Part 2: R.C 3D Depron air-plane. MK2 R.A.F Bulldog
Feb 23 2011 by FaTe
So here's part 2, we start building our plane using very simple methods that anyone can follow. Depron is a great material to work with.

Below you can jump to other project build pages (4 total)

View part 1 View part 3 View part 4

Click any of the images to view the full sized image.
Before jumping into the build I would like to point something out.
Which knife blade is best to cut Depron?

Depron is a compressed foam product and using the wrong knife will result in ripping or tearing out clumps. On the right you can see the result of different knife tips, but to save you time:
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  • Long flat angled blades are best for long straight cuts.
  • Rounded tip knifes are best for angled cuts or none straight cuts.
For the following build I used:
  • UHU por (expanded polystyrene glue - transparent)
  • Hobby knife kit
  • 3MM carbon fibre rod
  • 5MM carbon fibre tube / 3MM inner diameter
  • 10MM * 2MM carbon fibre strip
  • Transparent tesa duck-tape.
So using the plans from part 1 printed out, cut out the wing half, fuselage and tail. Simply lay them on a Depron sheet and using an empty Biro pen or anything rounded trace the outside of the cut-outs, this will leave a nice imprint for you to cut out using a long straight not rounded knife tip. Please remember my photos will vary after I made an extra chop off the front for my own purposes.

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The fuselage needs 2 shock pieces down each side to prevent flex, I didn't specify size in plans at all because it's up to yourself for the shape you want. Mine are 25MM wide. The piece runs from the very front all the way too the tail. Keep the front in the center of the motor mount area creating a cross section. The tail section should sit flush at the top of where the tail slides in. With the UHU glue you apply a layer too both pieces too be stuck together, then leave APART for 12 minutes and then stick them together. You will get an instant bond. I used a square section of marine plywood as a motor mount however a proper mount is provided in the plans.

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Cutting the wings out is a case of using the half print out then flipping it over if you want a single piece, if like me you want folding wings then just cut out 2 half's! Cutting out the ailerons is straight forward, however you need to create a trim on the aileron and on the wing where it joins. You simply hold the knife at a 45 degree angle and cut off the corner. Do the same on each side so it creates a "V" groove when the wing and aileron are put together. You will need to do this on the rudder and elevator also, so practise on some Depron cut-off's before doing it for real. Using the duck-tape cut off roughly a 40-50MM / 2 inch wide strip and place it on the top of the wing and aileron (the opposite side of the V groove) with a 1-2MM gap in between the aileron and wing. Do the same on the inside of the wing so the aileron is held on at each side.

Once a control surface is hinged on the top flip the wing over and fold the aileron over so its flat against the wing. Apply another piece of tape on the opposite side, so the tape is applied with the aileron at maximum bend so when you let it go it can freely move in both directions. Again if your not sure, try on scrap pieces of Depron.

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Using the carbon fibre strip I re-enforced the engine mount area, it's not totally necessary but I personally think it's worth the extra weight. Now the wings need to lock together. To do this I'm using the 5MM carbon fibre pipe on each wing bottom keeping it center as in the photo. I lined it up then pressed the pipe down to create an imprint in the Depron, using the round knife blade I cut out a "V" groove roughly 2-3MM deep for the pipe to embed in. Using the UHU glue I ran a bead of glue in the V slot I created and waited 12 minutes for it to set. Once the glue was ready I just firmly pressed the pipe into place and used my finger to smooth out excess glue, after it had dried I ran another line of glue on the top and bottom to make sure it was solid.

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Using the duck-tape I created a hinge on the top of the wings when pressed together, now the wings can fold and when made straight using the 3MM carbon fibre rod pushed through they become solid. The wings when folded look great, all my parts still need sanded down and made too look pretty but so far so good. Here you can see the 3MM solid rod push through, I plan on using some end caps that can be pushed on / pulled off. This is just a demonstration photo with pieces pushed into place to get an idea of the build progress so far.

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So far I'm very pleased with how it's coming out from something basically built from my head as I go along, I'm just hoping my many builds in the past serve this custom one some good now.

Next I'm working on re-enforcing the wings when slotted into position, Control horns and push rods, Motor mounting and maybe some radio gear placing.
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