Seaplanes Aircraft that typically take off and land on water...radio control seaplane discussions are in here.

Rudder Servo

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Old 11-08-2012, 08:04 PM
  #1
rsdonomoore
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Default Rudder Servo

I recently bought a 1/4 scale super cub on floats and have a few questions about setting up a float rudder. I bought the stainless steel kit from hangar 9 and have mounted it to the left float. I'm familiar with pull pull cables on my other plane but would like to use a servo for this one. There is a hatch on the float that was glued shut. The previous pilot flew without a float rudder and glued it shut. I carefully removed the hatch door with an exacto knife with no damage and am left with a servo arm I found in there with a clevis on the end just sitting in the float! I am going to remove the glue he put on the exit hole for the rod and re-install it. Now for the questions I have. What type of servo should I buy to put in there? It should not get wet but would like to have a waterproof one in there just incase some water ever gets in the float. I've heard traxxas makes a water proof one that is interchangle with futaba and have also heard the standard bluebird servo is waterproof. The plane is equipped with the Futaba 7C-2.4 Ghz system. Since I'm still learning I'd also like to ask the opinion of how to wire the servo to act in harmony with my air rudder. Do they sell a Y connector or can I go into another plug in the receiver? The plane is using ailerons, rudder, flaps, throttle and elevator. I'd also like to mount a kill switch too and need some suggestions on the best kill switch to use. I can also post pics if any of this doesn't make sense without seeing it. Thanks for any help!
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Old 11-09-2012, 05:33 AM
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Default RE: Rudder Servo

Hitec has a line of Waterproof servos, a standard strength servo should be fine

A Y harness is the common method, but I have seen a few guys with these larger birds actually use a separate RX and battery to isolate the water rudder servo from the Flight RX..

I use a the RcXel kill switches in all my gas planes, Easy to set up, cheap and so far for me very reliable http://www.rcuniverse.com/market/item.cfm?itemId=880656


Good luck
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Old 11-09-2012, 06:43 AM
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Default RE: Rudder Servo

I mix the water rudder and the air rudder together. This allows me to turn off the off the water rudder when I am checking flight surfaces on the beach. This method also eliminates a y connector.
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Old 11-09-2012, 06:51 AM
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Default RE: Rudder Servo

As Scale only noted the simplest way to set up a second rudder servo (makes no differance whether or not the second one is for air or water) is to simply use an ordinary Y chord on your channel #4 One leg going to the normal air rudder and second going on down to the water rudder.

You could on your radio slave another channel to your rudder #4 and use another separate extension from that channel on down to the WR. Regardless there is no advantage either way and you will still need a form of mechanical adjustment on the Wr. Either way you will still have to have an extension down to the WR regardless.

My preferance is to forget the separate servo and just use a long flex line from the opposite side of the rudder forward and bending around to near the trailing edge of the wing and back to the WR to hook up mechanically. Far easier and most important very easy to adjust out on a beach somewhere since water rudders are always getting banged around during operations. This is the setup I use on virtually all my float planes because of its simplicity and its functionality in use.

Note the simple cable in the pic from the air rudder to the water rudder. For the air rudder a second control horn is just installed opposite of the other side:

John
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Old 11-11-2012, 04:44 PM
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Default RE: Rudder Servo

Thanks for all the tips. John, I tried using your method but I need about 60" to get from the air rudder to the water rudder with the same routing you have on yours. I could only find a 48" jacketed cable at the Local Hobby Shop. Since I'm new at the building aspect of flying I bought 2 of the 48" kits and thought I would just use a coupling and solder the two together to make the size I need. The problem that I ran into was that I had to leave a gap in the jacket where my solder joint was because the diameter was too large to fit in the conduit. After I got it all assembled I've found out that the gap I had to leave in the plastic jacket creates slack in the cable and will not turn the rudder. It works great for pulling but won't push so now I'm left with a mess. I thought I'd resort to the servo in the float idea. Scale- I will order one of those kill switches thanks for the link.
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Old 11-17-2012, 05:39 PM
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Default RE: Rudder Servo

my personal experience with plastic control rods has been dissappointing....a bend in the run increases the friction enormously.....getting water in them increases the friction even more. End result was little if any throw on the water rudders. The ultimate system is pull pull cables like the full size use.

A servo in the float with a straight run would be very effective too. The traxas 2080 servo should be enough for the water rudder. The lowest cost Hitec waterproof servo puts out over 100 oz inches of torque (a bit of overkill) and is nearly twice the price of the traxxas 2080. If you want a full size servo, the traxxas 2056 is about 3 bucks more....
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Old 11-17-2012, 05:54 PM
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Default RE: Rudder Servo

Thanks wayne, I agree. I decided to go with the hitec servo in the float. My glow float plane has the pull pull cables and they have never failed me. I didn't see a way to route them on this plane so the servo mount was the easiest choice.
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Old 11-17-2012, 06:00 PM
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Default RE: Rudder Servo

The WR flex cable I use is stranded steel cable in a plastic housing. It is not Ny Rod. The brand I use is sullivan Golden flex and the longest is 48 inchs I think. It works well even in the wet evironment as the cable is not a tight fit in the housing and I shoot lube in before each outing. It has been the most reliable for me on a considerable number of ships. I would not try to splice the cable and housing instead its simple to just shorten the curve as it does not have to go all the way forward to the trailing edge.

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Old 11-17-2012, 06:05 PM
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Default RE: Rudder Servo

John, yeah splicing turned out to be a bad idea because the joint diameter was too large to fit in the casing. I thought about just curving it not at the strut but to where the length would work out. I thought it looked weird just hanging there so I abandoned the whole idea and went with the servo in the float.
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Old 11-18-2012, 04:29 PM
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Default RE: Rudder Servo

rsdonomoore,
I got a little creative with my 1/4 scale floats. I used the servo mounted inside the float (both right and left float) without any problems. I didn't want any external linkages, I feel they just take away from the scale fidelity of the plane. I just used a standard JR DS537 servo, but I made my own extension to bring it into the fuselage. I made a double female receptacle extension (I think you can get them online also) and used a Ernst charge receptacle on the underside of the fuselage. Inside the fuselage, I had to make a double male plug extension to go from the receiver to the Ernst charge receptacle. I used a separate channel for each water rudder and the flying rudder, that way I could adjust each one individually. A little overkill, I admit, but I had the receiver with enough channels, so I used it. 1 channel for throttle, 1 for engine kill, 2 for ailerons, 2 for elevators, 3 for the rudders.
The way I have it wired, I can change from floats to wheels in about 15 minutes, although, I've only flown the plane off wheels about 4 or 5 times. I spray the servo and wire connection liberally with some Corrosion X and after way more than 200 flights off water have never had any problems whatsoever. I do remove the servo hatches after a day of float flying just to let any moisture collected inside the floats dry out. If you have any questions, or want more pictures, I'll be glad to help.
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