I recently flew in F on SQ JFK-FRA-SIN. Upon arrival in FRA the F passengers were taken by cart to the UA RCC F lounge. This lounge was very small & crowded (at 11:30 am). I didn't notice anything special about this lounge, nor did I see any showers--the bathrooms were outside the F area and for use by the regular RCC & F passengers. So unless you normally have access to the LH Sen lounge (or other F lounge), this may be your only option.