Fierce Arrow air foil?

Would a "flying wing" type like the Fierce Arrow benefit from a thicker (20%+) airfoil with a more convex aft surface? This would be for slow speed (i.e. not a combat wing), high lift, low aspect ratio flying wing. The plans I have for the Fierce Arrow show a fairly thin airfoil with a flat surface aft of the spar.

Are you looking at the original '50s Arrow, or the Revival one that was in the mags a few years ago?

Google reminded me that there was a Fierce Arrow 400, a .15 sized ship. 1968 seems to early, though.

There's the original, the 400, and is there a third? I was thinking yes.

The one I'm looking at right now is the 15 powered one. I also have plans somewhere for a larger one but I don't think it goes back to the 50s late 60s early 70s maybe...

The FA was published 8/57 (MAN) and the FA 400 was published 5/68 (MAN).

LAST EDITED ON Aug-08-02 AT 03:09 PM (CDT)

>Google reminded me that there was a Fierce Arrow 400, a
>.15 sized ship. 1968 seems too early, though.
>
>There's the original, the 400, and is there a third? I
>was thinking yes.
>
Smaller than either of the older ones, perhaps, and really quite recently published, for Half-A?

The first two, in my opinion, won't benefit from being as thick as 20% overall. I do have a vague feeling about the potential for improvement from a deeper reflex close to the TE, especially at the elevator hinge line! (Having totally missed the smallest, I remain doubtful for it, but have much less reason for my opinion about it.)

P.S. For any who are interested, adding a "slot" between the elevator and TE on a Fierce Arrow, a Sassy Saucer, or any of the "plank" flying wing combat designs does help reduce the looseness of altitude control that seems to be somewhat characteristic of such designs.

TTBOMK, Wild Bill flew fullsize FA's with slots of that nature before the end of the Classic era. My only Sassy Saucer was flying with a slot added (I just cut the forward part of the huge elevator off enough for a 1" slot) within a year of the design's publication. Before modifying it, the thing was terrifically squirrelly!

P.P.S: While I agree that a true plank wing can never offer the same aerobatic capability available from moving the pitch control away from the wing itself, the delta shaped wings had a lot more going for them than the planks did. If anyone ever built a delta with a "small" slot like the one inch one I used on my 1955 ('56?) Sassy Saucer, and hinged it for some aerodynamic balance area in front of the hinge line, I suspect it would act somewhat better through the first part of sharper turns, where the normal tendency at aerobatic speed is a mushy, wallowing moment that seems to go on and on, way too long.

K.

Low weight would benefit an FA of any size more than anything. Low aspect wings tend to waste a lot lift in turns. My FA 400 was built with good wood, although I didn't get a weight on it, and an Enya 15-III. It needed to be about 5 ounces lighter. It was very difficult to do a square maneuver and not get the plane slowed down so much that it would fall out of the air.

> The FA was published 8/57
>(MAN) and the FA 400
>was published 5/68 (MAN).
>
> George is right, as usual. Currell

I've got a Fierce Arrow that I built about 8 years ago from the August 1957 MAN plan. To my knowlege that was the first of the published Fierce Arrow designs. My FA is 100% straight from the magazine plan - no mods. This '57 FA uses a "polywog" airfoil.

I was flying my FA again yesterday evening. I love flying it! It's sooo cool looking, with the upright engine and "57 Chevy" tail fin. I've got a 50s vintage Fox 35 Stunt in mine, and the flying weight is 51 oz.

How does it fly? It surprises people when they fly it. The feel is just like a "real" 35-size stunter. It feels good! There are however two things I wish it did better, and perhaps with some re-design, these things could be conquered.

1) It doesn't corner well. It will do squares, but if you hit the corner too hard, it will mush, yaw, and wobble through the turn. That has a lot to do with the fact that it's a delta wing configuration, I'm sure. It's my understanding that this is the primary reason that Wild Bill Netzeband changed the hinge line for the Fierce Arrow 400. Anyone know if that helped?

The 51 oz. weight of my FA may also be a contributing factor. Anyone remember if the magazine article told the weight of Bill's original? I'll have to look that up when I can.

2) The other thing my FA does is wander up and down just a little bit in pitch during level flight. Not too bad. If you concentrate harder than you ever have before, you can hold it pretty level. I've tried moving the CG forward and narrowing my line spacing, without much effect. Again, it may just be a characteristic of the short coupled delta configuration (or just old age on my part).

I've often had thoughts of building a new FA. Here are the changes I would make:

1) Use a 4" bellcrank and the tallest elevator horn I can find.
2) Take the concave shape out of the back of the airfoil. (Although I believe this would make it illegal for Classic events.)
3) Use a modern stronger motor, like an Aerotiger .36 or an HP40.
4) I'd talk to Bill Netzeband and decide about changing to the Fierce Arrow 400 hinge layout.
5) MAKE IT LIGHTER!

I'd be real interested to hear from any other FA pilots about their experiences. I just love this airplane!!!

While, like most of us, I hold the Fierce Arrow series particularly the original) in high esteem for its place in stunt history, I'm afraid the entire concept of utilizing a flying wing planform for aerobatic aviation is a idea whose time shall never come. One need look no further than the short lived history of the flying wing in the ranks of combat models for the proof of this pudding. The quick evolution from clip winged Ringmasters right through the short lived era of the flying wing to the almost ubiquitous pod and boom model of practically all successful designs since the '60s is all we need to know from a pragmatic point of view. They just don't do the job as well as designs which keep the more or less equally important jobs of lift and control separate functions...i.e. a wing for lift and a stabilizing/pitch control surface for maneuvering the device.

The aerodynamic theory (reality) in this regard is quite simple. Here's the problem.

A wing produces lift by virtue of several more or less predictable and measureable features. Size (area of the surface) angle of attack to the relative airflow, speed of the air over the surface and some measure of how good that angled to the airflow surface is at utilizing all these parameters to produce lift...widely hailed as the "co-efficient of lift".

Wing area and airspeed are the primary culprits. Given a flat surface and some forward motion at an angle below that at which the surface stalls (airflow becomes turbulent and non-uniform in flowing across the surface) you produce lift in significant quantities.

Of course, a flat surface, like a sheet of plywood on top of a van moving down the highway, lacks the thoroughbred features of a shaped cross section and proper aspect ratio planform to develop lots of lift over a wide range of angles of attack before reaching the critical angle of attack and stalling.

Thus, we've developed "airfoils" whose shape; primarily leading edge radius, thickness and camber; has been found advantageous in optimizing lift. This cross section, or airfoil, coupled with a planform appropriate for the task of the intended aircraft, i.e. a long thin high aspect ratio for craft designed for low induced drag and high lift capabilities at small angles of attack and shorter aspect ratios for ships intended to fly at very high speeds at to utilize lots of drag at low speeds through very high angles of attack to moderate approach speeds etc.

The quintiessential example of each is the high performance sailplane with wingspans typically 30 times greater than the average chord and modern jet fighters with, oftentimes, chords as great or greater than the span. The former flies at a very narrow range of speeds with tiny angle of attack changes throughout the entire flight envelope utilizing only the potential energy of its mass and altitude for power. The latter flies through a very high speed range, using huge differences in angle of attack to provide the lift needed to support its great weight and requires huge amounts of artificial energy to overcome lots of drag at both high and low speeds.

Finally, and most importantly for this discussion, let's consider the effects of airfoil shape, most especially camber on the ability to create the lift necessary for flight. For our purposes we can think of airfoils for our ships in very stark terms and describe them equally simply. A conventional stunt/combat airfoil is symmetrical with no *mean* camber. That means a line drawn from the forwardmost point of the L.E.to the aftmost point of the T.E. an equal distance from the top and bottom surfaces will result in a straight line. Such an airfoil must operate at some modest angle of attack to produce lift. This doesn't, however, mean the plane to which it is attached must be either climbing or descending as a result. More on this later.

Now, when we attach flaps to our symetrical stunt airfoils we do something very important. Flaps aren't "flippers" that want to flip the ship one way or another. The are high lift devices that achieve that function through the simple means of changing the *mean camber* from a straight line to a curved one (see the description of mean camber in the paragraph above).

The resulting *cambered* airfoil...commonly referred to as a "lifting surface" produces greater lift at a given angle of attack and thus allow a wing of a given area to produce more lift with the flaps deflected than without. We use this reality all the time in our flapped stunters which often have a wingloading which would make aggressive corners impossible without the increased lift capability supplied by the *cambered aifoil shape* produced by the flaps.

More in a second posting.

All the foregoing is pretty straight forward and well understood in practice if not in theory but most c/l modelers. What is less understood and very important to the discussion of the Fierce Arrow concept is the equally important aspect of "pitching moment" that happens as a result of cambering an airfoil. This is where the whole flying wing concept for maneuvering aircraft fall on its collective head.

The "pitching moment" of a cambered airfoil is a force which aerodynamically attempts to rotate the airfoil in the pitch axis in the direction of the camber. Thus, a down deflected flap will attempt to pitch the airfoil down and vice versa. One of the important reasons flapped stunters need bigger tails than unflapped ones is because of the need to overcome this pitching moment from the flaps before a pitch in the desired direction can be accomplished. You might want to re-read this paragraph before going on to the next very important discussion of why this is a problem.

THIS STATEMENT IS VERY IMPORTANT SO YOU'VE GOT TO UNDERSTAND ITS MEANING TO GET TO THE HEART OF THE PROBLEM!

*"THE ONLY WAY A FLYING WING CAN MANEUVER IN THE PITCH AXIS IS THROUGH THE USE OF THE PITCHING MOMENT OF THE CAMBERED SURFACE THAT RESULTS FROM DEFLECTING THE AFT PORTION OF THE WING (THE FLIPPERS OR ELEVATORS) TO CAUSE THE ANGLE AT WHICH THE WING TRAVELS THROUGH THE AIR TO CHANGE."*

Thus, to fly an inside loop the Fierce Arrow has to deflect the trailing edge of the wing (the *elevators*)"UP". This does two things as we've discussed; first, the airfoil becomes cambered and, second, a pitching moment is created as a result which forces the front of the airfoil "up". To do an outside loop the opposite is required.

So, you might ask, what's the problem?

Simply stated, the flying wing is attempting to turn (pitch) in the direction *OPPOSITE* that in which lift is enhanced by the elevators. In other words, if you want to increase lift to allow a tighter inside turn you must DEFLECT the trailing edge DOWN to camber the wing for the increased lift. Unfortunately, the only way we can get the flying wing to pitch in the desired direction is to deflect the trailing edge in the direction we want to pitch...utilizing the pitching moment for angle of attack control. By so doing we give precisely the *OPPOSITE* control to the trailing edge that would be desired to increase the lifting capability.

This dichotomy is even more debilitating than at first might be supposed. By using pitching moment for flight path control we are not simply "not improving" the lift co-efficient of the airfoil which results, we are actively making it much, much worse! The airfoil which results is no longer simply uncambered as in an unflapped wing, it is negatively cambered in regards to the direction we need lift to produce a pitch in the desired direction! This is more or less the aerodynamic equivilant of making the wing 25 or 30 percent smaller in terms of lift production just when we need it to be that much greater.

This results in a condition worse even than trying to do outside loops with a scale Piper Cub with its flat bottomed Clark Y style airfoil. This is a knife with no handle! It sticks both the stickee and the sticker!

The flying wing concept is an aircraft intended to maneuver in the pitch axis which is made less efficient rather than more by virtue of the control inputs necessary to make it function. I can't imagine a propostition more destined to failure.

My Agile Arrow is designed a bit different from the Fierce Arrow. The AR is 5 to 1. Center chord is 16 in, tip 8 in. one inch of sweepback on the LE, 60 (actually 61) in span. @720 squares, 18% airfoil. The airfoil profile is sort of a fiddled-with blunt leading edge simplex. More or less the 8% camber one. There is a 12 in wide center section extending back about 2 in past the center of the wing that one could think of as an attached stab. The elevator is 22 in long and 3 in wide with eliptical tips. Original was 52 oz with a K&B 40 and flew on 68 ft lines. It flew square corners very nicely and I was most happy with it. It was retired after several hundred flights and a few third place trophies.

I am presently fooling with a "Darter", a 70% Agile Arrow built as a profile for a 15. Looks like it is going to be pretty good, but still needs some fiddling.

If the foregoing didn't totally confuse you, perhaps a further discussion about more favorable configurations will make it even clearer...or not.

The flying wing experiments made it very clear very soon that we must separate the two primary functions of our devices designed to maneuver in the pitch axis. We need to effeciently generate lift to support our planes during maneuvering and we need to precisely and predictably control the rate and amount of pitch change.

To do both of these jobs well requires that they be performed with separate devices attached to the same mechanism. A wing for lift and a stabilizing surface (preferably a tail vice a canard) to control the angle at which both the wing and the entire aircraft pass through the air that supports it.

Thus the flying wing was quickly replaced in the combat circles with pod and boom ships with two surfaces, each with the clearly defined roles we discussed.

The Fierce Arrow and the even earlier Red Reinhardt Stunt Wing were lonely forgotten ancestors of more successful configurations better suited to the functions desired...lots of lift and lots of pitch control. In other words, plain old boring monoplanes with a tail stuck on the back. Boooooring, but best.

Not to expound too much on what Ted said, yep, one's at an aerodynamic disadvantage. I would suggest that a Fierce Arrow be flown with as far aft a CG as you can stand, so as to need as little airfoil-perverting elevator deflection as possible. As a consquence, controls should be as free of friction as possible, and the handle-to-elevator gain should be kept low. I would guess that it's really sensitive to CG position, too.

The FA is really cool. I remember seeing it at a contest in Kansas City in 1960 or '61. I saw Wild Bill win a big stunt contest in Wichita with a smaller version in 1962. He also won carrier and rat race the same day. It may have been his finest hour.

Though I understand what Ted's trying to say, and tend to agree with him, as well as Howards suggestion of rearward CG, My experience with the FA 400, brief as it was, is almost opposite in nature.

I built the plane for VSC back in the early 90's. It flew pretty decent round manuevers but the squares really mushed and wallowed. While practise flying, Wild Bill was recruited to evaluate the planes flight.

After watching it wallow through a square corner, Bill suggested that it was tail heavy, even though I felt I had the Cg right where the plans showed it should be.

I've since noticed, that most successful flying wing designs have the CG at about 10%. Bill Evans' Scimitar series of flying wing RC designs are all pretty aerobatic and yet stable.I've flown several versions and found them pretty wild with the exceptioon of being able to get them into a spin. The one time I was able to do this resulted in a non-recoverable very flat spin to the ground, damaging the landing gear, and nothing else.

Possibly, his use of a specific airfoil that counts on pre-weighting the rear portion of the wing with a small amount of up elevator style of reflexing is a significant consideration in the flight abilities these designs pocess.

Anyway, back to the FA in discussion, We added nose weight until I had over an ounce of additional weight through several flights. The square turns got better as the CG was moved forward. Finally the squares were about as good as we could get them. Not too bad actually, and I took it up for a final flight to check out the complete pattern. I lost the plane due to a total loss of line tension overhead.

Bill apologised and told me that he should have thought about the fact that the fixed leadouts were now too far aft, and would affect the line tension up high. He mentioned some trimming tricks, but, I can't recall at this time, what they were. If I ever build another, (I already have the parts cut out), I will extend the nose about an inch, and install adjustable over-under leadouts. The best position with the FA 400 seems to be almost 20-25% of the way back to the fuse,from the tip, on the tapered leading edge.

The 400 has more potential than the older, full sized FA, with it's stall fences, slightly balanced elevator, and small air fences along side of the elevator.

Will it outfly a standard design? Probably not, but is it fun, and different? Absolutly. A modern .09 or .10 would be terrific for power.

Mike, the F/A is my all time favorite fun aircraft. I've built two of them. They really draw a crowd and look fantastic in the air. I agree with everything you say about the flying qualities particularly in the squares. Mine has a Dixon K&B 40 for power and I fly it on 70 ft lines. It does bounce around quite a bit on a windy day but on a calm day it is a pleasure to fly.

http://www.prairie.ca/~malty/picarrow.html

One FA memory for me: 1960, at a model airplane Fly In on a military airport in Dahlgren, Va, where they also test naval guns. A married couple had a matched pair of Fierce Arrows, and they flew both at once. One was a little bit faster, and every 20 laps or so, it would pass the other.

Whomever said that these ships make a strong impression in the air is right. Too bad that they are flying with the equivalent of one hand tied behind their backs.

This has been a terrific thread, especially because of Ted's input. I learned a lot.

>Simply stated, the flying wing is
>attempting to turn (pitch) in
>the direction *OPPOSITE* that in
>which lift is enhanced by
>the elevators. In other
>words, if you want to
>increase lift to allow a
>tighter inside turn you must
>DEFLECT the trailing edge DOWN
>to camber the wing for
>the increased lift. Unfortunately,
>the only way we can
>get the flying wing to
>pitch in the desired direction
>is to deflect the trailing
>edge in the direction we
>want to pitch...utilizing the pitching
>moment for angle of attack
>control. By so doing
>we give precisely the *OPPOSITE*
>control to the trailing edge
>that would be desired to
>increase the lifting capability.
>
>This dichotomy is even more debilitating
>than at first might be
>supposed. By using pitching
>moment for flight path control
>we are not simply "not
>improving" the lift co-efficient of
>the airfoil which results, we
>are actively making it much,
>much worse! The airfoil
>which results is no longer
>simply uncambered as in an
>unflapped wing, it is negatively
>cambered in regards to the
>direction we need lift to
>produce a pitch in the
>desired direction! This is
>more or less the aerodynamic
>equivilant of making the wing
>25 or 30 percent smaller
>in terms of lift production
>just when we need it
>to be that much greater.

I drew a force diagram for this same effect based on Bob Hazle's Air Trails "Wing". I can't remember the date, but it was the one with the VSC 12 report, and one of Al's Mustangs on the cover.

The fundamental underlying concept is that you both have to apply torques to "rotate" the airplane, and forces to "translate" the airplane in a reasonable balance with each other to get decent corners.

I defer to your actual FA experience. I was just speculating.

Dave Gardner came over with some foam about 8 years ago to cut out some FA wings. The pile of foam is still there. A foam Fierce Arrow sounded like a bad idea anyhow.

Thanks for the great responses. Any other Fierce Arrow tips out there?

Kiwi-
"P.S. For any who are interested, adding a "slot" between the elevator and TE on a Fierce Arrow, a Sassy Saucer, or any of the "plank" flying wing combat designs does help reduce the looseness of altitude control that seems to be somewhat characteristic of such designs. ... TTBOMK, Wild Bill flew fullsize FA's with slots of that nature before the end of the Classic era. My only Sassy Saucer was flying with a slot added (I just cut the forward part of the huge elevator off enough for a 1" slot) within a year of the design's publication. Before modifying it, the thing was terrifically squirrelly!"

Kiwi. That's helpful to know. Just so non-FA flyers don't get the wrong impression, I have to say that my FA is not "squirrelly" in the least. It is very solid and very smooth! The "wandering" in altitude that I mentioned earlier is a minor annoyance. Hinging the elevator with "some aerodynamic balance area in front of the hinge line", ala the FA 400, sounds like it's worth trying.

ferocious-
"It was very difficult to do a square maneuver and not get the plane slowed down so much that it would fall out of the air."

I would never say that about my FA. It doesn't turn THAT bad. It does a respectable square corner if you don't hammer it.

Ted-
Excellent info!! I learned a lot. I hadn't given THAT much thought to what's going on. You are obviously right on! I never intended to imply that the FA concept could be a modern competition machine. That's not why I fly it and not why I love it. It's just a super cool, fun flying nostalgia trip! And I do think I'll build another one, with some mods to try to make it fly even better.

As my friend Crist Rigotti says; "It's a great time to be in C/L."

Thanks guys. Keep the (FA) cards and letters coming.

>Thanks for the great responses.
>Any other Fierce Arrow tips
>out there?
>
>Kiwi-
>"P.S. For any who are interested,
>adding a "slot" between the
>elevator and TE on a
>Fierce Arrow, a Sassy Saucer,
>or any of the "plank"
>flying wing combat designs does
>help reduce the looseness of
>altitude control that seems to
>be somewhat characteristic of such
>designs. ... TTBOMK, Wild Bill
>flew fullsize FA's with slots
>of that nature before the
>end of the Classic era.
>My only Sassy Saucer was
>flying with a slot added
>(I just cut the forward
>part of the huge elevator
>off enough for a 1"
>slot) within a year of
>the design's publication. Before modifying
>it, the thing was terrifically
>squirrelly!"
>
>Kiwi. That's helpful to know. Just
>so non-FA flyers don't get
>the wrong impression, I have
>to say that my FA
>is not "squirrelly" in the
>least. It is very
>solid and very smooth!
>The "wandering" in altitude that
>I mentioned earlier is a
>minor annoyance. Hinging the
>elevator with "some aerodynamic balance
>area in front of the
>hinge line", ala the FA
>400, sounds like it's worth
>trying.
>
>ferocious-
>"It was very difficult to do
>a square maneuver and not
>get the plane slowed down
>so much that it would
>fall out of the air."
>
>
>I would never say that about
>my FA. It doesn't turn
>THAT bad. It does a
>respectable square corner if you
>don't hammer it.
>
>Ted-
>Excellent info!! I learned a lot.
>I hadn't given THAT much
>thought to what's going on.
>You are obviously right on!
>I never intended to imply
>that the FA concept could
>be a modern competition machine.
>That's not why I fly
>it and not why I
>love it. It's just a
>super cool, fun flying nostalgia
>trip! And I do think
>I'll build another one, with
>some mods to try to
>make it fly even better.
>
>
>As my friend Crist Rigotti says;
>"It's a great time to
>be in C/L."
>
>Thanks guys. Keep the (FA) cards
>and letters coming.
>
>Mike
>
>

Mike (and others),

Please don't interpret my remarks to be negative toward the Fierce Arrow. Like all of you, I respect and enjoy it for what it is...a great slice of C/L stunt history...and a darned slick looking machine. My only reason for going on at such great length was for the educational aspects of trying to express my thoughts in an intelligible fashion. My inability to contribute "thousand words apiece" pictures to my ramblings means I've got to express thoughts verbally that are "difficult". That is pretty much the explanation for every minor thought in my head requiring "major" amounts of verbiage.

I LUV the F.A., I just wouldn't build one for the nats.

One last comment on the F.A.

It is worth noting that the F.A. (the original Fox .35 version) had somewhere in the vicinity of 650 to 700 square inches of wing area...and turns at best "O.K.". The Nobler of roughly the same vintage has 25% less wing and turns dandy corners. This is roughly where I come up with the W.A.G. figure of the flying wing reducing its efficiency in the neighborhood of 25 to 30% when attempting to maneuver in the pitch axis.

I.O.W. if you're going to throw away a lot of your lift capabililty every time you try to do a loop, you'd better start out with more wing area before doint so!

I have a Half Fast with the tail extended from the TE by about 7 in. the total lenght is near 24" or more. The airfoil is 15%% at the center and 18 at the tips. Weight is 23.8oz. with a 36x . It is a great flyer. 420Sq. in. I may do a flapped version with wheels and even longer moment . it does look cool.
I liked the shape so much that I reversed the sweep, actually added forward sweep to the LE and it flies even better, great squares. No tip stall at all. It will do "BI-Slob" loops/flops.
This wing is only 15% at the tips,less center. 22oz.
I suspect that the ideal , non flapped, is the thick wing and the foreward sweep.
Very fast 180* turns, for combat, helps . It flies much better than I. MM
PS I have the fixtures for a foam" F/A" wing up to 48"( 550plus in.)modern airfoil, not the classic legal one.

>I defer to your actual FA
>experience. I was just
>speculating.

I suspect a FA with the CGF set too far back would tend to try to turn too tight, leading to the mushing in turns.

>Dave Gardner came over with some
>foam about 8 years ago
>to cut out some FA
>wings. The pile of
>foam is still there.
>A foam Fierce Arrow sounded
>like a bad idea anyhow.

I was thinking of building one out of foam, myself. Foam's cheap, and this isn't Combat, so core the heck out of it.