More match drilling again, this time skins to the ribs.
Category: Aft Fuselage
Another session today drilling the J Stiffeners to the skins and ribs. The process was pretty much the same as the other stiffeners. Draw a centre line, fit the stiffeners and then back drill through the skins and ribs.
The first job of this session was to finish off the tailwheel skin trimming. On checking I wasn’t 100% happy with the clearance of the skin to the tail spring mount so I filed a bit more. I also opened up the forward hole to allow access to the nut that holds the spring in the mount.
Once I was happy with the tailwheel skin and mount it was time to start on the ‘fun part’ (actual words from the instructions!). First I laid out two saw horses.
Next I located the aft fuselage bottom skin and clecod on the F-708 & F-709 bulkheads and bottom J-Stiffeners.
Next I loosely placed the upper J-Stiffeners and clecod on the right side skin.
Then the left side skin.
Now I clecod the F-706, F-710, F-711 & F-712 bulkheads in place.
I tell you what the instructions weren’t wrong, that really was fun and it looks so awesome!
Motivated by my earlier session I spent the rest of the afternoon building the Aft fuselage. Instructions insist on removing any twist from the fuselage before drilling the stiffeners. I tried to do this with the fuselage the right way up but I soon realised it was much easier to make sure it was square by turning it over. I then put a plumb bob line at each end of the fuselage and used the tooling holes on the aft bulkheads to ensure that the string was centered over both holes. On the front bulkhead it was not so easy so I centered a ruler over the pushrod hole and aligned the plumb string with the tooling holes.
And the rear bulkhead…
Once I was sure that the fuselage was square I aligned the centre line I drew previously on the stiffeners with the pre-punched holes and then drilled the upper stiffeners to the structure on both left and right sides.
That’s all for today.
This is it! Making this cut will make this aircraft a tailwheel, a decision I agonised over for many hours. The plans gives a template for the cut but, like many other builders, I didn’t want to cut the original plans so I made a photocopy of the template from the plans and used that to mark the skin instead.
Once I marked the template I then used a 1/4″ drill bit to drill the end of the curve and broke out the dremel to rough cut the lines.
Next I used the dremel with the drum sander bit to tidy up the cut followed by hand filing for even more accuracy. The cut out is so that the tail spring mount can fit between the F-711 and F-712 bulkheads but when looked at the part it didn’t look quite square. I decided to check how far out of square it was…
Thankfully it looked worse than it was, it was actually only 1/32″ out of square. I can live with that. On first attempt I noticed the mount didn’t fit so I had to trim the cut I made earlier. Unfortunately it still didn’t fit but after referring to the instructions again I realised that F-712 also needs trimming to allow room for the welding fillets.
It took several iterations to remove just enough of F-712 bulkhead. I really didn’t want to take too much off so it was a case of trim a bit, check and repeat. Next I needed to drill the tail mount to the forward F-711 bulkhead through the vertical bars as well. The trouble is that is a deep hole and it was difficult to see in there. The instructions simply say to drill it square to the bulkhead, talk about understatement! Eventually I read Mike Bullocks blog which gave a fantastic tip of marking a line 12/32 from the top and from the edges. It worked a treat though it was an absolute bear lining it up and clamping it all. In the end I got it done and the bolt holes are drilled #30. I’ll final size them later on.
This session was a lot of work for not much reward. I’m pleased it’s done though.
That’s all for today.