About 8 years ago or so I designed a small electric sports model for low-cost gear and minimal build time. Now, I’ve brought it up-to-date with a FliteTest style reboot in our favorite foam board…
Crash-E Sports Trainer
Built from balsa and ply over a couple of evenings the Crash-E used the cheapest electric equipment available at the time. At only a 28 inch span it was small enough and light enough to chuck in the back of the car and throw just about anywhere.
Imagine my surprise then when it flew so well that the hand-drawn plans were picked up and published by a UK modelling magazine.
A couple of weeks back I pulled the original plans out and took another look. Using foam board and a Flite Test style folded wing and fuselage it certainly looked possible to recreate the Crash-E for a new generation.
Designing the Crash-E V2
It was easy enough to transfer the measurements to Sketchup although it soon became apparent that foam board being thicker than the original balsa was going to require an enlargement of the design.
The first draft went to 150% but a preliminary export of the wing showed that it was going to be far too big. I eventually pulled it back to 125% and got around a 36″ span.
The design in foam board followed some fairly normal Flite Test style conventions with a folded wing and folded fuselage. I replicated the under-cambered wingtips from the FT Spitfire and Simple Soarer as a way of creating a stable airfoil and preventing tip stalls.
I printed and cut the wings first. The whole thing was over in the blink of an eye…
The one piece wing has a full width spar with the aileron servos located at the edge of the bottom plate and connected via a Y harness that exits through hole in the center of the wing.
The fuselage didn’t take much more time than the wing. The hardest part was cutting the curves around the nose!
The original had a central “box” that gave rigidity to the fuselage. I replicated this in foam board to give a double wall to the central fuselage and also extra surface area for the nifty little CNC cut firewall I had made.
Both the main fuselage and central box are an “A” style fold – that is the sides come up and over the base. Everything else simply sticks to or slots into this main structure.
There’s plenty of room inside the Crash-E so you can spread your components around. The elevator servo was hot-glued to the side of the inner box and a wire/carbon pushrod run out through the rear of the fuselage to the control horn. The ESC was similarly stuck to a wall as was the Rx. This leaves plenty of room on the floor to Velcro in a LiPo.
For power I used a spare NTM 2826/1100kv outrunner and 30A ESC on 3S 2200mah cells. The motor turned out to be a bit short for the nose so instead of cutting the foam down I used some 10mm spacers to move it forward.
Ready to go then…
With everything ready to go the total airframe (including LiPo) came in at around 620g. The motor with a 9 inch slowfly prop produces more than 1:1 thrust so it’s all looking promising.
Of course, I’m writing all this before the maiden flight so it could all go horribly wrong…
Just like it’s predecessor I was pleasantly surprised by how the Crash-E flew. It’s no pattern ship and the smaller control surfaces and lack of rudder means it will never fly 3D. What it is though is jolly good, worry free fun…
The NTM2826/1100kv puts out more than enough power and after probably a good 8 or 9 minutes of trimming and filming for the video I still had only used 950mah out of the 2200mah pack so duration is pretty awesome.
The Crash-E is nice and fast but can be slowed right up due to the low weight. The stall is pretty much non-existent but inverted flight does require a bit of power and a thumb load of forward stick to keep the nose up.
So what are you waiting for?
The Crash-E is a great little model for anyone looking for a low-cost, low-stress bank n’ yank sport aerobat. Construction is about as easy as it gets and you still end up with an airframe that can take a knock or two.
Of course, it would be easier to build if you had some plans so here they are…
A lot of the fold lines in the fuselage and wing are marked red for a 50% score cut. This is because it is impossible to “crease” our heavy Australian board so we need ot cut it to bend it. If you are in the US and using lighter “Readiboard” you may get away with just a “rub and crease” on these lines.
It was pointed out to me that once again I neglected to put the CG on the plan. This has now been ammended and new plans are available on the link above. For the record, if you balance it on the spar at around 45-55mm you should be good to go!