side area vs rudder size
02-12-2006, 06:55 PM
#1
Thread Starter
side area vs rudder size
hi guys, just a simple question:
its well known that a big fuse side area helps in KE flight , but how does this influences in the size of the rudder?
do I need a small rudder area when increasing the fuse area?
what about the amount of deflection of the rudder?
thanks
its well known that a big fuse side area helps in KE flight , but how does this influences in the size of the rudder?
do I need a small rudder area when increasing the fuse area?
what about the amount of deflection of the rudder?
thanks
02-12-2006, 08:31 PM
#2
Join Date: Oct 2002
Location: Chilliwack, BC, CANADA
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RE: side area vs rudder size
The rudder is part of the side area. So you need to include it with your calculations. The only thing that is optional is where you place the hinge line and how much throw you use. For good yaw authourity, which is important when knife edging, you want a wide rudder and lots of throw. Also to obtain a good yaw control balance you want to design the model side view such that the 25% of the side area is ahead of the CG and 75% is behind. This includes the fuselage, fin and rudder when you figure this all out.
02-13-2006, 11:00 AM
#3
Thread Starter
RE: side area vs rudder size
BMatthews: thanks for the response,
but in order to make easer the KE, does the fuselage and fin area helps in reducing the throw of the rudder or the size of it ? " bigger fin and fuselage = smaller rudder "
i forgot to tell you that im talking of a pattern model, so i dont need such amount of throw like 3D models do
check this picture
but in order to make easer the KE, does the fuselage and fin area helps in reducing the throw of the rudder or the size of it ? " bigger fin and fuselage = smaller rudder "
i forgot to tell you that im talking of a pattern model, so i dont need such amount of throw like 3D models do
check this picture
02-13-2006, 01:13 PM
#4
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RE: side area vs rudder size
No, more side area just supports the weight better. For authouritative KE flight you still want a huge, by normal standards, rudder to provide the yaw forces required to kick it around. Look at all the pattern and 3D models and you'll find they all use huge rudder areas. You also want to keep the area low to avoid the roll couple problem. The center of the rudder area should be more or less in line with the center of area of the fuselage side area like is shown in your pattern models pic. I see that the rudders on those models are not actually that large by 3D standards but they are still large by the usual model standards. It's just hidden by the large fuselages.
I should amend this to say that IF the side area is balanced fore and aft of the model's CG quite well that a smaller rudder will still have the ability to yaw the model well. But if the area is biased towards the rear by too much the rudder ends up fighting the tendency of the side area to want to flly like an arrow or lawn dart. The better balanced the area to provide a neutral yaw force the less rudder you'd need.
I should amend this to say that IF the side area is balanced fore and aft of the model's CG quite well that a smaller rudder will still have the ability to yaw the model well. But if the area is biased towards the rear by too much the rudder ends up fighting the tendency of the side area to want to flly like an arrow or lawn dart. The better balanced the area to provide a neutral yaw force the less rudder you'd need.
