Archives for January 2014

Fokker Spin Plan Published

 

 

1911 Fokker Spin front view showing dummy balsa engine cover

1911 Fokker Spin front view showing dummy balsa engine cover

My design of the Fokker Spin was published in the January 2014 issue of Quiet and Electric Flight International magazine.  The editor did a nice job putting together the article, which included a pull-out plan and detailed construction photos. 

See more details here on what steps you can take to get one of your radio control model airplane designs published.  The Spin is my 6th model airplane design to appear in the press.  It takes a bit of work reaching out to the appropriate people at the magazine to get this process started.  But the task can be done, and it is very rewarding to see the finished product in the magazine.

The Fokker Spin is an historic aircraft, paving the way for the numerous fighter aircraft Anthony Fokker later designed for the German Air Force in World War 1.  The Spin takes advantage of Horizon Hobby’s microelectronics which is used in their ParkZone line of foam ready to fly models.  This control and motor suite is small, affordable and ideally suited for indoor flyers like the Spin. 

Page 3 of Jan 2014 publication in Quiet and Electric Flight International magazine of the Fokker Spin

Page 3 of Jan 2014 publication in Quiet and Electric Flight International magazine of the Fokker Spin

Enlarging Model Airplane Plans

 

One of the nice advantages of making an RC model from plans is the ease with which you can modify your airplane as you study the plans and start on the construction.

View of pilot and dummy engine in Werner's enlarged Fokker Spin RC model

View of pilot and dummy engine in Werner’s enlarged Fokker Spin RC model

Making any sort of change directly to the plans results in that modification being built in from the start.  You can also try design adaptations at any time as the model goes together.

The more you build from plans the easier this modification and improvement process becomes.  In effect, each model you create will be a one-off design, which is all part of the fun.

A standard technique with models made from plans is enlarging the original plan to a different size.  I mention enlarging, as most modelers seem to be enlarging model airplane plans these days, although one can certainly make a smaller version if desired.

Detailed underside view of Werner's 225% enlarged Fokker Spin

Detailed underside view of Werner’s 225% enlarged Fokker Spin

Today’s graphics stores make plan enlargement an easy task.  I use a local FedEx Office that has a large format scanner.  A plan is scanned in (to include plans made with your home printer on regular 8.5 by 11 inch paper), and then printed out on the wide format printer to a much larger size.

The enlargement is typically done via a percentage.  If you were to have a model with a 20 inch wing span, and you wanted a 40 inch span version, you would input a 200% enlargement ratio.

While it is easy to enlarge a plan, the modeler must then ensure the structure of this larger model is strong enough for the new aircraft weights as well as the higher flight loads.  In the previous example, the 20 inch model might have 1/8 inch square balsa for the spars.  The 40 inch wingspan variant would need some larger and stronger spars to ensure the wing’s structural integrity.

There is no science for changing wood size dimensions as plans are enlarged, but rather experience gained building other models and making design adaptations.  If in doubt, go with a stronger material, even though it might be a bit heavier.  As you gain know-how, strive to make any updated design as light as possible yet strong enough for the model to stay in one piece.

This is another great advantage of electric powered models.  The vibration free electric motors typically allow for less structure in the aircraft’s wing and fuselage as compared to comparable gas powered versions.

An example of enlarging plans is Werner’s build of my Fokker Spin plan.  Werner enlarged the plans 225%, taking it from a designed wingspan of 28 inches to 63 inches.

 

 

This is a significant increase in size and required Werner to do extensive redesign and strengthening of the wing and fuselage structure.  Another nice benefit of this enlargement is that Werner had ample area to do a very nice job with detailing the exposed engine, side radiators and pilot figure.  All of this adds up to a very appealing model of this historic aircraft.

Werner's 225% enlargement of the Fokker Spin showing structure details

Werner’s 225% enlargement of the Fokker Spin showing structure details

The generous wing area of the Spin combined with the positive incidence setting allows for takeoff at a slow and relaxing airspeed.  The model handles well at the larger size.

The one aspect of flight that really came out in Werner’s larger update is the skidding whenever the model enters a turn.  Skidding is typically encountered with a pilot uses too much rudder to try and turn, without applying sufficient bank to the wings.

In the case of the Spin, and this was common with a lot of the early design aircraft, the lack of sufficient side area to the airplane produced difficult flight control situations during turns. The Fokker Spin, with a flat frame for the fuselage, has essentially no side area to assist coordinated flight during a turn.

One should also keep in mind many of these aircraft were still experimenting with the concept of ailerons and wing warping.  The high camber airfoils, slow speeds, low power engines and various effects of the control surfaces all led to some challenging control situations.

An additional factor that likely contributes to the Spin skidding in turns is the effect of the swept wing on the aircraft maneuvers.  Swept wings are unusual on light weight propeller powered aircraft like the Spin, thus there is not a large body of experience in these matters.

In summary, the ability to enlarge plans opens a wide range of new and exciting modeling subjects to the builder.  Any design can be adapted to your needs.  The size can be adjusted to anything from the size of your car, home storage area of flying location.

There will be some work needed to ensure the different size of the aircraft is structurally sound.  But the results are a unique model that in a sense you designed.  Werner’s larger Spin is a great example of this art.

Author:  Gordon McKay