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Tasmanian Devil 13mm

for 1/2A and A Copter

Note: The following page was created for use with a very limited number of kits that were made up for use at BRB Contests. But the tips are generally useful for scratchbuilt versions too. So, ignore references to the kit and substitute your own 13mm and balsa parts from the original 13mm plan.

The Tasmanian Devil began as a sport-flying model, sort of like a flying saucer that spins fast. It spins SO fast, it reminded me of the old Cartoon character, therefore the name. Here is the Tasmanian Devil Spin-up sound.

It has also found use in contest flying. Sometimes as a "return" model, and sometimes as a "qualified flight" model .And even sometimes as a placing model when a contest would likely have very few entries in the Copter event, or better designs DQ'ed.

It will only fly for around 6 to 8 seconds on a 1/2A. So, it will not beat a Rotaroc that flies successfully. But there may not be a lot of Rotaroc models flown. Especially in the Junior Division. So this is an optional "Plan B" approach that has its place (at our November 2007 contest, the Junior Division fliers all used Tasmanian Devils).

Tony Williams drew up a plan that has been printed in the NAR's magazine twice, in 1986 and 2002. Tony's original drawing is included, as well as two more pages showing an updated PDF plan version based on the kit for the BRB contest.

The kit model's main difference over the orginal plan is the fact that I had a number of 14mm nose cones left over from a glider design that did not work out, so the kit uses a 3/4" long piece of 14mm tubing to join the nose cone to the 13mm (BT-5) type body tube. If I had had enough normal 13mm (BT-5) type nose cones, the kit would use those instead. If someone wants to scratchbuild one from their own collection of parts, just use a 13mm (BT-5) nose cone, and not the 14mm nose and 14mm tube.


Tasmanian Devil
Copter model

Below: pages from the PDF Plan


Original 13mm Plan

BRB Kit Plan Page 1

BRB Kit Plan Page 2

Read the following rows left to right, then down to the next row.

 

Comparison of Tasmanian Devil kit prototype and a very old Rotaroc model.

 

Prototype BRB kit model ready for flight.

The Prototype did not have any rounding or airfoiling of the rotor blades. But the model will fly a little better if rounded, and a bit better still with some airfoiling.

 

 

 

BRB Kit Parts: Three rotors at top

Left-right: 14mm nose cone, 3/4" long 14mm tube, and 3" long precut and pre-marked 13mm main body.

Bottom row is the launch lug and three rotor supports.

 

First, glue the 14mm nose cone into the 3/4" length of 14mm tubing.

Then glue the nose assembly to the 13mm main body, the 14mm tubing will overlap the 13mm body by about 1/2". The 14mm tubing is a loose fit over the 13mm tubing, so be sure to use enough glue to keep the 14mm tubing from blowing off at ejection.

 

 

 

Glue on the three Rotor supports, as though they are fins for a 3-finned rocket. Attach them so that the last 1/4" of the body tube will stick out after the blades are glued on.

 

Decide if you want to round the rotors, or give them an airfoil.

See the plans to take note of which side of the blade the airfoil will face when the model is assembled.

The root end of the blades will be glued on more strongly if an angled arc is sanded into the root of each blade. Wrap a piece of sandpaper over some 13mm tubing, and use that for sanding the arc into the tube.

Take note that the blade will be swept backwards, so hold the blade at about the same sweepback angle as it will have when glued to a rotor support.

A blade after the arc has been sanded in, as seen at the lower left.

If this rotor blade had an airfoil, the curved part of the airfoil would be on the opposite side, the flat side of the airfoil is facing up.

Glue on each blade to the model, applying glue to the rotor support and also onto the arc that was sanded into the blade in the previous step.

Be sure there is a slight pitch angle in each blade to make it spin. See the third page of the PDF plans for more information.

When the glue is dried, go back and apply more glue to the joints to make it stronger. If you build it using Cyanoacrylate (CA) glue, that is great for the primary assembly to get the parts to hold together. On this model though, it is useful to go back and apply some Titebond or white glue to make the CA joints stronger. Or, if you are using a THICK type CA, then more thick CA serves the same purpose. Regardless of type, watch out for glue running.

The corners of the blades just about touch each other. This leaves no room for the launch lug. So, after the blades are completely glued on, go back and cut out a notch into the corners of two blades to make room for the launch lug, then glue it on.

A near side view of the assembled model (in this case, the flown prototype)

The BRB Kit prototype has no airfoiling. This photo, with enlargement on the lower right, helps to show the slight pitch angle that makes the model spin.

Be sure each blade is angled in the same direction of rotation (as well as the airfoil)!

When you fly, insert the engine with about 1/4" of it sticking out of the back of the tube. Use some 1/2" wide tape to wrap around the engine and the lower 1/4" tube the body tube to secure the engine so it will not slide up under thrust, and will not eject out at ejection. Helicopter duration models can NOT have any parts come off, and that also means engines cannot be kicked out.

Use a 1/2A3-2T engine for contest flights. Later, you can sport fly it on an A3-4T. Do not use an A10 for sport flying, as it may overstress the model and make it shred apart.

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