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Micro 500MM balsa Delta wing - from my brain to maiden flight inside 2 days
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Published
Nov 26 2011 by FaTe
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A Delta-Wing also known as a flying wing is a design many decades old but still dominates the design world today for high speed and high altitude flying. I've been talking about wanting to fly a Delta-wing for a few years now but never found one I liked to buy, also our flying field has noise restrictions on push propeller models.



2 days ago (yes 48 hours ago from this project submitted) I decided I was going to build my own micro wing. The principle design of a flying wing is pretty straight forward, it's a wing with (not always) swept back tips. I wanted a 50CM/500MM span wing and 2 days later I flew the design from my head at our club, check it out:







COG is 18.5CM from trailing edge (NOT elevon edge), I did use a on-line Delta COG calculator but it said 13CM which I thought was too far back, as you saw in the video I was right to stick at 18.5! It was VERY windy (wind-force 5/6) so I cannot wait to try it out it calmer conditions for speed dives. Nose tip to trailing edge is 31.5CM/ 315MM with each support middle brace 14CM in from each tip.



Used on this model:



* 6MM competition balsa wood for almost everything.

* 2MM competition balsa wood for pod cover top/bottom.

* Red semi-transparent Solar-Film.

* Very thin glass material for structural support.

* CA super glue and UHU por glue.

* 2MM carbon fibre rod for control lines.

* 3 Hextronic 5G servos.

* Rhino 2C 7.4V 610mAh Lipo battery.

* 1450KV Turnigy A2204-14 brushless out-runner with built in prop saver.











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The basic frame starts with a full trailing edge section with the top frame joining on top, this transfers stress load back into leading edge and not outwards. Each corner then gets support blocks to further increase structural integrity. Now for the inside support struts (these are not ribs as they have no profile).



















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The pod is an air-foil I created to fit my electronics, the thinner the better really. Both sides are 6MM balsa as the rest. Bottom is 2MM balsa, note the grain of the wood is downwards in 1 single piece, this is very weak and normally opposite to what you do. But I now add in the same 2MM balsa grain side-on to increase strength. Now the bottom is very strong but the actual area that is viewable is 1 piece and much nicer. A Delta-wing has a very forward COG (Centre Of Gravity) so you want the back empty, I used the area for a support brace.


















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The back is then covered using the same 2MM balsa grain side-on so it shapes with the pod. A view from the nose to show the space. At the front I added a cover which joins to the outer frame. The middle area is the pod hatch testing in place, can see the general shape coming together now. Inside view of the space to play with.
















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Now for glass fibre to make our already strong frame rock solid. A piece on each corner over the join area of all the pieces then CA glued in place. The engine mounts also get a layer of glass fibre over top and bottom. The rudder is supported with triangle balsa on each side, here you can see me mocking up placement. The rudder I made over sized with a height of 135MM / 13.5CM for maximum stability.


















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Now the supports are CA glued in place I can test fit the rudder. It's not actually glued in place so I can cover the rudder and wing separate for a nicer finish. To help with COG I used an old trick of mine where I mount the servos on a rail at the top of the pod allowing the battery to slide under them. This technique makes best use of the weight you already have by keeping it all as far forward as possible. However because of the space you can very easily move the battery forward/back. Now the wing is covered, using a regular clothes iron carefully take your time and you'll get a nice finish.


















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Time to mount the motor, to support the motor I laced the motor mount balsa with epoxy to harden it and give the screws something to bite into. I wanted the ESC up front for maximum cooling, the wires I simply ran through the front cover panel. Elevons and rudder are 6MM balsa profiled down with a slight angle cut on the inside too allow movement. Delta-wing can go through some big forces on surfaces at speed, for this reason I used proper pin hinges for the elevons. I used my own home made control horns for the elevons but used a regular horn on the rudder for strength. The control line for the rudder bends too keep access open in the pod.














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It's a Delta-Wing how can I not have RAF tags?! Nice defaults on the top outer wing tips covering where the glass fibre was used. The well known yellow tiger on the tail with a botched FaTe text inside the rudder. On the bottom I used the outer yellow RAF circles to help identify normal/inverted flight.


















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All finished inside 48 hours (was maybe 5 hours total actual build time). Propeller mounted. Finally the top cover pod, need to order some earth magnets but until then I just used a little transparent scotch tape.





Construction on this model is nothing but calculating angles, cutting and measuring!
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