CNC Pietenpol Ribs & More

[Cunni5ac]

Hello Everyone,

I am considering building a Pietenpol and I have read through a decent amount of material related to the build.

I was wondering, has anyone tried to utilize a CNC machine to cut out the wing ribs and other items requiring more than one nearly identical parts?

I would think this would help cut down build time considerably especially at scale (multiple guys working on a Piet at once). I have not looked at how the plans are but I have seen many use a stencil for the ribs which should be able to be easily digitized.

Would /could the wing rib be as strong or stronger?

Any insights would be appreciated.

Thanks,
Charles

[rwanttaja]

I don't know if it's been done, but the same sort of thing has been proposed for the Fly Baby. Fly Baby wing ribs are 1/8" plywood and in three sections. The wing is untapered (until you get near the tip) so there are twenty identical copies of the center section and leading edge (trailing edge varies due to the ailerons).
http://www.bowersflybaby.com/tech/template_header.jpg
However, even when hand-cut, few builders make them one at a time. Many make a template out of thicker material as a template and use a router. Others stack multiple plywood sheets and cut them all at once with a bandsaw.

I don't know how much it would cost to get this CNC machined instead, but it's easy enough to do it yourself and save that money. Most people building Piets or Fly Babies are looking to do it cheaper. Jake S. is an exception (Hi, Jake!).

But if you want to do it, there's no reason NOT to do it. The templates exist for Fly Babies, and I'm sure they're out there for Piets, too.

As to stronger, if you use the same material, it'll be the same strength. Ribs are rarely the weak point when it comes to wing strength, so a stronger rib buys you nothing.

Ron Wanttaja

[Cunni5ac]

Thanks Ron,

The idea would be to decrease build time for repetitive tasks or multiple items with only a marginal increase in price. I have seen many home built CNC Mills for around $350 - $500 dollars (Check out the MaslowCNC machine for an example). So I was thinking if I could build a rig and convert the files, one could rapidly (relatively) spit out a slew of these with greater precision.

[Kyle Boatright]

Thanks Ron,

The idea would be to decrease build time for repetitive tasks or multiple items with only a marginal increase in price. I have seen many home built CNC Mills for around $350 - $500 dollars (Check out the MaslowCNC machine for an example). So I was thinking if I could build a rig and convert the files, one could rapidly (relatively) spit out a slew of these with greater precision.

The issue is that the router can make the ribs to very precise standards in a few hours. I'm not sure there are many other pieces in the FB where there are enough to justify pseudo-mass production.

The real time saver would be to digitize the plans for the metal parts and have those cut for you (or CNC 'em yourself if you have the ability). Hacking stuff out using a bandsaw is really slow...

[rwanttaja]

Thanks Ron,

The idea would be to decrease build time for repetitive tasks or multiple items with only a marginal increase in price. I have seen many home built CNC Mills for around $350 - $500 dollars (Check out the MaslowCNC machine for an example). So I was thinking if I could build a rig and convert the files, one could rapidly (relatively) spit out a slew of these with greater precision.
In terms of the percentage of the build time for a plans-built plane like the Piet, the time required to build the ribs is in the noise. If several people are building the same type of airplane, it makes more sense.

However, we build the airplanes for "education and recreation." So if it's something you WANT to do for the fun of it, or to learn how, have at it! I've made several decisions on my airplane that don't make sense, from the time expenditure or other logical reasons, but just because I wanted to.

Ron Wanttaja

[DaleB]

Charles, I know where you're coming from! I'll need to cut out a pile of plywood nose ribs. I already HAVE a CNC router, it would be child's play to cut them on that - if only I had the file. I have one, actually, but it's for a Shopbot (I think) in some oddball format that I haven't been able to translate into anything useful.

I know it would be less tedious to cut them on the CNC machine, and I know they'd all be exactly the same. Plus, I like to play with the machine.

[Cunni5ac]

Glad to head it Dale! I feel that with the significantly low prices of CNC machines, relatively low cost of computer software in 2018, why can't / haven't there been an effort to convert these plan's only aircraft to digital file formats that could be cut out on a CNC machine and assembled? I saw a good discussion going some years back discussing this concept and it took a turn towards creating an open source aircraft (not sure what came of that).

Even if 1/4 - 1/3 of the time could be removed from a 1000hr build time it would be well worth it for the community. I would think EAA as an organization would even want to lead the charge on this concept increasing, consistency, decreasing cost and build time. It seems like it would lead to a larger pool of aircraft owners and increased safety.

Thoughts?



Charles, I know where you're coming from! I'll need to cut out a pile of plywood nose ribs. I already HAVE a CNC router, it would be child's play to cut them on that - if only I had the file. I have one, actually, but it's for a Shopbot (I think) in some oddball format that I haven't been able to translate into anything useful.

I know it would be less tedious to cut them on the CNC machine, and I know they'd all be exactly the same. Plus, I like to play with the machine.

[Sam Buchanan]

Glad to head it Dale! I feel that with the significantly low prices of CNC machines, relatively low cost of computer software in 2018, why can't / haven't there been an effort to convert these plan's only aircraft to digital file formats that could be cut out on a CNC machine and assembled? I saw a good discussion going some years back discussing this concept and it took a turn towards creating an open source aircraft (not sure what came of that).

Even if 1/4 - 1/3 of the time could be removed from a 1000hr build time it would be well worth it for the community. I would think EAA as an organization would even want to lead the charge on this concept increasing, consistency, decreasing cost and build time. It seems like it would lead to a larger pool of aircraft owners and increased safety.

Thoughts?

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.

[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 (https://www.dospace.org/)" 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.

6970

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

[Fritz]

...I was wondering, has anyone tried to utilize a CNC machine to cut out the wing ribs and other items requiring more than one nearly identical parts?

Hi Charles,

...I only mention this because you asked about CNC ribs for a Pietenpol specifically.

I made a set of CNC'd plywood replacement ribs for an old Pietenpol that was damaged in a landing accident.

If it was a whole new "per the plans" wing it would have been very quick and simple to make the CAD and CAM files and cut the ribs (I've done several all CNC'd "per the plans" rib sets), but for this airplane I had to scan one of the old ribs and go from there. There's a short thread on the process here: http://www.homebuiltairplanes.com/forums/showthread.php?t=23156

IMHO you can build light, strong wings ...very quickly using a CNC machine. http://www.homebuiltairplanes.com/forums/showthread.php?t=20101

[Cunni5ac]

Hi Charles,

...I only mention this because you asked about CNC ribs for a Pietenpol specifically.

I made a set of CNC'd plywood replacement ribs for an old Pietenpol that was damaged in a landing accident.

If it was a whole new "per the plans" wing it would have been very quick and simple to make the CAD and CAM files and cut the ribs (I've done several all CNC'd "per the plans" rib sets), but for this airplane I had to scan one of the old ribs and go from there. There's a short thread on the process here: http://www.homebuiltairplanes.com/forums/showthread.php?t=23156

IMHO you can build light, strong wings ...very quickly using a CNC machine. http://www.homebuiltairplanes.com/forums/showthread.php?t=20101

Hi Fritz,

Thanks for sending these links. You and mmarien look like you have successfully utilized this process for building aircraft components. Do you think it would be possible to digitize the Pietenpol's plans and have the majority of the aircraft cut out?

Yes, I know for 1 builder it may or may not be a good use of time. I am looking at the long run. My thought is if a collection of individuals get together to fund this project, they could take a 1000hr project down to a 400-500hour project that are looking to get into homebuilding an aircraft.

I could see this being a situation where the project is crowd funded and the plans are given to a small group of people that can determine what parts of the aircraft can be CNC'd and what parts will need to be built traditionally, digitize the CNC eligible parts into workable files.

[SaltedTailfeathers]

I'm new to this.

One of the things I expected to see, (maybe I haven't looked in the right place yet) but haven't, is rental tooling.

If someone is building a tail feather for a Cub there is a fair bit of layout and lofting (boat building term I don't know if it applies) before the metal gets cut and welded together. Building the tools to build the parts is a significant amount of the work. The hydroform process for making ribs is another case.

For a few hundred$ you can ship a pallet box of tooling almost anywhere. I kind of hoped to find that there would be a rotation among the chapters. (Chapter 1, would build the dies and hydroform boxes for ribs and control surfaces. Chapter 2. Tail jigs. Chapter 3, engine mount jigs..........)

I understand that would require a significant number of people to want to build the same aircraft and have the faith to accept the next guys tool construction of a design that probably only a few folks could agree to.

At the least builders who have completed stages and tools could have an exchange?

[Sam Buchanan]

I understand that would require a significant number of people to want to build the same aircraft and have the faith to accept the next guys tool construction of a design that probably only a few folks could agree to.

And you are still wondering why the tool rental program has never been a success? :)

A couple of thoughts:

1) Custom-built aircraft take shape in an extremely fragmented manner--some build a set of ribs in two weeks, others are still working on them twelve years later...

2) Die-hard builders want to own their tools.....collecting a shop-full of airplaney tools is part of the fun!