Under floor fuel tank

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Hi all,

I’m new to the forum. I recently got a great deal on a used Alson Italian made 3.8m hypalon RIB and Yammy Enduro 25 which I now use as the tender for the sailing cat that I live aboard with my family.

I currently have the usual Yamaha plastic fuel tank strapped down to the floor, but I’ve been thinking of moving my fuel storage to below the floor for a couple of reasons: it’s tidier, gives me more floor space, and can’t be stolen. I was wondering if anyone has done this either by using a flexible fuel bladder (we had one on a MilPro rescue SIB on a commercial boat I worked on) or by creating a structural tank from part of the space below the floor. I have worked aboard GRP boats that had structural tanks formed this way, the biggest issue being the correct paint is used inside the tank.

Any advice regarding either option? I don’t want to install a stainless tank for various reasons: weight, expense, complication of cutting a much larger piece of the floor up etc etc.

Thanks for the help,

Mike