Foaming at the tank.

The tank is repaired. It's now double skinned, in that it has a polyethylene lining, made by Philton and it has the original outer tank which they also patched up.

With the chocolate powered lorry journey we loaded the fuel up in 2 IBC's which are made of similar plastic (but much thinner) and set off without a worry, however that vehicle was bigger and more stable but with this bus there is more movement shaking the tank as it goes over bumps. It's generating more G-force which the fuel then takes and uses to force itself against the side of the tank.

None the less, the tank is more squat than an IBC, and it's shape has ridges and curves which should dissipate the surge wave inside so it should be more resilient. However it's a more complicated shape inviting stress cracks along its edges, and the material is less flexible than an IBC and isn't supported by an aluminium cage. Plus the double skin means it could wear against itself.

Matt from Philton did an amazing job, and really got into the technical challenge of producing the liner as well as the practical hands on work of rewelding the outer tank. I had to cut a big hatch in the old tank to fit the liner in, then get half my body in to unfold it so it could be inflated with the mother of all air compressors. There are no guarantees on how long this will last but they've given me a spare fold up tank in case I need to to drain the main one in an emergency.

So now I am looking for an open cell, "reticulated polyurethane" foam that I can put in the tank to act as a sponge holding the fuel in position. Sounds simple, but it never is. Biodiesel and vegetable oil are hugely corrosive (more so than fossil diesel) so not all types of foam are suitable. (some get eaten away, some swell, some dissolve). Most of the foam salesmen I've spoken to today don't really know if their foams are biodeisel resistant, because no one has ever asked them before, and when I tell them I just want their offcuts they aren't that interested in researching it either.

I'm getting close to the point of giving up, and using some PVC hosing and floating foam to try to lessen the slosh effect, but it won't really be very effective. I think however I can persuade myself it's OK by remembering we never had any trouble with the chocolate powered lorry fuel tanks.

At this stage I still haven't even tested the new tank set up, because I'm wating for a filler cap which should arrive tomorrow.

Do I wait to fit the foam until after I've filled the tank (which means driving to wherever I can find some foam with a full tank and no foam risking it splits again)? or do I fit the foam first (and run the risk of discovering that the tank is still leaking and then I can't get my foam back out) or do I get a grip and think this is all overkill cos I've now fixed it twice over? Mostly it depends on finding some suitable foam, if such a thing exists.