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aeajr -> RE: RES vs. Full House - Which is better for Thermal Duration Soaring? (5/8/2008 3:30:00 AM)
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How much spoiler should you use?
Spoilers are like any other surface. You use what you need, when you need it. This may be influenced by the limitations of your transmitter and your ability to control the drop of the nose with elevator compensation.
I have my spoilers set up on a side slider on my Futaba 9C. I do that consistently across all my RES planes so they are always in the same place. My spoiler deployment is variable and has elevator compensation mixed in.
Once I am lined up to land and feel I need to start to lose some altitude I will add somewhere between 1/4 and 1/2 of my spoilers depending on my speed and height. When I want to drop it now I will add the rest, but only if I need it.
If I have managed my energy carefully I may not need spoilers at all. I just glide it in. I don't use spoilers on every landing, just when I need them.
Max Spoiler Amount
At full deployment on my Spirit they hit about 60 degrees. On my Sagitta about the same. Both are 2M planes with spoilers right behind the spar. Both get elevator compensation. The Spirit only needs a little, maybe 10%. The Sagitta needs much more, maybe 40%.
On the AVA, they go up about to about a 45 degree angle. These are in the mid section. Normally the AVA has one big spoiler but mine has split spoilers which means less spoiler surface but more air to the tail to help me maintain control at slow speeds. Everything is a compromise.
With that setting, at max, I think I have about 50% elevator mixed in. Seems to work just fine.
Nothing wrong with having an option for 90 degrees but it depends on the plane as whether you will ever need it. 90 degree spoilers would be full stop, war emergency, stand on the brake pedal for most RES planes. The drag, loss of speed and dive would be pretty severe on many planes. But if you have very small spoilers you may want this.
90 degree spoilers might be useful getting out of a super thermal but I don't need that to land with my planes. The plane would lose speed and drop like a rock very quickly. However if you practice with it, that is fine, especially if you can apply less.
Radio controls
Some radios may only give you three positions, closed, half and full. While that may seem quite limiting, if you practice with it, that should be enough control for all but the most precise work. In fact some people refer the 3 way switch because the response is known and consistent.
Even though I have fully variable spoilers that is probably how I use them anyway. The variability just lets me ease them in, but I have a half way stop on my slider. If you practice with those settings you will know how to use them and that should be enough control.
Spoilers vs Flaps
One advantage of spoilers over flaps is that they raise the stall speed, the plane will stall at higher speeds. If you slow too much you can retract them and the lift of the wing will increase and the plane will continue to fly. In this respect they are more forgiving than flaps.
With flaps you decrease the stall speed so you can slow the plane way down and keep flying. But if you slow down too much, pulling the flaps in increses the stall speed and you may not have enough speed to keep flying. So, if apply too much flap, then retract them, you may stall and drop. And if you do this at 30 feet you may not have enough room to pick up speed to reach flying speed again. That is where the ground comes to your unwelcome rescue, or you would fall forever.
I have tested this theory more times than I care to remember, unintentionally. It holds true every time. In my early full house experience I proved this over and over. My Legend has the scars to show for it. Combine this error with a high wing loading plane and you have a wonderful lesson plan for learning to repair wings and fuselages.
Net net, once you have flaps out and the plane slows, you may not be able to safely retract them. This situation does not exist on a RES plane.
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