Carlson Skunk Works

November 2nd, 2009

AMF-14H Maranda SN:1026 Construction Log November 2, 2009

Posted by Roger in AMF 14H Maranda SN1026, news

How about that? Less than a month since my last post!

Progress is being made and I now have something that most people would recognize as an airplane part. The fin is basically finished! There is still some trim work and sanding to be done, and then I will need to seal it, but the assembly is complete.

Last post I mentioned that I had been in San Francisco for Oracle OpenWorld. I found a couple of pictures of the area where the conference was held, so I thought I would post them. These were taken from the overpass above Howard Street. The first one is looking to the west and shows the corner of Moscone West. The second picture is facing east from the same location and shows the tent that covers Howard Street and some of Moscone South.



Now back to the airplane.

These two pictures show how the fin skin and gusset strip will fit on this side of the fin. I didn’t have the 0.050 steel sheet called for in the plans to make the bracket for the elevator wires to fasten to, so I made a tag board version of the bracket and used that to locate and size a hole in each of the fin gusset strips. The holes will allow me to install the bracket once I make it. In the mean time, I can complete the fin and seal it properly.



This picture shows the hole in more detail. The hole is 42mm in diameter and is centered on the center line of the bolt that fastens the bracket to the fin. The rear edge of the hole is at the leading edge of the fin spar.


I was too tired to tackle gluing up the fin plywood, so I moved on to the hinge plates. On Thursday I stopped at the Marlatt Machine Shop to see if they would happen to have some of the metal for making the various fittings. Gary did not have the 4130 sheet steel that I needed, but he did have the aluminum for the fin fittings.

The first thing to do is to make a template of the hinge plate. The hinges for the elevator and the rudder are identical, so I need to make 14 hinge plates, two for each hinge. When I made the template, I was a bit confused by the markings for the top edge of the hinge plate. Looking at the drawing one way, it appeared that the top edge was to be 12mm long, 6mm each side of the center line. When I cut that template out and placed it on the plans that top edge just didn’t line up correctly, so I re-did the template so it now has an 18mm top edge, 9mm each side of center.


In order to waste as little material as possible, I made a second template that extends the angled sides to their max. This resulted in an equilateral triangle.


Here the hinge plate template sits on top of the triangle.


Enough for one night. I was tired and decided to head to bed.

Sunday afternoon found me much better rested and well fed after a great lunch of pork roast, mashed potatoes and squash. I think we are practicing for Thanksgiving already. After lunch everyone else decided to take a nap, so I changed clothes and headed to the basement to glue the plywood to the fin.

Here are two pictures showing the finished fin. I added the clamps to the leading edge to ensure that the plywood would fit around the edge as much as possible. I had sanded the leading edge enough that the plywood easily contacted lots of the leading edge strip, but I just wanted to be sure that it fit as well as possible. I will leave the clamps in place for a couple of days to ensure that the glue is fully cured before I take them off.



Once the fin was fully glued, I moved to the garage to start cutting hinge plates.

The hinge plate material is 2024-T3 aluminum plate, 0.063″ thick. I had Gary cut two pieces of aluminum for me that were 2.5″ X 36″. These will make the hinge plates plus several other pieces. I started by laying the hinge plate template in place and tracing around it with an ultra-fine point permanent marker. Then I place the triangle template over that and marked the long edge so that I could have a full length line to follow.

My wife insisted that I purchase a new hacksaw for this project. She is so great about the airplane! She even paid for the saw! Anyway, the new saw made cutting the aluminum very easy.

Once I had the first hinge plate cut, I would start each hinge plate by using the triangle template.



Then I positioned the hinge plate template inside the triangle and marked the other three sides.


Then I used a piece of 2X4 and a clamp to hold the metal in position while I cut it with my new hacksaw.


First I cut the 14 triangles, then I went back and cut the corners off of each of the triangles. Once I had the hinge plates rough cut I used my file to smooth the edges a bit. That way the plates sit together very nicely and I reduce the chances of cutting myself on a rough edge.

I took some packing tape and wrapped the hinge plates so I could stack drill them. I temporarily taped the hinge plate template to the top of the stack and marked the locations of the holes with a center punch. Then I held the stack in my drill press vice and proceeded to drill the three holes.

The holes were drilled using a 3/16″ drill. When the first hole had been drilled, I put one of the AN-3 bolts through it to ensure that the hinge plates would stay positioned correctly. Then I drilled the second hole and put another bolt through it. Finally, I drilled the third hole. Of course, I forgot to take pictures of this process and the finished parts. Oh well, I will try to remember to have those in my next post.

The plan is to clean up each of the hinge plates as needed, then bolt the whole stack together and file the edges so that they are all the same. I cut each of them a bit oversize to allow for this. I will include pictures of this process in my next post.