Patrick's Sling TSi

Weeks 44-47: Finishing left fuel tank

Once I received the rivets I requested I installed them with plenty of sealant. I let the sealant cure for a couple of days then did a very low pressure leak test. The tank was clearly not holding pressure, and I quickly found a decent size leak where the back channel attaches to the skin.

After sealing that I again let the sealant cure for a full week before trying again. While waiting I filled and sanded all the rivets on the top of the left wing.

When I did the next leak test I found more leaks on the back channel. Again I added more sealant and waited. Then again found yet another leak in the same area. Each time the pressure would drop more slowly so I knew it was getting closer.

After the third attempt I couldn't find anymore leaks on the tank exterior, but the pressure was not holding during the leak tests. I confirmed with refrigerant and a leak detector that it was leaking in the nose area...again. This is despite my concerted effort to get that area properly sealed during assembly.

I removed the fuel level sender and found a suspect area I could get to, so I added more sealant. I also ordered a slosh sealant from Aircraft Spruce as a backup plan. Sure enough, there was still a very slow leak so I put in the slosh sealer and used it to thoroughly coat the leading edge surfaces, then drained out the excess.

I drained it through the refrigerant service port I had in the drain fitting, with the valve removed. This kept the fitting threads clean, and of course I masked off the fuel intake screen as much as possible.

After waiting a few days for the sealant to cure I reattached my leak test setup and soon found that the pressure was changing with temperature. After another day I added pressure and this time it held!

The next step was to attach the tank to the wing. After clecoing it in place I leak tested again, still without any issues. I then riveted the tank in place.

After I had it fully riveted I realized I didn't attach the nut plates to an angle ghat is used to bolt the tank to the wing. Fortunately I had extra AN3 nylon locking nuts so I just used those instead. It was only moderately difficult to get them installed, much easier than trying to put the nut plates on.

With the tank fully installed I filled the rivets on the top of the tank. I fortunately quickly got help flipping the wing over so I am ready to fill the rivets on the bottom of the wing.

I also refit the left aileron with the washers indicated by technical support. The rivets were still rubbing against the bearing bracket so I requested the 4.8mm flush rivets they said are sometimes needed. As soon as I get those I will get them installed then confirm that the ailerons have smooth motion over the entire travel range. That should finish the wing kit, then it will be on to the fuselage!

This post is from Patrick's Sling TSi