We have a tandem Island and often do 50-60 milers with ours. Our favorite place to go up here in sarasota is Egmont Key (near Ft Desoto,fl), problem is if we drive up to the ft Desoto boat launch (90 minutes plus drive by car), then sail the 8-9 miles to the Island (about an hour plus sail) plus launch and retreaval time, we are over 3hrs to get there then 3 hrs back. We burn about $30 bucks in fuel with our SUV. We live about 15 minutes from City Island park in Sarasota where I normally launch from. We have twin outboards and massive sails on our TI (heavily modified TI), it normally takes me around 2 hrs sailing time to get to egmont key, we usually end up using between a dollar and two bucks in fuel getting there and back (highly dependent on the real wind, less wind equals more fuel used). Also our fuel economy suffers a little when we have the boat overloaded with 3-4 adults and towing our equipment dingy (a 4 person inflatable raft where we haul our dive tanks and coolers), on those days we might use 4 bucks in fuel (ouch).
Actually believe it or not the best thing to tow along we discovered is a second TI (I'm considering getting a second TI specifically for towing people and equipment since we always seem to have way too many people and almost always way too much equipment (I think scuba tanks are around 30 lbs ea (times 8 for four people (two tanks ea) plus several coolers for food and drink for the day and catch coolers for our catch (we like to spear fish, in the hot Florida sun anything we catch has to go on ice or it is spoiled by the time we get home, (can't drag catch in the water (we have lots of sharks here).
We found out by experience towing the second TI on a 40 ft rope at a 45 deg angle behind us at full sail (with someone on board sailing the boat), they are able to take advantage of the apparent wind created by my TI (plus the added propulsion of their mirage drives when needed (I always yell at them if they are not peddling (lol)). With both boats together we only lose 1-2 mph speed, but then again we can take along up to 7-8 people. Once we get to the destination the boats can seperate and do their own thing. Once at the destination I tilt my motors up and sail like normal no different from any stock TI.
Bottom line we can now do everything we used to do with our powerboats, after selling our $60k SeaRay it currently costs between $400-$600 bucks a day to rent one (plus fuel (usually about $40-$60 bucks), we are able to do everything we used to do (including bar hooping (my wife and friends favorite pastime lol (all ocean side bars appear to have a dock (thirsty boaters I assume).
Hey it all works for us, and we can now go out anytime we like at a very small fraction of our previous costs, plus it's fun for us especially in the hot windless summers here (nobody wants to average 3mph (really boring, and way too hot). We typically only go out in flat water with winds under 7mph, which is best for diving and snorkeling (which is 90% of the time here).
Everyone makes fun of us, but hey what we have works for us and we use the heck out of our stuff most weekends, and we can afford a buck or two a week to go out and enjoy the water vs $400-$800 per week. Pushes all our buttons.
FE
EDIT: Before getting our TI we started out with paddle kayaks, we would do maybe 3-5 miles and didn't dare going more than a few hundred feet from shore and only in protected waters (intercoastal). When we bought our first Hobies ( an Oasis and a revo 13) we purchased those with the sail kits, we immediately quadrupled our distance capabilities, and also felt comfortable going offshore (but not too far). We realized early on that the ocean is huge and any distances to get to anything of interest is huge (it's all just bare boring sand and shallow near any land in the keys). We did kayak sailing most every weekend for many years before finally stepping up to the TI. After getting the TI our regular kayaks just sat in the garage and we finally sold them a couple years later. Anymore if we want to go just kayaking we just leave the big sails and AMA's back at the launch or the campground, and kayak with the Tandem Island in kayak mode (way faster than our Oasis ever was). We have even ran the rapids on the Huron river (Ann Arbor MI), and several mild rivers in Colorado and Wisconsin with the TI kayak. We do carry the standard Hobie kayak sail kit on the TI (strapped to the side), but the standard kayak sail is a little on the smallish side for the TI (wish they had something slightly larger). Pushes all of our buttons.
More recently we have been using our TI kayak with a 33 sq ft wing sail mounted (almost as fast as a full blown stock TI with all it's rigging and AMA's), the sail just furls up and is strapped to the side of the boat when we are not using it. This setup is more for rivers (like the Sante FE, Crystal River, etc) and small lakes (not offshore). We love kayak sailing obviously ( lol)