Ultralight aircraft fuel tank grommet failure.

Aircraft:
All ultralight aircraft using rubber gas tank grommets to hold aluminum, steel, or plastic elbows or fuel shut off in gas tank.

Incident report:
Several ultralight pilots flying various ultralights have reported loss of fuel, both on the ground and in air. Upon closer inspection it was found that the rubber grommets used to seal the gas tank where fittings are placed to supply fuel, had rotted and then cracked allowing fuel to escape.

In other cases the sharp edges of the plastic tank had actually cut into the grommets again resulting in leakage.

Suggestions:
The solution to this problem is to
1. round the inside corners of the holes that the grommets fit in.
2. replace the grommets yearly, or at the first sign of deterioration or leakage.