The Great Planes GeeBee has been sitting in my workshop for about 2 years now. I essentially got it for free from Tower-Hobbies with some hobby bucks I had that were almost about to expire. The plane seemed like a fun little critter but it had one major flaw. The firewall that came with it was a completely CA saturated brittle mess. I taxied it out on the flight line, brought on the power, and right before liftoff the firewall basically just exploded into pieces inside the cowling and the motor free from its mounts caused the plane to dance about on the runway, scratching up the cowl and wheel pants. Onto the wall it went after a 15 second maiden until I got up enough energy to scratch build a firewall.

I’m a NOOB to 3D printing, until today!

I recently purchased a PRUSA MK3S 3D printer from PRUSA Research, Josef Prusa’s company in the Czech Republic.

I have been researching printers for several months and decided that a Prusa presented the best option for immediate results without significant tinkering. After all, I wanted this thing to make parts for airplanes and other needs around the house. I tinker with planes. I don’t want to turn making a 3D printer work into a hobby! I just wanted something that I could use and get immediate awesome results. Its not the cheapest printer but its also far from the most expensive. This firewall was my first project with the printer and based on the results, won’t be the last. I’m in love with this little orange device! It just works!

The Design Software (Fusion 360 by Autodesk).

I’m forever doomed to be an engineer that at one time, used to have some pretty good 3D design chops back when 3D was in its infancy. The last time AutoCAD and I were friends was around 2006, so 14 years ago. I am blown away by the availability of FREE tools for us hobbyists. You can get your free copy of AutoCAD Fusion 360 by clicking on this LINK:

If you have some basic computer skills, know how to measure something with calipers, have a little patience and go check out Lars on YouTube to learn everything there is to know about this software, your in business. It took me about 5 hours of playing around drawing basic stuff along with watching Lars to get to the point that I feel like I could literally draw just about anything at this point.

Subscribe to Lars’ Series on Fusion 360 and you will be a master in no time!

The Part: Gee Bee R2 Firewall

Luckily I still had the pieces of my firewall so I wasn’t really starting from scratch, I just needed to measure what I had and recreate it with a few mods of course! I did want to change a few things about it and make a few 3D printer friendly modifications. I glued as much of the parts left of the firewall together so I could easily take measurements and I was off. The old firewall had a box with 6 giant ball bearings in it to make it CG. I took those out so I could CG her with a bigger battery. The hardest part with the design in Fusion 360 was getting the down and right thrust designed into the thing. A few videos on manipulating planes in 3D space and I had it down. I changed the bolt pattern for the motor as well so that I could tap into my inner Steve Ramonczuk and add a bigger powerplant to make the R2 go faster! Here is the completed design in Fusion 360:

Once you complete your design you have to export it into an STL file so that the 3D printer software can “Slice” it.

I used the PrusaSlicer software designed for my printer. There are others out there but this one was free and pretty much guaranteed to work with my Prusa 3D Printer since it was designed for it. After you drop it into your slicing software and make a few changes, you “Slice” it. Basically the software cuts the model into layers (488 in this case, one for every 0.20mm). A 3D printer cannot print into open space so everywhere there is a large overhang (the flange all the way around the top of this firewall) has to have “Support Material Added”. The support material is a light structure that holds the first few layers of the overhang up until the rest of the model can self support itself. The image below is the Support Structure shown on the model. I did not design the support structure, PrusaSlicer recommended this support and I accepted it.

From this point, you simply export your program for the 3D printer known as G-Code, save it to a SD memory card and go fire up the Printer!!!!

The printer did its thing flawlessly and I pretty much just hit start after loading a new roll of black PLA filament into it. For a more demanding part I would have used a stronger material than PLA but in this case I wasn’t too worried about strength considering this is probably 100x stronger than the horrible firewall the GeeBee came with. This part used about $3.00 of material and was completed in a little over 9 hours. I started it about 9:00 at night and this is what was waiting for me when I got out of bed. You can see the support material around the outside. I was worried about how easy it would be to remove.

The completed part. It looks pretty amazing. it was like Christmas Morning!

The part popped right off the metal flexible magnetic bed and here you can see the support material a little better as I started to peel it away from the part.

I was pretty much able to remove it by hand without tools. The finish is pretty amazing.

And here it is on the front of the GeeBee. Its a perfect fit. Once I get a feel for how strong and durable this material is I know I could lighten up the design. I wasn’t sure what to expect and didn’t know how hard the support material was going to be to remove so I was super conservative on this project. Next time I’ll go much lighter.

Here is the before and after parts. The total weight of the Firewall + the EF1 Motor and the bigger battery weighs roughly the same as the previous setup which had the six 1/2″ steel ball bearings in the nose to help the GeeBee CG.

3D printed part on the left, old horrible balsa and ply stock version on the right.

Conclusion:

This is a fantastic way to create parts for model airplanes or any hobby for that matter. I have avoided getting a 3D printer for several years due to hearing countless horror stories of how time consuming they were to figure out. If you want a no-nonsense 3D printer that just works, get a Prusa! I literally spent about 25 minutes setting it up and hitting start to begin printing this part! My next project is to see how it does with a replacement cowl for the Ryan STA!!!! I’m almost done with its design and here is the model before I put all the vent/airscoops on it etc. If this works, I’m going to design and print an entire airplane next. I’m thinking a GeeBee R1 would be perfect!

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