Carlson Skunk Works

August 24th, 2015

AMF 14H MARANDA SN:1026 Making Sawdust August 24, 2015

Posted by Roger in AMF 14H Maranda SN1026, news

Has it really been more than a year since I last posted??? Wow! Time does fly!

Things have been busy and life has sort of derailed many attempts at actually doing things to/for Sawdust. Now I think I am back on track and am once again beginning to make some progress. Much thinking and planning have been done and I have a spreadsheet of tasks that need to be done to move construction toward completion. A rough list of items that need to be purchased has been assembled and it should only take me another $10,000 to be flying.

The past weekend was very productive. I started building the trim control. I like the trim wheel type of control and have been puzzling over how to actually build one. Last year at AirVenture I purchased a sheet of plastic that was about a foot long, five and a half inches wide and half an inch thick. I was planning on using it as part of my comm radio antenna. However, there was more than enough material for that purpose, so I used one end of it to make my trim wheel.

The elevator trim tab is actuated via a Bowden cable. This cable will run from the elevator, through the fuselage to the trim control mechanism which will be under the seat. I will be using a bench seat arrangement, so the trim wheel will be mounted inside the seat support and will come through a slot at the front. Therefore, accessing the trim wheel will be similar to the way it is done in a Cessna 150. The other thing that I had to figure out was how to move the center wire of the Bowden cable in and out when the wheel turns. What I decided to do was to bend the Bowden cable 90 degrees under the seat so that it ends up running parallel to the wings in that area. Then I purchased a 3/4 inch diameter threaded rod at Menards and a square nut with the same threads as the rod. The rod and nut use coarse #10 threads.

I started by laying out the wheel on a sheet of paper. First, I drew a five inch diameter circle. Next, I divided the circle into twenty degree segments. Where each segment radial crossed the circumference I made a half inch circle. The paper layout was taped to the plastic and I drilled a small hole at the center, then drilled half inch diameter holes at each of the half inch circle locations around the circumference. It ended up looking like this:

Notice that the nut is sitting there as well. I drilled a hole at the center of the wheel that was the same diameter as the nut was wide. Then I used a Dremel tool cutting bit in my drill press to remove the plastic for the corners of the nut. I was careful to ensure that the nut fit quite snugly into the finished hole. Like this:

I drilled two holes through the threaded rod to facilitate a couple of AN3 bolts. These bolts will keep the rod from turning so that turning the trim wheel will move the rod right or left. The bolts will also be used to mount a plate with a clamp for the center wire in the Bowden cable.

In order to hold the threaded rod I cut a couple of mounting blocks from some left over delrin. This is the material that was used for making the elevator and rudder hinges. These blocks have a 3/4 inch hole centered in the block and located 1/2 inch from the front edge. Then two holes are drilled in each of them to allow them to be mounted to the front of the seat base with AN3 bolts.


So, at this time the assembly looks like this: