24 Jun 2023

Bent long-range fuel tank bundy tube to shape for the left wing. This was not easy, the pipe bender I used was of high quality but a bit oversized for the 8.4mm pipe, so it kinked and completely ruined the pipe. The KAI provides very poor visuals for how to bend the pipe, no dimensions either, no template and no pipe to experiment with. So I used the damaged pipe to create a template using trial and error - it eventually came out very well after I used a cheap 3-size pipe bender. I had tried experimenting with thick wire first as a template, but it just didn't work, the tolerances in the wing are too tight - the wire does not properly cater for this nor the specifics of the tube bender which needs a bit of an extended "tail" before the curve can be formed. Quite frustrating. Sling uses a cheap 3-in-1 bender from Force Tools (in South Africa), so I've ordered one

Once I got the pipework right, draft seal was wrapped around it per the KAI (10m is supplied, I cut the roll in half and had about 40cm left over). The 90 degree stainless AN fitting was bolted to the long-range tank and the bundy tube was then bolted to that. Loctite 577 thread sealant was applied liberally, and the fittings torqued to 9nm (about 80 in-lb, which is the midrange value per AC43-13 table 9.2 for 5052 aluminium which the bundy tube appears to be).

The left main fuel tank was fitted. This was quite a mission to do and required a lot of jiggling to seat correctly. I eventually found it easiest to invert the wing and work on the bottom first since it has to overlap the skin which is already installed. The bundy tube sagged a bit in the middle and caused some difficulty until I realised it was the problem. I also had an issue with fuel tank rib 1 being installed - the KAI is not clear on when this should be done. I had already installed it, which caused issues clearing the bundy tube. I had to de-rivet the lower rear point to allow the tube to pass through and then reinstall the rivet. Not a big issue, but for other builders it's probably better to install rib 1 once the tank is in place. Having an assistant to help with this is useful, I had to flip the wing over a few times to check it was properly seated prior to riveting the underside in place. The one 3.2mm rivet on the underside over the 90 degree stainless steel AN fitting needs to be shortened to accommodate the fitting. The 2x AN3-3A bolts were fitted with Loctite 243 and torque sealed. The 2x 991 rivets were also fitted (these seem to be way too long for the application). The top of the main fuel tanks (leading edge) were then riveted to the long-range tanks.

The long aileron pushrods were installed in each wing. I wanted to ensure they did not bind on the bushes, but as it turns out the pushrods are a lot smaller in diameter than the flap torque tube and fit through the bushings with ease (one did need a bit of encouragement due to the rivets at the end, but that's it). I also wanted to ensure that it cleared the pitot tube hardware in the left wing prior to everything being closed up. It looks good.

Fitted 4x ring terminals to the pigtails for the landing and taxi lights.

Left wing is ready for inspection and top skins to be fitted thereafter.