It’s starting to look like a plane now!
With the fuselage longerons complete, it is now time to start building out the fuselage side frames. Two frames are built as mirror images of each other and follow similar construction to other elements with gusset plates being used throughout to reinforce the joints. I am building the “long” fuselage variant as this provides the most flexibility for weight and balance when using motors lighter than the Ford Model A. The first task was to set out the profile of the fuselage onto our table surface. I drew this in pencil and then taped over the lines with clear tape so that the markings would be durable but removable. This turned out to be extremely difficult to remove – I would recommend something like a marker pen and isopropyl alcohol next time if trying this at home.
Blocking was added throughout to support the various truss members in the correct position. The bottom longeron is bent without steam/water as the bend radius is not that tight – I had no issues bending this into shape by hand. The bottom chord was locked into position by additional blocking.
Once the longerons were in place, the various truss braces were cut to length and fitted into the jig – this requires slowly creeping up on your line to make sure it fits perfectly. The various angles for the braces makes this a little tedious but progress is very satisfying as it’s starting to look like a plane.
There are a few locations where the plans require some additional blocking added. This is for the landing gear attachment point and the rear wing attachment point (for the “long” fuselage variant). I cut these out of some offcut spruce and added these to the jig.
With all members in the jig, final checks were done to ensure the geometry was correct and the section sizes for each member was in accordance with the plans. Then the truss was glued together using T-88 epoxy and left to cure. I made a lot of little clamps from scrap timber and some bolts – this made clamping the frame together much easier.
Once the glue was cured, the excess glue was removed from the areas where the gusset plates are required so that a smooth clean surface is available for the gussets – this was done with a chisel and file. The gussets were cut out of 1/8″ plywood and were test-fit to ensure the mating surface was leveled correctly. The gussets could then be glued to the frame using T-88 and clamped using staples.
The gussets are added to one side and a reduced set is added to the other side – being careful to note that the two side frames should be mirror images of each other – not identical copies. Once the glue had cured, the staples were removed and the excess glue was trimmed.
I was happy with the first fuselage side once out of the jig – it really put into persepective the overall size of the aircraft – it’s no model airplane!
The first fuselage side was stored under the workbench whilst I started work on the second fuselage side truss. The second truss being a mirror image of the first side. The process of creating the second fuselage truss was exactly the same as for the first. The only additional consideration was deciding on a location for the longeron scarf joint which was required as I had run out of sufficient lengths of clear longeron stock. I decided to place the scarf joint in the top longeron so that it was not permanently bent – as several sources suggested the added stiffness of the scarf joint would make the curve less “visually appealing”. The scarf requires some additional doubler plates and hence, I put the scarf in the pilot’s bay so as to place it as far forward as possible (for CoG considerations) given the stock dimensions.
I was relieved to find very little difference between the two sides once I could compare the pair. The second fuselage side shows a very minor deviation of the top longeron about halfway along. This is limited to approximately 1/8″ and shouldn’t affect things too much except for possibly requiring the wing struts to be slightly longer on that side. Overall, I was very pleased with the side trusses and could now move on to the daunting task of joining the sides.