I have an LT-40 that I have just recently fitted with a pair of floats and I thought that I was Ready To Float but then I discovered a problem with my water rudder. When I move the rudder stick right or left, it centers in a different position from when I push the stick right than it does when I push left. Has this ever happened to any of you? Is a hitec standard servo enough to push both rudders? I am including some pictures below, the one on the far left is a picture of where the rudder centers when I push right, and the one next to it is where it centers when I push left. I also have a few pictures of my setup.

Thanks again,

LT-40

Sorry, It didn't let me send all of the pictures here are the rest.

I think the problem is at the nose gear linkage. You need to adjust the control arm so that it is 90 degrees to the pushrod when the servo is neutral. That way you get the same amount of pushrod movement in either direction, and it will have the same mechanical advantage when centering from either direction.


Jim

Whether there is the same throw in each direction is not particularly important for a water rudder but I agree that it would be best to have everything set up correctly. I think the question had to do with the fact that the rudder does not return to the same center if deflected right vs left. This is a result of the long unsupported flexible nyrod used to actuate the rudders. This introduces quite a bit of slop in the setup. It could probably be improved if the nyrod was fixed firmly at a couple of additional points.

1) Probably doesn't matter a bit for normal flying purposes as long as it isn't so sloppy that it oscillates or flutters during the takeoff run. Correct centering for the rudder is far less important than for a flying surface.

2) A single standard servo should be lots to drive the rudders.

(I am assuming that the servo is OK and doesn't have stripped gears)

Ross

Sorry, see 'water rudders'
D.

Both of my float planes do that a little. One worse than the other. It really does not matter. Once you are up to speed on your take-off run, the water rudder shouldn't be in the water anyway. Only used at slow speed maneuvering. I can understand wanting it perfect, I'm like that too. Honestly, don't sweat it.

I think Ross hit it on the head. That pushrod looks like it could use some supports.

Thanks guys, I will try and use your suggestions to help make it work better. I don't know if you can see from the picture, but the pushrod is supported behind the front mouting strut also. I'm not sure if I will try to give it more support, or if I will do what N7OR said and not sweat it. From looking at the pictures are there any other problems you can see? If not, great!

Thanks,


LT-40

Maybe it's my eyes or the picture resolution, but the holes in the arm on the water rudder look pretty large - this may be a silly question but is are they a tight fit to the clevis pin? If so, I'd say one source of centering problems/slop may be the fact that you have several linkages in series - rudder servo to nose wheel (2 linkages) then nose wheel to water rudder (another two linkages), with ganging clearances. That coupled with the short moment arm looks like you have on the water rudder arm may be casuing some uncertainty about center. Slop is fixed, for a given hole diameter and clevis pin diameter. If you moved the clevis on the nose wheel arm to one of the outer holes and used a longer arm on the water rudder you might tighten things up a bit by reducing the amount of rudder movement due to any slop that may exist in the linkages. But as others have said, it will be under load in the water and may be less of a problem than you think it might. MJD

If you must use nyrod (not my choice, but one way to do it), then you have to secure the sheath to the structure of the plane at its end. I'm not seeing that here. So when you push the rudder one way you pull the sheath straight, and when you push the rudder the other way the sheath deflects, and there is enough internal friction to prevent accurate centering. Nyrod should be run as straight as possible. Excessive bends only add play and friction.

Also, previous comment is absolutely correct thet the nose gear arm should be at 90-degrees to the nyrod at neutral position.

Yea, so it should look more like this.

Wow, thats cool what you did with the picture MinnFlyer. I think I will do that. But I have noticed another problem, I cant get the laser rods to stop sliding inside of the little braces (the epoxy glue doesn't stick to the nylon very well). Do any of you know of a glue that will stick, or just another way to hold the rod there?
Thanks for all of the help and for stickin with me on this topic for so long.


LT-40

PFM/Shoe Goo will stick.

Lightly sand the outer tubing and use CA