Practice makes perfect [ish]
For someone who has never built an aircraft before, it seems like the hardest step is to take that initial plunge and start building something. It is almost like if you don’t start, you can have this perfect idea of what it will be like, but if you actually start it, then that illusion will be shattered. With this in mind – there is nothing left to do but start cutting some timber….
I knew it would be heartbreaking to mess something up straight away – therefore, I decided to create a “practice” elevator to start with. This would be built with some “less than ideal” (aka. crappy) pine from the local Bunnings. I chose the elevator as it is a reasonably small component that required a lot of the skills required for the complete airframe. This practice elevator was never intended to fly – just to practice the skills required to make one. I would soon find out that several of my attempts would become “practices”….
To start with, I ripped a piece of pine to the required sections for each of the elevator members. These pieces were then cut to rough length and checked that the shape was correct.
The elevator consists mainly of 1″x1″ timber with a T-shape profile. This is then connected with a 3/4″ centre beam and 5/8″ thick trailing edge. Due to the inconsistent thicknesses – it is left up to the builder as to how you want to connect these elements together. These differing thicknesses also mean that a jig is required to hold all the pieces at the correct height above the workbench so that all the centrelines match up. The jig required a lot of blocks to positively clamp the pieces in the correct positions.
At the connections between members, there are gussets made from 1/8″ plywood. These gussets act to strengthen the glue joint significantly and provide additional rigidity to the structure. The gussets are to be recessed into the members by cutting the flange of the T-Shape profile off. There is also some additional tapering and rebating required to get the different thicknesses to match up. Note that the specific approach shown in these pictures is incorrect – I’ll explain why later.
Once the rebates were cut, the main elevator frame was ready to be glued together. I decided to first glue the members together and then, once the glue had dried, do a second glue-up to attach the gusset plates. The glued frame is shown below.
The gussets for this practice elevator were cut from 3.0 mm plywood from Bunnings. The gussets are best cut on a band saw with final shaping on the disc sander. It is important to get a tight fit for the gussets – something i improved upon significantly on later attempts. The gusset shape was produced in AutoCAD and traced off print-outs. However, I found this process to be cumbersome so later attempts used hand drawn templates.
The gussets were glued onto both sides of the elevator and clamped in place using some “handmade” clamps fashioned from some scrap aluminium flat bar. These clamps worked well but would make the gusset slide around on a thin film of glue. Hence, on later attempts I switched to using an electric staple gun to secure the gussets whilst the glue dried.
Once the glue had dried for the gussets on both sides, the last pieces to add are the 1/2″ x 3/16″ ribs. These pieces are glued onto all three members they cross. These ribs help to transfer loads from the fabric covering to the main frame members – they also add a surprising amount of rigidity considering their small size. They shaped to final length on the belt sander before being glued in. The final assembly is shown below.
The build of the practice elevator gave me a lot of confidence that the project was within my ability – it just took a long time. The whole thing took weeks despite the simplicity of it. However, subsequent pieces of the empennage only got faster and faster.
Next up – building the real thing….. or so I thought.
Truth be told, I ended up building several “Aviation Themed Wall Decorations” in my quest to start my plane. The main issue with these attempts was trying to sort out a good approach to joining the 5/8″ trailing edge to the 1″ T-Shape edge beams. Several of my attempts ended up way too skinny through this area as shown below.
However, I eventually settled on an approach I liked and could proceed with actually starting work on airworthy components of the Pietenpol’s empennage.