PDA

View Full Version : Flaps versus Spoilers


Geoff_Gino
02-08-2006, 02:12 PM
Hi All

I know that to slow the glider down on approach spoilers are better than flaps, but what are the advantages of the "Crow effect" ?

I see the guys that have no motors in their planes use the throttle position and mixes to give various degrees of flaps with elevators.

Could the "Gurus" please help.

Thanks

RUSH
02-08-2006, 05:00 PM
I'm no "Guru", but here goes... Crow is when you fully lower both flaps at the same time as raising both ailerons a small amount. The reason elevator is mixed in is because when the flaps are lowered, the nose will pitch up. The lowered flaps create a bunch of drag which slows the plane down - like air brakes. Also, the raised ailerons create a negative camber that lowers lift on that part of the wing which makes the plane come down faster - kind of like spoilers; or another way to think of it would be when you give up elevator, the tail wants to come down faster because of the negative camber.

Jason T
02-08-2006, 05:55 PM
Ditto to what Rush said. I use Crow on my F5B model and my hotliner and slows the models down very well. I have it setup on my throttle stick as my throttle is on a swtich for both of these models. So when I want Crow I start easing back on the throttle stick and the surfaces gradually move in the correct directions (flaps down and ailerons up).

Geoff_Gino
02-10-2006, 05:32 AM
Thanks Guys

Sorry I didn't respond yesterday, but I was unable to get into the Forum for some weird reason.

Anyway you have answered my question, thanks.

I don't have seperate flaps on my glider so "crow" is out of the question and I'll stick to 30 degrees up on both airelons with a little up elevator.

Elfwreck
02-13-2006, 08:14 PM
Hey now,
Um, the aileron up on crow setting is to reduce tip stalling, it just increases wash out. If you can do full crow, that's the best way. I can stop my Millinium in mid flight by hitting crow, or dive for a landing at a very high angle. With spoilers I can't do that, not even close.
If all I have is ailerons, of course I'll use spoilerons, but if I've got the ability to set up flaps seperate I'll go with crow everytime.
RobII

Geoff_Gino
02-14-2006, 05:30 AM
Hi Elfwreck

Totally agree with you - problem is my Soaring Star does not have flaps so I am sticking to the Spoilerons.

Working fine for me.

Elfwreck
02-14-2006, 04:53 PM
Hey now,
I don't know the Soaring Star, and spoilerons may be olenty for this model.
I have however converted several models to "full house". My Dave's aircraft works 2m 126 was easy, I just cut the ailerons in half and made the inboard aileron half into flaps. The model was a lot more fun on the slope that way. I did it to a coupla built up ARFs too.
Sure it's a bit of work and may be overkill, so you prolly don't need it, but it sure was fun to fly.
RobII

Geoff_Gino
02-15-2006, 05:33 AM
Hey now,
I don't know the Soaring Star, and spoilerons may be olenty for this model.
I have however converted several models to "full house". My Dave's aircraft works 2m 126 was easy, I just cut the ailerons in half and made the inboard aileron half into flaps. The model was a lot more fun on the slope that way. I did it to a coupla built up ARFs too.
Sure it's a bit of work and may be overkill, so you prolly don't need it, but it sure was fun to fly.
RobII

Hi Rob

Spoilerons are working fine for me at this time - perhaps when I get better at soaring I'll have to look into seperate flaps. There is plenty of wing to mod for flaps.

Elfwreck
02-15-2006, 05:28 PM
Hey now,
As long as they're working for you, that's all that really counts.
Still when you're up for something um, more advanced, er, different? Give the flaps a try. You *will* be amazed and amused:D
More controls equals more control...
RobII

bhchan
03-01-2006, 07:45 AM
This discussion assumes plane without aileron; Spoiler "kill" lift, increase sink rate( also induce a little drag in the process). Flap increase lift and drag. For a lighter plane , spoiler works. For a heavy plane, flap works better. In average case, spoiler reduce up elevator to slow the descend rate. With flap deployed, down elevator is usually needed to over come the induced drag.