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  #16  
Old 08-10-2006, 05:43 PM
ShaleDC ShaleDC is offline
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Quote:
Originally Posted by SteveWrightNZ
question: why not just raise the nose an inch on its gear to improve the takeoff stance? nb. noob alert - I dont know jack about this.

Nothing wrong with this


Quote:
Originally Posted by SteveWrightNZ
nosetip water tank and rear(somewhere) water tank with little electric (washer?) pump to move the CofG on pilot command. or drain it entirely.. a gallon of water in the nose makes how much difference ?
about 5lbs, not nearly enough. Some people fly w/50 pounds of ballast. As you move your water tank aft (due to space constraints), you'll need to increase the amount. Maybe mercury - ha!

Quote:
Originally Posted by SteveWrightNZ
computer-controlled leading-edge slots on the main and the canard, extending automatically on inceasing AofA, and during takeoff, pilot-overrideable retract/defeat - (defeat it at your peril at high AoA.) and to the nay-sayers I say "BAH, are we men or are we mice!"
Yeah, ok. But the canard is a laminar flow airfoil, and wouldn't work w/a leading edge slat fouling the airflow. And who's going to program that, and the redundant backups. Or design the linkages. I guess you wouldn't need ballast by the time you've added the weight of those components.
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  #17  
Old 08-10-2006, 06:25 PM
SteveWrightNZ SteveWrightNZ is offline
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Quote:
Originally Posted by ShaleDC
about 5lbs, not nearly enough. Some people fly w/50 pounds of ballast. As you move your water tank aft (due to space constraints), you'll need to increase the amount. Maybe mercury - ha!
hee hee, you will look like the terminator if you spill that. uhh, a gallon = 4.54l = 4.54 KG times 2.2 ~= 10 lbs. innit? Wayy out on the (extended?) nosetip might be enough to faux "shift the wheels back" while its sitting unloaded though ? shrug.

Quote:
Originally Posted by ShaleDC
the canard is a laminar flow airfoil, and wouldn't work w/a leading edge slat fouling the airflow.
rats. yes the canard is real sensitive innit... any workaround for this ? or is there no point adding leading-edge slots to a lam-foil *anyway* ?

Quote:
Originally Posted by ShaleDC
And who's going to program that, and the redundant backups. Or design the linkages. I guess you wouldn't need ballast by the time you've added the weight of those components.
Modern microcontrollers(1) are really tiny and vastly powerful, and three processors running their own code on one motherboard is still only the size of the palm of your hand, and weighs only grams.

A fifth of my plane will be code (I'm sorry Dave..) It is already commonplace - radios, EFI, GPS, et al are fully electronic, and they are reliable to the point of being overlooked, almost..

(1) * http://www.jedmicro.com.au/avr200.htm

S

Last edited by SteveWrightNZ : 08-10-2006 at 06:26 PM. Reason: added AVR200 link
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  #18  
Old 08-10-2006, 06:27 PM
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Quote:
Originally Posted by ShaleDC
Dust -- I wouldn't put your engine 3" higher. That will only hurt takeoff performance, unless you change the thrust angle too.
takeoff performance will be fine

CS prop, 1/4" more elevator. 31.5 manifold pressure all the time, 30 extra horses. Just think of it as as less effect than adding wheel pants


may change the thrust angle slightly
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  #19  
Old 08-10-2006, 06:30 PM
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Quote:
Originally Posted by Wayne Hicks
All that translates to more weight on the nose gear, more lift needed from canard, more time to reach rotation speed, more takeoff distance, blah, blah, blah, blah, blah.
to me a fair trade off, longer nose strut, cs prop, no tipsey
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  #20  
Old 08-10-2006, 06:57 PM
SteveWrightNZ SteveWrightNZ is offline
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Quote:
Originally Posted by Dust
1/4" more elevator...
careful you dont stall your main flying surface. More canard authority *sounds* like a cool idea, but there is a perfectly good reason why it is set as it is.

S
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  #21  
Old 08-10-2006, 07:01 PM
ShaleDC ShaleDC is offline
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Quote:
Originally Posted by Dust
takeoff performance will be fine
Be even better if you left the thrust line where it was... Steve Wright moved his thrust line up 5" and the resulting unbalanced thrust significantly increases his takeoff roll. If you think of the main wheel axel as the line that the plane rotates on during takeoff, then any thrust above that line pushes OVER the line and forces the nose down. The higher above the axel, the more effect.

Quote:
Originally Posted by Dust
may change the thrust angle slightly
The thing is though, if increase the thrust angle, you'll get better takeoff performance, but then you're "wasting" thrust in flight by pointing it in a direction other than opposite of the direction you're going. Everything is a trade off -- add enough extra power and you won't notice the difference, that's the USAF way.
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  #22  
Old 08-10-2006, 07:13 PM
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mdswitzer mdswitzer is offline
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Quote:
Originally Posted by SteveWrightNZ
careful you dont stall your main flying surface. More canard authority *sounds* like a cool idea, but there is a perfectly good reason why it is set as it is.

S
I dont understand that whole line of thinking. There are many canard designs out there that will stall the main wing, in fact the only ones I know of that wont are derivatives of Rutan's designs, because he designed them to be "stallproof". And this design decision on his part is the main reason they use so much runway.

If you dont put yourself in a low altitude, low speed stall/spin situation you dont need a stallproof aircraft


and if I remember correctly, the Ares WILL stall, because it had to be able to perforn a wide range of maneuvers for the military tests
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  #23  
Old 08-10-2006, 07:54 PM
SteveWrightNZ SteveWrightNZ is offline
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Quote:
Originally Posted by mdswitzer
I dont understand that whole line of thinking. There are many canard designs out there that will stall the main wing, in fact the only ones I know of that wont are derivatives of Rutan's designs, because he designed them to be "stallproof". And this design decision on his part is the main reason they use so much runway.

If you dont put yourself in a low altitude, low speed stall/spin situation you dont need a stallproof aircraft


and if I remember correctly, the Ares WILL stall, because it had to be able to perforn a wide range of maneuvers for the military tests
Intentionally quoting the whole posting..

What happens when they do stall ?

Perhaps it is me who does not understand it - A common occurance.

I understand that too much canard authority will allow you to raise the nose to the extent that the main wing is now stallable. So one of two scenarios might exist ;

1.) If the main wing *does* stall before the canard, it will drop, consequently raising the AoA of the canard, thereby stalling it also. The canard then drops, unstalling itself first, and *maybe* and *hopefully* unstalling the main wing also. If it doesnt unstall the main lift surface, then the aircraft will settle into a unrecoverable main wing stall, descending in an uncontrollable nose-high attitude, that will likely require a roll inverted to recover from... thats if your stalled ailerons still work.

2.) If the main wing *does* stall before the canard, it will pitch the whole aircraft down, consequently lowering the AoA of the canard, thereby holding it unstalled, regardless of whether it was stalled to begin with.


g^HGurus, oh teach us the truth.. /me puts on sackcloth and ashes..
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  #24  
Old 08-10-2006, 07:56 PM
Marc Zeitlin Marc Zeitlin is offline
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Quote:
Originally Posted by mdswitzer
I dont understand that whole line of thinking.
Stalling the rear wing of any aircraft and getting into a "deep stall" is a very bad thing. That's the line of reasoning. A deep stall can get locked in, and then you're just going to have to ride it down or jump out.

Quote:
Originally Posted by mdswitzer
There are many canard designs out there that will stall the main wing....
Examples, please?

Quote:
Originally Posted by mdswitzer
...in fact the only ones I know of that wont are derivatives of Rutan's designs, because he designed them to be "stallproof". And this design decision on his part is the main reason they use so much runway.
It's one of the reasons, but not the main one. The main one is that they have high wing loading, so need to be going pretty fast before they'll rotate. Check the rotation speed and runway needs for Glasairs and Lancairs, which have similar wing loadings. They're not substantially diffrerent from the canards.

Quote:
Originally Posted by mdswitzer
If you dont put yourself in a low altitude, low speed stall/spin situation you dont need a stallproof aircraft
And if you never make a mistake, you don't need any safety equipment, either. But we're all human, and we DO make mistakes. Making one at 3K ft. is one thing, but base-final turn stall-spin accidents are almost always fatal (witness the Europa crash at OSH this year).

Quote:
Originally Posted by mdswitzer
and if I remember correctly, the Ares WILL stall, because it had to be able to perforn a wide range of maneuvers for the military tests
That's just patently false. The test pilot for ARES tells me that it has standard canard handling qualities with respect to stalling the main wing - namely, DON'T.

Any aircraft that regularly allows the rear wing to stall is an aircraft that's begging to crash. See:

http://en.wikipedia.org/wiki/Deep_stall

for a simple definition of deep stall in conventional aircraft. For canards, deeps stalls can be just as dangerous.
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  #25  
Old 08-10-2006, 08:10 PM
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the original cozy canard was 6" wider. A possibility of deep stall was discovered EONS ago and the canard was cut 6 inches and lower winglets installed. DEEP STALL all gone

the extra elevator should be a non event and nat even suggested it to me, was not my idea, just gives me, ima hope, a little more elevator authority

A non event.

as far as the thrust angle, i should be able to easily adjust it during flight testing, on the ground of course
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  #26  
Old 08-10-2006, 08:27 PM
SteveWrightNZ SteveWrightNZ is offline
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Quote:
Originally Posted by Marc Zeitlin
And if you never make a mistake, you don't need any safety equipment
The first thing that happens when I get out of the X-Plane Cozy and into the Parwan (like a Sentry) is the stall warning blares its head off the whole time.. /me blinks ewps, airspeed !! attitude !!

Is it just me, or X-Plane, or is it that anything that is not a canard is a flying(sic) rock ?

I soooo cant wait to fly a real canard. sniff. I dont think there is even a longEZ in NZ.


S

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  #27  
Old 08-10-2006, 08:44 PM
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Quote:
1.) If the main wing *does* stall before the canard, it will drop, consequently raising the AoA of the canard, thereby stalling it also.
Ah! You have a wrong assumption there. I have read all the Canard Pusher newsletters, (and all the Cozy newsletters, not just the ones my series plans require,) they are fascinating reading for historical perspective on the development of the Rutan stable, contain many hints & explanations that still seem relevant relevant, and clearly document the 'deep stall' phenomenon as it was revealed and promptly reported. I think it came as a suprise to Burt how obstrepterous builders would turn out to be.

There are many examples in the newsletters where they actually tested builder's aircraft and were bemused by wing drops & incipient deep stall on aircraft inside the w&b, and put it down to variation from the plans (I assume random, rather than deliberate sabotage of the plans). I have an aquaintance who is a test pilot for the GA Airvan. Every aircraft that comes out of the factory is tested to see if the numbers are the same as the certification prototype. If they are significantly different it goes back into the factory until they aren't. There can still be some variation. You can expect MUCH more variation in a plans built machine, and while the Rutan/Co-Z stable has been tested more thoroughly than most it is still (in comparison to FAR 23) virtually untested!

If you stall the wing there is no guarantee the canard will stall as well. If your canard is still flying and can't be stalled by full up, or the wing unstalled with full down, you are in a stable or 'deep' stall and your next trajectory change will be on impact with the ground.

If you stall the wing and the canard there is no guarantee that the nose will drop to fix it. The elevators will do nothing (even if .25" broader) & the outcome will be as above.

Mike Melvill has about as much experience of these things as anybody, I've read he recommends rocking the wings.
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  #28  
Old 08-10-2006, 08:53 PM
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tnt tnt is offline
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Quote:
Originally Posted by Spodman
Ah!

Quote:
Originally Posted by Spodman
obstrepterous
Now there's a combination of letters I've never seen. Neither has dictionary.com. Even their next recommendation I've never seen. 'obstreperous' We just don't use that around here.


Quote:
Originally Posted by Spodman
I've read he recommends rocking the wings.
Careful not to get distracted by people waving back.
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  #29  
Old 08-10-2006, 08:53 PM
ShaleDC ShaleDC is offline
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OFF TOPIC. Deep stall is a separate thread, really reaching to relate this to "landing gear geometry."
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  #30  
Old 08-10-2006, 10:02 PM
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John Slade John Slade is offline
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Quote:
Listen new builders and new designers. this is GREAT stuff
Listen sure, but check credentials and full flight test reports before adopting an idea just becasue it sounds good. New builders and new "designers" may, or may not know what they're doing. On the other hand, we know Burt's no fool - right. He didnt make it graze so it looks cute. Dust - you're gonna move the engine up 3 inches, and now you're gonna move the gear back a couple. Add some extra layups, and steel everywhere instead of al. All this based on "what you've read" here and there.

Sounds like me poking at the innards of a brand new SL30 with a screwdriver to see if I can make if receive better.

Me? I put the gear and engine thrust line EXACTLY where Burt & Nat said they should be. But that's just stick-to-the-plans stuck-in-the-mud ol' me.
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