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new speed brake idea ... what do u guys think ? - 3/23/2012 3:08 PM   
dirt kicker


 

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From: PretoriaGuateng, SOUTH AFRICA
Status: offline 		hey there

so ive been thiking latley , that i have a problem with speed when coming down , so ive designed my own sort of speed brake like they have on gliders ! , its only a rough thought and design for now , let me know what you guys think ???

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RE: new speed brake idea ... what do u guys think ? - 3/23/2012 5:56 PM   
hogflyer



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Status: offline 		You don't need spoiler nearly that big, and with that size you may lose control of the plane with them extended. The position is as important as the size, and it doesn't take much to spoil the lift with them.

Take a look at what the gliders are using for airbrakes and spoilers where they have many years of experience with them. This past summer I had a chance to fly a 2.5meter KA-6 and found the airbrakes, while they looking way too small, to be extremely effective.

Graupner makes some really nice airbrakes that open from the top and bottom and are extremely effective, and will be the type I'll put into a Sig Kadet Senior to be used for glider aerotow so I can lose a lot of altitude quickly (and be able to land it with an OS .91 Surpass on it).

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RE: new speed brake idea ... what do u guys think ? - 3/23/2012 6:02 PM   
bkdavy



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Status: offline 		Aerodynamically, it can work, although if you use as much of the wing as depicted on the drawing, you'll probably just stall, spin and crash. Most of our models will slow down very well without additional mechanical mechanisms because they're very lightly loaded wings. Learn to use the elevator as a break to pull the nose up and reduce airspeed rather than diving at the runway, and you'll solve the speed problem on landing.

Second observation, if you must use spoilers (they spoil the airflow over the top of the wing and reduce lift) you can usually just use a separate servo for each aileron and program your radio for "spoilerons".

Third, to reduce speed without killing lift, you're better off using a flap on the bottom of the wing. This will not interrupt the airflow over the top, and prevents killing lift. Again, think about using a "flaperon" function on your radio to use the ailerons.

If the plane is really large its possible to split the ailerons and use two servos on each side, so you can have separate flaps and ailerons.

Brad

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RE: new speed brake idea ... what do u guys think ? - 3/23/2012 6:54 PM   
Top_Gunn


 

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Status: offline 		Just to add a little to what Brad said. If you really need to slow your plane down for landing, flaps are the way to go. Not only do they add some drag, they allow you to fly slower without stalling.

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RE: new speed brake idea ... what do u guys think ? - 3/23/2012 6:56 PM   
jaka


 

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Status: offline 		Hi!
Why?? More harm then good!
Set up the plane /engine right and you do not need them!

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RE: new speed brake idea ... what do u guys think ? - 3/23/2012 6:58 PM   
bogbeagle


 

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Status: offline 		If you deploy spoilers, your airspeed must increase. (for a given A of A)

Flaps are the way to go.

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RE: new speed brake idea ... what do u guys think ? - 3/23/2012 8:59 PM   
dirt kicker


 

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From: PretoriaGuateng, SOUTH AFRICA
Status: offline 		okay , trhanks alot for the input guys !!! , il look more seriously at the flap idea

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RE: new speed brake idea ... what do u guys think ? - 3/23/2012 11:00 PM   
jetmech05


 

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Status: offline 		The set up you're looking at is used on 737, 727, 757 to name 3...the problem is if they don't deploy the same...same speed, same amount, same time then you'll have an uncommanded roll that you probably can't recover from......
If you're too fast on approach then the problem is the approach...or to fast of an idle......or CG
If your approach starts with too much altitude then the trade off for altitude is speed...if you leave power on too long on the down wind then you'll be too hot as well.....
Lastly if your CG is too far forward then the airplane will not want to slow either...
Flaps are not speed reducing tools...they are lift augmentation devices...yes they cause drag...but if your speed is too high flaps can cause the airplane to balloon up on you

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RE: new speed brake idea ... what do u guys think ? - 3/24/2012 1:26 PM   
KitBuilder



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Status: offline 		You have spoilers depicted there and not speed brakes. Spoilers "Spoil" lift and let you descend at a much steeper rate without dropping the nose of the plane so speed really doesn't increase. On sailplanes they are much much smaller in length and width. . Some have a fence that rise straight up out of the wing at the thickest section.. other are as you show, hinged at front. They have a tendency to want to lift up due to lift moving over the wing.. so many use springs to hold them closed and the servo "Struggles" against the spring to deploy them.

Another more modern approach the sailplane guys do is called crow... mixing flaps down... and ailerons up which is a very effective brake.

BKDavy.. on number 2.. spoilerons.. or do you mean flaperons.

A neat speed break idea I saw many years ago when computer radios first came out was the idea of using a split rudder. "both halves" of the rudder would move left and right like normal... but the mixing would have them split open. very cool...

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RE: new speed brake idea ... what do u guys think ? - 3/25/2012 6:12 PM   
jetmech05


 

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Status: offline 		Pull the speed brake handle on 727, 737 and the flight spoilers pop up...not as many spoilers as on the ground ....the more you pull the more they deploy......spoliers can also used in turns......some airplanes don't have ailerons at all..and use spoilerons I am pretty sure a B-52 uses spoilerons......
The set he has in mind will work for speed brakes just not as large as drawn......
But too fast on landing is another issue...
Good flyin to all

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RE: new speed brake idea ... what do u guys think ? - 3/25/2012 7:25 PM   
dirt kicker


 

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From: PretoriaGuateng, SOUTH AFRICA
Status: offline 		thanks for the input guys ! , so if i were to add spoliers to my wings would they aid in landing ? or would they make my landing detremental ?

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RE: new speed brake idea ... what do u guys think ? - 3/25/2012 11:12 PM   
jetmech05


 

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Status: offline 		Spoilers spoil the ability of the airfoil to produce lift...hence the name.....if you use to much spoilers your airplane will fall like a rock.....to me it isn't worth the risk...now borrow a page from the A-6 whose speed brakes were on the wing tips in the late models or on side of the fuselage in earlier models and alot of other aircraft as well....and then all you have is drag and not a loss of lift.....
Have you checked the CG to make sure you're not nose heavy...a nose heavy airplane will not setup in the approach allowing a bleed off of airspeed.....

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RE: new speed brake idea ... what do u guys think ? - 3/26/2012 1:36 AM   
BEAR-AvHistory



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Status: offline 		I would use F-86, Mig-15 style speed brakes & build then into the rear sides of the plane. A single servo could drive them.

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RE: new speed brake idea ... what do u guys think ? - 3/26/2012 1:46 AM   
jetmech05


 

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Status: offline 		Yep much easier and lighter

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RE: new speed brake idea ... what do u guys think ? - 3/26/2012 5:23 AM   
Charlie P.



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Status: offline 		Note that you want to be flying pretty slow BEFORE deploying flaps or spoilers.  Deploying either at speed can do surprising things to your flight attitude.  Some models nose dive and others balloon up at a steep angle.

Airbrakes are much different and just add drag. 

I have a Contender with an apron flap that is a lot of fun to experiment with.  But still, a super low idle and reduced airspeed on approach is the best solution.




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RE: new speed brake idea ... what do u guys think ? - 3/26/2012 12:24 PM   
a65l



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Status: offline 		Its been stated already but I'll say it again, if you're too fast over the threshold, then you need to modify your approach. I understand there are fields where there are trees, etc, obstacles that you have to dive down behind to land, but unless you're flying something very heavy, or exceptionally clean, most r/c planes will slow down nicely in level flight. What kind of airplane are you looking at putting these speed brakes on?

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RE: new speed brake idea ... what do u guys think ? - 3/26/2012 5:27 PM   
opjose



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Status: offline 		Yeah those should have been the first questions:

- What kind of plane?
- How heavy?
- How big?
- What size engine and brand?
- What prop?

There are many other things that often need to be addressed before looking at aero/speed brakes for landings.

e.g. Why not just use a lower pitch bit wider prop for better control?




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RE: new speed brake idea ... what do u guys think ? - 3/26/2012 5:32 PM   
Propworn


 

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Status: offline 		Simple balanced speed brake at 2:48 seconds into the video http://www.youtube.com/watch?v=zG9LlHcX8lg

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RE: new speed brake idea ... what do u guys think ? - 3/26/2012 9:56 PM   
KitBuilder



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Status: offline 		The "spoilers" on big jets and the like are more often located in the rear portion of the wing where they aren't spoiling lift but acting more like a one way aileron. A true spoiller is located at the height of the wing will not turn the plane but reduces the lifting ability of the wing as they are applied together at the same rate on both wings at the same time.

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