Re: Seeing individual boards on Single Sheathed cars
here is a link to a Rock Island car photographed by John Vashon at the Minneapolis Pillsbury "A" Mill.
https://www.loc.gov/resource/fsa.8a04504/ and the photo at a much higher resolution https://tile.loc.gov/storage-services/service/pnp/fsa/8a04000/8a04500/8a04504v.jpg
Gaps between the boards? To quote Roger Rabbit - Pleeeeeaasse. I'm not sure if it is a mastic oozing out however it is clearly proud of the surface. Not gaps.
Railroad house cars have sheathing to protect the commodity, as soon as they gets gaps or are warped to any great degree, the cars become practically worthless and generally speaking shippers would reject them.
Jim Dick - Roseville, MN