It takes a lot longer to charge from 80-85% to 100% than it does from 20% to 80%, so don't plan on charging the batteries to more than 90% with solar. And if you discharge them no lower than 50% for good life, that leaves you 40% of their capacity to work with. Meaning you need FIVE times your daily amp-hour use in battery capacity just to have one-day's use plus only one day backup for a rainy day. The thing about rainy days is that they often come in more than one at a time. Six times daily use gives you two days backup and seven times gives you three days backup. So if you only use 40AH/day, a pair of 6V golf cart batteries or a pair of 12V
Group 31 batteries will give you one day's use plus one day's backup. If you use 60AH/day, four batteries (450AH) should give you one day's use plus 2 day's backup.
You need enough panel capacity to serve your daily use under less than ideal conditions (i.e. a horizontally mounted panel in March and September) plus extra capacity to restore the backup day's use over maybe two following sunny days. So figure at least 1.5 times your daily amp-hour use in panel capacity. The popular 120W Kyocera panels put out 20 (spring/fall) to 30AH per day (mid-summer) under real-world conditions, so you need one of them (or a Shell SM-110) just to run a Fantasic Vent fan 8 to 12 hours per day while parking in the sun. If you use 40AH/day, you'd need 2-3 more (depending on time of year, 60AH/day) 110-120W panels to provide one day's use and have the capacity to replace one day's backup over the next two sunny days. If you use 60AH/day, you'd need 3-5 panels (depending on time of year 90-100AH/day) in addition to the one for the vent fan, to provide one day's use and replace 2 day's backup use over five following sunny days... if I did the math right.
There just isn't enough flat roof area on, or battery storage in, a curved Airstream to even TRY to be 100% solar with modern appliances. Even on our 34, there's only room for a couple of shorter SM-110 panels, and only two battery compartments.
Two 110-120W panels plus two 120-130AH batteries is a practical solar system for most RVs, but it WILL require a generator for backup during rainy days and in Spring and Fall. Since we had to have the generator anyway, we saw no reason to spend the money on solar... at least for now.