In July we will spend two days on Aero Island after some time in Copenhagen. I'm working on the plans for getting there. It appears there are two options: train-ferry versus train-bus-ferry.
Option 1 would start with a fast train from Copenhagen, with a transfer to a regional train in Odense, and then we'd walk to the ferry in Svendborg and take it to Aero Island. It appears that all trains from Odense arrive in Svendborg at 55 minutes after the hour and all ferries from Svenborg to Aero Island depart at 5 minutes after the hour. The Rick Steves Scandinavia guidebook says that "it takes about 10 minutes to walk from the station to the dock (5 minutes if you walk briskly). Don't dawdle--the boat leaves stubbornly on time, even if trains are running late. I recommend taking a train from Odense that arrives about 30 minutes before your ferry departure to give yourself time to absorb delays and find your way."
It appears that it's not possible to take Rick's recommendation. You're only going to have 10 minutes to get to the ferry, and if you miss that departure, you have either an hour or two hours to wait for the next ferry departure. (They aren't every hour according to the ferry timetable. The afternoon departures are at 12:05, 13:05, 15:05, and 16:05. )
If we choose option no. 1, what's the chance we're going to make it to the ferry in 10 minutes so we don't have to wait an hour (or two) to the next ferry? I have to believe the ferry departure is synced to the time the train gets in from Odense! Are the trains super reliable so that getting to Svendborg late isn't much of a risk? And if your train is on time, how "brisk" are you walking to get to the ferry in under 10 minutes? We don't want to have to run!
Option #2 involves a fast train from Copenhagen to Nyborg, then walk to the bus station, then a bus to Svendborg, then walk to the ferry port, and take the ferry to Aero Island. This option shaves off some time getting to Svendborg and thus will permit us to have the recommended 30 minutes in Svendborg before ferry departure time.
Option number 2 sounds like it's much more of a hassle. It seems that it would be far simpler just to switch trains in Odense than to have to walk to a bus station with luggage in Nyborg. But if the train from Odense runs a big risk of a missed ferry connection and extra hour wait in Svendborg, then option #2 may be better for reducing the total travel time on our day when we're going from Copenhagen to Aero Island.
I do favor option #1 but would like to hear from anyone who's made the walk to the ferry from the train station who can tell me if we should pretty much count on missing the first ferry that departs 10 min. after our train gets in, and having an hour wait. Or, if someone has done the bus from Nyborg and recommends that as an easy and pleasant way to get to Svendborg, let me know. Also, with option #2, can we just book the train to Nyborg and count on getting seats on the bus without an advance ticket? Or is it advisable to book the whole journey--train and bus--through the national rail website? The former would allow us to get an "orange ticket" price to Nyborg, whereas it appears there are no orange ticket options if you are booking both train and bus on the national rail website.