Speed or air brakes
11-05-2008, 01:06 PM
#1
Senior Member
Thread Starter
Speed or air brakes
Speed or air brakes
I have several Kougars that fly and land well with a good sink rate. However one of the places that I fly would be more comfortable with a slower landing speed.
I am considering an air brake on the bottom of the wing.
Has anyone experimented with an air brake on the Kougar?
What were the results?
How large should the air brake be relative to the wing area?
How much reduction is landing speed should be expected?
Thanks.
Bill
I have several Kougars that fly and land well with a good sink rate. However one of the places that I fly would be more comfortable with a slower landing speed.
I am considering an air brake on the bottom of the wing.
Has anyone experimented with an air brake on the Kougar?
What were the results?
How large should the air brake be relative to the wing area?
How much reduction is landing speed should be expected?
Thanks.
Bill
11-05-2008, 05:00 PM
#2
RE: Speed or air brakes
not a great idea Bill- the problem is actually the wing loading , so the real fix is to be lighter .
flaps would allow amore controllable approach but speed will NOT decrease.
flaps control angle of descent
they don't add wing area.
speed brakes will only add problems .
flaps would allow amore controllable approach but speed will NOT decrease.
flaps control angle of descent
they don't add wing area.
speed brakes will only add problems .
11-06-2008, 10:56 PM
#4
Join Date: Oct 2002
Location: Chilliwack, BC, CANADA
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RE: Speed or air brakes
Lighter will produce a slower stall speed. No doubt about that. But often landing overshoots are more about the difficulty in bleeding off airspeed to just get down to the existing stall speed. For that issue there's two options. First is learn to get the model into a slow forward speed mushing flight mode and then hold it there all the way to touchdown. In this mode you hold the model in the nose up glide attitude with elevator and then alter the glide slope with small applications of power from idle to 3 or 4 clicks open as needed. Never going over a fast idle setting. In this way the nose up high Cl flight mode produces the drag you need to land predictably.
The other option is to cheat like a Vegas card shark and add a speed brake....
It'll mean modifying the wing but if you can add a brake flap that is around 1.5 inches wide by 12 to 14 long under the wing's center and so that it is hinged such that the trailing edge of the flap/brake is just at the hinge line of the elevators it won't disturb the stip ailerons (at least I seen to recall that the Contender has strip ailerons). Ideally this brake would be inset into the wing to avoid drag. But if you don't mind the extra drag for regular flying then just mounting it flush with the lower outside and adding a taper of wood and covering in front of it would be sort of OK. No blame on me for any aerodynamic oddities will be tolerated... Then you need to arrange an extra servo to extend it to 90 degrees. To do this you will not be using a typicall control horn setup. Instead you want the horn turned backwards so that the hole you use is at a 45 degree rear angle (if external) and select the servo output arm so that it pulls the flap down to near 90 from the lower surface it's on.
Even with a drag flap of this size you will still want to learn not to dive in to your landing. The drag will help but it isn't a bandaid for poor landing approach practices. Look at how full sized airplanes land. It is always nose up in the glide to generate the drag and help steepen the glide slope. It's a practice that you want to copy with or without drag flaps.
Sorry for assuming anything if you're already doing it this way. But by far the majority of lower hours sport flyers dive their models down to the touchdown point so I figured it was worth the reminder.
The other option is to cheat like a Vegas card shark and add a speed brake....
It'll mean modifying the wing but if you can add a brake flap that is around 1.5 inches wide by 12 to 14 long under the wing's center and so that it is hinged such that the trailing edge of the flap/brake is just at the hinge line of the elevators it won't disturb the stip ailerons (at least I seen to recall that the Contender has strip ailerons). Ideally this brake would be inset into the wing to avoid drag. But if you don't mind the extra drag for regular flying then just mounting it flush with the lower outside and adding a taper of wood and covering in front of it would be sort of OK. No blame on me for any aerodynamic oddities will be tolerated... Then you need to arrange an extra servo to extend it to 90 degrees. To do this you will not be using a typicall control horn setup. Instead you want the horn turned backwards so that the hole you use is at a 45 degree rear angle (if external) and select the servo output arm so that it pulls the flap down to near 90 from the lower surface it's on.Even with a drag flap of this size you will still want to learn not to dive in to your landing. The drag will help but it isn't a bandaid for poor landing approach practices. Look at how full sized airplanes land. It is always nose up in the glide to generate the drag and help steepen the glide slope. It's a practice that you want to copy with or without drag flaps.
Sorry for assuming anything if you're already doing it this way. But by far the majority of lower hours sport flyers dive their models down to the touchdown point so I figured it was worth the reminder.
11-07-2008, 12:39 AM
#5
RE: Speed or air brakes
ORIGINAL: dick Hanson
not a great idea Bill- the problem is actually the wing loading , so the real fix is to be lighter .
flaps would allow amore controllable approach but speed will NOT decrease.
flaps control angle of descent
they don't add wing area.
speed brakes will only add problems .
not a great idea Bill- the problem is actually the wing loading , so the real fix is to be lighter .
flaps would allow amore controllable approach but speed will NOT decrease.
flaps control angle of descent
they don't add wing area.
speed brakes will only add problems .
uhm... i thought flaps added lift during the initial extension and then more drag as they are extended further. This allows you to come in slower and at a steeper angle under a more stable condition. And some flaps do add wing area (fowler flaps come to mind). Speed brakes are also worth while to help bleed off speed or come in at your normal approach speed at a higher angle of descent.
11-07-2008, 07:02 AM
#6
RE: Speed or air brakes
ORIGINAL: invertmast
uhm... i thought flaps added lift during the initial extension and then more drag as they are extended further. This allows you to come in slower and at a steeper angle under a more stable condition. And some flaps do add wing area (fowler flaps come to mind). Speed brakes are also worth while to help bleed off speed or come in at your normal approach speed at a higher angle of descent.
ORIGINAL: dick Hanson
not a great idea Bill- the problem is actually the wing loading , so the real fix is to be lighter .
flaps would allow amore controllable approach but speed will NOT decrease.
flaps control angle of descent
they don't add wing area.
speed brakes will only add problems .
not a great idea Bill- the problem is actually the wing loading , so the real fix is to be lighter .
flaps would allow amore controllable approach but speed will NOT decrease.
flaps control angle of descent
they don't add wing area.
speed brakes will only add problems .
uhm... i thought flaps added lift during the initial extension and then more drag as they are extended further. This allows you to come in slower and at a steeper angle under a more stable condition. And some flaps do add wing area (fowler flaps come to mind). Speed brakes are also worth while to help bleed off speed or come in at your normal approach speed at a higher angle of descent.
no
Fowlers on full scale do add area. I don't see much of this on models or even light aircraft.
Bottom line
airplane flaps can reconfigure shape of the wing and improve lift whilst adding drag
This can stabilize a steeper descent .
On a high wing loaded model, going slower gets dangerous quickly.
The theory and actual operation of speed brakes and flaps on large craft has value . On small models , the added weight almost always just complicated things by requiring yet more speed.
The more closely the fuselage and tail group point in the same direction as the direction of flight, the more stable the airplane.
The small size of the subject model, means weight is 1 thru 10 in the order of relevant factors thru low speed control.
The writer is after a slower landing and slow flight on the Kougar was never it's forte.
The experiment might be fun to try but I would not bet that in actual practice it will help.
11-07-2008, 01:17 PM
#7
RE: Speed or air brakes
Hot and long landings are due to high stall velocity.
Stall velocity can be reduced by reducing weight or increasing lift.
Flaps and slots are for increasing lift, achieving short take-offs and landings.
Long and shallow approaches are due low drag.
Brakes are for increasing deceleration by increasing drag.
That is good for a Navy carrier, because of the limited runway.
Even for those, steel cables and hydraulic breaks are preferred, once the aircraft is rolling on the deck.
Increasing deceleration of the flight implies reaching the stall velocity faster.
Better being close to the ground at that point!
Regards!
Stall velocity can be reduced by reducing weight or increasing lift.
Flaps and slots are for increasing lift, achieving short take-offs and landings.
Long and shallow approaches are due low drag.
Brakes are for increasing deceleration by increasing drag.
That is good for a Navy carrier, because of the limited runway.
Even for those, steel cables and hydraulic breaks are preferred, once the aircraft is rolling on the deck.
Increasing deceleration of the flight implies reaching the stall velocity faster.
Better being close to the ground at that point!
Regards!
11-07-2008, 02:44 PM
#8
RE: Speed or air brakes
ORIGINAL: dick Hanson
Model airplane flaps?
no
Fowlers on full scale do add area. I don't see much of this on models or even light aircraft.
Bottom line
airplane flaps can reconfigure shape of the wing and improve lift whilst adding drag
This can stabilize a steeper descent .
On a high wing loaded model, going slower gets dangerous quickly.
The theory and actual operation of speed brakes and flaps on large craft has value . On small models , the added weight almost always just complicated things by requiring yet more speed.
The more closely the fuselage and tail group point in the same direction as the direction of flight, the more stable the airplane.
The small size of the subject model, means weight is 1 thru 10 in the order of relevant factors thru low speed control.
The writer is after a slower landing and slow flight on the Kougar was never it's forte.
The experiment might be fun to try but I would not bet that in actual practice it will help.
ORIGINAL: invertmast
uhm... i thought flaps added lift during the initial extension and then more drag as they are extended further. This allows you to come in slower and at a steeper angle under a more stable condition. And some flaps do add wing area (fowler flaps come to mind). Speed brakes are also worth while to help bleed off speed or come in at your normal approach speed at a higher angle of descent.
ORIGINAL: dick Hanson
not a great idea Bill- the problem is actually the wing loading , so the real fix is to be lighter .
flaps would allow amore controllable approach but speed will NOT decrease.
flaps control angle of descent
they don't add wing area.
speed brakes will only add problems .
not a great idea Bill- the problem is actually the wing loading , so the real fix is to be lighter .
flaps would allow amore controllable approach but speed will NOT decrease.
flaps control angle of descent
they don't add wing area.
speed brakes will only add problems .
uhm... i thought flaps added lift during the initial extension and then more drag as they are extended further. This allows you to come in slower and at a steeper angle under a more stable condition. And some flaps do add wing area (fowler flaps come to mind). Speed brakes are also worth while to help bleed off speed or come in at your normal approach speed at a higher angle of descent.
no
Fowlers on full scale do add area. I don't see much of this on models or even light aircraft.
Bottom line
airplane flaps can reconfigure shape of the wing and improve lift whilst adding drag
This can stabilize a steeper descent .
On a high wing loaded model, going slower gets dangerous quickly.
The theory and actual operation of speed brakes and flaps on large craft has value . On small models , the added weight almost always just complicated things by requiring yet more speed.
The more closely the fuselage and tail group point in the same direction as the direction of flight, the more stable the airplane.
The small size of the subject model, means weight is 1 thru 10 in the order of relevant factors thru low speed control.
The writer is after a slower landing and slow flight on the Kougar was never it's forte.
The experiment might be fun to try but I would not bet that in actual practice it will help.
I agree fowlers aren't used much on models or lift aircraft b/c the complexity doesn't negate the need. Most light aircraft only need a conventional flap that changes the wing chord line to decrease the stall speed and increase the drag needed.
Lighter airframes are always ideal, but if you build the aiframe to originally accept the flaps, the only additional weight you would really have is the extra servo and linkage required to operate them.
11-07-2008, 08:46 PM
#9
RE: Speed or air brakes
I think what Dick is getting at is that , for this application, lift will always be equal to, or slightly less than the weight of the aircraft, cause the airplane is descending. Lowering the flaps will not increase the lift, but it might change the airspeed that this amount lift is generated at, and will increase the drag so that a steeper, slower approach can be used. It is not a cure for a heavy model, as the speed at which the stall angle is reached will still be higher than that achieved by a lighter model.
Evan, WB #12.
Evan, WB #12.
11-07-2008, 08:52 PM
#10
My Feedback: (66)
RE: Speed or air brakes
fowler flaps are the ones that add chord to a wing. there many types of flaps. some give more lift than drag and other more drag than lift. there is even flaps that are powered or known as "blown flaps". A conventional flap on most model airplanes are just part of the wing thats hinged to move like an aileron or other control surface. these provide a good mix of lift and drag. a good example of this is whats on the P-51 mustang. conventional flaps do not add cord to the wing, they change the AoA of the wing where the flap is. This is why strip ailerons are not the best for flaps mixed with roll control during slow flight.
For the kobra/kouger i would use a split rudder with two small servos( like 225's). very easy to set upand not hacking into the wing or fus for this.
For the kobra/kouger i would use a split rudder with two small servos( like 225's). very easy to set upand not hacking into the wing or fus for this.
11-07-2008, 11:26 PM
#11
RE: Speed or air brakes
ORIGINAL: airraptor
fowler flaps are the ones that add chord to a wing. there many types of flaps. some give more lift than drag and other more drag than lift. there is even flaps that are powered or known as "blown flaps". A conventional flap on most model airplanes are just part of the wing thats hinged to move like an aileron or other control surface. these provide a good mix of lift and drag. a good example of this is whats on the P-51 mustang. conventional flaps do not add cord to the wing, they change the AoA of the wing where the flap is. This is why strip ailerons are not the best for flaps mixed with roll control during slow flight.
For the kobra/kouger i would use a split rudder with two small servos( like 225's). very easy to set upand not hacking into the wing or fus for this.
fowler flaps are the ones that add chord to a wing. there many types of flaps. some give more lift than drag and other more drag than lift. there is even flaps that are powered or known as "blown flaps". A conventional flap on most model airplanes are just part of the wing thats hinged to move like an aileron or other control surface. these provide a good mix of lift and drag. a good example of this is whats on the P-51 mustang. conventional flaps do not add cord to the wing, they change the AoA of the wing where the flap is. This is why strip ailerons are not the best for flaps mixed with roll control during slow flight.
For the kobra/kouger i would use a split rudder with two small servos( like 225's). very easy to set upand not hacking into the wing or fus for this.
first - split rudders if they work whilst split are a bit tricky to get righrt.
also as the rudders open typically, the model pitches up
The center of vertical drag at the rear changes -sometimes a lot.\ As for actual "slowing" properties on this size model very meager. I did it on a 1000sq in 9 lb pattern plae with large rudders and finally junked the entire thing as tthe only benifit I found was the wow factor.
11-22-2008, 01:31 PM
#12
RE: Speed or air brakes
ORIGINAL: invertmast
im no aerodynamicyst, but i dont see how flaps can add/improve lift on a large scale or real aircaft, but they dont on a model airplane... Doesn't seem "logical" to me. Especially since on my turbine jets i use flaps for shorter takeoff's (improved lift) and for slower landing speeds (again more lift).
im no aerodynamicyst, but i dont see how flaps can add/improve lift on a large scale or real aircaft, but they dont on a model airplane... Doesn't seem "logical" to me. Especially since on my turbine jets i use flaps for shorter takeoff's (improved lift) and for slower landing speeds (again more lift).
(Not Fowlers)- Adding any amount of flaps does create drag and does create lift. When flaps are used to gain optimum lift (during take off) without creating a lot of drag, the flap setting is usually set at 9 to 10 degrees (for most common wing types). Any flap setting after 9 degrees will begin to add more drag than the desired lift.
Fowlers are great, but almost never seen on a model plane.
For the guys and gals out there setting the 'degrees' of flaps during bench set-up, it's measured at the chord line, not at the wing skin surface.
The 'balooning' effect is a result of the now changed chord line at the un-changed power & elevator trim settings.
12-16-2008, 06:50 PM
#13
RE: Speed or air brakes
Howdy, found this thread through the search engine since I have a pylon ship that is really tricky to land in my field - MUCH MUCH WORSE than my Sig Cougar - so I need your input please. Have tried sideslip and "mushy flying" but decided I do need some sort of speed brake to spare my nerves (and ship). Thought about split rudder already but I tend to agree with Dick above and please note that I only have one (strip) aileron on the plane..[
].....!
What about ejecting a small brake chute during the approach..?!?!....waddayathink..??
...Cheers/Harald
].....!What about ejecting a small brake chute during the approach..?!?!....waddayathink..??
...Cheers/Harald
12-16-2008, 08:55 PM
#14
Senior Member
My Feedback: (1)
RE: Speed or air brakes
Circa 1961 Hal DeBolt made up plans and model for the then new DMECO Viscount to use speed brakes on each wing. Then had a mechanizm that made one aileron work and on opposite wing the speed brake. Did same for both sides, and used one Annco servo for this. Did not come out in kit form nor was even mentioned on the boxed instructions or booklet that had been tried. Told me he flew it that way in one International event, but kept having to fiddle with the linkage in order to make work evenly. Then gave up.
12-16-2008, 11:16 PM
#15
RE: Speed or air brakes
canardlover:
I suggest flapperons with elevator mixing, if your model has independent servos for ailerons.
Also, using more rudder than ailerons during final.
I do not suggest slowing the model in the air with brakes of chutes without adding lift; flaps do both things at once by increasing the camber of the wing and the drag it produces.
The elevator mixing will compensate any reaction in pitch.
Regards!
I suggest flapperons with elevator mixing, if your model has independent servos for ailerons.
Also, using more rudder than ailerons during final.
I do not suggest slowing the model in the air with brakes of chutes without adding lift; flaps do both things at once by increasing the camber of the wing and the drag it produces.
The elevator mixing will compensate any reaction in pitch.
Regards!
12-17-2008, 09:49 AM
#16
Senior Member
RE: Speed or air brakes
The worst problem with trying to use flaperons is that this is the same as adding wash-in to the wing when you really need washout at low speeds as when landing. This increases the possibility of tip stall at the worst possible moment on landing which almost always results in a two point landing (one wingtip and the prop).
12-21-2008, 04:54 PM
#17
RE: Speed or air brakes
ORIGINAL: Rodney
The worst problem with trying to use flaperons is that this is the same as adding wash-in to the wing when you really need washout at low speeds as when landing. This increases the possibility of tip stall at the worst possible moment on landing which almost always results in a two point landing (one wingtip and the prop).
The worst problem with trying to use flaperons is that this is the same as adding wash-in to the wing when you really need washout at low speeds as when landing. This increases the possibility of tip stall at the worst possible moment on landing which almost always results in a two point landing (one wingtip and the prop).
12-21-2008, 05:57 PM
#18
RE: Speed or air brakes
Hi again guys, and first I want to congratulate BillS for your Kougars....sure envy you because I only have one (see pic) with a Saito.56 in the nose. A truly nice sport airplane which I like a lot.....pics of yours..?
Second, forgive me for "intruding" or "hijacking" your "Kougar thread" by introducing my pylon worries into it but this thread is relevant so I hope it is OK with you..!?..
..!
Thanks all for input above but please note that my pylon ship only has ONE SINGLE AILERON on the right wing panel so neither flaperons nor spoilerons will work for me..
..that is why I tried your views on the brake chute but I hear no hands clapping...[&o] Admittedly a bit cumbersome though so let me try another approach and see your response: What about "crossed aileron/rudder mixing"...was thinking in terms of having rudder as master and aileron as slave here in my radio..?!
See attached picture outlining two different ways of slowing down my ship by sideslipping with mixed rudder/aileron input, which one would you prefer..?..
...
...Cheers/Harald
..pics of yours..?Second, forgive me for "intruding" or "hijacking" your "Kougar thread" by introducing my pylon worries into it but this thread is relevant so I hope it is OK with you..!?..
..!Thanks all for input above but please note that my pylon ship only has ONE SINGLE AILERON on the right wing panel so neither flaperons nor spoilerons will work for me..
..that is why I tried your views on the brake chute but I hear no hands clapping...[&o] Admittedly a bit cumbersome though so let me try another approach and see your response: What about "crossed aileron/rudder mixing"...was thinking in terms of having rudder as master and aileron as slave here in my radio..?!See attached picture outlining two different ways of slowing down my ship by sideslipping with mixed rudder/aileron input, which one would you prefer..?..
......Cheers/Harald
12-23-2008, 01:42 PM
#19
RE: Speed or air brakes
canardlover:
Sorry I have missed the detail of single aileron.
I would not tell you what may work best, because I don't know.
Generally, any deflected surface will create increased drag where it is located; hence, the model will yaw toward the wing with aileron in either case, which should be countercated by the rudder (but only for landing mode).
At the same time, the model will tend to roll.
Your solution depends on the type of rudder-aileron coupling of the model during normal flight.
Air brakes installed as close to the fuselage as possible, and aft the CG, may be the best bet for this model.
Watch for reaching the stall speed sooner than expected with those brakes.
Regards!
Sorry I have missed the detail of single aileron.
I would not tell you what may work best, because I don't know.
Generally, any deflected surface will create increased drag where it is located; hence, the model will yaw toward the wing with aileron in either case, which should be countercated by the rudder (but only for landing mode).
At the same time, the model will tend to roll.
Your solution depends on the type of rudder-aileron coupling of the model during normal flight.
Air brakes installed as close to the fuselage as possible, and aft the CG, may be the best bet for this model.
Watch for reaching the stall speed sooner than expected with those brakes.
Regards!
