<<I thought that the fuel tank swelling issue had been resolved. Is
anyone else still experiencing tank swelling to the point where it
would bulge the fuselage?>>
There are two issues here which keep getting confused, the best thing is to stop
thinking of the plastic tank as a rigid entity and imagine it more as a large
square plastic bag with strong seams!
The two seperate issues are linear expansion (ie change in size of the outside
dimensions of the tank) and distortion (bulging). We filled our MK2 fuel tank
with a cocktail of Avgas and Mogas, part filled for 4 weeks to allow the vapours
to absorb into the polypropelene first, then we brim filled it for 3 weeks and
topped it up each day. Our observations were that linear expansion was very low,
less than 1%, however distortion of the tank walls was high. This is because
they are unsupported and will bulge out. This can add almost 10% to the tank
capacity!!
I don't see the bulging as being a problem as it is amply supported and
contained by the fuselage and cockpit module. The 1% expansion in size doesn't
seem to be a problem either, as little if any further expansion was observed
after 2 weeks. One point to note is that if the tank is left empty for a long
period it will shrink to it's original size.
Allan J Hall #177
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