HELP! I'm in the process of replacing my aft stub spar and now a top spar cap. The spar cap repair requires I open up the fueltank. I realized that my tank doesn't have the typical polysulfied sealant. It had an stc in 2002 to install a urethane  coating EFC100.  How do I remove this stuff? Mechanically?with chemicals? Dynamite? I did some research apparently it is tough stuff and used in some military  aircraft fuel tanks. The coating is almost an inch thick in some areas. I