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Forward swept wing?

Old 06-01-2002, 08:49 AM
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Cactus.
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Default Forward swept wing?

If you wanna go on about yanks claiming inventions where theirs but not.. the Brits invented the all moving tail plane to work at mach 1 and above, The US said, "hey, we're going for the sound barrier too, wanna swap ideas?, stupidly we said yep, they nicked the all moving tail plane and gve us nothing, we quit our attempt soon after, then Chuckles cheated by using a rocket with wings. lol
Old 06-01-2002, 10:46 PM
  #27  
Jeremy Sebens
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Default Re: wing warping

Originally posted by stick
The wing warping idea worked great. But to me the prize in roll control had to go to Glen Curtiss and his crew for the ailerons. Yippee
Oh, by all means... ailerons are better than warping in the long run... It was simply the concept of roll control (which the Wrights tried to patent - led to a lot of bad blood with Curtiss for a little while) that made real flight possible. That's what I was talking about. Bleriot et al. never implemented x-axis controls until much later, and it was the ability to use roll to effectively turn the aircraft that made actual controlled flight possible. Ever notice that Bleriot never seemed to be able to land his aircraft reliably? Imagine handling a bumpy gust profile or a crosswind without ailerons (or wing warping, or roll spoilers, etc.) No fun.

BTW, apologies for the lack of spell-checking in my last post...
Old 06-04-2002, 01:23 PM
  #28  
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Default Forward swept wing?

Hi,
Interesting combination. Is the only reason for the anhedral, to keep the landing gear short? Corsair used this anhedral to make the gear shorter and stronger I suspect. Smashing itself on the carrier deck. Also maybe to keep the big prop from digging trenches in the runway. We had a guy in the club that had a forward swept , no dihedral kit he bashed and it flew great. Couldnt tell any difference in flight from a swept back. It appeared to be flying backwards.
Old 10-10-2002, 08:27 PM
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SimitarFlyer
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Default Forward Swept Wings

Hi everyone, I'm new on the block. For the past year I have been
flying Bill Evans Simitar Tailless Planes. Currently experimenting
with forward swept wings. One model has a 46" span with 5 degree FWS and is powered by Thunder Tiger .25. The other is
a 33% larger copy of the same plane with a 56" wing span that
has a O.S. .40. This design was copied from Bill Winter's electric
soarer called Pipe Dream. They fly very well. I haven't fully gotten the planes debugged. The CG needs adjustment on the larger
model. When you complete a roll it takes a sudden nose down
attitude. The vertical stabilizers are huge. I would guest about
twice the size of one on a conventional aircraft. If I can figure out how to post pictures I will let you see them.
Old 10-10-2002, 09:06 PM
  #30  
banktoturn
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Default Forward swept wing?

stick,

I haven't read all the replies yet, so I hope I don't repeat too much. From a stability perspective, forward sweep is destabilizing in pitch and anhedral is destabilizing in roll. The amount of anhedral shown in your sketch looks pretty modest to me, and could be reduced if needed by extending the gear struts a bit. I am tempted to say that there is no effective forward sweep at all, since the horizontal stabilizers are coupled to the wing at the forward most point, but I am not sure that is valid. The only thing that strikes me as a possible issue is the fairly small tail volume. You might have an easier time if your booms were longer.

Good luck,

banktoturn
Old 10-11-2002, 05:39 AM
  #31  
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Default Forward swept wing?

What the hey.... as long as we are all trying to help out.......

I like the concept. It's sort of like the "what if" scale models that some people design from time to time to try out their aeronautical engineering ideas.

First off, I assume the main landing gear is a tandem set under the main pod and the boom wheels are the "heavy fuel load" wing support wheels that will loose contact long before the aircraft actually lifts off. Right?

I like the Pterodactyl look but the pods and stabilizers sort of ruin the effect. What about going for flying wing airfoils? The outer panels that are forward would use zero or low positive pitch airfoils. The center panels would use a strongly negative pitching moment airfoil near the main pod and transition to the airfoil used at the tips at the panel break. This would put the stabilizing work on the rear placed center panel and the lift out at the tips.

To combat the positive twisting action that comes with forward sweep you could use the same trick that I read about for the X-29 wing composite layup. What you do is design your main spar to be closer to the leading edge at the panel break than it is at the root by the pod. This way the wing will want to twist in a manner to add some washout during heavy loading rather than washing in as forward sweep wings tend to do. Guessing here but something like the main spar at the 35% mark at the root and 25 to 27% at the panel break should work. Or just build it up super strong and stiff with composite vacumn bagging so it CAN'T twist.

If you went the flying wing route then the vertical fin area is a problem. Swept back wings have a certain degree of self stabalizing action as opposed to the swept forward type that requres a large amount of fin area. With your swept forward design you're going to need a fair amount of fin area to counter the design's negative stability. A propeller shroud ring would add a lot of area but it wouldn't be enough. Abbreviated pods located just outboard of the prop and extending to a point just behind the prop could be used to hold fins. Or sharply swept back fins that mount to the wing but extend back could work. For that matter you could mount them that way and then add a horizontal stab across the tips of the fins. This form would certainly accentuate the Pterodactyl image.

And finally I think you're going to need to put the prop and engine in the front of the pod. That wing planform is going to need the center of gravity to be located somewhere in the front part of the center pod. With very little structure forward of that point to add nose weight to the engine at the rear will ensure that your first flight would be a short one at best.

Your design has a lot of possibilities as a very unique powered soaring model. I know it's "mission" is meant for high altitudes but as a model you'll have to find a closer and more mundane mission. I see that being something to keep the hawks and gulls company....... :thumbup:

PS: Moving the engine to the pod's front would free up the rear for mounting the fin and possible T tail. If you stayed with the flying wing airfoils then this tail could be very small even with the super short moment arm. There's a full size glider that uses this scheme. It's a true flying wing but it has a small full flying elevator mounted on the top of it's fin. This acts as a top plate for the fin to reduce drag and give a very positive elevator action by being somewhat behind the wing.

If you're interested I'll kick up a sketch on the ol' CAD for you to look over. Ah hell. I'll do one up anyway Look for it in a day or two.
Old 10-11-2002, 12:53 PM
  #32  
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Default Forward swept wing?

Stick, I agree with and respect all of Ollie's theories and comments, BUT, I also like novelty for the sake of novelty.

There are some who probably will claim the Pizza Boxes and Flippin discs won't fly. But they are a blast to fly, just for novelties sake.

Let me know when you are ready to test fly this puppy, and I'll drive over and offer you my moral support.

Cajun
Old 10-11-2002, 02:34 PM
  #33  
BernieG
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Default Forward swept wing?

Originally posted by Al Stein
A question for Stuka, you say that the French flew long before the Wrights, but that it was never documented... can you point to any proof of that?
Clement Ader Eole flew on October 9, 1890, or 13 years BEFORE the Wright brothers. The Wrights were the first to have a CONTROLLABLE machine, but not the first to have a flying machine. The first TAKEOFF (powered) of the Wrights occured 20 years AFTER Clement Ader's !!!! http://home.earthlink.net/~rastagnac...o.html#various

Bernard
Old 10-11-2002, 02:38 PM
  #34  
BernieG
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Default Forward swept wing?

Originally posted by phillybaby
the Brits invented the all moving tail plane to work at mach 1 and above
You sure ? Have you looked at the Me 262 tailplane ?

Bernard
Old 10-11-2002, 03:23 PM
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Default Forward swept wing?

it was designed first to sort the loss of control problems with the new fast fighters like Spit and Mustang i *think* this was before the 262, if it has one i didnt know about it.
any ways, the yanks still nicked that one and didnt give us any info in return
Old 10-13-2002, 05:09 PM
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Default Forward swept wing?

Originally posted by BernieG


You sure ? Have you looked at the Me 262 tailplane ?

Bernard
The me262 used a standard stabilizer and elevator.
Old 10-13-2002, 08:37 PM
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Default Forward swept wing?

Well, I don't see a lot of action here anymore. Anyone still out there?.......

Anyway I had some time finally to do up a quick sketch of what I was suggesting about earlier. Here ya go....
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Old 10-13-2002, 11:29 PM
  #38  
Ollie
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Default Forward swept wing?

B Mathews,
Your revision has cured most of the difficulties with the original. Yet, it still has plenty of novelty. I think it still may require plenty of lead in the nose and the landing gear mass so far out on the wings will still make it a bit sluggish in yaw and roll. The reflexed airfoil won't have a very high coefficient of lift so the high aspect ratio won't have much benefit. Reducing the length of the center panels about 30 to 50% would reduce the roll and yaw moments of inertia, improving roll and yaw response and make it easier to achieve balance too.
Old 10-13-2002, 11:36 PM
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Default Forward swept wing?

Originally posted by BMatthews


The me262 used a standard stabilizer and elevator.
Wrong ! The me262 had a full moving tailplane, but it was used only as "trim", AND an elevator. This was to be able to have the stabilizer "neutral" even with the huge difference of AOA between high speed and low speed, with flaps and slats open. The Sabre f-86 had the exact same mechanism, as well as the Grumman Panther and Cougar. (Command systems was slightly different, but the principles were the same.)

BTW, the Me P 1101 (built has prototype, not sure if he actually flew at the time, had not only full moving tailplane, but also moveable sweept wings ! I honestly doubt the Yanks took that from the Britts, evrybody, Popof included (Soviets) took everything from the Germans. The Mig15 was an evolution of a Focke-Wulf study, and the Sabre had the Airfoil, studied but not used on the Me 262, plus number of other technical solutions used on the 262 (automatic slats being one of them).

How, about the Flying tailplane, it was already used by different planes during WW1, so nothing really new about that ! (Fokker DV among others)

Bernard
Old 10-13-2002, 11:54 PM
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Default Forward swept wing?

Originally posted by BMatthews
Well, I don't see a lot of action here anymore. Anyone still out there?.......

Anyway I had some time finally to do up a quick sketch of what I was suggesting about earlier. Here ya go....
That's very pretty, but I doubt it can fly as is. Your nose moment is too short, it should have a very forward center of gravity, as a flying wing your elevator surface, with such a forward CG, would be unable to give enough longitudinal control. I would design that with a longer nose and a canard configuration. Just my .2 cents.

Bernard
Old 10-14-2002, 05:02 AM
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Default Forward swept wing?

Originally posted by BernieG


Wrong ! The me262 had a full moving tailplane, but it was used only as "trim", AND an elevator. .......

BTW, the Me P 1101 (built has prototype, not sure if he actually flew at the time, had not only full moving tailplane, but also moveable sweept wings ! .........

How, about the Flying tailplane, it was already used by different planes during WW1, so nothing really new about that ! (Fokker DV among others)

Bernard
Well in that case there were lots of other planes for many years before the 262 that had the same "moving tailplane". I believe the Stearman SR series used a jack screw trimmed stabilizer as did the Westland Lysander just to name 2.

I think the original concept was the use of an all moving stabilator as a primary pitch control and hooked directly to the stick or wheel.

Can't comment on the P1101 but I do believe you're right and that was about the time of the concept coming out.

And of course you're right about the original use of the all moving stabilator in WW1. I think we all forgot about that. That Morane Saulnier engineer must have thought his planes were pretty fast if he was already thinking ahead to the control reversal of near sonic speeds.......
Old 10-14-2002, 05:37 AM
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Default Forward swept wing?

Originally posted by BernieG


That's very pretty, but I doubt it can fly as is. Your nose moment is too short, it should have a very forward center of gravity, as a flying wing your elevator surface, with such a forward CG, would be unable to give enough longitudinal control. I would design that with a longer nose and a canard configuration. Just my .2 cents.

Bernard
You're probably right. I was trying to keep it fairly close to the original concept.

OK, here's my rethink to bring it up to a more model based practicality. The line through the top view is an approximate CG. I havn't bothered to do a MAC calculation on this so it's just a guestimate but I suspect it's pretty close. As you can see there's now enough moment arm for the nose to get a reasonable chance of building it with an engine and having it come out balanced. Also I didn't mention it earlier but the roll control uses spoilers in my renditions. I've also moved the "fuel tank and wing gear" pods in a little and extended the tips along with some sweep back to restore some of the stability that would be lost to the sweep forward. The outer panels could be built flat or with a small amount of dihedral. You're quite right in that those pods are going to be pretty heavy in any real sized versions but bear in mind the original concept of this being a high altitude research plane. In that light we aren't expecting fighter like maneuvering so a heavy mass that far out wouldn't be a big deal. Real fighters like the T-33 and Scorpian used tip mounted tanks and weapons pods and they still managed.

Anyway I kind of like the forward +back sweep look of this version. It's more suggestive of the Pterodactyl look that hit me in stick's original sketch.

Maybe by the time he gets back to this thread we'll have his model built and flying......
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Old 10-14-2002, 01:26 PM
  #43  
BernieG
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Default Forward swept wing?

Originally posted by BMatthews
OK, here's my rethink to bring it up to a more model based practicality.
A like that design much better ! Might fly with the right airfoil....

Bernard
Old 10-15-2002, 09:33 PM
  #44  
stick
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Default Forward swept wing?

Almost have the Autocad plans finished. When I get through wit them if anyone would like them To change or modify just for fun let me know. My fist hand launch model was to small to get the CG really close so I'm building one a little bigger to try to help. Will defiantly need more tail area though so will have to work on that. Will let you know when the plans are through.
Old 10-16-2002, 09:16 PM
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Default Forward swept wing?

i am not sure at all, but with the twin tails mounted behind the "corners" on the wings, they might catch some turbulence and/or vortices coming off those corners and maybe the landing gear too...

also make sure those tails dont stall; if one does but the other doesnt, it might have some nasty consequences
nasa did a study of the X-29 at high angles of attack. it has lots of pictures of the model with a whole bunch of different-colored dye tracers. it might help some
www.dfrc.nasa.gov/DTRS/1994/PDF/H-1997.pdf

splurk

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