Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Victor Bravo, Feb 19, 2019.
Now that is some good advice right there.
I take this subject to ask you a question
you use CNC cutting so no problem for glues
What about when using laser cutting that burns wood
is this cutting technique allowed in aeronautical construction?
If your landing is harsh enough to tear the gear off, cancel the touch-and-go. You’re already having a bad enough day.
The cut edges on the ply parts don't really come into play (structurally) on this kind of construction. It's usually gluing a stick or a block to the surface of the ply, like gluing a longeron to the side skins. I don't think there would be a problem doing it with a laser, maybe just sand the burnt edges very lightly to knock any charred stuff off.
I've never heard of any rule/regulation/guidance that would prevent someone from using a laser to cutout parts.
For thin 2D parts a laser would sure make life easier. You don't need to worry about holding your parts down and a laser won't fling wing ribs across the room like a spindle can :gig:
Making *cutting files from a set of plans is pretty trivial. Anyone with a CNC machine should be able to create those on the fly. ...having the DXF files to make the cutting files would be a real time saver though.
*a set of cutting files for one machine won't necessarily work on a different machine without some tweaking (table size, machine settings, post processor, etc.)
Since everything would be open source (plans, DXF, and g code) I'd imagine there would be a library of cutting files for different machines.
Like we talked about on the VP21 thread: the ideal situation would be you take your thumb drive and material down to your local CNC guy and he cuts you out a kit.
For someone willing to build or buy a hobby cnc router what size machine would be required? Looks like you split the fuselage sheeting into two large pieces and curious what size blank would be required to cut these? Also material thickness?
Would 4' x 6' work?
Wow that's very nice of you, but there should really be some kind of benefit for you financially for your time and effort. I know this is not a business for you, and you are not looking for wealth out of it, but... Maybe a donation to your church or the EAA chapter? I know erkki will keep you in Swiss chocolate for life !
The biggest piece is 83" long and the side skins are 1/8". It could fit on a 4'x4' machine if it was split it into two pieces. It would require another doubler like the split between the top and bottom side skins. Another way to do it on a 4'x4' (or a 4'x6') machine would be to cut one end of the sheet, move the sheet 4' and cut the other end. That works but the table can't have rails sticking up on the ends (most don't) and you need to be able to index the sheet very accurately when you move it. The next longest parts are the spar webs at about 46".
If someone was going to build a CNC machine for this kind of work it could almost be 'disposable'. It would only have to cut ply and softwood. One of the DIY plans built machines with a MDF frame, cheap ebay electronics and a router would work. I think Rienk had a thread about that a while back.
I'm not being all that nice :gig: I'm just going to post "Design Study" files for an airplane that I want to build. If someone else wants to build one it's on them (like building a Pietenpol from the Flying and Gliding Manuals). There wouldn't be a build manual so it wouldn't be for people who need to have someone hold their hand on every little detail.
Yes Reink mentioned a CNC machine that had the long axis on a Rack & Pinion gear that fed full sheets of plywood back and forth using conveyor supports with rollers. Its a simple solution to space constraints and a cnc router. Downside is you need to store a 4' x 8' shuttle and the conveyors. I designed a 4' x 6' machine years ago but never built it. Now it just does not make sense with the Workbee and such being so cheap. For low tech accuracy on the thin sheets any belt driven cnc machine would work just fine. For a bit over 2K a 1200mm x 1800mm laser system could be made using parts from www.lightobject.com and its non contact cutting so it would be even more accurate. However the router has more flexibility in use for other needs...
Since I plan to get a router eventually, maybe I can set myself up to make parts for the group... Semi Sub kits of sorts...
The choice of Ranger got my attention. Lots of folks like the name. I wonder if it is a Tab Ranger or a Scroll Ranger. BIG difference you know.
If Fritz had been an Army grunt instead of a Marine grunt, then that might have meant something different. But I think he was making references to old model airplanes instead of military rank/experience
Not a reference to Aragorn? ;-)
What is the worktable size required to build the Ranger?!
I'm digging the direction this is going and if the design goes open source I'm pretty sure I'd cut out the parts for at least the fuselage.
I'm into the idea of something simple from wood. But I am also a fan of aluminums, and so I'd be curious what a 6061 sheet version of this fuselage design might look like. Some tweaks are inevitable, but, the overall concept seems like it probably doesn't change much. Use angle in the corners vs sticks, maybe a few funky gussets, but in general I think it could be a good option for those who prefer the rivet.
I was thinking the same with VB and seeing what I could come up with in solidworks married to a Skylite wing. That way I could start the wings now since I plan to build a set anyhow for a Skylite and if I can make the same wing work for both than great. Not wanting to step on Fritz's toes however but I could see myself designing something quite similar in Aluminum. If it turns out heavier worse case is I bump up the tubing wall on the main tubes. Or run the numbers on the stock wing to see if they can take the extra weight as is..
The Ranger is, essentially, the front half of the CE with a tail boom in the back. And the original CE was aluminum. I think this pod and boom layout would work great in aluminum. The fuselage spar mounts would take a little rework to accept a Skylite wing but that would be pretty simple.
some of the skins are removed to show the innards
...just for fun, an exploded stereo image (for those who can get their eyes merge the images)
I worked on the wing fold models for the Ranger for a few hours before I realized that what I was drawing wasn't going to work :ermm: ...oh well. there's lots of ways to do it. ...maybe VB's "rope trick" wing fold idea (at least I think it was VB's)
I get a headache when I try that, and keep bumping into things when I am done. Or is it the glass of wine I just had?
Wow Fritz that looks great. How on earth can you model parts so fast. I do this for a living and know how much work that takes. Impressive as usual.
+1, wow ! Really interesting.
There are what look like four angle rails in the lower fuselage on the rendering, with oblong and rectangular holes in them. Are these bent sheet metal angles, or extruded angles with holes cut in them? Looking closely at the rendering, one or more of these rails appears to have a fairly thick wall, maybe 3/16" or so judging by the edge of one of the holes. What was the reason for using a fairly labor intensive and complex shaped part here?
The rope trick instead of a U-joint for wing folding was indeed something I had suggested. Seems like a poster child for the KISS principle on small minimalist airplanes like this.
FWIW, my take on this kind of wing fold mechanism is based on many years of experience with trailering sailplanes and then one UL powerplane recently. My version of this Ranger concept (or, more properly, a humble suggestion to the Man) is that a one-piece horizontal stabilizer (stabilator) be mounted on top of the tailboom just forward of the vertical fin, similar to the way the horizontal tails are mounted on the small R/C hand launch and tip launch gliders. The pivot bolt or pin can be a thumbscrew or a shear pin (clevis pin) that slides out of the pivot point. The elevator pushrod connection is one of the "L'Hotelier" fittings used extensively on sailplanes (a miniature ball trailer hitch).
So when you want to put the Ranger away after flight, you:
1) disconnect the elevator fitting (one hand, no loose fasteners)
2) remove the Cotter Pin or Safety Pin from the pivot pin (one hand, one loose part)
3) slide out the pivot pin and lift the tailboom (two hands, one person)
4) reassemble the pivot pin and safety pin into the pivot so you do not have loose parts
THEN, when you remove the pins from the main wing root, the wing panels can be handled by one person at the tip, and the small loop of rope at the root:
1) rotate wing panel nose down
2) walk the wingtip around until the lower surface is against the vertical fin
3) hang the wing leading edge on the tailboom, sitting on a simple sawn plywood yoke fixture
I can verify from many many, many assembly/disassembly sequences on the sailplanes that removing the all-flying stabilator this way takes approximately 30 seconds (Schempp-Hirth Mini-Numbus sailplane) The glider used an over-center capture hook instead of a removable pivot pin, so add another 60-90 seconds for the "loose parts" safety pin and pivot pin. My other sailplanes used the "L'Hotelier Fitting" for separate elevator instead of stabilizer (AS-W20, Ventus) and this took less than 10 seconds.
So I am very comfortable saying that removing a one piece stabilizer can be done in less than two or three minutes, and by getting the H-stab out of the way of the main wing folding, a lot of (time, fabrication, engineering, complexity, money) can be saved on the main wing folding scheme. I do believe this represents adding one small amount of complexity at the tail which eliminates several moderate amounts of complexity at the main wing. Importantly, the one-piece stabilator allows the main wings to fit against the fin without having cable brace wire or struts between the tail surfaces.
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