4shizzle

I am pretty new to gliders and soaring. Just wondering if rudder and ailerons should be mixed together and if someone could explain the differance between the best thermaling speed and best sink ratio speed??? thanks

SoCal GliderGuider

Ailerons travel three times as much up as down. Differential. Terribly noticeable on a long wing. I mix in half rudder throw for full aileron throw and put it on a switch. I also mix in flaperons and put that on a switch. Which plane are you thinking of?

BMatthews

The best thermalling speed is the minimum sink rate speed. For most classic RC gliders this is usually the slowest speed just shy of the stall speed. For more modern airfoils it can be a few mph above the stall speed.

Your use of the second term is pretty much the same as above. Or did you mean the other often used Best L/D speed? This is the speed that the model covers the most ground for foot of altitude lost. This is usually about 1 1/2 to 2 times the minimum sink speed. But nothing is fixed here. Different airfoils provide you with different ranges of speed between these two very important speeds.

Basically if you're not at the minimum sink speed and circling in lift, or where you THINK there's lift, then you should be at the other Best L/D speed cruising the sky looking for air to let you switch back to that first speed.

4shizzle

Ok.... thanks guys... i did mean l/d speed. Sounds good in theory but it is much harder to make happen in the real world. I am flying an art hobby thermic and it is a very thin airfoil. Oh... and another question.... why three times more up than down on ailerons??? And any other tips to get this thing flying to its full potential would be great thanks

SoCal GliderGuider

One to one ratio ailerons on a long wing causes the nose to skew opposite the intended turn direction when both move the same up and down. Three times more up movement to down is a good place to start on the differential. You check this with out the added rudder and decrease the ratio until you see a axis roll response and not so much of a dropped inside turn wing and yaw response. Although some like the dropping wing and yaw response.

On long wings a bit of flap mixed in as aileron helps the roll rate tremendusly. There is also the advantage of cambering (drooping) the entire trailing edge to get a bit more slow speed (thermaling) lift.

BMatthews

SoCal mentioned it in passing but may not have made it clear enough. This aileron up to down ratio is known as the Aileron Differential Travel setup. The reason longer winged aircraft such as sailplanes use this differential travel is to avoid the adverse yaw effect where if you roll the model the up travelling wing shows signs of extra drag and the nose points the wrong way. IE: Left bank produces right yaw. This is because a down traveling airleron increases the camber and also the drag of a wing section compared to the up traveling aileron that actually reduces the drag of that part of the wing. And with longer aspect ratios the extra drag of that up traveling wing wins out and drags that wing panel back. Differential goes a LONG way towards controlling this tendency.

Sorry SoCal, didn't mean to steal your thunder but I figured a bit of the basic "what n' why" would help.

SoCal GliderGuider

Doesn't bother me! Can't have too much learnin'!