Slowly building the fuel tank

I guess I’ve been distracted a lot lately, as I’m making very slow progress on this fuel tank! I think it’s partially because I’m afraid to work with the sealant, which is messy and has a 2 hour working time once mixed. I’ve also been doing a lot of reading about best practices to seal and chatting with fellow Sling builders, since I don’t want to ever have to deal with leaks.

I found a helpful diagram on a long thread on Van’s Air Force, I think it makes it very clear:

There are some slight differences since I’m using blind rivets instead of bucked flush rivets, but still very applicable.

The TAF manual makes a handy recommendation to heat up the tip of a large syringe with a heat gun and then squash it with pliers in order to make a nozzle that dispenses a ribbon – that was a good suggestion! That creates the “fay” layer in the figure above.

A few more tips I’ll note here that I didn’t recall seeing in the build manual:

  • Put down blue painter’s tape to keep the sealant fillets clean (inspired from Pascal Latten’s build)
  • To achieve the fillet, I used a smaller 10mL syringe to run a bead along the edge and then used a popsicle stick edge to press in the sealant and shape the fillet
  • I used just a few clecos to tack the stringer in place and immediately started riveting –as opposed to clecoing it in, waiting for sealant to cure, and then coming back days later to remove clecos and replace with rivets, re-sealing the rivets as I go
  • After setting the rivets, I applied sealant around the body of each rivet to encapsulate it per the figure. To reach around to the back side of the rivet body (hard to do inside the U-shaped stringer), I used a little hook-shaped wire to reach around to the back side of the rivet to spread the sealant evenly.

Anyway here’s a few pictures of attaching a stringer to the upper side of the skin and sealing it. It took me the full 2-hour working time to do just this stringer, but now that I have the process practiced, I think the ribs will go faster.

A 60mL syringe filled with fresh sealant, ready to dispense

The hook is fashioned from a piece of 14AWG solid copper electrical wire

My helper for the day – our dog Kooper!


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