A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Home Built
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

High thrust line on canard design?



 
 
Thread Tools Display Modes
  #1  
Old March 3rd 05, 08:11 PM
Shin Gou
external usenet poster
 
Posts: n/a
Default High thrust line on canard design?

I read a while ago in a thread that someone said canard design doesn't
like high thrust line but he didn't elaborate. I like canard design but
I have little aerodynamic konwledge so I am begging an explanation for
this statement.

The only reason I can think of from my layman's view is high thrust
line (say, an engine mounted on a pylon) on a canard airplane will
cause a large nose-down force and this force is specially bad for
canard airplanes which have elevator in the front. Many conventional
airplanes have high thrust line engine installation (like Lake
amphibian) and handle fine. So how more severely and to what extend
does this nose-down force affect canard design than a tail airplane,
not even allow a canard take off at all?

Thank you in advance.

Shin

  #2  
Old March 4th 05, 12:42 AM
George A. Graham
external usenet poster
 
Posts: n/a
Default

On 3 Mar 2005, Shin Gou wrote:

I read a while ago in a thread that someone said canard design doesn't
like high thrust line


Having flown a canard for the last six years, I say that you are correct.
They usually need over 1000 ft for takeoff, and a high thrust line would
lengthen that somewhat.

But, I just opened an ASF safety mailing, about accidents while
manuvering,
the graph showed that about one half of those accidents were stall/spins,
the other large percentage was buzzing accidents. Very comforting to
a canard pilot.


George Graham
RX-7 Powered Graham-EZ, N4449E
Homepage http://bfn.org/~ca266

  #3  
Old March 4th 05, 02:14 AM
Jim Carriere
external usenet poster
 
Posts: n/a
Default

Shin Gou wrote:
I read a while ago in a thread that someone said canard design doesn't
like high thrust line but he didn't elaborate. I like canard design but
I have little aerodynamic konwledge so I am begging an explanation for
this statement.

The only reason I can think of from my layman's view is high thrust
line (say, an engine mounted on a pylon) on a canard airplane will
cause a large nose-down force and this force is specially bad for
canard airplanes which have elevator in the front. Many conventional
airplanes have high thrust line engine installation (like Lake
amphibian) and handle fine. So how more severely and to what extend
does this nose-down force affect canard design than a tail airplane,
not even allow a canard take off at all?


Think of it this way-

A significant advantage to a canard is you can design it so the
foreplanes to stall before the wing. This improves the handling, in
that when the airplane "stalls," the main wing is still "flying" and
providing lift. The canard airplane and conventional airplane will
tend to drop their noses when stalled, but the canard loses much less
altitude recovering than a conventional airplane. (When a
conventional airplane "stalls," the main wing stalls and provides
much less lift, so you lose more altitude.)

Now, if you have a large nose-down moment from a high thrust line,
the foreplanes will have to make more lift to overcome that. There
are two ways to make the foreplanes produce more lift.

One way is leave the foreplanes physically unchanged but make the
airplane go faster- as you say, this requires a higher takeoff speed.

The other way is to make the foreplanes produce more lift at any
given speed by physically changing them (larger, different airfoil,
whatever). During flight if you take away the nose-down moment, for
example testing the airplane's handling in a power off stall, and
suddenly the foreplanes are able to produce much more lift than
necessary. If they produce so much lift that the main wing stalls
first, the airplane will suddenly pitch up and who knows what next.

I hope that makes sense the way I explain it.
  #4  
Old March 4th 05, 03:59 AM
Shin Gou
external usenet poster
 
Posts: n/a
Default

Thank you, Jim. It makes sense. Now what I need to do is some serious
caculation to figure out how much distance between thrust line and
verticial position of CG is tolerable for a canard design. Any idea?

Shin

  #5  
Old March 5th 05, 04:06 AM
Eric Rood
external usenet poster
 
Posts: n/a
Default

Or vary the sweep of the canard as Beech did with the
StarShip.

Jim Carriere wrote:
Now, if you have a large nose-down moment from a high thrust line, the
foreplanes will have to make more lift to overcome that. There are two
ways to make the foreplanes produce more lift.
One way is leave the foreplanes physically unchanged but make the
airplane go faster- as you say, this requires a higher takeoff speed.
The other way is to make the foreplanes produce more lift at any given
speed by physically changing them (larger, different airfoil,
whatever). During flight if you take away the nose-down moment, for
example testing the airplane's handling in a power off stall, and
suddenly the foreplanes are able to produce much more lift than
necessary. If they produce so much lift that the main wing stalls
first, the airplane will suddenly pitch up and who knows what next.

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Space Elevator Big John Home Built 111 July 21st 04 04:31 PM
Fwd: [BD4] Source of HIGH CHTs on O-320 and O-360 FOUND! Bruce A. Frank Home Built 1 July 4th 04 07:28 PM
us air force us air force academy us air force bases air force museum us us air force rank us air force reserve adfunk Jehad Internet Military Aviation 0 February 7th 04 05:24 AM
High Flight NOTAM Kirk Stant Military Aviation 1 September 10th 03 03:31 AM
Brake line design question Charlie Smith Home Built 0 July 2nd 03 12:31 PM


All times are GMT +1. The time now is 09:14 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2023, Jelsoft Enterprises Ltd.
Copyright 2004-2023 AviationBanter.
The comments are property of their posters.