The stringers along the top of the fuselage need drilling for the pop rivets which will keep the fabric attached. I'm using 48" lines of rivets at 2" spacing on the outer stringers and 54" of rivets at 2" spacing along the centre stringer as per advice from Jim Clement. So the challenge was to drill 70+ holes in the centre of the circular stringers accurately spaced out without the drill bit wandering off centre and wrecking the fabric! After a bit of thought I decided to make a jig which would align the drill along the centre of the stringer and provide the spacing. I used a semi-circular router bit in the CNC router to machine a shallow channel in a bit of scrap aluminium. Then the router bit was exchanged for a 1/8" drill bit and the router programmed to drill two holes exactly 2" apart in the centre of the channel. The channel accurately located the jig over the stringers. Once the first hole was drilled in a stringer a spare drill bit was inserted through the jig into the ready drilled hole and then the second hole drilled through the other hole in the jig. Then it was just a case of moving the jig one space, with the spare drill bit popped into each new hole in turn and drilling through the other hole. It took about 30 minutes to make the jig and less than 10 to then drill the holes. I also then applied the finishing tapes over the bottom stringers and those on the left side of the
aircraft. I now need to wait for the rivets to arrive from ACS before I can finish up the top of the fuselage and also still need to do the finishing tapes along the bottom longerons. I've also run out of 2" finishing tape which I need to complete the horizontal stabilisers and will also need for the elevators, flaps and ailerons so an order went in for another 50yds of that as well.
The stringers along the top of the fuselage need drilling for the pop rivets which will keep the fabric attached. I'm using 48" lines of rivets at 2" spacing on the outer stringers and 54" of rivets at 2" spacing along the centre stringer as per advice from Jim Clement. So the challenge was to drill 70+ holes in the centre of the circular stringers accurately spaced out without the drill bit wandering off centre and wrecking the fabric! After a bit of thought I decided to make a jig which would align the drill along the centre of the stringer and provide the spacing. I used a semi-circular router bit in the CNC router to machine a shallow channel in a bit of scrap aluminium. Then the router bit was exchanged for a 1/8" drill bit and the router programmed to drill two holes exactly 2" apart in the centre of the channel. The channel accurately located the jig over the stringers. Once the first hole was drilled in a stringer a spare drill bit was inserted through the jig into the ready drilled hole and then the second hole drilled through the other hole in the jig. Then it was just a case of moving the jig one space, with the spare drill bit popped into each new hole in turn and drilling through the other hole. It took about 30 minutes to make the jig and less than 10 to then drill the holes. I also then applied the finishing tapes over the bottom stringers and those on the left side of the 
aircraft. I now need to wait for the rivets to arrive from ACS before I can finish up the top of the fuselage and also still need to do the finishing tapes along the bottom longerons. I've also run out of 2" finishing tape which I need to complete the horizontal stabilisers and will also need for the elevators, flaps and ailerons so an order went in for another 50yds of that as well.
