Carlson Skunk Works

November 29th, 2013

AMF 14H MARANDA SN:1026 Making Sawdust November 29, 2013

Posted by Roger in AMF 14H Maranda SN1026, news

How about this? Another post within a month! Yeah, I know. Just barely. BUT I did make it!

Yesterday was Thanksgiving. I have a huge amount to be grateful for and I praise God for all that He has provided for me, my family and friends. We enjoyed our Thanksgiving meal with three of our children, our grandson, and our friends Sandy and Una (pronounced EE-oo-na). Una and Sandy are single ladies that our family has adopted, especially for celebrations like yesterday.

Since we had two “adult” sons home with us, and they had arrived on Wednesday and spent the night, I had two “willing” helpers to provide some lifting assistance to mount the wings on the airplane. So Sawdust is now looking much more like it will eventually fly!

The temperature was in the high 20’s and low 30’s as we loaded the left wing into the back of the pickup and headed to the airport. We repositioned the fuselage and mounted the right wing first, then we moved the sawhorses, unloaded the left wing from the pickup and mounted it to the other side of the fuselage. Then I opened the hanger doors as wide as I could get them and found out that the east door has a problem and won’t open all the way. We ended up getting the plane out of the hanger by swinging the tail around and maneuvering the left wing outside first, then turning the fuselage around and backing it out to get the right wing out of the hanger. I am going to call the airport manager and let him know about the door problem. Right now it is not a big thing, but when the plane is ready to go in and out of the hanger more often it will become quite an issue.

OK. So, of course, you are wondering where the pictures are. We were so busy and excited to get the wings on, that we didn’t get any pictures until after the fact, but what I have follows:

Front view. You can see the full wingspan and the hoerner wing tips.

It is starting to look like an airplane! Here you can see the “gull wing” look that the tapered leading edge provides at the wing root. The horizontal stabilizer is finished, so I need to get it mounted to the fuselage on the next warm, sunny day.

Well, the fuel tank is currently where the seat will be. One of the next tasks will be to figure out how to mount the fuel tank. Also, the ailerons need to be built and mounted. Building the ailerons and doors will be the focus of this winter. Those can be built in the basement where it is warm. I already have most of my tools moved back down there, so they are ready to get going. The first item is to finish the elevator, then it will be on to the ailerons.

I followed the lead of Randy Holland and built up an area of a rib for the purpose of providing a mounting point for the pitot-static tubes. The area of the rib just behind the forward spar that has been built up is right in the middle of the picture. If you don’t know what you are looking for you will probably miss it.

The plane is back in the hanger and I am busy digesting turkey and pumpkin pie.

November 11th, 2013

AMF 14H MARANDA SN:1026 Making Sawdust November 11, 2013

Posted by Roger in AMF 14H Maranda SN1026, news

I had a really good weekend! The leading edge skins have been installed on the left wing, except for the small inboard section where the leading edge makes a break. The wing has sort of a gull wing look like some Stinsons that I have seen.

Friday afternoon I got the chance to work on the pitot-static tubes. Saturday morning I cleaned the carpet in the dining area. Once the carpet was done it was starting to get quite nice and my wife gave me the go ahead to spend the rest of the day working on the plane. I was careful to take a bunch of pictures, so here is what I got done.

Friday afternoon I gathered materials and tools to try to make the pitot-static tubes. I had done quite a bit of research about the cost of purchasing these and decided that trying to do it myself would probably cost about as much, but would deliver a great deal of satisfaction. So I bought a ten foot roll of 1/4″ copper tubing, some solder, a #60 drill, and two #10 x 1/2″ belt rivets. Tony Bingelis provided instructions and a basic design in one of his books and this information is also available in the homebuilder section of the EAA web site. I went to the EAA web site and grabbed the image of the drawing and printed it. I also have the book, but wanted a copy of Tony’s drawing that I could make some notes on.

I dug around in my plumbing box and found a tin of flux and my tubing cutter. I also had a propane torch from when we built the house in Minnesota and I plumbed in the hot water heating system. At this point I was ready to go.

My biggest concern was how to plug the end of the tubing for the static tube. The tubing cutter made it easy to cut the tube. Tony only said to seal the tube and suggested crimping it, putting a screw in the end of it, filling it with solder, etc. I wanted something that looks fairly nice, so I started hunting around and came across some belt rivets at my local Ace Hardware store. These were #10 x 1/2″ long and had a large, nearly flat head on them. I got two just in case and they were $0.32 each. These were copper, so they worked quite nicely.

I started by figuring the length of tubing that I would need for my tubes. I calculated that a two foot length would provide plenty of tubing, but would still be small enough to be relatively easy to work with.

The plans call for eight holes and show them as being positioned in two radial groups of four holes about 1/2″ apart. I measured where I wanted the holes to be and chucked the #60 drill into my drill press. Then I used my tubing jig for positioning the tubing in the drill press. I position the bottom of the V so that the drill hits the bottom of the V and clamp the jig in place, then I position the tubing and drill the holes. It is not fancy, but it works pretty well. The hard part with soft copper tubing is that it is pretty difficult to get the tubing to be perfectly straight. I decided to drill these holes before I put the plug in the end of the tube just in case things got messed up. That way I could be sure that these holes were done correctly before I committed one of my plugs.

The next thing was to cut some small pieces of solder. The order of assembly is to use a pop-cycle stick to stuff some flux into the end of the tube, push the rivet into the end of the tube, then drop the pieces of solder into the tube from the open end and have them end up at the rivet end. Once all the parts are in their assigned locations I just needed to heat the end of the tube by the rivet and let the solder pieces melt. Unfortunately, the matches that I had in the garage had gotten soggy, so I had to go find some other matches before I could heat things up.

I don’t know if the tubing had some protective coating, or if my torch wasn’t burning cleanly, but the tube seemed to get pretty sooty. I was careful to hold the rivet end down while I heated the tube so that the solder would melt. The flux bubbled up nicely and some bubbled out of the holes that I had drilled in the tube. At least I was sure that I had heated things enough to be sure that the parts were soldered together. Next I needed to grind the rivet down to the same size as the copper tubing. I tried using a hand file and that worked reasonably well, but I found that my bench sander worked really well.

I found some paper towels and a Scotch Bright pad and got the static tube cleaned up pretty well. Then I took it back to the drill press and made sure that the holes were open. I am able to blow through the tube without difficulty, so I think I am ok. The rivet shaft is 1/2″ long, so I should be able to safely file the end to a nice rounded shape without compromising the finished product. However, I don’t think that is really needed, so I am leaving it as is for now.

The next thing to so was bend the tube. I happened to have a set of tube benders that I had bought for a plumbing job. These are basically coils of wire that the tubing fits inside of. With the tubing in the bender one gently bends the tube while making sure that the bender continues to slip along its length. Of course, I needed both a static tube and a pitot tube, so I needed to cut another two foot piece of tubing and bend it appropriately. The pitot tube is a lot easier to make because it is just a tube. I didn’t need to plug the end or drill holes crosswise through it. Just cut it to length and bend the end. Then I soldered the two tube together so that they became a single unit.

The final task will be to make a mounting bracket for the unit. Once again my local Ace came to the rescue with a piece of copper sheet. This is fairly thin, but yet thick enough to make a durable mount. I still need to complete this, but the intent is to make a U channel just wide enough for the two tube to lay in. Then I will solder the tubes to the bracket and bend the copper plate to make mounting ears. The plate is about four inches wide and a foot long, so it gives me enough material to make a couple of mistakes if I need to.

I took Randy’s lead and made a mounting place for these tubes on a rib just behind the front spar. The rib I chose is between the strut mount and the jury strut mount and is about 66 inches from the root end of the wing. This will be mounted on my left wing, so that the length of tubing to the instruments is as short as possible. Having the pitot tube located in the triangle formed by the strut, jury strut and wing should help to protect it from people accidentally running into it.

Saturday afternoon was very nice and provided a good time to finish applying sealer to the areas of the wing that would be covered by the leading edge skins. Then I needed to scarf and bend the skins. Once again I used the heat gun to apply heat to the plywood in the areas where I wanted to bend it. This works really well! Heat the side of the plywood that will be on the inside of the bend. Gently bend the plywood as it heats, but be sure to spread the heat over the entire length of the bend. When the plywood is bent about right I grabbed some of my clamps and held the bend in place while the plywood cooled. Using this method allows me to bend a sheet of 1.5mm plywood to a 1″ to 1 1/2″ diameter without any problems.

The next thing was to seal the inside of the nose skins. I held the plywood in place and marked where the ribs would go, then taped the areas where I would apply glue when it was time to attach the skins. I put on a good solid coat of sealer, reapplied the clamps to retain the curve and called it a day.

Sunday was colder, so I moved my wife’s car out of the garage, positioned the wing where I could work on it and closed the garage door. I removed the tape from the areas where I now needed to apply glue and went over the surfaces to be sure that everything looked right. I mixed up a batch of T-88 and started smearing it over the inside areas of the skins that did not have sealer on them (where the masking tape was). Then I held the skins in place (one at a time) and stapled them in place.

This time I used 3/4″ wide scarf joints and took a bit more time in applying the skins and the joints where the skins met turned out much nicer than on the right wing.

Today and tomorrow are supposed to be a bit cool, but after that things are supposed to be in the mid to upper 50s. I am very hopeful that I will be able to finish this wing before the winter weather sets in.

November 8th, 2013

AMF 14H MARANDA SN:1026 Making Sawdust November 8, 2013

Posted by Roger in AMF 14H Maranda SN1026, news

Wow! Another month has gone by since the last post. Well, I am still making progress, but have not taken many pictures of the steps that have occurred in the past few weeks. What I do have is project pictures and a report about the EAA Sportair Workshop that I attended in Dallas, TX on October 19 & 20. The experience was fun and I learned a great deal!

The EAA Sportair Workshops are presented at multiple locations around the country. This was my first workshop, but I am already considering attending another one as Sawdust progresses. I went to the Electrical Systems & Avionics course, but there were other courses being held at the same site at the same time.

I chose to go to the workshop in Dallas because I can get free lodging while I am there and can see my son and grandson at the same time. So I took some vacation and did the ten hour drive on Thursday afternoon so I could be with on a school outing on Friday with my grandson. I left Kearney just at noon and arrived at my son’s apartment at 10:30pm even with a supper stop at Braum’s on the north side of Oklahoma City. I can make pretty good time if I am by myself.

This is what I came home with from the workshop. The manual has lots of good information, includes a copy of every slide that the instructor talked to and notes about what he said. There is enough room around the edge of the slides to include quite a few notes. The hands on portion of the workshop provided instruction and practice of soldering and crimping and the theory portion helped me to understand why things need to be done in a particular way. The projects that I completed were mine to keep and take home with me. I should be able to reuse some of the parts.

The manual is really well done and has lots of additional material that will be useful for reference.

The first project was learning to use crimpers to connect wires together and to attach terminal ends. What I found really interesting was that using crimped connections is the preferred technique for aircraft wiring. My electronics background had me prejudiced toward soldering, but in our airplanes there is a lot of vibration and soldering the multi-strand wires that we use turns them into a solid wire which becomes quite susceptible to work hardening and breaking where there is vibration. Anyplace where the wires are soldered we need to add strain relief such as shrink tubing collars.

The second project was to wire up an intercom harness. We only wired it for one headset, but it gave us experience with crimping and soldering and applying shrink tubing and planning ahead. Be sure to put the shrink tube on the wire before you solder it to the connector, or you will have to unsolder it and put the shrink tubing on and re-solder it. This also provided experience working with shielded cables.

Sunday morning’s project was to install a BNC connector on a coax cable. This was a bit more involved and required some careful measuring, cutting, trimming and crimping. Not hard, just detailed.

The final project was to wire up a circuit by following a wiring schematic. This circuit simulated something that most people will end up doing in their planes. There is a switch that will turn on the navigation lights and the cockpit lights. If you need the cockpit lights it is probably dark enough that you will need the navigation lights, so one switch controls both. The cockpit lights may need to be dimmed, so there is a rheostat for dimming them. Each circuit needs to have a protective fuse so that a short in that circuit will not remove power from other, possibly more important, circuits. Therefore, there is a fuse in the circuit. Then there needs to be a power distribution bus and a power supply. Our power supplies were a AA battery that is in a holder on the underside of the chassis.

When the switch is turned on the lights come on.

Adjusting the rheostat dims the cabin light, but leaves the navigation lights on full.

I really enjoyed the class! They also had coffee and cookies available at the start of each day.