Rudder Assembly

Rudder Assembly

Assembly of the rudder can be the most demanding of the several sail pieces. It has been the source of several problems over the years and this assembly sequence will discuss the problems and the solutions.

A couple problems have arisen regarding the use of grade 8 bolts. These were considered to be be 'really strong' but in actuality, they ended up brittle and extremely subject to corrosion. They should never be used. The proper bolt would be a cad plated grade 5 of appropriate length. For the rudder this would be 1 3/4 inches long. And since the internal fitting is aluminum, and also a small diameter, it should be a coarse thread bolt.

The first two pictures show the tools and the parts for assembly. The tools are household tools except for the hot knife shown. This is a professional unit but you may substitute a soldering gun with a flattened end. It is uded for sealing the sail material as it is cut.

The wrenches are 3/8 and 7/16. A centerpunch is recommended when drilling into tubing to keep the drill point on the tube centerline.

A couple of things are different from standard quicksilver parts. I have found that the rudder balance strut, the shorter front tube, requires more than just a bolt per the original MX, and even more than the small triangle plates the newer planes use. I install long plates that sandwich the front balance strut and the longer rear compression strut. This assures that the front of the rudder and the aft portion stay in line, thus not changing the yaw trim during flight.

Older leading edges may be drilled for these plates by carefully drilling at 90 degrees to the original bolts hole, 3/16 diameter, 1/2 inch above and 1/2 inch below the 1/4 inch front to back hole. Some older planes also had a straight tube for the front balance strust. This should be replaced with a bent tube to provide better clearance for the upper tail wires during full rudder application.

Also, the lower end of the rudder leading edge has a 4 inch piece of 7/8 diameter tubing installed flush with the lower end. This keeps the tube from crushing during assembly.

Another item that has been found to be a problem are the rudder horns. During hard rudder applications, the horns can be bent forward. This causes severe slack in the rudder cables and with a steerable nosewheel, may reduce rudder effectiveness a great deal. Drill another hole near the upper flanges, 3/16 diameter and during assembly, a 1 inch spacer will be installed here. This fourth hole may be seen in the above picture.

The rudder frame should be bent to maintain a tight sail along the upper leading edge. The bow should be even throughout the straight portion and be no more than 1/2 out of straight. This picture shows the method for bending this frame.

The first step is to carefully thread the sail onto the frame. Start at the front of the frame by threading the lower aft sleeve on first. Buch the sail and thread the longer rear pocket, then the top, then the front, ending with the whole sail at the top of the rudder frame as shown below.

Slide the sail down along the frame. Install the leading edge tube making sure the small blind nut faces to the rear. A pivot eyebolt will be installed in this near the end.

A small triangle shaped cut out is needed near the top for the leading edge to contact the frame as shown.

Different techniques can be used to install the rudder horns, but due to the required tightness of the sail, a lot of effort may be required. I typically install the bolt in the leading edge first, then the front bolt in the rudder frame and then the second bolt in the ruder frame. Make sure there are spacer washers between the horn and the smaller 7/8 diameter frame at the two lower horn bolts. Then install the spacer and the fourth bolt.

The aft tube is the next part and it has a small aluminum tubing connector at the front with a 3-11a bolt, thin nut down, and plastic 7/8 tubing connector at the aft end. Use a grade 5 bolt here. A small oval must be burned to allow it access to the rudder frame as shown below. Remove almost all of one side of the plastic tubing connector so that the assembly can easily slide against the frame tube. The aft end is installed easily by using a carpeted floor and a shoe applied so as to push the tube towards and down into the cutout.

I generally install all the bolts from the right side, just to keep things looking like I thought about it. The plates install next using the three closest spaced bolts. The extreme front and rear bolts will be installed after the rudder is completed. Use 3-14a bolts with nuts. The balance strut is installed and the technique to pop the front in place is shown below. Make sure to pull the brace down to properly tighten the sail before marking the 1/4 inch hole for drilling.

The hole for the front is drilled inline with the end of the balance strut. The technique to tighten this is shown below. A hard table edge that isn't too high off the floor is best.

The last operation will be to remove the excess material at the ends of the outer frame. File the ends and deburr them with a dull knife on the inside, a file on the outside. Hammer the tube caps in the ends. To install the rudder brace kit upper wire assembly, melt a small hole just to the front of the small hole at the top of the leading edge. the hole should be even with the front edge of the tube, inline with the small predrilled hole, about 3/8 high and no more than 1/2 inch front to back. Install the rudder brace upper pivot with the nut to the rear. Install the upper wire assembly through the burned hole and install the pin and ring. Install the rudder pivot eyebolts on the lower end of the leading edge. One will thread into the blind nut discussed earlier. The other will go through the 1/4 inch holes near the botttom. To prevent the upper eyebolt threads from bottoming out in the hole blind nut, install two washers.

Our completed rudder is shown below. The new design features are summarized as the sleeve at the bottom of the leading edge, the larger triplates at the center, the bent balance strut, the extra bolt in the rudder horns and the optional rudder brace kit.