a pic of the burgess version of the 10,adapted to a float plane.Be warned- you may be gone a while,some good stuff on the site,and links to more
That's where I get most of my reference pictures from. Didn't realize that there's a pic of the D.10 on there.
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Old Jan 24, 2013, 10:30 AM
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More progress on the plans. It was holiday today in my state so had a bit of time to work on this.

Did the landing gear so most of it is done now. The landing gear drawings does not include the hockey stick skid so I've still got that to do. Not sure how I'll include them in the plans though. May have to do an instruction sheet because the structure is quite complicated.

I thought through the build process and realized that my initial idea of building the fuse top and bottom first wasn't workable. The structure on the sides were way more complicated so it makes sense to build them the traditional way - build the two sides then connect them together. But the fuselage isn't a straight box. It's actually a hexagon. It tapers top and bottom. So I drew up some parts to hold the fuse in shape during the build.

The plan is getting crouded. May have to separate the plans proper (what you build on) form the templates, jigs and references. Was hoping to fit everything onto a single sheet of A3 but now I don't think I can.

I'll try to finish up as much as I can tomorrow and then start the build even if the plan is incomplete. I have another project in the pipeline and can't afford to spend too much time on this.
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Old Mar 09, 2013, 06:02 PM
KlonWarz
Joined Dec 2012
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Quote:
Originally Posted by slebetman View Post
Yeah, the rigging looks challenging
Frankly it's not the rigging that scares me. It's the spoked wheels that looks more intimidating. I'm planning on scratchbuilding them using cotton thread as the spokes. Saw a video on Youtube that shows a technique to do small spoked wheels that looks doable:

http://www.youtube.com/watch?v=gk5e8bs9Sac
I didn't watch the vid, yet, but sewing is ez enough!
Hurts a bit :-) but ez enough to do...

fix the hub rigid, and the rim, too... then stitch it, and apply some CA to the thread.
Should work well enough!
Best
rc
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