HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old May 15, 2012, 01:27 PM
Registered User
Joined Oct 2004
2,726 Posts
I too think that what is being described is a dart. The only configuration I could think about is an odd one with more than one horizontal surface, set up so that it is stable at a slight angle either way up by playing with a wing with a thick trailing edge and a noticeable wake. Essentially using the same effect that causes sometimes control surface hysteresis. And even that sounds very unlikely to work.
[edit] another possible option: flat plate canard, proper "thick" wing section, CG set far back and the canard partially stalled. It might end up being stable only at a set speed, but could be stable either way. Again, not sure it would work.
Brandano is online now Find More Posts by Brandano
Reply With Quote
Sign up now
to remove ads between posts
Old May 15, 2012, 01:35 PM
Wreckreational User
Joined Sep 2007
211 Posts
Quote:
Originally Posted by Sparky Paul View Post
.
Other than a symmetrical airfoil having no lift at zero AOA?
And the horizontal at zero AOA?
There must be longitudinal dihedral for stable flight, upright.
Either the wing will have (must have) incidence if symmetrical, or the tail is deflected from zero to give the download the plane will need for stable flight.
With the surfaces fixed, it can not fly stably inverted, it will dive.
In the interest of learning my error, how do you explain this plane with symmetric sections. He claims no trim change from upright to inverted.

http://www.rcgroups.com/forums/showp...7&postcount=35
Steve Anderson is offline Find More Posts by Steve Anderson
Reply With Quote
Old May 15, 2012, 01:47 PM
Registered User
richard hanson's Avatar
United States, UT, Salt Lake City
Joined Oct 2007
6,566 Posts
Quote:
Originally Posted by Steve Anderson View Post
In the interest of learning my error, how do you explain this plane with symmetric sections. He claims no trim change from upright to inverted.

http://www.rcgroups.com/forums/showp...7&postcount=35
Again - glider powered by gravity.
IF your claim worked for level constant speed - there would be no need for a motor .
Gliders move due to gravity and or updraft. One moves it down -the other moves it up
Neither creates a steady speed at constant altitude.


The condition - -level constant speed - plane simply rolled from inverted to upright requires something to restabilize the required wing angle in either case The amount of trim required for either case may/may not be the same amount but not the same setting
richard hanson is online now Find More Posts by richard hanson
Reply With Quote
Old May 15, 2012, 01:57 PM
Wreckreational User
Joined Sep 2007
211 Posts
I would like a response from Sparky Paul.
Steve Anderson is offline Find More Posts by Steve Anderson
Reply With Quote
Old May 15, 2012, 02:03 PM
Ascended Master
Sparky Paul's Avatar
Palmdale, CA
Joined Oct 2000
13,370 Posts
Quote:
Originally Posted by Steve Anderson View Post
In the interest of learning my error, how do you explain this plane with symmetric sections. He claims no trim change from upright to inverted.

http://www.rcgroups.com/forums/showp...7&postcount=35
.
Didn't hear any claims about anything, just the usual inappropriate pirated music.
There's no demonstration of anything relative to the setup of the plane.
Constantly moving the control sticks isn't a way to show stable flight with no trim changes due to how the sticks are being held.
There is that pesky gravity and the wind to help it fly.
Sparky Paul is online now Find More Posts by Sparky Paul
RCG Plus Member
Old May 15, 2012, 02:56 PM
Wreckreational User
Joined Sep 2007
211 Posts
Quote:
Originally Posted by Sparky Paul View Post
.
Didn't hear any claims about anything, just the usual inappropriate pirated music.
There's no demonstration of anything relative to the setup of the plane.
Constantly moving the control sticks isn't a way to show stable flight with no trim changes due to how the sticks are being held.
There is that pesky gravity and the wind to help it fly.
Here it is.

Quote:
Originally Posted by Jitter View Post
While it is individual preference, I know a lot of individuals who prefer to do things that are bad habits. I think that having the plane trimmed so that it flies on a straight line without any control input whether upside down, right side up, or in some extreme cases on a knife edge (as much as possible) is the best way to go for anyone looking to advance their piloting skills. I wouldn't want to drive a race car that constantly pulls to the left unless I was on a nascar track. It's a hindrance and a distraction just like a plane that constantly tucks while inverted.
Steve Anderson is offline Find More Posts by Steve Anderson
Reply With Quote
Old May 15, 2012, 03:25 PM
Ascended Master
Sparky Paul's Avatar
Palmdale, CA
Joined Oct 2000
13,370 Posts
A section cut through the flight path of the projectile tossed from the cliff.
It's a "projectile" because by definition, a zero-zero setup has no lift.
There's only gravity... always, and drag.. depends on the shape.
There's simple physics equations that can relate the distance the projectile impacts from the point of toss, and the time of plummet.
Sparky Paul is online now Find More Posts by Sparky Paul
RCG Plus Member
Old May 15, 2012, 04:26 PM
Wreckreational User
Joined Sep 2007
211 Posts
Sparky Paul, thank you for the post with the drawing.
Steve Anderson is offline Find More Posts by Steve Anderson
Last edited by Steve Anderson; May 16, 2012 at 05:25 PM.
Reply With Quote
Old May 16, 2012, 12:28 AM
Registered User
The Willamette Valley, Oregon
Joined Dec 2008
1,101 Posts
Come on guys

This thread is degenerating away from common sense

Say the downwash angle hitting the horizontal stab is only 2 or 3 degrees

It will still have a significant effect on pitch trim and pitch stability dynamics

Who would deny that?

Steve

Quote:
Originally Posted by richard hanson View Post
THIS ONE-- I gotta see- using a glider ??
Have you ever flown a model or full sized craft ?
The slope glider relies on upwards air currents and gravity to generate movement
In order to demonstrate your "idea" - you would need a constant ,calm air environment
Oh yes - and power .
aeronaut999 is offline Find More Posts by aeronaut999
Last edited by aeronaut999; May 16, 2012 at 07:45 AM.
Reply With Quote
Old May 16, 2012, 12:36 AM
Registered User
The Willamette Valley, Oregon
Joined Dec 2008
1,101 Posts
Btw I was filming the downwash angle behind my wing the last 2 days. It is definitely more than 2 or 3 degrees! Steve
aeronaut999 is offline Find More Posts by aeronaut999
Reply With Quote
Old May 16, 2012, 12:56 AM
Registered User
The Willamette Valley, Oregon
Joined Dec 2008
1,101 Posts
(Duplicate)
aeronaut999 is offline Find More Posts by aeronaut999
Reply With Quote
Old May 16, 2012, 12:57 AM
Registered User
The Willamette Valley, Oregon
Joined Dec 2008
1,101 Posts
Btw I'm still on the fence re the original thesis of this thread. I certainly concede that that the momentum involved with the downwash associated with x pounds of lift depends on many variables. Yet it seems to me that once the downwash is created, it must perpetuate until it is absorbed by the ground. The shear forces between air molecules simply propagate/ disperse the momentum of the downwash out to a larger volume of air, right?
aeronaut999 is offline Find More Posts by aeronaut999
Reply With Quote
Old May 16, 2012, 01:02 AM
Registered User
The Willamette Valley, Oregon
Joined Dec 2008
1,101 Posts
And btw I'm still 100% convinced that the ground feels a downforce equal to the weight of the plane, no matter what fraction of that downforce is due to the downward momentum of the downwash and what fraction is due to some sort of downpressure not associated with momentum... steve
aeronaut999 is offline Find More Posts by aeronaut999
Reply With Quote
Old May 16, 2012, 01:05 AM
Registered User
The Willamette Valley, Oregon
Joined Dec 2008
1,101 Posts
Quote:
Originally Posted by Steve Anderson View Post
I agree the zero-zero setup would be a projectile. I made an error when I missed that an example airplane in a book I was using had everything falling on the same reference line and symmetrical but the wing is mount with 3 angle of attack. So, I am sorry guys.

Sparky Paul, thank you for the post with the drawing.

I think 0 0 need not be a projectile. The zero angle horizontal stab meets the airflow at a negative a-o-a, because it is in the wing's downwash. So the configuration can be positively pitch-stable. I will check the rc slope glider thread tomorrow to see if they have chimed in... steve
aeronaut999 is offline Find More Posts by aeronaut999
Last edited by aeronaut999; May 16, 2012 at 01:14 AM.
Reply With Quote
Old May 16, 2012, 01:09 AM
Registered User
ShoeDLG's Avatar
Germany, BW, Stuttgart
Joined Mar 2012
755 Posts
The glider I described back in post 141 shows an interesting behavior. If I release it with a slight downward flight path at the right speed, it will establish a climb. If I turn it upside down it does the same thing. This does not sound like a projectile to me. Perhaps those who are so certain a 0-0 setup will be a projectile ought to actually try it.
ShoeDLG is offline Find More Posts by ShoeDLG
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Dymond D47 servo, Which version do you have on hand, how can you tell??? TDboy Hand Launch 5 Apr 21, 2012 02:26 AM
Discussion Is there anything listed that you can't live without? P-51C Life, The Universe, and Politics 44 Aug 05, 2011 02:55 PM
Discussion Fast food that you just can't do without. Bilbobaker Life, The Universe, and Politics 101 Aug 17, 2010 11:30 AM
Joke What Would You do to get that Aircraft You Can't Have ? Chophop Humor 10 Feb 09, 2010 07:00 AM
Discussion HELPIf you have a problem that can't be solved here ccowboyearl Beginner Training Area (Heli-Electric) 2 May 14, 2009 12:31 PM