Going Scale Plane Crazy,,,
Once I got that big Sig Cub home I gave it a complete inspection. The original builder had used top quality components and accessories. Except for the damage to the covering in the nose area the rest of the plane looked good. The builder had done an excellent job covering and painting this aircraft. He had even added pinked tape in all the right locations (ribs, leading and trailing edges, seams, etc.). The wings needed nothing done to them so I set them aside and gave some thought about what I wanted to do to make this plane stand out.
In previous posts I told how I had been buying RC magazines and books. One of the soft cover books was about making large RC planes. I think it was called "Giant Steps" and had lots of information about engines, radios, covering and detailing. The was one chapter about Bob Nelitz and his super detailed 1/3 scale Piper J-3 Cub. There were page size plans of this Cub included in the article. This Cub was probably the best example at this time of the scale builders art. The plans showed how he had added many details like a complete interior, working windows and door, scale cowl attachment, simulated tube frame and much more. I decided to try to duplicate in 1/4 scale much of what he had done.
I made a list of changes I wanted to make and placed some orders with Sig for decals and photos and with Bob Dively Models for a Cub cockpit interior kit. I also had picked up locally a DGA Pilot kit and a Tatone instrument kit. I found a resin block of different sized miniature bolt heads and nuts with threaded rod. Plastic military modelers add them to vehicles like tanks and trucks to enhance the realism of the vehicle. I thought I could use them on the Cub especially in the cockpit. I also saw some very fine mesh and realized it was perfect for the carb heater box at the front of the cowl.
At the top of the list for changes was simulating the tube frame of a full size Cub. Bob Nelitz had used wooded dowels during the construction of his Cub to achieve this look. I would need a different approach as a Sig Cub uses a sheeted box fuselage. I removed the covering from the fuselage and tailplane and saw that this plane had been well built. Tight glue joints and no filler showed me this plane was constructed with care. My first idea to simulate the tube structure was to cut or gouge a 90° wedge out of a dowel and glue that to the corners of the fuselage. This proved impossible to do. Trying to keep a straight and true 90° cut in a long flexible dowel was beyond my abilities. I needed another solution. It was then that I noticed one of the bits for my rotary tool was a round cutting ball. The diameter would allow me to cut a rounded channel on the corners of the fuselage that I could glue a dowel into. Anyone who has ever used a rotary tool knows that it will cut through wood pretty quick. Trying to make a long cut to the same depth freehand would not be easy. The rotary tool can get away from you and make a real mess of your project. I needed to make up some kind of jig. I had a couple of pieces of some some flat steel stock I had picked up at some time in the past. It was about 1 inch wide and about 1/16 inch thick by 12 inches long. I thought that if I attached one piece to the top of the fuse and one piece to the side I could use them as guides to make a straight cut to the same depth. I made a quick mock-up of one side of the fuse and using a small dab of hot glue I placed each piece a little bit back from the edge. I turned on the rotary tool and by holding it at an angle the shaft on the cutting ball would ride along the bottom piece and cut a rounded trough in the edge. I had to play around with the spacing of the two pieces. The top piece I used as a guide. If I was getting sparks I was cutting too high. Once I had the spacing correct I again used hot glue and attached the steel to the fuse and made cuts on all the square corners. Since the steel pieces were only 12 inches long I had to reposition them many times until I was done. To add dowels to the top and sides I need to cut a flat spot the length of a dowel the was straight and true. Turning once again to the rotary tool bits I saw one that was a cylindrical cutter. I had a Moto-Tool holder and base that that you could adjust vertical or horizontal and anywhere in between. I decided I would made a planer table to cut the flat spot in the dowels. First I drilled a hole the size of the dowel in a piece of scrap wood. I sawed down through the hole at about the 25% point. I clamped this to my workbench and hand planed it until the gap was uniform. When I inserted a dowel into what was left of the hole about one third of the dowel was exposed. I screwed a block of wood across part of the opening. I set up the rotary tool in the holder just in front of that block and positioned the cutter horizontal and 90° to the slot and just making contact. The block behind the cutter would trap the flat spot and not allow the dowel to twist. I hoped! I turned on the rotary tool and started to feed a dowel into the slot. That cutter had no trouble cutting a flat spot and the block behind it worked as planned. I soon had many feet of dowel all cut perfectly flat on one side. I installed all the dowels in the proper locations and was pleased with the results.
I had purchased a fiberglass cowl as they are much more durable than a plastic cowl. I was using a twin cylinder engine that was wider than the cowl. I would need to cut it in half horizontally and make cutouts for the cylinders. The Nelitz article showed the scale location of where the cowl should be cut and how it was attached to the airframe. I carefully cut the cowl in half and then slowly make the cutouts for the cylinders. Finally I had the cowl cutouts symmetrical and was ready to affix it to the fuse. The cowl used posts and cotter pins to keep it in place. I first tried to drill holes in some brass rod but did not have much success. Looking in one of my model plane catalogs I saw that Du-Bro had some rigging couplers. They had a small hole in one end (good) and were threaded. Off to the hobby shop I went and picked up several packs of the 2-56 sized couplers. These worked out perfectly. I taped the cowl to the fuse and drilled three holes through the cowl and into the fuselage on each side. Since the couplers were threaded I screwed them into the holes. Even though they were machine threads they screwed down into the holes.I didn't glue them in yet because I still had to make the cotter pins and add the washers to the cowl. I wanted a snug fit and until I had those parts on hand I was unsure of how deep the post should be installed. The cowl also attaches to itself in the front of the cowl using more posts and cotter pins. To accomplish this I first drilled two holes in the upper cowl. I then cut a strip of thin brass sheet. I formed it to the shape of the upper and lower cowls pieces. Holding it in place I marked the location of the holes in the upper cowl. I drilled out those holes and took one of the couplers that I had screwed a nut onto to see if everything was going to line up. All looked OK. I had some brass rod that fit the hole in the coupler like a glove. I also found some small 2-56 size washers at the hobby shop of the correct diameter. I glued the washers over each hole on the cowl. I now used the brass rod to screw down the couplers for a snug fit. At the front of the cowl I also had added the washers. I placed the couplers through the brass strip then
through the cowl and inserted the brass rod. This time I screwed the nut on the coupler to snug the rod down against the washer. I removed the rod and proceeded to solder the nuts and couplers to the brass sheet. Once the solder had cooled I again put the coupler assembly through the cowl holes and inserted the brass rod. I marked where the brass strip in the lower cowl was positioned and mixed up some epoxy. I spread epoxy onto the lower cowl and clamped the coupler assembly into that marked space. I had drilled a number of small holes in the lower half so the epoxy could ooze up and out and make a better bond. I went back to the posts in the fuse and put a tiny drop of thin superglue on each post. It would work its way down the threads and those posts would never come out.
Making the hairpin style cotter pins was easy. First look at an actual hairpin cotter pin. It is just rod with a rounded end and three 90° bends. A pair of needle nose pliers and the aforementioned brass rod is all that is needed. Grab the rod with the pliers and wrap the long end around the rounded part of the pliers. Stop when you meet the rod gripped by the pliers. Grab the rod at the point it meets the half round you just made and bend up, then a bend down and another bend up. Clip off, Repeat a bunch of times as you will lose some of these tiny cotter pins.
The full size Cub has an adjustable stabilizer for inflight trimming of the aircraft. Depending on the center of gravity or airspeed, to maintain a level heading without constant pressure on the control stick you trim the elevator or rudder. Most planes have trim tabs at the trailing edge of those flight surfaces. The Cub moved the whole stabilizer. You could do this from the cabin. Nelitz showed how to do this on his plans but it would have required major surgery on a finished airframe. Having already been down that road when I added a retractable tail wheel to a P-51 I decided I would fake it instead. I drilled some small holes above and below where the slot is located on the fuse. I enlarged these with a half round file until I had the shape needed. I now had an opening from one side to the other above and below the stab. I painted everything you could see inside this area black. I took a piece of small plastic tube and cut it in half. I made them long enough to reach both stabs.I beveled the ends and filled the end with balsa and sanded the balsa to a round profile. I painted these two pieces Cub yellow and glued them into the openings on top of the wood crosspiece in the fuse that was located there, top and bottom. It gave a reasonable approximation of the rod that connects to both side of the stab. I then cut a small gap completely around the stab next to the fuse and painted this flat black. When I covered the plane I left this gap visible. From a couple of feet away it did look like the stab was separate from the fuse. Overall the illusion of an adjustable stabilizer came out all right.
Close to the End,,,
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