Fuel Tank Sealant Breakdown?

[Mark Castle-Smith]

We have been flying our RV7 for less than a year and have out around 30 hours on her. Our RV is a 'quick build' with the fuel tanks pre built.

On our last flight the fuel pressure started to drop. When we reduced manifold pressure the fuel pressure increased. After landing we looked at the fuel injection fuel filter (in the fuel distribution block on top of the engine (she is a FADEC engine). The fuel filter was full of what appeared to be a grey sediment. We cleaned out the filter and noticed after checking the fuel drains that mainly in the left tank there was a very fine sediment on the sides of the fuel 'checking bowl'.

We drained the left tank. Looking through the fuel filler hole you could see very fine grey sediment on the bottom of the tank (the same colour as the tank sealant. It was also very obvious that around each rivet in the fuel tank that the sealant had disappeared in a ring around the rivet.

I can only conclude that the fuel tank sealant is breaking down into fine particles and blocking the fuel filter.

Has anyone else either had this problem or heard of it happening to anyone else? Next port of call is Vans on Monday.

Many thanks

Mark

[jsharkey]

That shouldn't happen.

When I built my tanks 5 or 6 years ago I made some aluminum to aluminum bond samples with each mix and have stored them in a jar of gas ever since. There is no break down so far and the aluminum lap samples are still very well stuck.

I was thinking the other day that I should have made some samples to leave in air since the tanks have been dry since I built them

Jim Sharkey
RV6 - Ever so close to first flight!