CNC for WWI Replica Aircraft?

[Joe Perkel]

Gentlemen,

A brief introduction and a question or two if I may. I am building a full size airworthy replica Sopwith Baby seaplane, (a WWI aircraft), that effort can be seen on my website at sopwith-baby.com

I've identified the CNC machine designed by Patrick Hood Daniel, which is featured in both his book and on the website, as a likely candidate for the purposes of my project. This (CNC) would compliment my CAD work quite nicely and add an element of precision and productivity that if in fact viable, would be a boon to me. It is however, outside of my area of expertise and as such, I do have some specific assumptions and questions that if answered by knowledgeable and experienced individuals, could quite possibly save me some grief. Therefore, assumptions and questions are as follows....

1) Assumptions: Machine likely capable of fabricating all wing rib webs, capstrips, compression struts, all wooden fuselage members capable of fitting within the dimensions of the base table, and routing out same to "I" section as specified???

2) Question: Due to a confined shop space, it would be my intention to construct a dedicated CNC deck directly above my CAD station (72" span). Therefore, the viability of this scheme from a flexure and or vibration standpoint comes into question? Comments and or suggestions welcome.

Regards

Joe Perkel
Miami, Florida

[revwarguy]

Hi Joe,

As someone who has some overlap in building airplanes and CNC, I am happy to respond to your project! I am a friend of an individual who restored a real Sopwith Snipe two years ago, so I know what their insides look like. I am also an EAA tech counselor, so I have seen a lot of technique. And, I built my CNC machine last year and am having a ball with it.

I offer the following comments.

1) Not sure how much time you are going to save in the long run using CNC. The effort needed to jump the learning curve (being a CFI and A&P you know all about learning curves) is pretty time consuming that a guy just cutting his ribs by hand doesn't have to expend, even if you have to make 40 of them. If you were going to make 10 of these aircraft, then the payoff is lots better. THAT being said, it is a hoot to make parts with the CNC, so if you're going to do it, do it for the right reason - its just fun to CNC those things, but I wouldn't be disappointed when it turns out to take a while. Plus, when you're done with the plane, in between hops around the patch or when the weather is down, you've got a machine for making lots of other things!

2) Don't know much about the CNC machine you mentioned, but you're going to need both a router table for cutting wood parts (ribs, spars, runners, longerons, etc. as well as a CNC torch (or waterjet, laser, etc) to cut all the steel fittings. Kind of hard for them to be the same machine, but it could be done. You could always use the controllers, steppers, linear travel mechanisms for both tables. You would need a torch and a torch controller as well as a router. You will save yourself some $$$ by having the DXF for the fittings to give to someone with a waterjet, though. Let him own the expensive machine, but still take advantage of your CAD. You could do the same with someone who has a CNC router table, too, but that's not nearly as much fun :^)

3) Probably not practical for the fuselage frame - notching and welding the chromolly the "traditional" way with TIG is still probably the way to go. Don't think its practical to CNC the fabric cut, either, but you might surprise me.

4) As a fan and a wannabe aviation historian, I think you've picked a really unique project. Good luck and I'll keep your site bookmarked!

[Joe Perkel]

Revwarguy, Thank you for taking a moment to respond.

Your friend must know Nick Caudwell in Melbourne AU, he is about 2/3 complete on his awe inspiring Snipe.

I would say that my interest here is partly due to an interest in using the Baby as a proof of concept aircraft in producing one-off "kits" for other Sopwith versions. This is something I am considering as an enjoyable sideline hobby business in retirement, and is not the original plan, but something that is morphing as I go along. Productivity enhancement, would go a long way in making that viable.

The image above, is your typical Sopwith fuselage without the fittings. Note the routing on the vertical and horizontal members. These also taper down toward each end, making these parts all very labor intensive. To my view, these home built CNC routers should be able to produce these unless I am mistaken? These along with the wing internals, fuselage formers, seat bearers, panel, etc, again if doable on these machines, would make this a viable option down the line.

I like the thought of complimenting my already acquired CAD skills with this rather neat "in house" capability, and will not mind investing the next year or so to make it happen. What I need from folks like you, is to identify any potential fatal flaws in the plan. For example, consider the image below....

http://i240.photobucket.com/albums/f...FS/CNCDeck.jpg

My intention is to construct a CNC deck above this CAD station. I will no doubt deal with the upper shelf supports for clearance, but I am wondering about vibration and flexure here, I'm thinking (3) 2 X 6 joists supporting a 3/4" ply deck should do the job?

Much thanks!

Joe

[Benonymous]

While I'd never dissuade someone from building their own machine, for this project, wouldn't it be more practical to find someone with a machine and work with them? I admit that having the machine in your shop and be able to run off parts as needed is unbeatable but building the machine and learning all of the software etc (not to mention troubleshooting) is going to delay your main project seriously.

[Joe Perkel]

Originally Posted by Benonymous While I'd never dissuade someone from building their own machine, for this project, wouldn't it be more practical to find someone with a machine and work with them? I admit that having the machine in your shop and be able to run off parts as needed is unbeatable but building the machine and learning all of the software etc (not to mention troubleshooting) is going to delay your main project seriously.

Benonymous,

For the reasons specified in my reply to revwarguy, I think it worthwhile to give this at least a very close look.

I'm in no hurry. I spent the last two years whittling away at CAD work late at night while my house was being built. (long story, bad contractor).

It's only now that I started the wing ribs when my attention was brought to this possibility. Assembly time frame for this aircraft is just under 10 years. Whatever I get done in that time will in fact be a head start. I'm prepared to dedicate the next year or so to this, if I determine it to be viable.

Thanks!

Joe

[Benonymous]

Nice website Joe and a superb project. There is no doubt the job will proceed much more quickly with a CNC than without one! You might actually consider making a reasonably large scale router using rack and pinion drive. That would be very handy :-) Too bad you won't be able to whiz up a nice radial engine on it!

[revwarguy]

Hi Joe,

My friend and I are in St. Louis, not AU - his name is Glenn Peck. I am sorry, I've got other things on my mind, working on a book of this era, the Snipe was a different project - I was referring to a Pup restoration, not a Snipe. The LeRhone driven Pup here was completed about 3 years ago.

http://www.peckaeroplanerestoration.com/Sopwith/SP.htm

If I can offer any help by taking pictures of its construction details, etc. just let me know. This same guy restored a DH-4 (I got to work on that!), a JN-4 Canuck, and right now he is doing a J-1 Hisso that was used in filming The Great Waldo Pepper.

As for putting a CNC above your computer loft, I am not sure that will work out very well. You can certainly build small machines, but you need a larger one to do ribs, etc. than I see room for in your picture.

One of the primary requirements of a CNC table is rigidity - it must be very stout and solid. In order to get any speed out of it, you need very strong materials to withstand the constant changing of momentum of the router, which makes the gantry and carriages large, so you have a lot of mass flying around, so the table (whether its a router or a torch) must be very solid. Most purists look down on wood construction for the table as not good enough, but many of us do just fine with it, depending on what we're cutting.

The other thing is that a CNC generates lots of dust and particles that go everywhere. Even with a strong fan blowing out that window, there will soon be a layer of dust everywhere in your loft.

I really don't want to sound like Mr. Negative here, but putting a CNC machine where you've placed it to make airplane parts doesn't seem like you'd be very happy with it there.

My machine can certainly do the pocketing operations for those supports and make the wing ribs. Here is the size of mine:

www.liming.org/cnc

It has a cutting area of 26 by 48 inches.

Hope this helps.

[ger21]

My intention is to construct a CNC deck above this CAD station.

That would be a serious PITA!!. Very difficult loading and unloading, and unless it's completely sealed, you'll be looking at dust everywhere.

[Joe Perkel]

Very constructive comments gentlemen, thank you! These opinions seem to be forming a consensus regarding several issues, and if one is not well versed in a particular subject, mining for consensus of opinions offered is the order of the day. Now I will list these issues with my own take on potential solutions or evaluation for each, please evaluate and comment on my solutions as to viability or error in judgment as appropriate.

Issue: Stability of MDF for the proposed application. Superiority of aluminum frame, and moving table vs moving gantry.

Evaluation: Appears adequate for lightweight nature of application, I'm basing this on performance of the machine carving an intricate sign as displayed in YouTube- CnC Utube BullsheadSign, and a field report from a trusted source. Lack of knowledge base requires me to follow through with a proven design with significant support such as the textbook, and website tutorials provided on buildyourowncnc.com Same lack of knowledge base precludes me from venturing off from a pre-determined plan-set in an attempt to improve the design in any manner.


Issue: Proposed location of machine on overhead deck.

Evaluation: Heavy nature of machine rules out portability. Confined shop space in my city location offers no other solution, otherwise it will be a decade before I can retire to the rural location with adequate space. Access would be via step stool, light nature of proposed parts render loading unloading as fairly simple. Location rules out moving table in favor of moving gantry design, must allow for adequate vertical clearance.

Issue: Dust Control

Evaluation: MDF machine in the video uses an attached dust collector, this would be a likely addition. Fan unit would need to be wall or ceiling mounted nearby. I already cover the CAD station for woodwork and wear an appropriate mask. Suggestion of enclosing the machine with lexan panels front and back, is seriously considered.


By now my M.O. regarding unfamiliar subject matter should be apparent. I am open to suggestion, look for consensus and or corroborating facts / evidence, then apply it all as best I can to make as informed a decision as possible.

Thank you all for your input!

Joe