Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Victor Bravo, Feb 19, 2019.
My recent question on that subject (structure) was actually about the overall design engineering and load analysis... is that something you are doing yourself, or is it something that the local EAA guys are doing, or is it being done within SolidWorks ?
I am not by any means making a negative comment or firing off a 'pointed question', because I sincerely don't know anything about the actual capabilities of any of the three possibilities I mentioned. And for darn sure I do not have those analysis/structural capabilities myself.
But it is certainly a relevant question, because this particular aircraft sure looks like it will actually make the transition from an iteresting idea, to inspiring digital artwork, to an actual physical reality.
All of the above and a lot more. A lot of the dry detail work is right out of the step by step formulas in the Evans Lightplane Designers Handbook 2nd edition, ... and a house full of other aircraft design books and books on structures and material properties collected and read over 50 years of screwing with airplanes. Not to mention spending a lifetime studying all the plans I could find for this sort of airplane. And yes, this airplane (and a thousand others) has been discussed, in depth, with a chapter full of NASA and WSMR engineers.
There's nothing new or novel about this design except being a scratch built optimized for CNC and having downloadable G-Code instead of paper plans.
Of course the smart thing for anyone interested in a tab and slot, CNC runabout would be to wait until I build one and put some time on it. ...**** few prototypess are ever ready for prime time.
Are those printed plastic guides and bearings grease restisting
What would you recommend, to disassemble the parts once a year and grease those bearings or install a small greasenipple and squeeze out the dirt and whip it off?
Once again the blue foam ribs for the wings are not my first choice, but since you've convinced me that foam ribs with thin wood caps are sufficient... I had an idea for how scratchbuilders might do these ribs more easily using common materials.
Using the 3 inch thick common blue or pink styrofoam insulation boards (Dow Styrofoam or Owens Corning Foamular), a plywood wing rib template can be pinned to the board.
Cut out the rib shape with a common band saw and sand it to the template shape. Now you have a 3 inch thick foam rib.
Now run the rib through a table saw set to cut a 3/4 or one inch wide slice. You will get 3 or 4 wing ribs out of each blank. This is definitely not any new rocket science but it does eliminate having to slice the foam board into uniform thin slices using a hot wire saw.
The idea here is that the smaller "height" of the rib-sized blank (instead of the whole board) will allow the blank to be put through a table saw (or re-sawing band saw) which is probably more common to find in a wood shop than a hot wire saw.
Still not entirely in favor of the foam ribs, but if they're truly protected from UV and covering chemicals then they may well be a viable choice for a quicka nd inexpensive airplane wing.
Ive found after a quick search a friend of mine that could print those small parts.
I checked the web quickly and found at least one supplier that can provide a printable material that is selflubricating, thus no external greasing required.
As the aim of this plane to be cnc feasible, so also those small parts that are time consuming to produce.
I’ve no idea how those parts can be mechanically loaded without breaking, but I believe this worthwhile to think about it.
But there are parts, I’ll keep them in steel or aluminum alloy, like the wheels and brake brackets aso...
This is my question also. After seeing our EAA chapter president bring in several small printed plastic parts, they definitely did not appear to have enough stiffness to make parts that would support any loads, or have long-term wear tolerance. We all agreed that these parts would make great rapid prototypes for visualization, test-fitting, etc. Also good for a male mold "buck" to pull a composite mold off of. Probably really good for making sand casting molds. But not for anything that takes any significant load.
Has there been a change in the material available for printing that yields a stiffer and longer lasting part?
Re: 3D printed rudder bushings...
Those are still in the idea stage so don't get spooled up over them. The bearing (the red part) would be printed or cut out of Nylon or Delrin. The whole assembly might get printed out of Delrin. There's still a ways to go with the idea but I suspect, even as they are now, they'll far out last the airplane. And if they start to show some wear after a few years, spend .50 cents and print another set.
Re: foam ribs...
I'd say they were more than sufficient, I'd say they were better for this application. As far as scratch building them. Just get a few sheets of 3/4 or 1" (TBD) XPS foam, cut it into 8x50 (?'ish) chunks (score it with a pocket knife and snap it apart). Make one rib template out of 1/2" MDF with a few short nails poking through it. Stab/poke the template onto a rib blank and zip around it with a small hand router and a flush cutting bit.
...here we go
Your basing a huge assumption on **** little information. What kind of material are you talking about? What kind, and how much infill? What are the actual bearing surfaces? What are the loads? What's the duty cycle? etc...
Uninformed, snap assumptions just chap my knickers
Speaking only for myself, my opinion was based on holding and flexing and touching the parts myself. Not a snap assumption, a personal experience. The parts I saw had very little stiffness compared to other plastic parts I've seen (nylon, glass-nylon, styrene, PVC), and plain old common sense told me that you would not want to use them for anything that takes much load or requires much stiffness.
That's why I asked whether there had been some advance or new options in print-able plastic raw material, because I didn't want to make an assumption that the plastic I saw was representative of the plastic being talked about in this thread.
But it does seem that my observations, questions, and thought process have somehow become a frequent mild abrasive, and having this project become reality is a very worthwhile goal. Far more important to me than standing my ground on whether my opinion/experience is uninformed, or chapping someone's hide. I'll watch from the bleachers.
There is a lot to be said for looking at well proven designs (Minimax, for example) and following suit.
A Volksplane tubular spar type rudder could pose another problem for material sources outside of the US, 6061t6 tubing is not generally extruded in Australia, almost all tubing is only architectural grade. The load concentration at the base of an all flying rudder is not good for a narrow fuselarge boom, a conventional wooden fin with a conventionally hinged rudder is simpler to build, probably lighter and far easier to attach to the boom using the fin spar as a sternpost.
For miniature versions of any project, you can just save the CAD file in inches, and then set the CNC software for millimeters. Ask me how I know...
1/25.4th scale is very popular.
IF I were to build this fun looking little airplane. I have enough VW engine parts to build a 1/2 VW engine and a few months ago someone gave me 40-- 4'x8' sheets of the foam for the ribs. Still think I would need LARGE, HIGH arm rests for the seat.
I came across this Australian supplier of Aerospace Aluminium Extrusions as well as other aluminium materials used in recreational aviation.
I have never heard of them before yesterday.
I'll be ringing them tomorrow and check their pricing.
I have used Calm before. They seem to be able to supply just about anything you need. Including all sorts of 6061-T6 stuff.
Slicing out ribs from a thick blank might be tough with any reasonable table saw. What's the propose thickness of the wing? I'm thinking it might be 6 inches or more, which is certainly more than I can do with my table saw. OTOH, it would be easy to set up a hot wire to do this. No infernal, clinging dust that way either.
An ‘all flying rudder’ like the VP is an unusual solution which I have only seen on the VP, this solution precludes the use of bracing wires to stiffen the fin/elevator/fuselage junction, it is heavier and more complex structurally than a simple fin with hinged rudder and is more difficult to build requiring large bearings and an anti-servo tab for control feedback.
This area of the design should be scrutinised and debated. A tail group more like the Minimax would be simpler to build and stiffer.
I’m wondering what the material costs will be for the Ranger Firewall aft and firewall fwd?
Regarding the Firewall fwd, what are the engine options we are looking for?
For sure a B/S is going to be the choice #1, but which one?
Other engines might be of interest too, 1/2vw was mentioned, what about the Harbour Freight, GK-Engines, Polini Thor, Simonini Victor, Hirth, Moster, Wankel, Gaoking, Loncin, Kohler, Kawasaki, Honda, ....
What must be done to mak’em fit our bird of desire?
Separate names with a comma.