How many of you guys fly RC Planes too?

Ah, you got through Nickel! How did you find it. Maddening and enlightening?

I think a small model would be able to show gross characteristics, even for something as esoteric as zero-net-moment flaps. Fine-detail characteristics, though, probably would go missing at that level of scale. Still, I've played with a lot of small free-flight gliders of the sort Nickel is discussing, myself, and yeah, you can learn a lot that way that you'd struggle to understand, just reading in a textbook. Makes the concepts in the book much more concrete and easy to comprehend.

My dad had piles of flat foam sheeting (only about 1/16" thick) that came between the floor tiles when he built his house. The stuff was easily cut with scissors, but rigid enough to hold a firm shape in-flight, and was closed-cell on the flat surfaces, for a nice smooth skin. Perfect for this sort of use. Some tape and soda straws, and a couple of paper-clips to position the CG, and you had airplanes. Or just the foam and some tape for a flying-wing.

I went through all of it, making gliders of various configurations and trying them out. Boy, did that ever clear up some things I'd been reading! And it was a lot of fun.

I found getting Nickel maddening. Took more than four months (and two changes of address) for the print-on-demand house to actually get it to me... but it was still cheaper and easier than finding it used.

I found it... limited but interesting. The math (thanks for the errata!) is nice and all, but AVL was already sufficient for that (and for things like winglets, likely more accurate than the rule-of-thumb equations). The focus on "optimal" flying wings makes a whole lot of sense, and the SB-13 is pretty close to what I'm doing (although I had already incorporated both of his recommended changes, more sweep and smaller winglets, to the basic SB-13 design); but it's a bit light on consideration of deliberately sub-optimal flying wings, for those of us with power who care more about handling.

The chapter on hang gliders is somewhat out of place, especially without a companion chapter on paragliders (although I'm of course biased here). Many times throughout the book he mentions that he's ignoring vertical CG position / pendulum stability, yet I'm discovering in my own research that this is really not at all a negligible effect for even an SB-13 style glider; and, having flown hang gliders and paragliders, I know from experience it's not at all negligible there.

The vertical CG discussion only real omission that I feel he could have addressed (since paragliders grew up after the book was written), and it's not as if he could have had more case studies. It would have been nice to have a Raymer-style walk-through of, say, designing a flying wing RC glider as an appendix, to pull together the math and establish a process (and there's really quite a bit of process implied in the book). It would also be nice, and probably quite possibly, to put together an appendix with critical stats (span, power loading, planform, etc) for all "successful" flying wings (including the military ones), just to get that complete and get it in one place; there's an awful lot of hopping back and forth between diagrams.

After reading Riblett and similar recently, though, I'd definitely give Nickel two relative thumbs up.

Your impressions largely match my own. The hang-glider stuff was a sop to Mr. Wohlfart, who is an avid hang-glider enthusiast.

The vertical CG material is lacking, yes. The larger omission for me was really anything at all about dynamic stability issues - other than a brief discussion of short-period motions (his "pecking" treatise) that is not developed numerically, he avoids the subject altogether.

A Raymer-style walk-through would be a huge improvement on the book, as would the table of aircraft data you mention. It's neat to see all that data for the Horten gliders, but seeing similar data for, say, the Northrop 'wings and such would provide better basis for comparison.

The gold in the book is the basic approach to flying-wing design: Lift distribution is king. That's what really turned me around and allowed me to get beyond 'eyeball engineering' with tailless designs.

I disagree about the induced-drag emphasis. Everyone should be flying sailplanes.

At some pretty deep level, the purpose of a fast cross-country machine for me is to get my sailplane (paraglider) to the good launches. Hence the paraglider baggage compartment specced into all my designs (and yes, it fits in the 701).

Yeah, the pecking thing is interesting. It sort of seems that, between the lines, the summary on the SB-13 is "great plane, great performance, but no fun to fly because of pecking." Solution to pecking? We don't know, but we haven't seen it on anything with sweep > 20°, so recommend that. It's an annoying way to handle it, but I don't really blame Nickel for it; I'm not convinced the material is out there, and the book is a synthesis, not original work.

With "lift distribution is king", I had sort of already arrived there... but Nickel probably could have done a bit more treatment of constrained lift distributions. Two examples come to mind...

1) Hang-gliders, as he mentions, have a washout induced by air flow, and influenced almost entirely by trailing edge pressure. As such, the designer can choose maximum washout, and washout at the tips (which, on a hang-glider, is always less than maximum washout)... but the curve between them is basically a catenary, no option of doing an arbitrary distribution shape.

2) Metal designs, if flat-wrapped, have (piecewise, if multiply flat-wrapped) linear washout distribution.

In these cases, his guidance is still usable (calculate the full lift distribution and work from there), but his fancy "optimals" are not obtainable. Here you have tradeoffs of buildability for induced drag. A more practical approach might have come in handy here.

Originally Posted by addaon

...Yeah, the pecking thing is interesting. It sort of seems that, between the lines, the summary on the SB-13 is "great plane, great performance, but no fun to fly because of pecking." Solution to pecking? We don't know, but we haven't seen it on anything with sweep > 20°, so recommend that. It's an annoying way to handle it, but I don't really blame Nickel for it; ...

You're right. Nickel is of an older generation, with a different mindset. More math-theory, more simplification of the models, because they simply didn't have the computational capacity then to handle more detailed, intricate modeling.

I think there is a quite adequate solution to the 'pecking' problem, but it's simply beyond the reach of homebuilders and amateurs. It's no different than any other airplane - you 'simply' perform a full six-DOF dynamic stability analysis, in great depth. The 'pecking' is a very lightly-damped, short-period phugoid, as far as I can tell - or at least a similar motion. It would require accurate inertial and aeroelastic modeling as well as the aerodynamic modeling, but I see no fundamental reason that "pecking" should be different than any other dynamic motion of the airframe. That kind of analysis was cutting-edge, I believe, even for the aerospace majors in the 1980's when the SB-13 was designed, and really wasn't done for that aircraft. They did some aeroelastic work, but not a full CFD dynamic stability analysis in the sense I'm talking about here.

And yes, my understanding of the SB-13 is that you're right: Highly competitive with 'conventional' sailplanes of the time, but very tiring and annoying to fly in rough air. Which, of course, is what sailplanes are looking for...

Originally Posted by addaon

...In these cases, his guidance is still usable (calculate the full lift distribution and work from there), but his fancy "optimals" are not obtainable. Here you have tradeoffs of buildability for induced drag. A more practical approach might have come in handy here.

Mmmmmm... Yes and no. Their focus upon induced drag can be annoying when you're working upon a powered aircraft - being sailplane designers, they'll throw just about anything on the fire in sacrifice to that. Nickel caught a bit of that bug from the Hortens, although they took it to greater extremes. You can get into Nickel's 'optimal' parameters, as he describes them in the book, but it places severe constraints upon wing geometry, twist, and other factors. As for methods, I agree with you. I don't like his. They're fine if you want to do theoretical studies of the math of flying wings, but not well suited for finding a practical geometry that satisfies a given set of goal parameters. You end up iterating over and over to get where you want to go, which is annoying. Or you use his graphical solutions and constrain your design to the parameters he used for those. It's not really practical at all.

I just bought a Morris Hobbies Spinsation. It's just a box of balsa and a roll of plans. I flew the Morris Hobbies Gee Wiz Bee for years, it was a really fun plane to fly. I still have it. It's ragged out.
The Spinsation will go on my stack of kits. The stack is short. A Top Flight P-40, a Page Aviation Bee Gee R2, and now a Morris Spinsation.

I can't do any R/C until the Tiger Moth is finished. I do have a scratch built Dornier DO 335 I work on every now and then.
It is rubber powered and has a 18" wing span.
I love to build scratch built balsa models.
Here is a picture of the Spinsation. If I build mine, I'll put the fuel tank in the wing like I did my Bee Gee.

Steve

I have design and built rc airplanes since I learned how to use a toilet. I really started getting interested in micro airplanes when I was 12. I was design and building successful models like a p51 and a micro tigermoth that weighed in at under 12 grams. the equiptment was wildly expensive (tiny magnetic actuators and that....) but man I could fly the little things in my bathroom!

I also built a dual tail design pusher brushless that used an old firebird wing and incorperated a seperated inverted v-tail. I had the best flying characteristics of any rc plan I ever had.

Ps. Happy fourth everyone!

Been into R/C since around 1970, intermittently... last time I flew an R/C was about 8 years ago. Got a room full of stuff, both my own and my decased fathers. I keep saying I gotta dust one off and fly it, but other flying pursuits keep getting in the way...

-Dana

Can a Cessna 150 truly "slip the surly bonds of Earth"?

I fly RC about twice per week. Several of the club members are homebuilders. The RC club meetings are better than the local EAA chapter.
BB

My latest model almost ready to cover.

My latest Sailplane model:

YouTube - Czapla Slope 30 sept

YouTube - Czapla Slope 30 sept
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Mitja

That's mine...

Project Restoration - RC Groups

Still in that state sitting in my room right now. Haven't touched it since the last post on that forum. Not so much not enough time to repair as not having a place to fly it. I used to drive 1-1.5 hours out from my house with my dad to a club where I could fly it. Just too far. I doubt I'd fly it even if I could do it in the park next to me. I just don't find them exciting anymore. I only really have a desire to build nice, detailed replicas for aesthetic purposes to just hang in my room. But I don't have the tools for it just yet. When I get those tools I'll probably spend all my time building the real deal anyway. Other than that, I prefer to fly around in Flight Simulators. Hence me being on the forums as the next logical step is to actually get airborne for real.

I am usually building and flying R/C. I don't get fancy I just scratch build.

YouTube - Super Lazy Ace 2

YouTube - Super Lazy Ace 2
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R/C, Control Line and Free Flight. For R/C, started with an old escapement system and then to a pulse (galloping ghost) and eventually to proportional. Haven't done much model flying lately, but still prefer the free flight (especially scale) for the challenge of creating a stable flyer.

Favorite R/C planes: my 6' Sig PT-19 with a K&B .61 pumper, my Mark's Models Windfree sailplane (99"), and my 3-channel Midwest Esquire (ever do aileron rolls without ailerons?).

Bruce

This is my Matrix. I made the molds to this jet and I am down to the wing mold now I hope to market this jet in early 2010.This is a electric fan jet capable
of 200mph.I also have a jet called the Phoenix on the market now and has gone over 170mph on
electric power.