CH-47 Chinook

In 2007 I became interested in helicopters, and in typical fashion, I no sooner mastered the basics of flying one than I started looking for a military scale subject.  Having read an article on control systems for tandem-rotor helicopters, I set out to design a CH-47 Chinook (nothing like jumping in the deep end of the pool).  The design was featured in the Winter 2008 issue of Air Age's RC Helicopter Magazine. 

This has been one of the most rewarding projects of my aeromodeling career.  The Chinook is challenging to fly, but it looks terrific in the air. 

UPDATE:  The CH-47 body is no longer available for online ordering.  I'm leaving these pages up for reference for modelers currently working on this build.  Please contact me with any questions. 

Click here for assembly notes for the heli mechanics.
Click here for assembly notes for the body shells.
Click here for tips on assembling the engine pods.

Scale:  1/24
Rotor Span: 25.4"
Body Length: 25.6"
Weight RTF: 40 OZ

Here's the Chinook ready for another sortie.  The 'Hook is a modest-sized and affordable project, but it's a little more challenging to fly than most conventional tailrotor helicopters.  The complex drive train is also targeted toward more experienced builders.

Here's the CH-47 on an early test flight.  Note the characteristic nose-high attitude in hover.  The Chinook was designed this way so that it would assume a level attitude in cruising flight, making for a more comfortable ride for the crew and passengers. 

Here's another shot of the Chinook hovering on an early test flight.  Note that the rotors are synchronized to be 90 degrees out of phase.  The Chinook requires gyro damping on both yaw and pitch, and four custom mixers control lateral cyclic and DCP (differential collective pitch) on the front and aft rotors.

Here's the Chinook climbing out.  The tandem rotor system is very efficient, and the CH-47 hovers on just 10 amps of current.

This photo shows the Chinook with one body shell removed.  As you can see, the hardware installation is pretty snug.  The aluminum truss is the main structural member, providing a frame for the helicopter mechanics and the drive shaft that connects the two rotor systems together.  The truss is tilted 6.5 degrees relative to the Chinook's body to give the two rotors their proper orientation (this accounts for the 'Hook's characteristic nose-high attitude in a hover).  Power is provided by a Scorpion HK-2221-12 motor, a Castle Creations Phoenix 35 controller and a 2200-3S lithium polymer battery. 

This photo shows the CH-47's mechanics.  I used crown and bevel gears from the popular Corona 120 helicopter to fabricate the drive shaft assembly.  You can see that the pitch servo pushrod has been screwed to a rigid post to disable pitch input.  Just two servos (roll and collective) control each rotorhead.  The fiberglass side frames of the Revo-CP helis I used to build the prototype made mounting them to the aluminum truss relatively easy. 

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