The I2-EZB Design and Build: An Indoor Free Flight F1L Spec Flyer

The design knowledge and build skills have come along way since the initial venture into indoor free flight began. This post will carry forward the goal of designing and building a competitive F1L model. This model design was formally known as the I2-EZB, however as the design progressed, has been renamed the XYZ-EZB. As a reminder, the F1L specs are listed below, with a side note that our Revision 1 Model came in at 4.17g with a target of 4.00g.

Note: we have finished documenting a free set of templates and build notes here.

F1L Requirements / Specifications:

• Minimum Weight without rubber motor: 1.2g
• Maximum Wingspan = 457.2mm (18″)
• Max Wing Chord = 76.2mm (3″)
• Stabilizer Area < 50% of Wing Area
• Build Materials: Wood and Covering (no microfilm).
• (Note: need to understand “no microfilm” a better prior to covering)

Here is a photo of the I2-EZB Revision 1 Indoor Free Flight Model:

Initial flight test of I2-EZB Rev 1 revealed it could sustain level flight without stall, but with the chosen rubber (motor) was under-powered for its weight. Two major areas for weight reduction are:

• Prop: very heavy, came in at 1.8g (reminder, goal is to get entire model @ minimum allowed of 1.2g)
• Balsa Frame for fuselage, wing, fin and stabilizer.

Decision for the I2-EZB Indoor Free Flight Model is to basically keep the spec’s, and change the model material size drastically. Also will tweak on several different prop designs to improve weight goals and efficiency. Revision 1 had a constraint of utilizing readily available Local Hobby Shop material. This is not the case in Rev 2 and beyond. Will procure material and parts locally or online to get closer to the desired specifications.

Official FAI Specs can be found here. Enjoy this wonderful video of what the goal looks like!

(Dec 26th, 2018)

Decision to rename I2-EZB Revision 2 to TU-EZB, which stands for Tail Up-EZB. It is part of a decision to make two different versions of this Indoor Free Flight EZB model, off the same general drawing. One will be the Tail Up version and the second will be a Tail Down version (aka, the TD-EZB).

TU-EZB

The TU-EZB is complete and ready for flight. Final weight is still far from goal of under 2.0g (w/ no motor), but progress was made! For this Indoor Free Flight F1L model, the weight came in at 3.22g vs. the Rev 1 weight of 4.17g. Resulting in a weight savings of approximately 23%. Major changes in this design include:

• Two piece wing instead of 3 piece
• Used smaller sticks for stabilizer and fin
• Changed covering to a lighter version
• Less mass on propeller

Here is a photo of the TU-EZB. It is unknown at this time, but it is believed this model will fly very well. It appears well balanced and glides beautifully. Of course, the load of the rubber motor and its torque can change everything.

(Dec 29th, 2018)

(Side Note: initial name was to use the “F” in Fin, for Fin Up, but it became obvious that would not be good!)

TD-EZB

As discussed earlier, a decision was made to make two notably different Indoor Free Flight Models off of one basic design. Though the TU and TD EZB’s look different, they are really built off the same basic concepts and will share a set of templates when final drawings are created. Here is the TD-EZB, (the Tail Down version). This first revision came in at 3.25g and differentates from the TU-EZB in the following:

• Wing is one piece with dihedral on the ends
• Fin (Tail) points down and is mounted directly inline with the stabilizer, rather than in front of it.

(Jan 1st, 2019: Happy New Year!)

The obsession to pull weight out of the model is starting to pay off. Rather than focusing on a complete model type for the Indoor Free Flight EZB, a focus on the individual components has begun. Focus individually on efforts to reduce weight have been on:

• Prop Assembly
• Motor Stick
• Tail Boom
• Wing

This effort is resulting in a modular approach to building out different EZB models. It is suspected the final results will allow us to mix and match Wing Assemblies, with different Motor Sticks, Stabilizers and Fins . For now, we have successfully broken the 3.0g barrier with this model, currently called the FAM-EZB (which stands for Flat Middle Section Wing, Standard Stabilizer and Middle Fin).

The build documentation and templates for the XYZ-EZB are here.

Stay Tuned for More as we fine tune them in flight!

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