Stability in a swept wing with no washout from the elevons alone.

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

c p skeates

Well-Known Member
Joined
Feb 9, 2010
Messages
98
Location
canberra australia
with a straight wing like a ruler and no sweep back and-or a little diheadral the air craft dose have stability but limited because the center of gravity and center of pitch and center of pressure are about one quarter chord from the leading edge so if the wing slews sideways the pressure moves in such a way as to correct it self but you only need to be a little off center and it will stay slewed side ways ..to test this get a ruler or piece of pipe plastic or something equal all along its length then put a pin in it near the leading edge at the half way piont and it will face square into the wind with a certain amount of ability to hold this position ..so straView attachment 10022igtht wing can be stable but very sensitive ..
i find the trouble with ailerons and and an elevator on a flying wing is the subtile confusion in stalling when trying to opperate the in- sequence where as a tail takes the elevator away from the confusion ...:ponder:
 

Topaz

Super Moderator
Staff member
Log Member
Joined
Jul 29, 2005
Messages
14,092
Location
Orange County, California
with a straight wing like a ruler and no sweep back and-or a little diheadral the air craft dose have stability but limited because the center of gravity and center of pitch and center of pressure are about one quarter chord from the leading edge so if the wing slews sideways the pressure moves in such a way as to correct it self but you only need to be a little off center and it will stay slewed side ways ..to test this get a ruler or piece of pipe plastic or something equal all along its length then put a pin in it near the leading edge at the half way piont and it will face square into the wind with a certain amount of ability to hold this position ..so straView attachment 10022igtht wing can be stable but very sensitive ..
Some amount of vertical tail area is usually beneficial unless one is trying to reduce parasite drag to an absolute minium. Piloted aircraft generally have a requirement to land in a cross-wind, and a strong yaw control and some level of yaw stability is beneficial to flying them.
 

c p skeates

Well-Known Member
Joined
Feb 9, 2010
Messages
98
Location
canberra australia
new ridgid wing hangliders are using just spoilers but because they can weight shift the pitch and to a small degree roll they can avoid the cross wind disadvantages but control aircraft cant ..we realy do know everything about aviation now compaired to the wright brothers 100 years ago so i believe the cannard-tail aircraft they started on has come a full circle with triple wing tandem wing aircraft now .. and modern materials to cut down drag so putting a very small cannard out front to oppose the pitch and a full moveing tail with no incidence is very efficient and stops tail slides as well as the benifits of a cannard wing because the cannard envolope is restricted due to tail slide and the tail aircraft are over simplified so materials are out of bounds but a triple tandem wing aith a full floating tail and no incidence with the smallest cannard up front to oppose the pitch can give a whole new lease of life to aviation with the sophistication we are about now with aerodynamics .. the european eurofighter cannard delta wing formation is the most sort after fighter aircraft in the world and the usa rapter is still to be past by congress for the last 20 years because the tail concept of an aircraft is no loger viable no matter how much they proprgander that it is still to come it will never be accepted due to materials limitations but the eurofighter useing a cannard and delta wing type of tripletandem type wing developement is selling like hot cakes ..
 
Last edited:

c p skeates

Well-Known Member
Joined
Feb 9, 2010
Messages
98
Location
canberra australia
a tandem triple wing developement type aircaft are now the future with absolute certainty ..triplewingtandemwingcpsuntitledreveresd.JPG sorry to go off track a bit but its relavent to the original thread so you can at least compair your self with it for a highly refined ruler type wing as the original thread here is maily concerned with ..thank you for your patient though ..
 

c p skeates

Well-Known Member
Joined
Feb 9, 2010
Messages
98
Location
canberra australia
yes ... but back to elevons on a ruler type aircraft so you dont need an elevator and use the elevons for roll and pitch with out stall problems has been the way most craft of this nature have been made but sooner or later the manufacturere has opted for a tail because of sensitivity so the elevons have to 'friz' nature so the up aileron-elevon needs to produce a small amount of drag and the downuntitledfriz12.JPG going aileron-elevon has to reduce drag or adverse roll will happen .Early 'PC' laminar flow aerofoils of the 1970's were used for full length flapperons on sailplanes to do every thing but lost favour .. if it wasnt for homebuilt aircraft scavengers like us where would the 'class' be ??
 

c p skeates

Well-Known Member
Joined
Feb 9, 2010
Messages
98
Location
canberra australia
too much stability is as bad as not enough ..:roll: every thing has a life until it dosent ..many home builders have come up with something which works only to find out the hard way later if they modify it to some degree they crash ..why .. if it works dont change it ..
untitledanhedralfin12.JPG
 
Last edited:

Topaz

Super Moderator
Staff member
Log Member
Joined
Jul 29, 2005
Messages
14,092
Location
Orange County, California
Hi c p. Either I'm not following you very well, or there's a real lack of focus with this series of posts. Could you clarify the point you're wanting to make?
 

c p skeates

Well-Known Member
Joined
Feb 9, 2010
Messages
98
Location
canberra australia
:ban:untitledstablecock.JPGthe mitchell wing ultralght as i under stand it has sweep back and elevons adjusted for washout instead of putting it into the wing it self so the elevator and ailerons act together as one so stall is delaid where if a elevator was made in the center it would over shadow the ailerons when stalling and upset the stall progression so the tips would stall before the center and cause a spiral turning dive spin ..hence the ideal is to stall the center of the wing first:devious:..so it is the belly piont where the air must separate first and work its way to the tips then escape from the wing in vortecies out side the wings envolope ,untitledmitchellwingcos.JPGlast making it all understandable to the pilots ability .
 

c p skeates

Well-Known Member
Joined
Feb 9, 2010
Messages
98
Location
canberra australia
early 1970's flying wings had elevons and sweepback wings as well as bombay doors for foot launch mandatory for legal status:mad2:untitledcpswingreve.JPGmodern hangliders-ridgid wings are useing spoilers but are ineffective near stall so friz-ailerons-elevons still allow control and can enhance control near stall.
 
Last edited:

danmoser

Well-Known Member
Joined
Feb 1, 2010
Messages
641
Location
Sandy, Utah, USA
The Mitchell wing designs B-10, A-10, and U-2 all have external airfoil type elevons, which are noticeably more effective in a stalled condition than normally hinged elevons.
Spoilerons are not effective as elevators for pitch control, so they cannot be considered as a substitute for elevons, per se.
As you point out, spoilerons on modern rigid HGs are not as effective near stall.
However, that is not really a problem on those HG designs that use the spoilerons, since they use the spoilers primarily for turning and glide path controls.... pitch is controlled via weight-shift, so no elevator is needed.
 
Last edited:

c p skeates

Well-Known Member
Joined
Feb 9, 2010
Messages
98
Location
canberra australia
i just dont trust the spoiler idea ..its effective except if a stall blankets over the whole wing i'd rather have a aileron or elevon as well for that final moment of control and be able to dive to get the flow over the wing back again than use the spoiler ..ridgid wing hangliders with just spoilers have shown to have little or no effect once the stall breaks the cord and so pitch is controled by weight shift but there is virtualy no control once the spoiler is in stall shadow though ..even if you have to use reverse aileron at least its controlable in stall ..
 

henryk

Well-Known Member
Joined
Mar 8, 2010
Messages
5,165
Location
krakow,poland
Votex lift requires some axial /spanwise flow to maintain the vortex, so it generally is seen on swept wings.. the delta wing being the extreme example.
Airfoils with a reflexed trailing edge probably helps to trap the vortex as well, but it's mostly the sweep.


One of my goals is to try a modern version of the K-wing using less sweep, far fewer draggy wires, and modern lightweight construction.
I'm still in the early stages of design with this, so I invite any constructive suggestions on that.
=we have composite KASPER-wing for vortex testing and orginal BEKAS glider for reconstruction,
soon we shold be moore clever in this matter...

PICT4976.jpgPICT4978.jpgObraz=SONY,rysiek,bekas,pobiednik 131.jpgObraz=SONY,rysiek,bekas,pobiednik 134.jpg
 
2
Top