Ex RNLI D class mystery leak solved.

[Black Frog]

Just found out something that might help others with leaking d class boats. My boat is a black boarding boat. The chamber on the starboard quarter developed a slow leak about three years ago. Local crews thought I was dreaming because their operational boats needed topping off more frequently. I eventually found some AH valve cores in a station but it didn't solve the problem.
The leak was the hypalon skin bubbling up from the white solid cone reinforcement that the valve body sits on. The exposed face of the cone material is not sealed in the hole for the valve. I sealed the face of this white material with silicone and the leak has stopped. Both quarter chambers are bubbling up around the valve and I can only suppose that as these are the two most heavily loaded the skin is delaminating in this area. None of the other five valves show any signs of the delamination.

[m chappelow]

I had one similar leaking on the bow section of my Y boat as its an identical recessed valve ,
what i found was a small crack or split in the recessed rubber cone itself where it joins to the main mating surfaces of the sponson , i peeled back the edge of the hole thinking it was weeping through a bit of delamination but then found the small split it took a few goes to sort it but i put it down to deflating rolling up & putting it in the back of the car with the engine laid on top perhaps making it fold over then causing a stress crack especially if the rubbers gone a bit hard as the rest of them on the boat are fine it was just the bow one ,

In a worse case scenario i was going to just patch/ blank off the existing valve hole & move the valve to a different place doing away with the recessed valve .

[Black Frog]

Rolling it up into the car is one trick I haven't mastered with the D boat.
Is it possible that underinflation could contribute to this?