Thread: Discussion IOM General Discussion View Single Post
Dec 11, 2009, 07:53 AM
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Joined Apr 2002
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Quote:
 Originally Posted by k4s I dont understand exponential throw let alone variable camber rudders.............please explain so I can get a handle on what you are saying. Please do it in laymans terms if at all possible. Thanks in advance, Richard
Variable Camber; have alook at what the advanced RC glider boys can do with their wings. Wings, like rudders, work by creating lift on one side of the surface which then sucks the surface towards the lift. You will find very few symetrical wing or flat plate wings on gliders because they rely on the angle of attack to create a relatively inefficient lift where you get more drag (Drag = brakes) for the same amount of lift. Instead by effectively changing the camber of their wing the glider boys aim to get more lift and less drag. (Aerobatic slope soarers don't need lift, the slope provides their lift so they do have symetrical wings) Most rudders are either flat plate or symetrical sections and rely on dirty draggy lift to change the course of the boat and they are doing it in water which is a comparitively thick fluid for 1 metre boat.

Rudders ar great for quick and coarse changes of direction but the penalty is drag, you put the brakes on. Anyone sailing with any weather helm is sailing with the handbrake on.

Exponential is fairly common in most radios these days. Instead if have a linear (equal change) of servo movement per equal movement of the transmitter stick it is possible to dial in "Expo" travel, where it is possible to move the servo only 5% of its travel when moving the stick by 25% of its travel. This gives a very accurate and delicate touch to the centre stick movements (lots less movement = lots less drag = more speed) In the heat of battle shaky fingers are dabbing in little bits of drag every time you touch the rudder stick. Every single correction adds more drag.