CNC Pietenpol Ribs & More

[Cunni5ac]

You asked for thoughts......

Compared to the entire custom-built aircraft community, there is an insignificant number of wood aircraft such as the Piet and FlyBaby being built. I am assisting a friend who is building a FlyBaby and he is only aware of one other plane currently under construction. There would be a few more Piets...but very few.

I can't think of any other wood components of the FlyBaby other than ribs that would lend themselves to quantity reproduction. As Ron stated, rib construction time doesn't even register compared to total build time. These are custom-built planes in the strictest sense which means components are built to fit each other, not necessarily to fit the plans. Tolerances can accumulate, and by the time fabrication reached the point of needing prefab parts, they may not fit what has been previously constructed. I realize this may be difficult to understand if one has never built one of these wood aircraft and doesn't appreciate the uniqueness of each particular airframe.

In regard to total time savings, as a general rule the airframe comprises about 1/2 of total build time. In other words, when you have something that looks like the bones of an aircraft, you are only half way to a flying aircraft. This means saving a little time on prefab ribs is meaningless in total build time.

However....if you want to take the time to set up production of ribs and enjoy that process, then do it for the educational and recreational benefit. But I doubt the CNC-capable builder will save any time, precision or gain any safety over the builder who is handy with a bandsaw.

The only wood aircraft I've seen that relied heavily on CNC process was a wood version of the TEAM Airbike but I don't know if that kit ever came to market. It was a totally different design from the Piet or Flybaby consisting primarily of plywood for the entire airframe. While I was building and flying a Legal Eagle a builder geared up for milling the nose ribs, but again there was no saving of time, just the fun of knowing it could be done.

Thanks Sam,

I think you are right that since I have never built an aircraft, there are some elements of the build I am envisioning that likely doesn't match up with reality.

[rv7charlie]

If you can come up with the files to cut them, check with your local college, technical college, or community college. You might find that you have access to their CNC equipment for free, or nearly free. The instructor might even give the project to a student to generate the cutting file for you. My local community college has a nearly new 'fab lab' that already has a half dozen Dremel 3d printers, a MarkForged *carbon filament* 3d printer, a large format (3' x 3' x 20") 3d printer, a 30 watt laser (unfortunately the bed is too small for wing ribs), etc etc, and they are expanding rapidly. On the way is a blue/white light scanner (you just walk around the object you want to scan), and a 3d printer for concrete. I'm a senior citizen, so I can audit courses for free, and the fab lab is open to the public in general, for just the cost of materials.

All this, and I live in one of those backwater states that's behind the rest of the country. You might be shocked at what's available to you in your area.

Charlie

[Frank Giger]

I have found that the "backwater states" are far more amiable to access, as they are seemingly less afraid of litigation.

I put the whole idea of CNCing the ribs as just part of the "Education" you'll experience in building your aircraft. So go for it.

[DaleB]

There's a "Do Space" here in town. Sort of a public maker space, built in a former Borders location. 3D printers, laser cutters, vinyl cutters, all kinds of neat toys. Free for most of it, you pay for materials. One of our chapter members used their laser cutter to cut some acrylic panel mockups to test control and instrument placement, etc. I don't see they they have a CNC machine, but laser cut ribs would work.

[mmarien]

I used a CNC router for a lot of the wood parts for my Hatz Classic. The rib nose and tail pieces were a minor part of what I used it for. For a while it was my favorite tool. I also had all the metal parts laser or water jet cut. It saved hundreds of hours of work. As mentioned, the problem for most people would be creating the gcode files. I have a background of using AutoCAD for work so it wasn't a problem. I redrafted the parts I needed and bought some software to translate the AutoCAD to gcode.

The recent article about the Skyote in SportAviation is a good example of using modern methods to build classic airplanes. The idea of having the gcode for the CNC cutting in public domain is also a good one. Whether the CNC work is done in house or hired out is mute. For the most part my metal pieces cost a few dollars each to have laser or water jet cut. My CNC router cost $2G but is limited to wood and the max size is 21"x15". Cutting a full rib was out of the question. But there was no end of small pieces that I could CNC cut much better than I could by hand. The wing walk tail piece was the most complicated part I CNC cut.



My blog: http://myhatz.blogspot.ca/