How much separation do we need between fuel and extruded polystyrene?
If we married an XPS solid-core wing (from the spar aft) with a tank forward of the spar constructed using PVC core, is this inviting disaster? My understanding is that we do not use styrene cores on composite fuel tanks because of the possibility of pinholes in the epoxy (and possibly other reasons--please enlighten me). But if the spar's web is made of say four or six plies, has the XPS aft of the web been adequately protected?
I think this is probably not the best practice, but maybe the multiple plies of the spar are enough to eliminate any concern about pinholes? What say you?
Sidebar: ACS sells Rhino 9700, a chemically-resistant epoxy coating, and they state it is commonly used in Lancair tanks (which, yes, I know are not constructed like the above diagram). But when I look at the data sheet, it says not to use it over previously applied epoxy. Interesting; I wonder how well it adheres to epoxy and whether the Lancair crowd has problems with it. Also it is interesting that it appears susceptible to toluene (which, following the G100UL kerfuffle, I became aware is also present in 100LL).
If we married an XPS solid-core wing (from the spar aft) with a tank forward of the spar constructed using PVC core, is this inviting disaster? My understanding is that we do not use styrene cores on composite fuel tanks because of the possibility of pinholes in the epoxy (and possibly other reasons--please enlighten me). But if the spar's web is made of say four or six plies, has the XPS aft of the web been adequately protected?
I think this is probably not the best practice, but maybe the multiple plies of the spar are enough to eliminate any concern about pinholes? What say you?
Sidebar: ACS sells Rhino 9700, a chemically-resistant epoxy coating, and they state it is commonly used in Lancair tanks (which, yes, I know are not constructed like the above diagram). But when I look at the data sheet, it says not to use it over previously applied epoxy. Interesting; I wonder how well it adheres to epoxy and whether the Lancair crowd has problems with it. Also it is interesting that it appears susceptible to toluene (which, following the G100UL kerfuffle, I became aware is also present in 100LL).
