Rudder Control Horns

[mstone]

I have a Soprano with a GRP fuselage and cross tail. The rudder hinge is part of the skin, "live hinge"? The other side of the rudder has a wiper installed, see picture.

I am having trouble getting the rudder control cable, carbon rod, to move smoothly. The manufacturer has a hole on the wiper side of the model for the control cable to exit.

Since this is a RES model the rudder needs every bit of throw it can get. If I place the control horn on the wiper side the amount of movement backwards and forwards is quite long. Shortening the horn doesn't work as it will hit the fuselage on the forward movement and the control cable hits the rudder going backwards. The other problem is the amount of lateral movement makes it difficult to get the fairing covers in place.

If the control horn is on the hinge side things would seem to be simpler.

What side do other molded planes put the control horn ?

Mark

[Mark Miller]

I have put the horn on the non-hinge side in all of my Sopranos. Check out my manual on my web site. I have not had an issue with things hitting and get full movement. You do need to keep the horn as close to the rudder surface as you can so as to put the hinge line to pushrod lenght short enough to give you full movement. I have attached a few photos of what I do.

One of my customers put the horn on the hinge side and I can see where this makes things simpler. It is simply having the control rod coming out of the fuselage . Sorry that I do not have a photo but can get one for you.

Mark Miller
Isthmus Models
www.isthmusmodels.com

[mstone]

Mark,

I would be interested in seeing a picture of the installation from the hinge side.

What is the distance between the rudder and the hole in the control horn in your installation?

Thanks

Mark

[mstone]

Well I ended up doing the rudder as per Mark's instructions.

Flew the Soprano today for the first time in less than ideal conditions.
Winds started off at 16 knots gusting to 20, enough lift about but going down wind quickly. Only launching on a tired bungee but the wind helped to get some good height. Haven’t made the ballast up yet but today would have been a good day to test it.

Later in the day a fellow club member turned up with his F3B winch, thanks Don. The wind also died off and we had great conditions just before sunset. The Soprano launches very well with a good strong ping off the end, not quite F3B altitude. This one is a keeper.

Mark

[Mark Miller]

Mark,

Good looking Soprano. I forgot to post pictures of the horn install with the horn on the other side. Here they are. I do not see a real advantage but to each his own. I will be adding these to the Soprano manual.

Have fun with it. Our season is winding down. It's good to see yours will be starting up.

Mark Miller
Isthmus Models

[BMatthews]

Another solution is to use a longer output arm on the servo. The servo setup may need to be played with a little but using more output throw at the servo would seem like the easier option at this point.

It also has the advantage of reducing the effect of any play or backlash in the system. Mechanical play is a fixed amount and in a system with shorter total travel will be a bigger % of the total movement. If more control throw is used and longer horns then the play issue will be a smaller % of the overall movement and tighter controls will result.

[Mark Miller]

I always try and use full length servo arms. You will have to offset the servos a bit to fit them under the Soprano nosecone. I like to have as much mechanical movement as I can and tune it back witht he radio as needed.

Mark

[mstone]

I didn't want to cut a hole in the fuselage, for obvious reasons. I ended up buying a set of the Dubro HD horns for the servo.

Mounting the servos at 45 degrees with the longer arms enabled me to get full movement of the rudder without having to revert to putting the horn on the other side of the rudder.

Mark

[Mark Miller]

Just as an FTI, here is a photo of how I install my servos. I just offset the servo from the center line as much as possible.

Mark