Howard DGA-5 "IKE”
a "Damned Good Airplane”

User Guide for Version 3

Figure 1: 3D-printed Howard DGA-5 "IKE” using pre-foamed PLA.

The user guide can be downloaded HERE.

Print test parts can be downloaded HERE.

Content

Content 2

The original 2

What you get 3

3D print files. 3

Decal sheets. 8

What you need. 9

3D printer specification. 9

Required materials. 9

Radio control components. 10

Assembly. 11

Step by step video guide. 11

Noteworthy changes in assembly for version 3. 11

Pre-flight setting & check. 14

Change log. 15

The original

The Howard DGA-5 "IKE” evolved from one of two almost identical prize-winning racers "MIKE” and "IKE”developed by Benny Howard in 1932 [1]. From 1932 to 1936 both planes won plenty of racing prices culminating in 1935 when Howard aircraft won the Bendix, Thomson, and Greve Trophy – a season of racing events that became unofficially known as "Benny Howard National Air Races” [2].

Figure 2: Harold Neumann with Miss Chevrolet in Miami, Florida. "Ike” (NR56Y) was sponsored by the Chevrolet Division of General Motors and was therefore also known as "Miss Chevrolet” [3].

What you get

This is a thoroughly designed 3D printable scale version of the original Howard DGA-5 "IKE”. I spent considerable amount of time with prototype testing and continuous refinement to improve printability, surface quality, scale characteristics, flight characteristics, and rigidity.

This aircraft can be built

·       with or without landing gear

·       with or without flying wires

·       completely in PLA+ or partly in LW-PLA

3D print files

The package includes a complete set of STL files, a set of PrusaSlicer project files, and the hereof generated gcode. PrusaSlicer is a powerful open-source software that can be used for free. The project files were created with version 2.7.1 and contain all detailed print settings required to optimally print each airplane part. Exemplary project files can be downloaded at rc3dmarket.com.

Note: If you want to use a different slicer software, please make sure to check and reapply all part-dependent print settings provided in the PrusaSlicer project files. Otherwise, some parts may not print as desired.

Figure 3 depicts an exploded view of the Howard DGA-5 "IKE”. Together with the following part list it provides an overview of all 3D printable parts. The color code of the index numbers visualizes to which project file and gcode the part belongs.

Figure 3: Exploded view with labeled plane parts.

Figure 4: All printed parts at a glance.

Figure 5: Assembled plane printed with pre-foamed PLA.
Left: 478g without landing gear and flying wires. Right: 554g with landing gear and flying wires.

Decal sheets

The set includes PDF files (600dpi, letter and A4 format) to print decals for the Howard DGA-5 "IKE”. The original plane used black aircraft registration letters in the first years which were later partly replaced by golden letters. Unfortunately, gold is a special color that can only be approximated by the RGB or CMYK color space. Therefore, black registration letters are provided as an alternative.

Figure 5: Decal sheets with golden registration letters.

Figure 6: Decal sheets with black registration letters.

What you need

3D printer specification

All STL files have been successfully tested with my Prusa i3 MK3S.

Required materials

Most plane parts are printable except for a few components such as steel wires or nylon screws. For the parts printed with white PLA I recommend using either PLA+ (Premium PLA) or pre-foamed PLA.

Overture PLA Professional (PLA+) is my first insider tip. It has a much higher tensile strength compared to standard PLA and a higher glass transition temperature. Structure details and surface finish are excellent.

Overture Air PLA (pre-foamed PLA) is my second insider tip. Compared to PLA+ it weighs approximately 20% less. This pre-foamed PLA can be printed with almost same slicer settings as used for standard PLA. Thanks to lower nozzle temperatures, stringing can be handled much better compared to active foaming LW-PLA. Printing of multiple parts at the same time is possible. Also, stiffness of the printed parts is notably better compared to LW-PLA. The following filament print setting modifications are typically sufficient to successfully print Overture Air:

·       Nozzle temperature: ~205°C (high enough for good layer adhesion, low enough to minimize stringing)

·       Retraction length (direct extruder): ~3mm (effectively reduces stringing)

·       Retraction speed (direct extruder): ~30mm/s (lower is better to avoid negative side effects)

·       Deretraction extra length: 0.08mm (to improve z seam)

Let me emphasize that the recommendation above is based on my personal experience. I do not get anything from Overture.

Radio control components

There is a large variety of products available which fulfill the requirements to provide enough power and precise control for the Howard DGA-5 "IKE”. The following set is what I am currently using and can recommend. It provides a maximum thrust to weight ratio of 1.2 to 1.4 (according to ecalc.ch) and a mixed flight time of more than 7 minutes.

Assembly

Step by step video guide

This video guide is based on version 1 of this 3D printable Howard DGA-5 "IKE”. Some parts of version 3 look slightly different. Relevant changes are explained in the following subchapters.

Howard DGA-5 "IKE” – step by step video guide

Chapters:
00:15     >    Right wing
04:02     >    Left wing
05:18     >    Combine wings
06:49     >    Servo cover
07:43     >    Fuselage
16:59     >    Tail
24:04     >    Landing gear
31:24     >    Decals
33:56     >    Radio control
39:06     >    Flying wires
41:26     >    Final check

Noteworthy changes in assembly for version 3

Partly applied selective brim instead of continuous brim to reduce the post-processing effort of the printed parts before assembly. The connection of the wing parts has changed to avoid additional post-processing steps in case of an elephant foot of the printed components. The landing gear crossbar is printed as one part.

Since version 2.1 there is the option to insert a carbon fiber pipe into the center area of the wing. Doing so, further increases the stability of the wing and ensures sufficient endurability for all cunning aerobatic figures. Please make sure to check if the pipe fits into the prepared hole in the wing parts before gluing them together. Insert the carbon pipe latest when you glue both wing halves together.

Since version 2 the rudders, stabilizers, ailerons, and wing servo covers of the airplane are optionally available for printing with active foaming LW-PLA. The design of these parts has been modified to minimize extra travel moves of the nozzle during the print process and to partly compensate for the reduced stiffness of the foamed PLA. At one side of the print (bottom side except for the rudder) the rib structure becomes more visible along the surface. As shown in Figure 7, this visual effect can be easily minimized by sanding the area of the rib structure.

Figure 7: ElevatorL2 before (left) and after (right) sanding.

The active foaming LW-PLA horizontal stabilizers and fuselage part 6 have tubes to optionally insert a 2mm carbon fiber rod to improve rigidity and simplify the assembly as can be seen in Figure 8.

Figure 8: Optional 2mm carbon fiber rod

The main landing gear has been weight-optimized with version 2. This is mainly realized by reducing the diameter of the spring steel wires from 2.0mm to 1.5mm. To ensure robustness, the crossbar became slightly thicker. Overall weight reduction is approx. 13g resulting in a total weight of 68g.
Also the tail wheel became more light weight by reducing the diameter of the spring steel wire from 1.5mm to 1.0mm and optimizing the weight of rim and tire. Despite these optimizations the landing gear remains robust.

Figure 9: Weight-optimized landing gear and tail wheel

Since version 2 connectors can be used to simplify the step of exactly aligning and gluing both wing halves together. The assembly process is comparable to the fuselage parts. Figure 10 (left) depicts WingL1 and WingR1 with connectors inserted in WingR1. Please note that this change only applies to the central wing parts.
Fuselage1 now offers the possibility to fix the motor cables with a cable tie as shown in Figure 10 (right).

Figure 10: Connectors are available to simplify the alignment of left- and right-wing halves (left). Motor cables can be fixed to the fuselage (right).

Another useful modification is the extension of the battery compartment. Version 2 provides more degrees of freedom in the choice of battery type and size which is especially useful in combination with active foaming LW-PLA printed tail parts to adjust the center of gravity. Also, the required manual cut-out has been simplified.

Figure 11: Extended battery compartment to adjust center of gravity.

In version 3, the size of the battery compartment has been increased to support additional batteries. Maximum supported dimensions are 140mm x 38mm x 28.5mm.  

Pre-flight setting & check

Figure 12: Center of gravity (CG) and rudder deflection angles

Figure 13: Aileron and elevator deflection angles

Change log

Version 3

·       Optimized inner structures to improve compatibility of the STL files with freely available slicer versions such as Ultimaker Cura 5.3.1 or PrusaSlicer 2.7.1. It is possible to rescale and print this airplane with other nozzle diameters. Correct downscaling of the original 3D print size to 60% could be confirmed with Ultimaker Cura and PrusaSlicer. Upscaling should be only limited by the print volume of your printer.

·       Moved from Ultimaker Cura to PrusaSlicer due to notably improved print quality of PrusaSlicer with my Prusa i3 MK3S. Latest slicer versions include a feature called "Arachne” which causes surface quality degradation for several parts of this model. Unfortunately, Ultimaker Cura does not allow to switch off this feature completely. On the other hand, PrusaSlicer allows to deactivate this option which I’ve used for all print parts except for the canopy. In summary, I recommend using PrusaSlicer 2.7.1 (tested) or later together with the newly created project files and optimized print settings.

·       Increased battery compartment to support batteries with larger form factor.

·       Optimized connection of wing parts. It now features an improved 3mm continuously overlapping outer perimeter to simplify alignment and gluing of the parts which also results in an improved surface finish.

·       Added carbon tube support for horizontal stabilizer in PLA.

·       Modified rib structure of tail and aileron parts to improve rigidity and print quality.

·       Improved tires by replacing internal structure with gyroid infill.

·       Optimized print parameters with respect to print time and quality.

·       Partly replaced continuous brim by selective brim to reduce assembly time.

·       Merged landing gear crossbar halves. By default, the crossbar will be printed in PLA. Nonetheless, I recommend printing it with white TPU to improve stability and add some suspension in case of hard landings.

·       Fixed a small issue with the wing servo covers.

·       Changed filament recommendation for the wind shield from PETG to PLA. The Fillamentum PLA Crystal Clear Iceland Blue is easier to print and looks amazing.

·       Added filament recommendation to use Overture Air instead of PLA+ to reduce the weight of the printed parts by ~20%.

Version 2.2

Minor modifications based on customer feedback.

·       Increased engine side pull from 3 degrees to 4 degrees. This change improves the take-off behavior.

·       Slightly increased the wheel opening of the landing gear wheel pants.

Version 2.1

·       Added carbon fiber pipe support for wing reinforcement to have an additional robustness margin for cutting flight maneuvers. Normal aerobatic figures with limited g-force such as a larger looping, turn or roll do not require such additional reinforcement.

·       Increased fuselage louver openings for improved scale impression – looks even greater!

·       Reinforced landing gear wheel pants and crossbar.

·       Reinforced internal structure of main wheels.

·       Fuselage bottom seam part optimization for print quality improvement

Version 2.1 weighs 35g more compared to version 2 at the benefit of reinforced structures where needed. This additional weight has marginal impact on the center of gravity. 

Version 2

·       Support of active foaming LW-PLA printing for weight-critical components with a total print weight reduction of approx. 50g.

o  Stabilizers, rudders, ailerons, and wing servo covers can be optionally printed with active foaming LW-PLA. Note that the weight reduction of the tail parts allows to additionally save motor and/or battery weight of up to 70g due to leverage with respect to center of gravity.

o  The active foaming LW-PLA horizontal stabilizers and their connection to the fuselage feature tubes to optionally insert a 2mm carbon fiber rod. The rod is intended as alternative for the tail flying wires.

o  Provision of modified STL files, gcode for each part and Cura project files with all required active foaming LW-PLA print settings.

·       Extension of the compartment for the battery (and the ESC).

o  Provides more degrees of freedom in the choice of battery type and size, especially in combination with active foaming LW-PLA printed parts. Maximum supported dimensions are 140mm x 38mm x 28.5mm.

o  Simplified the required cut out of the battery compartment.

·       Weight reduction of the landing gear by approx. 13g.

o  Mainly realized by reducing the diameter of the spring steel wires. The crossbar is now a slightly thicker to ensure robustness.

·       Improvement of all wing part connections resulting in increased stability and print quality.

o  Added connectors to central wing parts to simplify the step of exactly aligning and gluing together both wing halves.

·       Further optimization of general and part specific print parameters

·       Several smaller improvements