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Edge 540

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A classic Edge 540 profile sports plane built from 2mm Depron foam.

Specs
Receiver: DTrx35 bare     Flying Weight : 18grams
micro 3amp ESC ESC: Micro 3A ESC     Airframe Weight : 9.5g
AP02 brushless motor Motor: AP-02 Brushless     Wingspan: 35cm
GWS 2510 Propeller Propeller: GWS 2510     Length: 29cm
Battery: FullRiver 90Mah     Bracing : 1mm Carbon
Depron 2mm foam Foam: Depron 2mm     Undercarriage: 0.35mm
       

Plans Link:On RC Forum

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As usual the most time consuming part is tracing all the plans onto the Depron sheets and cutting it all out. The plans are not actually for a plane this scale but you can easily resize them when printing and print them out to whatever size you desire. 2mm Depron was a good choice for this plane as it allowed the frame itself to come out at just under 10 grams and the only bracing needed was a wing span carbon rod 1mm thick.

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Depron2mm Depron 2mm sheets

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Seen here weighing in at 5.81 grams are all the foam parts. The frame weight as stated above in the specs is 9.5 grams and this includes the undercarriage, wheels, control horns and pushrods. Plus of course the UHU Por glue used to hold it all together. For Depron I wouldn’t really use anything besides UHU Por glue. I don’t know how many times I have had a hard landing with this plane and it always bounces back. This is where the flexible nature of UHU Por glue is a real advantage.

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UHU por Glue UHU Por Glue

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All the parts assembles but not sanded down around the edges.
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For this model I set the area of the elevator to be roughly half the total area of the tail plane. This seemed to work well and gave more than ample control over the pitching even allowing for the plane to be pitched up in slow flight just under the airflow over the tail plane from the motor. This is also an advantage when using micro servos which typically have a throw or 3mm in either direction.
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It may be a bit hard to see in this picture but the best way to get a good hinged surface is to not sand both edges of where they join. Basically you just sand back one surface (usually the under surface) and then hinge with some Blenderm Hinge Tape on the top. This allows you to have the tail surface and the elevator very close together with little gap and still have enough room for a good amount of throw.
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The big secret to bending Depron is heat. In this case I wanted to put a bit of camber on the wings so I used a can with hot water in it and as well as that I poured some more hot water over the foam before forming it to the shape of the can. It’s a rather crude type of airfoil but quite adequate for this type of model.
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This image shows the amount of curve put in the Depron by heat forming. Juts a slight camber on the top of the wings is enough. This also gives the wings a bit more strength as opposed to just having flat wings.
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This image shows the ailerons cut away from the main wing. They have been lightly sanded on the trailing edge on both top and bottom. As mentioned above, where they hinge should only be sanded back on one side at about 45degrees or even less. The Blenderm Hinge tape then goes on the top surface which has not been sanded.
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A good method for sanding is to put the surface on the edge of a table where it can be supported as you are sanding it. Use 400 or 600 grit sandpaper and work smoothly. Depron is great for sanding and basically whatever you can do with balsa in regards to sanding you can also do with Depron.
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For hinges I always use Blenderm Hinge Tape. It has great strength but at the same time it is super flexible. It is also very sticky because it was designed to stick to skin. Another good point about Blenderm tape is that it can be stuck to a smooth clean surface and then peeled off and re-stuck on to the control surface without losing it’s stickiness. You can see here that I always stick it to a metal ruler and then cut it with a hobby knife. I then use the hobby knife to lift it off the ruler and place it on the surface. If cutting Blenderm with a knife use a sharp pointed one not a razor blade. Puncture it close to the meta ruler in the centre and cut to one edge then to the other.

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Blenderm Hinge Tape Blenderm Hinge Tape
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A good idea is to pin the surfaces into place on a cutting board and that way you can set a constant space between the two surfaces. Of course this also stops it all from moving as you’re working. For most park flyers you only need a slice of blenderm about 5mm wide. I put 3 pieces on each wing and have found that this is more than adequate.
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The completed tail section with elevator attached.
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So the bare frame came out at 6 grams which is quite acceptable for an airframe with a wingspan of 35cm. This is due in no small part to the use of 2mm Depron foam.
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Now to the business end. A bit of 6mm Depron used for bracing and support of the engine mount. Then a piece of plastic to be glued on to the front of the plane which the AP-02 motor can be screwed onto.
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It’s all about balance. Using the CG from the original plan the next step is to arrange the various components on the airframe and stick them there with tape and get the plane to balance on the CG. Make sure you know where you need to have everything first before you start mounting parts. Many people start mounting receivers in the best place and just think “I can fix up the balance with the battery later” – try to avoid this! A bit of planning now will save you a lot of work later.
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This is a mounting block for the receiver unit (Dtrx35) cut to shape to fit on the back of the receiver. The cut out in the corner is to accommodate the FET on the back of the receiver. This block can then be attached to the plane using some fine Servo Mounting Tape and will allow the receiver unit to sit flush with the surface.

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servo mounting tape Servo Mountijng Tape

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A look at the final installation of the DTRx35 receiver. Just a note about the receiver setup. I have used the DTrx35 model without any JST or Molex connector sockets and this saves some weight. However when doing this you will need to solder the servo wires directly to the receiver circuit board. Removing the plugs from the servos also brings their weight down from 1.0 grams to 0.8 grams. It’s a small weight saving but it all adds up.

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On the other side of the fuselage the ESC unit is mounted once again using a mounting block made of 2mm Depron and stuck on with thin double sided servo mounting tape. This is a micro ESC unit and weighs only 0.34 grams. Once again you will need some good soldering skills to solder directly to the PCB. This ESC unit is very small but still has a 3 Amp rating.

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For the control linkages I have used the Plantraco wooden horns. These micro horns weigh virtually nothing and you can mount them by just making a cut in the Depron foam and securing them with some UHU Por glue. They are lazer cut and just pop out from the sheet easily. The two holes are also lazer drilled and you just need to push through a piece of piano wire to open u the hole. Also, for this build I have used 0.35mm piano for the control linkages. This is a very basic design but quite effective.

 

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The airframe with all gear mounted and tested.
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The airframe with all gear mounted and tested.
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This view shows the mounting of the AP-02 motor and bracing needed from 6mm Depron. Although this gives adequate strength you still wouldn’t want to have too many hard impacts on the front.

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AP-02 Brushles Motor AP02 brushless Motor

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A couple of shots with the gear mounted and landing gear in place.
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For this plane I have chosen the GWS 2510 prop. It gives ample thrust but I could have used a GWS 3020 for more power at the expense of battery life.

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GWS 2510 prop GWS 2510 Propeller

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Side on view
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Top view - makes the wings look overly large but that's just the camera angle.
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Here’s the undercarriage which have been made form a single piece of 0.35mm diameter piano wire. Just a bit of an explanation on this design which I have used for many years now. The undercarriage is held on by only one thing – the pin at the top which can be removed and the undercarriage then taken off. The reason it stays securely in place if that the wire folds over the bottom at the front and back. I think you can see by looking at the picture how secure this is. So the wire you see on the near side in the photo actually crosses over at the front and supports the wheel on the far side. It’s actually easy to fold these up yourself with a pair of fine pliers as long as you get the angles right.
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Decorating – well there are many ways to decorate Depron, but the most fun for me is to just take a felt pen and start coloring it in. You can be as creative as your imagination. Juts a note on felt pens though, not all pens will adhere to Depron so do some experimenting and find something which sticks. I found a brand called MonAmi and also Starpie worked well and both can b purchased at Office Works. Of course the only drawback is that the colour will run if you get it wet so no landing on wet grass.
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Another shot of the colour design. The MicronWings logo on the wing was actually printed on adhesive clear plastic. You can get these at most art shops and they are used for making labels for glass jars.
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A good side shot - there's no mistaking that Edge 540 profile

A short video showing the operation of the control surfaces and motor. Unfortunately I don't have any video of this plane in flight but it's quite a quick plane and with wings which have limited airfoil you really need to be active on the controlls to keep it going where you want it to go.