In article ,
"Stuart & Kathryn Fields" wrote:

Is there anyone out there using fuel tanks filled with open cell foam? I've
heard that explosions are tamed as well as fuel slosh. I've also heard that
the foam must be replaced periodically. How often is the replacement
necessary? I'm using 100LL Av gas.

Most of the foam is polyurethane foam, which decomposes after exposure
to water vapor. It is not an instantaneous process, occurring over
several years, but the decomposition product is a black powder, which
can clog fuel filters, injectors, etc.

It is good for race cars, which have a limited useful life, but may
impose problems in aircraft, which operate for years.