The Fuselage – Page 1

The fuse began with the workbenches. Two 3’x 8’ maple topped workbenches borrowed from good friends made a great base. (Good friends are Bill and Cliff and any reference to “we” here usually involves one or both of them. Thanks, guys!) I covered them with ¾” MDF. Using digital levels we made sure the top was level and flat. The fuse was drawn directly onto the workbench and holding blocks were put down in the places indicated in the plans, plus a few other places. Spruce was cut and placed. I used maple as the hardwood pieces and ¾” basswood plywood for the filler blocks. The first slab was glued together.

When the glue was dry, the stubs of the longerons were cut to finished length and the framework was removed from the workbench and hung on the wall temporarily. The other slab was done likewise. The plywood for the sides was ripped to rough dimensions and the ends were squared. Now it was time to scarf the plywood. I must admit that I had dreaded this step for some time. With the help of a scarfing tool (from West Systems) that attaches to a circular saw, some head scratching by myself and friends, and several trial runs, the 12:1 scarf joints were cut and turned out really nice. (Note: The scarf attachment mentioned is designed to cut 8:1 scarf joints. Some minor adjustments are necessary to get the 12:1 joint.) We put the aft section of the plywood on the workbench and placed the framework on top of the plywood with the forward edge of the scarf at the forward edge of the backer strip. We marked all the longerons and diagonal locations and began to spread T88. We held the framework down against the plywood by clamping sticks of wood across the structure about every foot. The same was done to the forward plywood to finish out the sides. This obviously is not the method that the plans suggest but it worked for me. I used a router with a trim bit to trim the plywood edges flush with the framework. With the finished slabs on the bench, we fabricated the ¾” plywood filler blocks that go between the intermediate and lower longerons. These will be installed later but it was easier to cut them to fit while the slabs were flat on the bench.

After a recheck that the bench was level in all directions, a centerline was drawn on the bench and a line representing each fuse side was drawn to either side of the centerline. Holding blocks were put along these lines to hold the fuse sides in place. Two of the spreader bars were made and placed them on top (bottom) of the fuse. Everything was squared and diagonals were placed across the vertical sides to hold them square. Pictures below are as we began build up of stations 3 and 5.

After stations 3 and 5 were built up, we decided to go ahead and bend the tail sections. We did this while the fuse was still inverted on the bench. Again, using the centerline on the bench, we marked the appropriate widths of the fuse from the plans. We used holding blocks on the bench and bar clamps to hold the shape. We cut and glued in the top and bottom ¾” pieces to form boxes at stations 6-8. We then built in station 4 using a solid piece of spruce covered with plywood. We also put in the filler blocks around stations 3-5. Plywood covers over the lower and intermediate longerons were added with the cutouts for the aileron torque tubes and the wing spar plates. Also, the horizontal and vertical diagonals were added with gussets.

A sharp observer may notice that stations 3 and 5 are slightly “taller” than called in the plans. This was a builder error and I considered fixing it after the fact. However, I determined that the benefits of fixing this were not significant. It simply means that there will be about a 1 inch step over to the floorboard forward of station 3 instead of the floorboard being flush with the top of that station. Station 5 is the seat back location so I saw no reason to correct it. Stations 2 and 4 will be the appropriate height.

With station 4 installed it was time to start the tail post. It is made similar to the rudder post. I used maple as the inserts in the lower section and middle sections and spruce for the top filler section. I extended the top section downward (like the rudder post) because I was not sure where the upper hinge would end up since you need to make sure the bolts will clear the diagonal spar.

Before we began to mount the post, we made sure that the upper longerons were the same length and square to each other at the rear of the fuse. The aft ends of the longerons were beveled so that the tail post would fit flush against them. After beveling the station 11 uprights to match the longerons we glued them in place after gluing in the plywood doubler side the left side of the fuse. We also glued in the small triangular and semicircular horizontal stab blocks. To mount the tail post we made sure the fuse was level from side to side and front to back. We then clamped the post in place and used a plumb bob hung from the top of the post making sure that it followed a centerline drawn on the aft face of the post. We also used a framing square to ensure the post was square vertically to the top of the fuse. At this point we fitted the metal tail post mounting bracket. When we were satisfied with the location of the tail post and the mounting bracket, we drilled the six holes in the fuse for mounting the metal bracket. We marked the thru the holes onto the metal bracket and drilled the holes in the bracket as well as the holes in the rear of the bracket for the lower hinge and the top mounting hole. We then glued the mounting bracket and the tail post into place and made one final check that the post was correct in both axes. We installed all the hardware permanently except the hinge. The hinge interfered with the plumb line. After the glue had dried several days we removed the temporary bolts and installed the hinge permanently and trimmed the plywood aft of the tail post.

Attention was then turned to the tail spring support and its anchors. I used maple for the support. This piece is somewhat interesting to construct as the sides are beveled to match the angle of the fuse sides, the bottom is notched to fit between and above the lower longerons and it must fit in a space left between two diagonal fuse uprights. The anchors for the support require some patience and trial and error to get a really good fit. I recommend using some hardware store plywood to develop a construction technique prior using expensive aircraft plywood. I also added the cross pieces on the top side of the fuse.

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