Bertram Fuel Tanks

Tests of fiberglass fuel tanks from a 1967 and 1970 Bertram:

Testing Summary:

To date, the testing done by IMS, LLC indicates that the two fuel tank samples have undergone some aggressive degradation (40% of their strength) from gas - ethanol fuel blends. The bottoms of both tanks have lost more strength than the tops. The older tank (1967) was laminated to a much higher level of quality in terms of entrapped air and fiber roll out. The mode of property reduction in the newer tank (1970) appears to be both resin softening and loss of adhesion between fiber and resin. This is evidenced by a moderate loss in both strength and stiffness. The older tank has lost nearly a similar amount of strength but has retained all its original stiffness. This indicates some resin degradation has occurred but no loss of the fiber/resin interface’s integrity has occurred.

Should check for presence of ethanol using the following methods -

To check for ethanol in gasoline - use two bottles, with calibrations in ounces.
In one bottle put ten ounces of gas from the suspect tank, in the second bottle - put two ounces of tap water.

Pour the water in to the bottle with the gas, cap off and shake.

Let set and the water will settle to the bottom and if ethanol is present it will absorb the water and the fill line will change from twelve ounces to something else. If this is the case - then the tank should be viewed as suspect - replacing tanks can be a trick.