hookedonrc

I have a long control rod to my rudder on my Ultra Stick Lite. I am using 4-40 rods, but am thinking it needs to be stronger. I did have pull pull on it for a while, but the geometry was not perfect, so I went back to the pushrod. Since the rod is quite long 18"+, I am wanting to use a ball joint on the servo and a carbon fibre rod over a threaded 4-40 control rod. Problem is what size of carbon fibre rod to use. When I look online to order them, they all have outside diameter measures. Can anyone tell me what size of carbon fibre rod goes over the 4-40?

JohnBuckner

My Feedback: (1)

This is where you need to go. Derrol stocks the perfect slip fit for both 2/56 and 4/40 rod ends. I use these rods in virtually all my aircraft anymore and I finally was able to get my LHS to connect with Derrol and now almost all at our field now use these.

Derrols tutorial is also an excellent tretise on using these rods.

http://www.darrolcady.com/Carbon_Fiber/carbon_fiber.htm



John

hookedonrc

Thanks John, I will contact Derrol and will read through the tutorial. And while I am doing the rudder I might as well swap out the elevator rod too. It's much shorter, but it could use the extra strength.

JohnBuckner

My Feedback: (1)

Your welcome. Here a few of mine done with these rods. All of my pylon ships of course but these are some others. Even have one controline ship using this rod.

John

Jetdesign

My Feedback: (8)

I know this is not answering your question, but:

A ball joint on the servo horn is one of the 'weakest' connections. If you are concerned about the strength of a 4-40 rod than I would be concerned about the integrety of the ball joint connector.

There are a few easy tricks to getting an imperfect pull-pull setup to work. Crossing the lines adjusting the position of the cable end with respect to the servo horn pivot are two of them.

Mounting your rudder servo in the tail will give you a simple, strong, and reliable control surface if you can compensate for the change in balance. I had a plane with a long push rod for the elevators. I installed two mini servos in the tail and was very happy with the results.

Carbon rod over your push rod is an effective method. It is best if you can find a bi-directional weave (tough to find that small but can try Graphtechrc.com). Unidirectional carbon will resist bending, but there is not much holding the carbon tube together to keep it from splitting. So you want to minimize any 'slop' between the carbon and steel. You can put a few wraps of cotton (or carbon or whatever) thread around the carbon rod and glue with CA. I have fixed a few landing gears this way and it works well.

hookedonrc

Thanks Joe, I appreciate the input. As far as the servos location is concerned, they are in the tail already, and the plane has flown before. The elevator push rod is about 10" in length, but the rudder is the longest at 15". I did have a pull pull set up before a dead stick landing took the horizontal stab completely off the tail. Then it sat in the attic for about 4-5 years while I took a break from the hobby. I think the rods from Darrol Cady will fit the bill. I have attached a picture showing the servo location. I have completely recovered the fuse and reinstalled the G-26 and Dubro makes a 4-40 ball joint the appears to be strong enough to handle the load.

Well I thought I had a pic with the servos installed and the pushrods attached. I will upload one after I take a new pic.