Rudder and Outdrive Alignment - Gemini 105M - Jim and Deb Faughn

Some may know I built my own airplane and drag reduction was very important to me. I also learned a great deal in the 15 years I flew the plane from others about drag reduction. I attended Sun-n-Fun in April of 2007 and after talking to a friend about his KR-2 and drag reduction possibilities for him, it got me to thinking about our Gemini 105M. I began seeing the bottom of the hull and thinking about possibilities of reducing drag. The first thing I though of was - Were all of the moving surfaces aligned? What I found out was, they were not. Who knows why or if they ever were. I will outline what I did to find this out and then to align them.

First I decided the easiest thing to do was to pull both rudders up and center the trailing edge of the rudder on the starboard side with the crack in the lifting mechanism. I then took the picture you see to the right. Yes, I do need to repaint the bottom already (I am very disappointed in Interlux Ultra with Bioguard!!!) but the lack of paint really shows the line.

Then without moving the wheel, I went to the port side and took the picture you see to the left. As you can see the trailing edge is not the same. Therefore what is happening is the rudders are creating an induced drag on the boat. In my opinion, they should be aligned and that is what I set out to do.

I also took this picture of the outdrive, again, without moving the wheel. Again, you can see that it is not aligned.

I didn't worry about the outdrive at this time because it should be the last thing you align.

The first thing you should do is to make sure all of the nuts and bolts on the steering system are tightened. Even though I had tightened them before I left to go cruising, about 500 engine hours ago, I found several needed tightening again. After you do this, you can proceed with aligning the rudders.

Next, I loosened the clamps on the steering cables and moved them such that the rudders would be in alignment. In my case, I had to move one of them almost a quarter of an inch to achieve the result. After tightening the clamps, I then took the wheel and moved it both directions to the stop and then back to the center. I found I still needed some more alignment and kept tweaking the clamps until both rudders would both come out centered after the wheel movement stop to stop. Finally, I loosened the lines which steer the outdrive and centered it.

I will report on the outcome when I can test it (we are looking at a storm coming our way with 40 knot gusts forecast) but this has to help even if only a tenth of a knot or so. If I were a racer or someone who really cared about speed, I would pay even closer attention to the adjustment. As it stands, I'm simply a cruiser who likes all the details taken care of.

Later Report - What I found is the speed has increased by at least a tenth of a knot. I think it is more like .15 knots. I probably should have done time trials on the same day, before and after, but that is an after thought and somebody else might be able to do this and report back. I believe it is a good project if nothing else just to get it out of my mind.

Web Page by Jim Faughn