I'm currently replacing the two fuel tanks and three of the water tanks on Nerissa with plastic tanks. The two stringers that run along either side of the fuel tanks sound hollow when tapped. One of these I have accidently cut into when removing the port side fiber glass water tank which was made as part of the hull and the stringer (this was a bit odd as all the other tanks are aluminum). This has revealed the foam core in the stringer. The boat is still in the water at present and I'm unsure what is the best approach from here.

Has anyone had a similar issue?

Thanks

Mark

Hi George, thanks for that. I'm presently getting quotes for the new tanks. These will be plastic, all hand welded with baffles and inspection ports. CE certified. Adding on the stand offs sounds like a good idea I'll look into doing that. The old tanks had wooden stand offs mounted to the sides of the well, we also have  1" high  ribs running along the bilge to hold the tank up. The old tanks were all aluminum except for one water tank that was fiber glass (I think this was because the fridge used it as its cooling tank now disused). The fuel tanks developed leaks near the bottom on the sides where muck had built up over time. The water tanks failed from having tap water in that has pitted the walls. 

The main stringers are fiber glass 2" thick with foam inside. when tapping them they sounded hollow but this I have now found to be the low density foam all the glass is thick and well bonded. I need to clean up the fiber glass where the fiber glass water tank was but other than that it is looking good.

I'm also looking to leave the bow tank as is, as its going to be hard to replace and does not leak. This tank I'm going to change its function so I can use it as a wash down tank for the deck wash pump so I can also use fresh water. 

We have six water tanks, I'm replacing three. The bow I intend to leave as above. The aft two I will replace maybe next year. One may get changed to a water maker.

  Cheers

Mark