From Prototype to Final Robin II Construction Plan
Design a model plane – from original sketch to Robin II final plan
Introduction | Parameters | Initial Plan | Prototype | Test Flights | Final Plan | Robin Plan Download
Robin prototype and Robin II RC model airplane
Now that the Robin prototype has successfully flown, it is time to evolve the TurboCAD plans from the Robin’s outline sketch and parameters to the Robin II final plan. This is the fun part of RC model aircraft design. We know that the prototype Robin’s structure and control arrangement are satisfactory. We can now take this as a baseline and make minor changes for a more attractive final Robin II model and plan.
First, we take the Robin model plane design outline draft and use this as a starting point for the Robin II frame. The Robin prototype employed straight lines for ease of construction. For the Robin II, I decided to add a few curves to the nose section. The Robin prototype was slightly tail heavy, so I made the nose a half inch longer to help the aircraft balance at the proper center of gravity location.
F-8 Bearcat profile and F-4 tail provide Robin II design ideas
I used the distinctive shape of the Grumman F-8 Bearcat as an inspiration for the Robin II’s fuselage and added the unique vertical fin shape of the F-4 Phantom. As you design your own RC model airplane, use any other full size aircraft to guide your own personal RC model look. The Robin II’s profile construction technique makes this a simple task. I elected to make the rear fuselage slope down a bit, and included a canopy frame outline. I added two inches of length to each wing, tapered the ailerons and added some aft sweep to the stabilizer. By staying close to the prototype Robin form we can be assured the Robin II will share similar flight characteristics.
Robin II on left, prototype Robin on right - easy to draw with TurboCAD training CDs
Once the Robin II RC model airplane outline is complete, it is now time to add internal structure. Note that I cleaned up the Robin II’s nose engine mount considerably from the prototype installation. This is where TurboCAD is invaluable, as I could draw the E Flite 4-Site electric motor and gearbox and fit it correctly onto the Robin II plan. The 1/16 inch plywood mounting tabs work very well, with a slight cut into the 1/8 inch balsa of the nose to allow the plastic tabs to slide into place.
The Robin II’s flat structure for both the wing and fuselage make adding the internal balsa structure straightforward. I used 1/8 inch square balsa and 1/8 inch sheet balsa as with the prototype. Always use the minimum material to achieve the lowest possible weight for this park flyer, yet keep the framework strong enough to resist warps from the covering. TurboCAD again comes to the rescue by allowing the RC model plane designer to prepare just one half of the fuselage or wing and then use the mirror command to instantly draw the second half.
CAD view of Robin fuselage with structure added
On the Robin II I installed the aileron servos under the wing to hide them from view. I added the 1/8 inch balsa sheet for mounting the aileron servos as far forward on the wing as I could to aid with the center of gravity. I also added some carbon rod reinforcement to the wing’s midsection front and aft 1/8 inch square balsa for strength in this critical area.
The balsa canopy frame adds a lot to the model’s visual appeal. I laminated 1/16 inch balsa sheet cross-grain for strength and painted the frame with craft store red acrylic paint to match the fuselage Coverite Microlite iron-on covering.
Robin II electric RC model airplane
The pilot figure is easy to make. I sized a digital profile photo in PowerPoint to 3/4 inch high, making a mirror copy. I printed out the two images and pasted onto card stock. Thin plastic from an office file folder installed with clear canopy glue completes the cockpit installation.
The Robin II is great fun to fly and handles very well both indoors and outside. This is the time to build your own RC plane. The 4-Site motor provides plenty of power. I used some exponential control on the Spektrum DX6i transmitter to permit smooth controls in cruising flight yet have enough throw for the occasional tight turn or pull up.
Continue to the next page to obtain a full size set of CAD plans for your personal build of the Robin II radio control model airplane. You can easily build a Robin II in a weekend.