Clmbngfrk18

I'm building a boat and it's going to have a dual rudder setup. I came across an idea in a plane forum where you control the rudders using a 2 strong pieces of fishing line. They called it a pull pull system. In short you have 2 lines coming off your servo and you connect them to either side of the rudder. In this case 1 to each rudder then run a line between the 2 rudders. I'm wondering if this will work with boats they were using t on float planes but I think boats are gonna have more force to deal with.

Hydro Junkie

It will work, but not with fishing line. Fishing line is designed to stretch up to a given weight of pull. At that point, it will break. What will work is some of the fine wire leader lines or purpose made control cables. Since they won't stretch, if you can keep them tight, they won't fail due to crossing or jumping while running

TFLHOBBY-Candy

First time to hear that to use fishing line.

somebody are used of Music line.

A few warried about the fishing line seems not to be stronger.

If you did it .how about to share some pictures with us.

But ,it is really a new idea

mfr02

I've been using braided fishing line as both standing and running rigging on my sailboats for the last 25 years on the understanding that it didn't stretch, and I'm still waiting for a problem in that department.  The only downside is my inability to ever put a knot exactly where I want it, and, since it has very low surface friction, keeping it as a knot.  Superglue is wonderful stuff.  Racing yachties tend to 50 or 80 pound terylene line, and on a large rig, there's a lot of force involved.  Venetian blind cord is available in many thicknesses and therefore strengths as well.

Clmbngfrk18

The line I'll be using is 30# braided spiderwire it's supposed to not stretch. If it does fail I'll have to goto a wire of sorts i just have the line already. And there will be bends in the system so wire may not work. I'll hopefully have it rigged up this weekend I'll try and post some photos if I think of it.

If I wasn't on my iPod I could draw a rough idea of what it would look like.

Good call on the glue I would never have thought of that and woulda run it and lost steering.

chunkyplunker

Being an aircraft guy and fooling with boats on occasion I have a suggestion from the airplane world.
Sullivan Products has a product called Golden rod that can be picked up at Towers or many R/C aircraft shops. This system uses two hollow tubes, one outer tube that is used as a guide and the other used as the push rod.
Dubro also makes one similar but uses a hollow tube and braided cable, which I prefer because it seems to be a bit more flexible than Golden Rod, and is available from most suppliers.
Granted you would need two to do a pull-pull system.

Apismelifera

Hi Clmbngfrk18.

Model boaters usually use push rods for rudder control. its the easy way.

Example A: you have the simplest setup, one servo one push rod one rudder. When the servo turns clockwise its pulling on the push rod, when it turns counterclockwise its pushing on the push rod.

Example B: has two push rods. This is whats commonly referred to as a "Push Pull" setup. When the servo turns clockwise its pulling one one push rod and simultaneously pushing on the other push rod. When it turns counterclockwise its still pulling one one push rod and simultaneously pushing on the other.

Example C: Simple dual rudder setup.

Example D: Push Pull setup for dual rudders. If the rudders are close enough to each other then you would only really need one of the green push rods. Easier that way.

Look at a couple build threads for the type of boat you're working on, see what other people are doing, might get some good ideas too.

Clmbngfrk18

well i set it up this weekend its yet to hit the water but its looks like it will work ignore the boat its my 2nd attempt at glassing a boat the reason i was avoiding push rods my last boat it would fall off no matter what i tried to get it to stay and by using linesi could mount my servo anywhere and not have to worry bout bends etc

1 photo is of the rudders i may move them out from the prop more but that was the easy spot to mount

the other is of the servo line come off and go into a couple rubber hoses ill pack with grease to keep the water from leaking in

Apismelifera

An interesting experiment to be sure. Let us all know how it turns out, we want to learn too.

Justaddwata

My Feedback: (3)

Pull pull setups are used in full scale boats so I no doubt it will work with models. Some of mine have that setup (only with wire).

You might want to smooth some of the holes where you have the line passing - looks like some edges on the rudder that will wear your line in short order. It looks an easy install but I do not think nylon line optimal.

w3bby

As pictured it looks destined to fail unfortunately.

Complete system [link=http://www3.omnimodels.com/cgi-bin/woi0001p?P=M&I=AQUB9536]here[/link]. This is for a 3,5 ouboard but you get the idea of how it is set up.

mfr02

Avoid the monofilament, as soon as it starts to fray, the wear will accelerate.  With braided line such as blind cord, if the outer braiding shows signs of wear, its just a warning - the inner core is still there and doing its job and you get some pre warning of imminent failure.

Clmbngfrk18

well i got it on the water today i works quite well i could use slightly longer servo arms to get a little more movement but thats it overall i liked how the set up works im gonna try and move the out a little my prop is cavitaing bad so i gotta solve that issue now

Apismelifera

From the picture of the rudder setup you posted I would say that the rudders are in front of the propeller. That being true I noticed that the trailing edge of the rudders are squared off. The faster you go the more that flat trailing edge is letting air into the water, directly in front of the propeller.

Usually the folks with the go fast boats put the rudder behind the prop and off to the side a little, where the prop can get clean undisturbed water. Not water thats full of rudder bubbles. Perhaps if you moved the rudders sideways further away from the prop?

I suppose if you don't want to move the rudders you could taper the trailing edge so its thin, like the leading edge is...

Clmbngfrk18

I already moved the rudders out I figured that could be an issue just at them time that was the easiest set up. I woulda preferred behind the prop but I don't have the means to fab my own aluminum brackets.

As for monofiliament the line I'm usig isn't mono it's a braided line. there aren't any real sharp areas for it to wear on even the holes in he rudder arms have a convex edge. I don't see my line snapping for any reason short of a real hard crash but I feel if the line breaks then the boat probally will too.

1QwkSport2.5r

Another thought on the control lines for the rudders.. There are pull-pull kits that come with kevlar line. Kevlar thread is the same thing used in bulletproof vests, so its very strong. I believe the kit comes with control horn connections and tubes. I can't remember what brand I saw; perhaps it was Sullivan products.