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Help on Rudder limits of movement

SHORTRV7

SHORTRV7

Well Known Member
I need some help on how you guys figured the throw of the rudder. I thought I had it on the bench, but I was wrong. How do you measure the angle?? Would this work knowing the distance from the center hinge to the end of the rudder is 20 inches and measuring the amount of movement to one side or the other and using a triangle formula work? Look at this to see if I am thinking right here or not.
http://www.mathopenref.com/trianglesideangle.html

I put 20 inches in for the distance from the center piviot point to the aft end of the rudder and then swang the rudder. On the two long legs of the triangle they both have to be 20 inches. The formula shows I need from 10.3 to 11.9 inches of swing to get from 30 to 35 degrees, am I on the right track here or is there an easier way of doing this, help!!!
 
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Is the Vertical Stab on the airframe??

If so, drop a line (plumb bob) down from the rudder pivot bracket and place a mark on the floor. Then with the rudder centered on the Stab, and center line of the fus marked on the floor, swing the rudder left and then right. At each extreme, again drop a line from the trailing edge of the rudder to the floor and mark. With these marks on the floor, you can connect the dots and measure the angles with a protractor.
 
I believe there is a dimension given in the plans that states the required clearance between the elevators and the rudder.

It's not to difficult to set the rudder travel limits when you have empennage mounted on the fuselage. The elevators limit the maximum range of rudder travel and of course you don't want to be banging the rudders into the elevators.:eek:
 
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also at this point

I am also looking at measuring the angle of the rudder. The instructions have some information on how to measure for the 35 deg angle but I am not following their logic.

I am going to try using a protractor against the Vertical Stabilizer to see what the angle of the rudder swing is.

I am using the internal rudder stop sold by Craig Vincent. Here is Craig's thread for these stops: http://www.vansairforce.com/community/showthread.php?t=52483&highlight=rudder+stops

I would be anxious to read any ideas that come up on this topic.
 
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Still looking for the best way!!!!

A protractor on the side of the rudder just dosen't seem to work... I like the idea of using a plumb bob to measure the angle on the floor, but seems to me it would be much easier to just use that triangle formula to compute the swing distance knowing the distance from a given point on the hinge line. I am still thinking of doing it that way instead of setting everything up with a plumb bob on the floor. Just looking for the best way!!! it's a tail dragger and I need the authority and I want all of the 35 degrees.
 
Full travel is......don't hit the elevators.

I didn't even measure the actual angle, I just set everything so nothing touches, plus a little clearance if things get bent.
 
Make a quick paper template from a file folder. Layout (with protractor) a straight line with the 35 degree angle. Cut it out and lay the paper on top of the rudder with the straight line down the rudder centerline and the angle point above the rudder hinge line. Swing the rudder out to aline with the 35 degree cutout out. Flip the paper over and do the other side. Build on!!
 
Done Deal

I went ahead and set up a 3ft ruler at the trailing edge of the rudder with a step ladder, moved the rudder outbound and measured the distance it traveled (11.5 inches) and put it to the formula found here with 20 inches on both long axes, which is from the center hinge point to the trailing edge.

http://www.mathopenref.com/trianglesideangle.html

One can play with this triangle, just keep the two rear angle the same. I got 33 degrees. I am happy with that!!! All of your ideas sound great. Thanks for your input.
Don
 
Bingo

gereed75 said:
Make a quick paper template from a file folder. Layout (with protractor) a straight line with the 35 degree angle. Cut it out and lay the paper on top of the rudder with the straight line down the rudder centerline and the angle point above the rudder hinge line. Swing the rudder out to aline with the 35 degree cutout out. Flip the paper over and do the other side. Build on!!
Click to expand...

I thought that's how everyone does it :)
 
It's not the angle, it's the clearance,...

to the elevator tips. Should be right at 1 1/8 inches clearance at full travel between the face of the rudder and the inside aft tip of the elevator.



There is enough flex in the rudder that if you hit the stops hard with less than one inch clearance, it can flex enough to actually hit the elevator and dent the rudder.

Hope that helps.

Bill S
7a finishing
 
Rudder stops not symmetrical

My rudder stops are not symetrical. Have I done something incorrectly?
THey stop the rudder evenly however, at 35 degrees in both directions.
 
Straight edge and protractor

Remember that piece of DIY store architectural aluminum angle you used to build the wedge style rudder?

Use it as a straight edge for this task. Center the rudder and clamp it stationary. Lay the straight edge next to the rudder surface and clamp it to elevator/rudder spar structure. Unclamp rudder and swing it. Use protractor to measure.

See images here:

http://websites.expercraft.com/rzbill/index.php?q=log_entry&log_id=52900

The plans give a spec range of a few degrees. As stated earlier, it works out to approx an inch from the elevator.
 
Phil Cowan said:
My rudder stops are not symetrical. Have I done something incorrectly?
THey stop the rudder evenly however, at 35 degrees in both directions.
Click to expand...
Normal. Remember, your whole VS is offset (if it's a later model RV) so the rudder is going to hit the stops on the fuselage at different angles.
 
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