I have received an extract from an old interview with a riverman talking about blueprints of riverboats. There is one word I simply can't identify as I haven't heard this term ever before. It sounds like "cenwheelers" or "sandwheelers" which doesn't make any sense to me.

Maybe anyone can identify what he is talking about? Here is a link to the audio file:


And that's what he's saying with som emore context than in the audio file: "That's where the word blueprint came from. The background was blue, and the designs of the ship or whatever the project was, that was in white. And so we had all of these shallow draft barges, (((cenwheelers???))), sternwheelers that ..."

Thanks so much!