Dennis,

Thought you'd like this. From a contest a couple of years ago. Powered with a Stalker .61 RE on a pipe.

Randy:
Yeah I like it - a lot! I like the basic design layout, but then the color scheme and excitement in the trim really light it up.  This is a great looking bird!

Is this the one you mentioned that was the really good performer?

Randy:

SHORT flaps!  What kind of Elevator/Flap ratio did you have?

Looks like you kept a pretty healthy flap chord ratio (20%-25%?)

BTW GREAT name for the bird - the design really sets convention on its ear!

Dennis,

Half span flaps, 20% chord. They worked fine. The design really didn't need flaps at all, but tests showed that the flapless version of this plane (built as a hack profile "test of concept" plane) was way too fast in the corners. Without the even short flaps to provide a bit of negative pitching moment, the thing would just rotate around the center of gravity. Made for a very fast and somewhat "funny looking" corner. You'd just have to see it. This way, I got a bit of negative pitching moment and allowed the still very tight corners to be a bit more controllable. Made for a wicked tight corner, but one that was very flyable. The controls and balance ended up kinda funny, too. The hookup was 1 to .90 or so. Just a bit more flap than elevator. The balance (CG) was a whole 'nother thing. When I built it, I set the balance at about the spar. Flying indicated that it was too far forward. I started moving it back...and back...and back. I kept going until it started to get a little touchy then came forward about a 1/4" inch. It ended up about 50% of MAC or less than 4" ahead of the trailing edge of the wing. Made setting the leadouts interesting.

The plane has a very long tail moment (about 24" in the classic "hinge to hinge" measurement) with a tail plane about 35% of the wing area with it split about 62% to the stab. Made for an enormous tail volume coefficient of about .62. The upshot was a plane that turned on a nickel. But that wasn't as impressive as a plane that would stop turning on a penny. You neutralize the control and it stops turning NOW! The thing would turn the most impressive, flat corners of any plane I've ever flown. As long as the wind didn't come over the trees. It was fine in even heavy wind as long as the air was pretty clean. But put it in a turbulent site (like pretty much any contest in the Northwest) and life got very interesting, very quickly. I always find it disconcerting to see both the top and bottom plan view when I hit the control in turbulent air.

When I started building these things, it seemed there were several issues to overcome. Initially, the planes were unpredictable in corners. Any change in airspeed had a huge effect in the amount of control input it took to make a turn. Trying to turn in the same spot twice was almost impossible. I managed to figure that out and eliminate that problem. Next was the tracking. I think because the wing I was using at the time (8.5 or 9 to 1 AR with a 28% airfoil and very far forward high point with very blunt LE) just generated too much lift. It tended to be jumpy in round maneuvers even when it work track in level flight like it was on rails. Managed to fix that problem and got the overall design to track through all maneuvers. That came mostly with changes to the high point of the airfoil, some changes to the LE entry and a reduction in the flap area. The next problem was the lift vs payload issues. These things just don't fly worth a poop is they are too light. I built one that was 8 to 1 AR with about 640 square inches of wing area (a profile test bed). It weighed right around 52oz when built. And it was almost unflyable. No matter what I did, it was jumpy like a cat in a dog food factory. Absolutely blinding corner. I mean really awesome, but it took a lot of flights to get the timing to fly it. It was just unpredictable as heck. In desperation, I started adding ballast. I used those stick on Prather weights right over the CG (or as close as I could get) on the top and bottom of the wing much like Ted Fancher did with the Tucker Special he built. I kept sticking them one and the plane slowly got more tractable. When the all up weight got to around 65oz, the plane actually became pretty nice to fly and still had that unbelievable corner.

I finally figured out that you just had to balance the lift potential of the wing with the payload. There was definitely a window you had to hit or it just wouldn't fly. The plane above (the second one) weighed about 72oz with a 7.8 to 1 AR wing, 25% thickness with 20% high point and a very blunt LE. Again, about 640 square inches. The thing was great and as near as I could figure, right in the middle of the payload window for the wing design.

That last plane was the last of the series (of about 10 or 12 planes - 7 full boogie competition ships). It was the best of the series but was still somewhat sensitive to turbulent conditions. Better than it's predecessors, but not right yet.

What I'd really like to try and probably will at some point is an 8 or 8.5 to 1 AR, 25% thickness, 20% high point, blunt LE wing with an elliptical layout. I think I could overcome a lot of the turbulence sensitivity issues with a modified elliptical platform and the same basically aerodynamic layout as the last Heretic.

And yea, I thought the name was appropriate.

Anyway, I've rambled enough.

  Hi Randy,

 I have always been fascinated with high A/R designs, just haven't had the " gumption" to build one yet as I have always heard they tend to amplify (if thats the right word) the effects of turbulence and at times the wind here is quite nasty.

 I don't like to waste time building (unknowingly) a model that I won't be happy with, especially if I am stepping into an area that I don't really understand. 

 Funnily enough a fair portion of the "known quantity" designs I have built have been pretty ordinary though, mostly through my own fault. I guess that is partially what drives me to keep building stunt planes, mine could always be better.

 If one was to start playing with higher A/R design is there a formula or ratio that you would suggest to start with or is it a case of suck it and see?

 I suppose that so many variables come into play that there is no set rules as such.

 Thanks for the cool photos.
 
 Rob.

Been out opf town for a couple days, thus my delay in responding.

Randy said:

"Feel free to ask questions. I've certainly built enough of these things. Hopefully, Dennis will chime in here. His Orange Crate started me on this track."

FORGIVE ME RANDY!   

All seriousness aside:
* Randy has actually built MORE high AR stunters than I with more variations among them.  Maybe the 'Crate sparked a flame, but Randy has definitely carried the torch farther than I.  Thus his comments carry more direct experience than mine.

* I completely concur with the LONG fuselage argument.  One of the biggest changes in Eclipse versus Orange Crate was the fuselage was substantially lengthened.  STOP thinking about monent arms relative to the flying surfaces or hingleines.  Instead thiink of the tail as being a certain distance from the CG, then install the wing on the correct location to get it to balance.

* I am not sure the LARGE tail area is needed, but since I have never tried it...  Eclipse was around 22% tail area and I thought that becasuse the tail was so long I should try a SMALLER tail.

* Interesting comments on the weight & wing loading - it closely parallels what has been happening in RC sailplanes over the past 15-20 years.  There, airfoils have been getting thinner with less camber (faster) and wing loadings have been climbing.  Sailplanes will, without an engine, penetrate as much wind over a much longer distance than we will EVER fly CLPA.

* My OPINION: Wing loading affects response to turbulence  - AR has nothing to do with it.  If in doubt, go to a sailplane contest on a breezy day...

*  I have not had the trouble Randy described flying high AR at different speeds.  Airplanes I have seen or had that were speed sensitive usually were because of airfoil trauma - like a too sharp LE.  I am sure that is not the case in Randy's airplanes - maybe too blunt has speed issues too?  After the Orange Crate I abandoned my own super blunt LE in favor of a nice boring NACA 0018 airfoil.

* Let's put it in perspective, we are not transitioning from clipped wing Reno Air Racers to unlimited sailplanes here.  I have seen high AR credited with everything from good cornering - to global warming.  I only pushed AR to 7:1, and Randy has taken it farther than that.  I read where increasing AR from 4 to 6 yields about the same effect as taking it from 6 to 12.  Still there are a LOT of things we can do that have a bigger affect on performance than that.

* Personally, I think high AR is DIRECTIONALLY the right thing to do.  However, Randy's comment was right on - there are a LOT of really good flying designs out there that do not exhibit high AR wings.  BUT if you want to build an Impact on "health food" (ie, put a skinny wing in it, and beg Paul W. for forgiveness!) just to see what it would do, GO FOR IT!  Maybe you will find some pieces to the puzzle that have eluded Randy & I...

Dennis,

You may be right on the blunt LE. I used the same airfoil in my current PA plane that is very conventional (5 to 1 AR at about 625 square inches). It seems fine with turbulence, but the combination of a blunt LE with a fairly far forward high point and higher AR may contribute to the issue. I suspect that if I cut down the thickness of the wing and sharpened the LE a bit more I could go with somewhat larger flaps and possible mitigate the turbulence issues a bit. I still think that a high aspect, elliptical arrangement would offer the best of both worlds and will probably try that when next I dive into high AR designs. I have something on the board I've been dinking around with for awhile that is along those lines.

I agree on measuring moments from MAC to MAC and ignoring hingeline stuff. Ultimate, that's all that matters. I ended up using pretty big TVCs mostly out of self defense. I too figured that with such a long tail I wouldn't need a very big TVC to get the same effect I got with shorter moments and larger tails. But earlier planes with much smaller tails but long tail moments tended to be pretty unstable in corners and were kinda hard to control. As I went up in TVC the problems went away. And, of course, I really liked the authority a big tail gave when it came time to stop a turn. That's just impressive as heck when you're flying the plane. Let's see, I'll stop the turn right there and BANG it stops.

On the sensitivity to speed changes: When I started getting more reasonable on the AR, this became less of an issue, but I still think the more "one-speed" you can make the run, the better this sort of design reacts. You should have seen a couple of test beds I built soon after I built the Orange Crate. Someplace I have a picture (if I could find it) of an early high AR design I built. 9.8 to 1 with full span flaps (an I-Beam - Wow, can't believe I did that) with about 23% flap area. It was enormously sensitive to speed changes in turns. And way, way, way too light (650 square inches and about 45 ounces with an OS45FSR). I'm sure I was getting some flex in the wing, too. That probably contributed to it. I'll have to see if I can dig up pictures of that plane and an earlier one. Bot just looked so incredibly cool, but had real issues. The original high AR plane I built, first in the series, was called Dragonslayer and had some interesting features. it was heavily influences by the Orange Crate, but had a trike gear and an anhedral stab. That was interesting. I really liked that plane. Probably should have built another one (circa 1982).

Anyway, I think the combination of too high an AR along with too much flap probably caused most of the speed sensitivity. Since going to slightly less AR (in the 7.4 to 7.8 range) and cutting the flaps way down along with more consistent power delivery, the problems went mostly away while keeping the great turn and turn stability.

As far as payload and wing loading issues. I've always believed that every competitive plane has an ideal design weight. Certainly Paul has confirmed that with a standard Impact, the ideal weight is around 62 oz. As you go either way, lighter or heavier, the performance degrades. I think that generally, high AR planes seem to fly better when the wing loading is slightly higher than what you'd normally figure for to the wing area. You can't go crazy, but if a run of the mill Trivial Pursuit (645 square inches) performs best at 62 to 66 oz (this from Ted) and can still be competitive at up to 70oz, my layout at about the same wing area probably has a window of 65-70oz as the ideal weight for the lift potential. Figuring wing loading is all well and good, but I think more critical is the payload vs lift potential of the wing. There is clearly (at least from my experiments) an ideal you have to hit rather than just trying to make the plane as light as possible. But that just the way I look at it.

That's one of the problems with this. It seems that unlike conventional design, there are a lot more factors involved. Or perhaps it's just that more conventional designs have had more people working on them and so the various factors are more clearly understood. But it seems that while the general idea of these high AR designs is very good, there's just more to overcome. An Impact doesn't really have any "bad" habits. It does pretty much everything reasonably well (I'm just picking on the Impact because I've built a few and know the design pretty well). I really doesn't have any substantial deficits. It also isn't particularly outstanding in any particular area. It just does everything pretty well. In the hands of an expert pilot, it can be very, very successful (as Paul has illustrated). My high AR designs have some areas that they do pretty well also, but they have some areas that they are horrible and some that they are outstanding. Most of my goals with these things has been to keep the stuff that they doing extremely well and try to mitigate the things that drive you nuts. You probably can't entirely get rid of the bad stuff without also losing the good stuff. I just want to make the drawbacks livable.

This last design (last picture) pretty much did that. While it was still somewhat sensitive to turbulence, it was controllable and not too bad (it was a sheer joy to fly in an open field with no turbulence creating obstructions---even in pretty high winds). It had a corner second to none and was fun to fly. The tracking was superior to just about any other plane I'd ever flown. But did have a tendency, every once in awhile, to get a little weird if the engine wasn't right on or I selected the wrong prop or whatever. Consistent torque was a must.

OK, I rambled on on this subject ad nausium. I haven't built one in 2 or 3 years because I wanted to have some planes in the stable that were dependable and consistent. I've just about got that now and may go back to experimenting again. Stay tuned.   

Dennis,

Now see, that's what I'm talkin' about!!

A PA 40 Merlin on a pipe and I think that would be a killer. Heck, just send me the plans and I can quit all this design noodling.

I usually have to draw the thing out in order to get an idea of where I'm going. Usually I draw the plans, get them photocopied then cut up the photo copy for templates. Then as I build the thing, I make notes on the plans along with traced parts that are invented on the spot. And anything else I can think of while I'm building.

But your Futurist is more or less what I envisioned for my next high AR effort. Elliptical layout to minimize some of the sensitivity to turbulence and long moments as you have outlined. Very nice setup. With the right power, I bet it would be a blast to fly.

OK, Dennis, I found the first of the series. Man, that was a long time ago.

Rob,

When I was flying the plane just above (The Dragonslayer), I got Paul Walker to fly it. I watched it do a wingover and was pretty much hooked for life. That planform was just awesome in the air.

Yes, the control do tend to feel light, I guess. Usually doesn't take much effort to snap a really sharp corner. The plane above was build more than 20 years ago. Hopefully, I've learned at least something since then.

But it sure looked cool in the air.

Part 2
What a lot of people may not realize is that Paul Walkers Impact is a very high AR plane. But, what Paul has done so well is that he has balanced the various elements to provide a relatively "mainstream" plane that is quite controllable. Notice that the Impact has a slow ratio control system.  It has a moderately close tail moment. And most important, it has a very low aspect ratio stab taken from Gid Atkinson's Laser to "balance out" and control that "hot wing".

Another surprise. Big Jim Greenaway was working on High AR ships many years ago. Windy Urtnowski built and flew most of those ships.  The Patternmaster is a high AR ship. The Miss BJ is a very high AR ship. Why were these ships so successful while others were not-Jim was a genius with aerodynamics. He understood the effects of airfoils IN CONJUNCTION with AR. Even still, the late Bob Baron had to use relatively slow control systems in his Patternmaster on his way to winning the Nats with his in 1996.  You see this very high leverage-slow control system in action on video in the 1997 Team Trials where Bob Would place 5th-second alternate.

I built my high AR ships in reaction to a plane I designed specifically for the purpose of groove. It had a low AR foam wing cut by me and it had a low AR stab with slow controls.  Trust me, trust me, the plane had NO CORNER!!!  Larry Renger also flew this plane and he yelled out from the circle with Bob Whitely standing right next to me, "Where's the Corner".  But, the plane could groove 2 feet off the ground inverted without missing a beat. More important, it could maintain that groove long after other planes would have been all over the sky.

From this, I learned the important of balance, and that, stunt ships are really quite complex pieces of machinery that require serious study, engineering and development.

Just to make Don happy, I found another one of an early very high AR plane. This was about 4 in the series.

Don,

It was the first with a catalyzed polyurethane topcoat. Imron, I think. Sure learned not to use much of that quick.

Has some interesting vents in it. There are others but the pics have been lost. Too bad. I really wish I had a picture of the most "out of the envelope" version. It was a 10 to 1 AR, full span flaps, very long tail moment, I beam plane. Something like 620 square inches and an 80" wing span. Absolutely scary to fly. A turn that no one believed until they saw it, but as stable as a long term crackhead. Pretty too, with a red and white paint scheme, bubble canopy and trick venting on the cowl. Aesthetics inspired, as I remember, by the Aquila. I was into long and slender then. That plane hung in the ceiling of a Nampa, Idaho hobby shop for years and years. Don't know what happen to it. A picture of it appeared in Stunt News back when Windy was editing it. But no pictures here survived.

Don,
I personally  can testify to the nature of this nastyness,, I have been in the autobody trade since 85, when this "magic" material was coming into its own. Just for a perspective and to give people a sense of how important it is to becarefull, most of the Urethanes I have been around are catalyzed by Isocyanates,, a cianide derivative. It is CRUCIAL to take all precautions if you use any of this catalyzed material. These are not idol warnings that we see so many places like "warning coffee in cup is hot". I know of several Old school painters that cant walk by a car on a sunny day that is freshly painted without reacting to it....
With proper,, PROPER , precations , this material is great and works extremely well. However it is NOT to be toyed with, it can cause seriouse damage to your system.
Just my perpective FWIW

Yep, that first time I used an organic filter in an enclosed space with just a fan going. Put me in the hospital for most of 3 days. You haven't lived until you've had your lungs flushed. I'm still sensitive to the stuff and make sure I'm covered head to toe and only spray it outside with suitable breather. Mark has access to the killer paint booth, so he at least can shoot it inside.

aS A FURTHER NOTE,  The catalysing agents in this material have no inherant smell, the manufacturer actually adds perfume to it so that you can detect it. the catalyst,, (of the ones I deal with) are attracted to moisture, hence our booth has a "wet" floor, there is a contstant flow of water under the grate that comprises the floor. The really pertinant thing about this tendancy is that you not only need to protect your lungs, but,, your >>>>.EYES<<<<<< the amount of moisture in your eyes is like a magnet to this stuff. I have a full face resporator that I  use look like a scuba diver,, best method is a pressurized system, they are available now on a "reasonalbe budget... but also keep the skin covered as Randy states, if its warm and  you are perspiring,, well guess what, more moisture.
Please dont take this as a conspiracy doom and gloom thing, with the CORRECT precautions, there is nothing more risky about this than flipping a carbon fiber prop on your superblatz stunt motor,, and we all know thats safe right?

Interesting info...about the catalysing agents have NO SMELL? In other words...that smell is just from the thinners and paint evaporating instead? Amazing how our human bodies react so quickly...from just the fumes, even though the smell itself as we know isn't the "killer part!" but the hardner cat' instead? Hummm?
Randy...and Mark! Thanks for sharing your concern also and knowing most mortals, no matter how safe we try to be...often POO-POOOO-OOOPS! happens during the rush to paint and clean up..etc. Plus all that toxic left over crap was always sooooooooo unsettling, to say the least. LONG, DROP DEAD OVERTIME HOURS...with limited budgets and short time frames...at the Wind Tunnel was always an ACCIDENT JUST WAITING TO HAPPEN.

 SO BOTTOM LINE: KNOWLEDGE IS POWER and should go a very very long way to keep a good paint artist (reasonably healthy?) but only to a point...because of our mortality and humanity to me. After all those years...GADS! I DON'T MISS THE DEADLINES AND PANIC-ANTICS OF THE TEST DIRECTORS AND UPTIGHT PAYING AERO-CUSTOMERS...who just want everything--YESTERDAY?

I use Omni catalyzed polyurethane. I have goggles and a iso-cyanide approved mask and spray the stuff outside on a relatively calm day with a wet lawn. I use coveralls, a hat, gloves and stay upwind. The stuff is treated like plutonium as far as I'm concerned. But the ultimate product is nice. And once catalyzed, the stuff is fairly inert. No danger from the dust from sanding and such other than the usual precautions of a particulate mask. I use those when sanding balsa, too.