Our tandem only gets the "wet rag" treatment. When we first purchased the bike, we hauled it home on top of the van, it rained for three hours, very unusual in CO, but when we went to do some seat adjustments, guess what I found in the seat tube? (water) I try to keep the water away, Carbonfiber has no chance, but, "that's the reason I use a good chain lube and sealed bearings."
R&J