work continues on my Viper, however I have this nagging issue of the rudder on my mind. I have been thinking of a way to help the problem. I came up with an idea to help stabelize the rudder. As we all know, the bottom hing is well above the rudder horn creating a large moment arm for twist and leverage on that bottom hinge.
I have attached a few photos of a mod I did today. Quit simply, I added a ball bearing race in the fuse, and a pin in the base of the rudder in the center of rotation to help support the loads placed on the rudder from the horn and air loads.
A few issues were encountered. First, the angle at which the pin comes out of the bottome of the rudder, and the angle at which the tail slides down the carbon rods wont allow a pin to slide directly into the bearing. So, the amount of pin that extends into the bearing had to be rather short. About 2mm to 3mm. But, thats more that enough. Its all supported.
I located the center piont of rotation in the rudder, drilled and slid in a sharpened rod. Put the rudder/fin on the plane to locate and mark the fuse. Drilled a hole in the fuse fro the 3mm ID X 10mm OD bearing. I then drilled a 10mm hole in a piece of 3/8 inch plywood with a step drill on my drill press set at 12 degrees. This is the same angle of the rudder/fin relationship. This will allow the bearing to be held at a 12 degree angle when the wood block is attahced inside the fin area. I then fit and glued the block with the the glued bearing in place in the fin area of the fuse. I gluee the 3mm rod into th bottom of the rudder. Before the Vpoxy set, I put the fin and rudder in place on the model. I set the depth of the rod to about 2 to 3mm into the bearing. This is the only small issue. The pin moves forward as the assembly slides down as you install the fin/rudder, so you need to pull/push the rudder a small amount to get the pin to alingn with the bearing. The last photo is of the rudder in place and the pin can be seen.
I used a 3mm ID, 10mm OD 5mm deep Boca Bearing and a nice 3mm pushrod from an RC car maker. Simple stuff to find. Could just use standard hardware as well. The glue is setting up as we speak.... so i wont see the finished product until the morning, but I think this may well be a worthwhile mod for the Viper.
Here the pix. as always... feed back is welcome and encouraged. Any thoughts?