Getting Serious with F1D

F1D Design Log

F1D! Time to get serious with a Design

The Journey to design and build an entry level, competitive Indoor Free Flight model was and is highly educational! Thinking one could jump into this area of the hobby and go straight into F1D was naive to say the least with such an incredible learning curve it presented. From our blog, the output resulted in an nice, first indoor free flight model design, in the F1L-EZB class. This model meets specification and fly’s very well. Naturally, it is time to attempt the same but on the very complex F1D Airplane Kit.

This article will document the progression of learning, designing and building an F1D which can meet entry level competitive specifications, if so desired. At the end, the build documentation and templates will be available for free download, no strings attached, on our site, as is the XYZ-EZB files. This is done in hopes to help move this incredible hobby segment forward!

MAJOR UPDATE: Prototype #2 Design/Build has begun! Scroll to bottom! Templates will be released after this version is complete.

Specifications for F1D

  • Wing Span no greater than 550mm
  • Max Chord of lifting surfaces 200mm
  • Max Tail Span 450mm
  • (more specs to be documented)

Research Phase

Currently researching many different design and build references and old articles. This can be tedious but it is a lot of fun as well!

Design and Build Phase

Designing and Building the Wing

Since success was experienced with the XYZ-EZB design approach for that wing set, it has been decided to follow the same process. The wing template will be designed and drawn in such a manner that multiple wing types can then be fabricated from it. For this F1D Airplane Kit design, the following wing specifications have been settled on:

  • Wing Span, when flat on the board (no dihedral) = 546mm
  • Wing Chord = 197mm
  • 4 % Arc for Ribs
Wing Half Template for F1D Indoor Free Flight Model Design. F1D Airplane Kit
Wing Half Template for XYZ-F1D Design

Building Tools: Just a reminder, here is a partial list of tools and supplies used. If you looking for something specific and cannot find it, please contact us and ask. Here to help!

Drawing the 4% Arc Template

Drawing the Wing Half Template above was straight forward and not worthy of additional information. However, drawing the 4% Arc for the Wing Ribs is.

  • First, a simple straight line is drawn the length of the chord.
  • After calculating 4% of this length, a line is drawn perpendicular at the center at that length.
  • Calculate the radius (r) for a 3 point arc using the following equation: r = (H/2) + (W^2/8H), where:
    • H = Height of Arc at the midpoint
    • W = Width of Arc
    • Here is an online calculator to help
  • Using a string & pencil compass setup, draw the arc.
  • The drawing is then printed on standard card stock paper, and the template is cut.

After cutting the template out on card stock, ribs for the wing are cut out of 1/32 sanded balsa sheet.

F1D Wing Half without covering
F1D Wing Half being built
F1D Wing Halves Mocked Up for future F1D Airplane Kit
F1D Wing Halves next to each other.

Designing and Building the Horizontal Stabilizer

For the Stabilizer, the following specifications have been decided upon:

  • Span = 440mm
  • Chord = 136mm
  • 2.5% Arc for Ribs

Same process for designing the template and ribs used for the wing will be used on the stabilizer. Once the templates are finished, they will be printed on card stock and cut out. Hopefully, a easy to follow instruction set and F1D Airplane Kit will follow!

F1D Indoor Free Flight Stab Template
Stab Half Template Cut Out (X2)
XYZ-F1D Stabilizer Uncovered
XYZ-F1D Stabilizer Ready to be Covered

Designing and building the Vertical Fin

Nothing of special interest here. The Vertical Fin is a simple 75mm High and 100mm Wide Fin with a slight taper on the front edge.

F1D Airplane Kit Vertical Fin Template
F1D Vertical Fin Template cut out…
Building Vertical Fin for F1D
Vertical Fin Build

Designing and Building the Motor Stick and Tail Boom

This part of the design is where new experiences and skills are obtained. Learning the ‘art’ of wrapping balsa wood around a metal mandrel and baking it to get its final form has absolutely been crazy! (In a good way).

Have successfully rolled both the motor stick and tailboom from 1/64th in balsa sheet! The Motor stick is a 9″ tube, created from wrapping the balsa sheet around a .250″ metal mandrel. The Tailboom is approximately 18″ long and it is a tapered tube, made in the same manner. This area of building was completely foreign, so watching this video was extremely useful! For the .250 mandrel, a piece of brass tubing purchased at Hobby Lobby was used and for the tail-boom mandrel, it was purchased at Indoor Specialties. It is a bit pricy, but worth it.

Here is a picture of the completed motor stick and tail-boom.

F1D Motor Stick and Tailboom Assembly
Formed Motor Stick and Tailboom

Covering the Surfaces

Next up was to cover all the flying surfaces built earlier. Encourage you to read through the XYZ-EZB Build Documentation for more info on covering.

XYZ-F1D Airplane Kit Covered Surfaces
Here are the covered surfaces for the XYZ-F1D…

Designing and Building The Prop

Nothing is straight forward when designing and building an Indoor Free Flight F1D model and the prop is no different! After researching many patterns and tools, a decision was made to draw up a prop shape which would be easy to form the 1/32″ balsa stick around. Also, for the first prop, another decision was made that the forming of prop shape would utilize a simple ‘wrap it around a cylinder’ technique, rather than building up a pitch block. Future designs will focus on such!

The prop is a 1/32″ x 1/32″ framed outline which will have a 16.5″ (420mm) diameter. The blades will be built separately and then aligned to a third component, the hub at final assembly. Individual Spec of the Blade is:

  • Total Length = 210mm
  • Blade Length = 180mm
  • Blade Max Height = 54mm
  • Framed in 1/32″ x 1/32″ balsa stick and covered with Ultrafilm (same as wing, stab and fin).
F1D Blade in Jig
Blade in Jig Template
F1D Airplane Kit Blade with Hub
F1D Blades with Hub Ready for Covering and then Alignment

Putting it all together!

Unlike our post of learning to build an F1L, where we documented in detail the learning and building process, we are skipping ahead and showing the final assembly. The reason is two fold: 1) it is clear from this build that a second and third pass will need to occur before templates can be uploaded, so final documentation will occur after. 2) most of the process to assemble the final model is the same as the F1L and duplication isn’t required. The biggest differences for final assembly include:

  • Wing Mount Tubes: these are mounted on the leading edge and trailing edge of the wing itself, rather than the motor stick. This works out really well actually and it is much easier to set the tubes.
  • Stab Mount Tubes: so that there is the ability to adjust the angle of attack of the stabilizer, it to is mounted via tubes.
  • Mounting Sticks, for Stab and Wing: these are carefully mounted on either the motor stick or the tailboom. Both are rolled 1/64th sheet balsa and are very delicate!
  • Load Bearing support for rubber band: with the motor stick primarily a tube of thin balsa, with support webs in the front and rear to hold the bearing and tail hook, there needs to be support to carry the load when the rubber band is wound tight. If this didn’t exist, the tube of balsa would collapse on itself. This support is consists of strong thread between the bearing and the tail hook, supported in the center at an approximate 1.5″ height.
XYZ-F1D Indoor Free Flight Protot;ype
XYZ-F1D Prototype Ready for Test Flights!
XYZ-F1D Airplane Kit Prototype

XYZ-F1D Prototype Ready for Test Flights!

Prototype #2! Here we go….

Our flying of the first model went fair to medium. The issue truthfully was how fragile the model is and honestly, we did more repairing than flying. Rather than continue with prototype #1 of this F1D Airplane Kit, it is onward to #2! There are X goals for this next version, they are:

  • Get the weight under 3 grams
  • increase robustness around wing supports
  • round the leading edges of all surfaces

Modifying the templates

First step is to modify each template to include the rounded edges. Here is a image showing all templates modified. Note: our Snoopy vs the Red Baron mug we bought here and mentioned on our facebook and instragram pages. Perfect build companion! All templates will be made available after this build, once we are comfortable no major changes required!

F1D Airplane Kit Templates
F1D Airplane Kit Templates modified, ready to build Prototype #2

Building The Stabilizer and Fin

Because curved portions are new on this version, the plan is to work from the smallest part to the largest and learn the best method. The FIN had no issue being formed, using 1/32″ by 1/32″ stick. The Stabilizer, on the hand is still under evaluation! Our first attempt with the stabilizer was not successful. The stick (same as Fin) easily formed around the template, however it created a spring like effect once removed. This caused an odd shaped trailing edge to form. Next attempt is shown in the picture below, where the balsa was sprayed with water before placing around the template. Will let it dry a half day and see how it went.

forming stabilizer
Balsa stick is wetted before wrapped around Stabilizer Template

Next Step: Build The Wing!

Another side note: ran out of 1/32″ x 1/32″ stick and had to order more! Went ahead and ordered more of the misc parts and film covering as well. In the meantime, will draw up a “Mini-D” which will be a hand-held glider that has the same ratio of dimensions of our F1D, but smaller!

here is a great short video of why this pulls us in!
Final Version of F1L-EZB Indoor Free Flight Model
The XYZ-EZB Design and Build Journey Documented Here….
Must Reading for Rubber Powered Projects!
F1M Indoor Free Flight
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