Fiberglass hull diesel saturation: consequences?

Cored Hull that’s not cored

Just putting it out while Uniflite are known for solid fiberglass hulls they did make a balsa cored Hull in 1984 on the 36’ aft cabin,,,,besides that I think what the surveyor was referring to about the “ core “ being saturated is that Uniflite used a closed cell foam core in there strings so there was no wood to rot…

"They never think about the fact that the boat is 40 years old and every component had a design life of 25 years."

A properly built GRP boat probably has a hull life of over 100 years.Many of the cruisers on this forum were not built for long life and are 40+years old, as are their agricultural engines.

The big hull question is simple , does it flex?

If its rock solid , no cracks seen from overloading in the gel coat , it should still have a long way to go.

The OP was talking about a 1978 42' Uniflite. This model is built with NO wood below the waterline, the stringers are formed with closed cell foam covered with 8 layers of woven roving, minimum with extra layers added in joints, engine beds and other areas, the entire hull is hand laid glass and closed cell foam with no coring below the waterline. There is nothing to 'absorb' any diesel, the bilges would need a thorough cleaning to get rid of it and that would be hard without removing the aft tank. However the core can't be 'saturated', there is no core that can 'saturate'. The aft center mounted tank was an aluminum tank, mounted in the bilge, about 40 gallons. It's very common for this tank to fail and leak and be removed/disabled as it's an Aux tank and not needed for operation.

I have the structural drawings, layup schedules, lines and hull materials list for this model from the manufacturer.

There is nothing intrinsically wrong with fiberglass and fuel. There are many high end boats with fiberglass fuel tanks (Hatteras, Nordhavn, etc). Compared to steel and aluminum fiberglass tanks are bullet proof. If this hull is not cored, this is much ado about nothing.

sbman said:

The OP was talking about a 1978 42' Uniflite. This model is built with NO wood below the waterline, the stringers are formed with closed cell foam covered with 8 layers of woven roving, minimum with extra layers added in joints, engine beds and other areas, the entire hull is hand laid glass and closed cell foam with no coring below the waterline. There is nothing to 'absorb' any diesel, the bilges would need a thorough cleaning to get rid of it and that would be hard without removing the aft tank. However the core can't be 'saturated', there is no core that can 'saturate'.

Click to expand...

This is all moot as the OP passed on the sale, but...
It's not just about the hull. Any enclosed space full of wood such as teak or mahogany subjected to diesel fumes for 10 years will smell like diesel fumes forever. Not to mention upholstery, headliners, etc.

Several years ago, from an estate, there was a 42 GB woodie offered to me for basically no cost. There was plenty to repair. However I was considering it. Then I opened the floor hatches to get into twin screw diesel area. That was it for me. Once in there... I could not even see with eyes watering too hard from the putrid old diesel fuel odor.

Gasoline evaporates and its odor dissipates in not too long a duration. Diesel fuel is not similar.

"There is nothing intrinsically wrong with fiberglass and fuel. There are many high end boats with fiberglass fuel tanks (Hatteras, Nordhavn, etc). Compared to steel and aluminum fiberglass tanks are bullet proof. If this hull is not cored, this is much ado about nothing."


This is true today but , in the past many small boats were constructed with built in fuel gas tanks.
Worked fine , BUT Unkle Sam decided ethanol was required in gasoline and the alcohol softened the GRP as well as raised heck with some rubber parts , fuel lines , carb gaskets.


Happily the mandated changes to diesel fuel did not cause as much havoc.