Tank assembly advice

[Iluke]

I'm working on my -7 fuel tanks and I'd welcome opinions on an idea: Is there any reason not to test the tank for leaks before installing the rear baffle? It seams to me that once I get everything except the baffle done I could install the access plate, plug the fuel and vent outlets, set the tank in the cradle and fill it with water to see if any of the rivets or the end ribs leaked at all.

Seems like a good idea because if I do have a weeping rivet somewhere I could fix it easily before closing up the tank for good.

Again, I'd appreciate any thoughts on why this might or might not be a good idea.

[Mike S]

What you say is certainly possible, but I wonder if viscosity issues may keep water in when fuel will leak???

[blueflyer]

I am at your same build stage. Your idea seems like a good one to me because it would be easier to fix any leaky rib rivets prior to installing the baffle. What about filling it with auto fuel rather than water? When you're done, you can siphon the gas into a gas can and use it in your lawn mower or car. Just make sure your cradles are build sufficiently to hold the extra weight. My cradles are very flimsy and would need to be reinforced.

[mill2978]

Originally Posted by Iluke

I'm working on my -7 fuel tanks and I'd welcome opinions on an idea: Is there any reason not to test the tank for leaks before installing the rear baffle? It seams to me that once I get everything except the baffle done I could install the access plate, plug the fuel and vent outlets, set the tank in the cradle and fill it with water to see if any of the rivets or the end ribs leaked at all.

Seems like a good idea because if I do have a weeping rivet somewhere I could fix it easily before closing up the tank for good.

Again, I'd appreciate any thoughts on why this might or might not be a good idea.

My tanks are completed except for the back baffle. I have an EAA tech inspection tonight and then I plan to fill mine with water. I've considered using fuel(auto or 100LL) but I am leery of having that much fuel sitting in the tanks as my shop is in the basement.

At least 2 other RV builders I know have used this technique, one has been flying for a few years and has no leaks, the other did this, sealed, pressure tested and still found leaks when they started flying.

I think it is a good test, but no magic bullet for tank success.

[WAM120RV]

I have done this on every tank I have built, but then gone on to pressure test when the baffle fitted.