Month: March 2016
Since the last post I have been working on a few things all at the same time.
Firstly I have found that to keep work going without interruption a need to keep an eye on what is coming up and what material I need. In Aus I have found it hard to get timber. Spruce is impossible to find (we dont grow it) and Aviation ply, whilst possible to get is in metric sizes not imperial. This means that to get what I need I am having to import from the US. Right now that lead time is about 4 weeks if there is no issue. We have a whole quarantine process here that makes getting timber into the country more difficult and expensive. So…I need to keep one eye on what is coming up and what components I need and making sure I have enough lead time factored in.
Next I installed a new 2.4 metre long table for use with timber and will be used for construction of the wings.
Recently I have been working on the attach fittings. These are the tabs that are attach to a bolt that runs through the spars and are the attach points to the landing wires (wires that hold the wings up) and the sway wires (wires that stop the top wing centre section from moving laterally. Check out the journey that I have been on reading the the post on the design and location of these things.
As far as building is concerned I notice I am getting much faster at producing steel parts. I have the cutting down pat, the linisher makes the edge finishing really fast and the quality and consistency is getting better too.
Here is a pic of the fabrication part way through. The small ones are sway wire attach and the large the landing wire attach.
March 4 2016: Over the last two weeks I have been questioning the design of the top wing centre section. My question first came from my incorrect reading of the plans for the front cabane attach points of the fuselage. What I thought the plans were saying was to have a single front sway wire. This was in part influenced by a photo I had seen in a thread in the Biplane Forum.
Turns out that the sway wire fittings are a dual pair of wires, not a single.
What I did uncover in the course of this is that the sway wire design changed in 2006. This occurred when some hand drawn Curtis Pitts plans were changed to CAD. The biggest change was the sway wires moved from the centre section rear spar to the front spar. A whole heap of debate ensued and it will result in me modifying the plans and moving the sway wires to the rear as per the Pitts model 12.
If you want to see the whole story have a look at this thread. This is really worth a read if you are considering building the three piece delta wing. Make up your own mind!! Biplane forum R&D Design