Fuel Tank Testing (30m)

I think I’ve been putting off testing the fuel tank for leaks but Teri leaned on me heavily to get over it and get ‘er done (as they say around these parts), the heat is coming and we really want both wings finished before then. So, before we seal the tank inside the wing we need to test for leaks. But before that we have to plug up a hole that I had paid no attention to.

One side of the tank has a hole for a fuel return line and as we’re not using it(*), this needs to be plugged. Someone on the Zenith forums suggested a nice little brass plug that fits flush with the hole. It required purchasing a new hex wrench but it does the job nicely.

We next purchased several gallons of costly gasoline to put in the tank. I had been advised to use aviation fuel but then I’d be stuck with avgas in the garage until who knows when, so we bought Premium with the intention to put it in the MINI when done.

I bought some PVC piping to put over the fuel outlet and rigged it up to a stool so that gravity would prevent it from just running out of the hole, after all that hole is supposed to leak. The good news is that nowhere did it leak. We picked the tank up and turned it around to make sure that everything got a good workout and it all looked good.

With that done, we put the fuel into the MINI and the tank back into the wing.

and the top skin back on top.

At this point I noticed that there is a lot of flex in the top skin. If you push it just a little in the middle of the skin it flexes into the fuel tank which doesn’t seem like a good trait to have in an airfoil. In this picture you can see that the top of the tank doesn’t reach as high as the rib line so I can see why the skin flexes so easily.

I put some cork on but it isn’t enough to make a difference. I can see that one solution is to layer some more cork until it is high enough for the skin to rest on but before I do that I have sent an email to Zenith technical support about it just in case I’ve done something wrong. I do not want to have to unrivet the wing because I did something stupid. Looking at the forums it seems that other people have done what I thought so I expect this is what will happen next weekend.

Finally, at someone’s suggestion I bought some fancy filler neck trims to make the fule neck look nice. I didn’t get to install them in case its position on the top skin changes after I hear back from Zenith but they put a nice finishing touch to it.

Sadly I have to trim off an edge as when the nose skin comes over the neck trim will overlap but it is still going to look good.

(*) Those of you paying attention might be saying “but Paul, what if you go for a fuel injected engine won’t you need the fuel return line then?” and you’d be right. So if that does end up happening I’ll almost certainly be going with a header tank solution instead (which is what the Viking engine install does).

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