nnChipmunk - 800mm
Part 6 - How to Design DTFB Planes
I recently posted instructions and build plans for a swappable Messerschmitt bf109, the bones of which were based on David’s Spitfire plans. The concept was to change everything about the shape EXCEPT where any two parts joined, the idea being you can use the Spitfire build instructions and end up with a plane that flies just as nicely but a little different, and which looks totally different. That worked really well, and the plans have been pretty popular (I hope to build as well as look at).
So here I hope to extend this a little further, from swappable to super-swappable. The idea here is to make another popular WWII plane, but this time even re-using major parts. In this case, its the much-loved P51D Mustang. At first glance the Mustang is very distinctive because we focus on the bits that are different - the air scoop and the bubble canopy. But in fact much about its shape is similar to a Messerschmitt (evidently their silhouette was often mistaken during the war, and I even read an amusing story about a Mustang pilot flying in formation with some 109s by mistake for a few minutes). Anyway, that is all good news, because it means we can swap whole parts of the planes and make new planes, which I do here.
I recently visited the RAF musem in London and have updated all my old posts with pictures of the real thing. Here are a couple pictures of their mustang.
Below I outline the build, but not in so much detail because it is almost exactly the same as the Messerschmitt. The plans for Mustang-specific parts are attached as PDF files, and the parts that are identical to the Messerschmitt are not, just download them from my Messerschmitt post (Aug. 28, 2013). Actually making the Mustang was easy - I got carried away with the taping as you will see, which was about 80% of the work. This was because I wanted to see if I could make it look like a real one by using aluminum foil tape (“real” duct tape). The results are pretty interesting, but one could make the plane and spray paint it silver and save a lot of bother.
Before you bother making one, here is how it flies.
This video shows some low and slow passes from the first flight. The set up was the same as the Messerschmitt - and NTM 1350Kv motor and a 220mAh 3S battery and 35A ESC. The balance is a bit different, and it was a little tail heavy so I taped a coin under the battery compartment (probably because of the longer rudder) and that sorted it out. Once it was trimmed and balanced it flew like an arrow. It does not glide quite as well as the Messerschmitt (maybe due to the weight of the foil), but it was adequate to glide across my field and land, so still ranks as “good” I think. It performed loops and rolls as you would expect. The weather was poor for movies, so below I concentrated a bit on close ups to show the stability and how it looks in the air, but this is mostly at 1/4 throttle. When I gave it full throttle it zipped around wherever I pointed it.
Below are some building instructions, similar to the Messerschmitt, and full scale plans are found at the end of the post.
The Fuselage and Air Scoop:
The fuselage is pretty much the same as the Messerschmitt, except I altered the nose a bit (not enough to bother re-drawing the plans, just smooth out the lines on the bottom forward of the wing). I considered making the scoop an integral part of the fuselage. This would be cleaner, but also would have meant changing the plans a lot (which I am trying to avoid) and two seams rather than one. So build the fuselage as normal, and then build the scoop separately and glue it on. The scoop is made of two identical side pieces, a small top piece at the very front (where the scoop is separated from the bottom of the fuselage), a former (or add more formers if you like - they are easy to make), and a tapered bottom piece. To get the bottom piece to follow the arc of the scoop, remove the paper from the inside to make it flexible. Glue the bottom to one side and let it set, then do glue the other side on. Last, put the top and formers in to make sure the scoop sides meet the fuselage sides roughly evenly. Make a slot where your former tab hits the fuselage, and glue the scoop into place (you can see where it fits by the angle in the top line of the side pieces, which corresponds to the angle on the bottom of the fuselage).
I put aluminum foil tape tape on the fuselage, along with some stripes and a big red nose all the better to see it in the air.
Above: Top of wing.
Above: Bottom of wing
The wing is identical to the Messerschmitt wing. I made the distinctive black and white stripes with tape, and covered the rest with aluminum foil tape. It puckers at the edges, which gives it a nice effect like rivets on sheets of aluminum. It also catches light and reflects well - since it is really made of aluminum, so it looks real. I gave it some red wing tips on the bottom.
Attaching the Wing to the Fuselage:
Once the wing is inserted, you could make it removable by cutting right though the scoop. I did not bother, but don’t see why this would be a problem.
Turtle deck and Top Formers:
The turtle deck is a bit different from the Spitfire and Messerschmitt because the P51D had a bubble canopy and no elevated rear spine. I used the same overall layout of formers and some of the same actual formers, but to get the right effect for the canopy made one major modification.
The rear-most former is similar to the other planes, but the large former normally behind the canopy is cut short and serves as a support for a flat cockpit piece (with black tape sitting on an angle in the photo). This piece and the first front former that it buts against will form the cockpit.
The Messerschmitt had four front formers descending in size from the cockpit to the motor (from largest to smallest numbered 1, 2, 3, 4). The Mustang also has four, but they are 2, 2, 3, 4 (ie the first two after the cockpit are identical to one another).
The forward turtle deck (black here) is similar to the Messerschmitt, with the angle cuts moved back to correspond to the position of the second former. The back turtledeck (silver) is very different because it will form the cockpit (kind of like the blender).
Put the rear turtledeck on first, glue it to the formers first (including the horizontal cockpit piece) and then tape the sides. Be REALLY careful to make sure it is centred so the arc of the deck matches the horizontal cockpit former. I left some space above the actual cockpit because I liked the look - you can trim this down a bit with a sharp blade after installing. Once this is done, install the front deck. It is installed as for the Messerschmitt, but line up the slits with the second former, and trim the front when you are done.
I tidied up the scoop with some foil around the edges and black paint inside. I also made a canopy out of some clamshell packaging (a half-sphere), but a drink bottle would also work. This plane needs a canopy more than the Spitfire or Messerschmitt because there is no elevated rear spine. The canopy is not too hard if you find the right piece of garbage to make it out of.
Here are the plans for pieces that are different from the Spitfire/Messerschmitt. As with the Messerschmitt plans, dotted lines are the same as the Spitfire, so just use David’s plans and copy my changes on top.
I would love to see comments, especially if you build and fly it. Mine flies great, so let me know how you go with it (same goes for the Messerschmitt) - please post any comments.