Rudder stops and rudder deflection

JurgenRoeland · #1 08-12-2019, 01:52 AM

I'm working on the rudder stops and start filing them to measurement. While doing so I stumbled upon these findings which are puzzling me.

The manual says : " The proper 35 degree swing is attained when the clearance between the inboard trailing edge of the elevator skin and rudder skin is 1 1/8" when measured perpendicular to the rudder skin with the
elevator in the neutral position. "

I made a cardboard with a 35 degree angle and held that against the vs and rudder.
When I measure on the pilot side and hold the rudder along to the cardboard, I only measure 1/2 inch between the trailing edge of the end of the trim tab and the rudder with the elevator in neutral position.
On the passenger side, it's even a little closer, here I only measure 13/32 inch.

I'm not quite sure what to do now. What is the most important ? the 35 degree deflection on the rudder or the 1 1/8" distance between the elevator and rudder.

Actually I'm wonderiong if the cardboard method is correct ? The vertical stabilo skin has a little curve to it and the rudder is tapered and triangular. So i'm not sure if the 35 degrees measured should be 35 degrees according to the centerline of the rudder and the centerline of the fuselage. In that case I would probably end up close to and inch distance but then the 35 degrees seems hard to measure.

How did you guys measure this ?

rzbill · #2 08-12-2019, 03:10 AM

Quote:

Originally Posted by JurgenRoeland

*SNIP*

I made a cardboard with a 35 degree angle and held that against the vs and rudder.

I'm not quite sure what to do now. What is the most important ? the 35 degree deflection on the rudder or the 1 1/8" distance between the elevator and rudder.

Actually I'm wonderiong if the cardboard method is correct ?

How did you guys measure this ?

Cardboard not correct. Where is your zero degree line? Is it parallel to the taper of the rudder with the rudder centered? If not, it is wrong.
I measured angles during construction too, and the manual is correct.

JurgenRoeland · #3 08-12-2019, 04:03 AM

Quote:

Originally Posted by rzbill

Cardboard not correct. Where is your zero degree line? Is it parallel to the taper of the rudder with the rudder centered? If not, it is wrong.
I measured angles during construction too, and the manual is correct.

What I did was make a 35? cardboard and hold one end against the vertical stabilo and the other end to the skin of the rudder. But that way, the rudder comes way closer to the elevator than the manual describes.

So if I understand your response well, the 35 degree angle is or should be the angle between the centerline of the fuselage and the centerline of the rudder. (so middle line of the triangular R-903 tip rib).
That looks very hard to measure with a cardboard but it's sure that that would explain why I'm much closer.

noelf · #4 08-12-2019, 05:34 AM

On my -6A build, I drew a line on the froor that represented the centerline of the fuselage. This was done using string and plumbobs fore and aft. Then I extended this centerline another 3feet aft.

Then, using a plumbob line from the trailing edge of the rudder, I swung the rudder full left and marked the floor, then full right and marked the floor. Next, connect these marks with the reference of the extended rudder pivot bolt on the floor. Then measure this angle with a protractor. Done.

tgmillso · #5 08-12-2019, 06:27 AM

Dipping into a 100,000 word document know as my build log, I found the following. Looks like the stock version of the rudder stop doesn't work. The main thing is have the clearance they dictate so there's no risk of conflict with the elevator. At the end of the day there's more rudder authority than any other aircraft I have ever flow. Tom.:

15 Dec 2016 6W: Drilled the bottom holes where the VS mounts to the WD-409 tail wheel spring mount to #27 and installed some #6 screws and torque the up, as these holes are too deep to use clecoes for temporary fit purposes. Checked the hinge line again and it appears that between the bolting of the back and the riveting of the F-781 bracket, the hinge line was now off in the center by 1/64?. Thus the middle rod end on the rudder was adjusted half a turn to account for this, then the rudder installed. All the bolts dropped easily in place indicating perfect alignment, and the rudder swung freely to its extents. The rudder stops were then fabricated. These were the second set to be fabricated, since the stock version made according to the plans was WAY too short and allows too much throw. The rudder was aligned to the VS by clamping the counterbalance, then a plumb line dropped for a zero degree mark. The plumb line was then dropped from the hinge point and also marked on the floor. Target angle marks were then scribed on the floor (32 deg to start with, determined via trig to make it more accurate rather than a protractor). The range is 30-35deg each way from center. The stops were progressively filed until the same distance from each elevator tip in the neutral position was achieved. I slightly overshot the 1 1/8? target specified in the plans, and have 1 1/16? gap on both sides, which results in 33 degree throw to the right, and 34 to the left. Dropped a plum line at the trailing edge of the VS skin down past the fuselage skin, and it appears that the final position for the top of the VS is only ?? forward of vertical. I called Van?s about this (Scott) and they said that to not worry at all and that it should not affect anything except maybe the screw positions on the fairing. He agreed in hindsight that a second washer could have been fitted on the right side of the elevator stop bracket. Hindsight?

griffg · #6 08-12-2019, 06:35 AM

I thought that I would throw in my comments on my experience with setting the rudder angle.

I manufactured the rudder stops P/N: F-792 as per the Van's drawing 27A. However, when I checked the rudder maximum deflection I found there was at least 5/32 inch gap between the rudder stop and P/N: R-405 on the rudder.

I then redesigned new rudder stops out of the same material using Van's dimensions for the vertical face (i.e. that sits against the fuselage) but modified the horizontal surface to achieve the correct rudder deflection.

The reason I used the original Van's dimensions on the vertical face is the rudder comes in close proximity to the fuselage skin at full deflection. If you extend the length of the stop beyond the skin it may contact the rudder and damage the skin.

I have included a drawing showing the finished dimensions of my new rudder stops (click on the link below to view). I would suggest that you mark out the horizontal surface but then add at least 1/16 inch extra material on the face that contacts with R-405. This will allow you to 1. remove the required material to obtain the stated rudder deflection (i.e. I used the 1 & 1/8 inch gap from rudder skin to elevator trailing edge) and 2. shape the rudder stop so that the entire surface will contact R-405 instead of a point.

My other piece of advice is to do all of the above before riveting the rudder stops on (i.e. easier than having to drill out rivets if you make a mistake).

I hope this information is helpful. The second link below is a photo of my installed left hand stop.

Happy building.

https://www.flickr.com/photos/141779426@N07/25775267443

https://www.flickr.com/photos/141779426@N07/26105124980

fl-mike · #7 08-12-2019, 07:22 AM

Use the tooling holes in the tip ribs of the VS and rudder to find your centerline. Four 1/4" clecos, then use your cardboard template against those.

jcarne · #8 08-12-2019, 07:40 AM

I had to make my rudder stops like Gordon did. I wouldn't worry about the angle, I just went for the 1-1/8" gap as per the manual.

wirejock · #9 08-12-2019, 07:55 AM

I installed the Flyboy rudder stop. No external stops. I haven't fine tuned them but the swing looks pretty close.

rzbill · #10 08-12-2019, 10:18 AM

Quote:

Originally Posted by JurgenRoeland

What I did was make a 35° cardboard and hold one end against the vertical stabilo and the other end to the skin of the rudder. But that way, the rudder comes way closer to the elevator than the manual describes.

So if I understand your response well, the 35 degree angle is or should be the angle between the centerline of the fuselage and the centerline of the rudder. (so middle line of the triangular R-903 tip rib).
That looks very hard to measure with a cardboard but it's sure that that would explain why I'm much closer.

Yes, centerline of aircraft to centerline of rudder. There are a number of ways to do it as noted in other posts. By your description of the cardboard, the baseline was not parallel to craft centerline (held on Vstab skin which is close but not exact) and the rudder centerline was not being measured but rather the skin. Rudder is tapered so this will give a centerline deflection much greater than 35 degrees.

And as others have already said, make your own rudder stops, the versions in the blueprints are way too small and will not stop the rudder in the correct position.

Good Luck.