Archives for December 2015

Build a Rough Prototype

ParkZone electronics installed in the Spin prototype

ParkZone electronics installed in the Spin prototype

I added a page today discussing the concept of a “rough prototype” for model aircraft design.

Aviation has always embraced the idea of a prototype with any new aircraft design, power system, construction method, etc. Perhaps one of the most interesting examples of this is the first Boeing 707 jet airliner.

There were so many new techniques and procedures with constructing and flying the world’s first swept-wing jet powered airliner that Boeing elected to not certify the initial B-707 aircraft with the FAA. Boeing kept it as an “Experimental” aircraft with no FAA issued “N” registration number (and of course no ability to carry any passengers), just so Boeing could figure out if this type of design was worthy of a full production variant.

This historic B-707 is on display at the Smithsonian Museum Udvar-Hazy Center aircraft collection outside of Washington Dulles Airport. Worth a visit.

The idea of using a prototype for model aircraft design makes full sense. I advocate the approach of using a “rough prototype” to work out aircraft sizing, incidence settings, surface areas, etc. before taking the time and effort for a fully finished product. See further details here!

Yard Ace Flight Video

Yard Ace electric powered RC model airplane on a fly by

Yard Ace electric powered RC model airplane on a fly by

On my December 1st blog post (below) I shared some pictures of Russell’s build of his Yard Ace electric flyer. The Yard Ace is a simple to construct RC model that makes a great first time plans-built project.

Russell did a super job with his build of the Yard Ace, electing to add ailerons to his version.

Yard Ace three channel RC plane front view

Yard Ace three channel RC plane front view

Russell shared a video of his completed Yard Ace. Russ unfortunately had a minor crash during a flying session. He took the damaged aircraft back to his workshop, made the required repairs, and flew a “reborn” Yard Ace with the wing now mounted on the fuselage underside.

This is a perfect example of the fun with learning to make a model aircraft from plans. After making modest changes to a vertical or horizontal tail outline, converting a high wing mount to an under fuselage installation is one of the most common modifications one can make to an original model design. The flying characteristics typically remain similar yet you have the satisfaction of creating a much different look to your RC plane.

In my TurboCAD training videos I go over exactly how easy it is to make a change of this nature to a using the Yard Ace as an example. Russell, thanks for taking the time to do this modification and share your flight results!

 

Swedish Chickadee Pictures

Top view of Stefan's completed Chickadee

Top view of Stefan’s completed Chickadee

Stefan, hailing from Sollentuna, Sweden recently completed his build of the Chickadee. Following are some details of Stefan’s useful modifications to the original airplane. Chickadee CAD plans are included with the Blackburn plan set available here. The Chickadee sizing, wing incidence and moment setup were the prototype basis for my Blackburn plan.

The Chickadee is one of my early designs. The model uses a simplified construction method detailed here and is easy to modify as the builder sees fit. The Chickadee is a great choice for a first time RC model airplane builder.

Top rear view of Stefan's Chickadee

Top rear view of Stefan’s Chickadee

Stefan did a wonderful job with his Chickadee modifications. Further insights follow:

1. Stefan elected to keep the wing spars square instead of sanding them to a round shape. Stefan added a matching notch to the wing ribs to account for the square shape of the spars.

2. Stefan employed sheets of 0.4 mm carbon for the wing spar reinforcements instead of the plywood strips used in the original. He also wrapped the inner 10 cm of the wing spars with some Kevlar thread, wetting the assembly with thin CA glue.

Detail of string control setup for Stefan's Chickadee

Detail of string control setup for Stefan’s Chickadee

3. This was Stefan’s first time covering the wing and tail surfaces with Japanese tissue, looks like it came out very well.

4. Stefan decided to go with pull-strings made from Kevlar thread for the rudder control instead of pushrods.

5. Stefan used a Dualsky XM2215RTR-17 20 gram electric motor with a built in electronic speed control. He added a 2S-360 mAh Lipo battery for power the arrangement.

Detail of nose section of Stefan's Chickadee showing engine installation and wing attachment

Detail of nose section of Stefan’s Chickadee showing engine installation and wing attachment

The resultant savings in weight meant that he had to move the wing to the rear 10 mm and the motor 5 mm forward to achieve the correct center of gravity location. The final flight weight is a very respectable 194 grams.

Stefan offers an excellent example of the benefits of constructing an RC model from plans, with the ability to make simple modifications as desired to personalize your version of the aircraft.

As a final note, Stefan’s eight year old daughter came up with the neat idea of using a ping-pong ball as a pilot figure. Well done!

 

Top view of Stefan's ping pong ball pilot figure

Top view of Stefan’s ping pong ball pilot figure

 

Top view of Stefan's Chickadee

Top view of Stefan’s Chickadee

Chickadee Prototype Design

Quiet and Electric Flight International magazine published the Chickadee plan in their Sept 2009 issue

Quiet and Electric Flight International magazine published the Chickadee plan in their Sept 2009 issue

Front view of the completed Chickadee park flyer

Front view of the completed Chickadee park flyer

I added a new page to the website, under Design, that discusses my approach to laying out the plans for the Chickadee. This method to come up with an original aircraft design can be of use to any new RC model plane designer.

With the Chickadee I adapted some construction and sizing techniques from an earlier kit-built model (Sig’s Demoiselle) and employed them with the Chickadee. The Chickadee uses a straightforward and uncomplicated structure to permit quick modifications. Once the design parameters are confirmed during test flights, follow on model plans can be drawn using these aircraft constraints.

 

Chickadee in flight

Chickadee in flight

For example one item that needed adjustment on the Chickadee was the wing’s incidence. The prototype had plenty of power from its brushless electric motor, but would not lift off during the takeoff run.

The solution was easy with an increase wing incidence by raising the wing’s leading edge. As the construction was open frame this modification entailed lengthening the two forward wing mounting posts. The result was a smooth takeoff and a pleasant flying model.

These dimensions and settings were transferred directly to my Blackburn design, to include the same motor and battery arrangement. Interestingly, the handling and flight characteristics of both models are remarkably similar.

The idea of using a rough prototype that can be readily modified, to iron out the proper aircraft parameters, is a sound way to design RC model aircraft and can be used for a variety of model airplane designs. I will expand on this concept in a later update to this blog at the end of December and show how I used this same approach with the Fokker Spin.

 

Detail of the Chickadee nose section and control system layout

Detail of the Chickadee nose section and control system layout

Yard Ace Build

Yard Ace electric powered RC model airplane on a fly by

Yard Ace electric powered RC model airplane on a fly by

The Yard Ace is one of my favorite designs. The airplane’s layout is simple and construction employs normal building techniques and materials. The Yard Ace is a great first choice for a plans-built model.

Yard Ace wing under construction, note addition of aileron servos

Yard Ace wing under construction, note addition of aileron servos

Russell recently sent in some photos of his Yard Ace. Russell is working on a third version with students as part of a classroom project. Note the addition of ailerons and wing mounted servos, an indication of just how straight forward “kit/plan bashing” modifications are to this flyer. Russell, many thanks for sharing your Yard Ace building experiences!

Russell has given me a great idea, and that is to make a smaller indoor version of the Yard Ace designed around using the ParkZone microelectronics. It will be easy to produce the reduced size plans printing with TurboCAD, or employing the tile feature contained in the print box of a PDF file.

Yard Ace fuselage under construction

Yard Ace fuselage under construction

Based on experience, I think about a 25 inch wingspan variant of the Yard Ace will be about right for the motor and prop used by the ParkZone equipment, looking towards a finished weight of under three ounces. Note that I used this empirical sizing technique designing the Fokker Spin, which came in at a 28 inch wing span and a three ounce flight weight.

As my December Mesa flying schedule with United Express permits I look forward to sharing progress with you on this construction process!

 

Yard Ace after a slight landing accident, with motor mount needing a replacement

Yard Ace after a slight landing accident, with motor mount needing a replacement

Front view of Russel's Yard Ace

Front view of Russel’s Yard Ace