I just received a PM question about my post, but the system apparently doesn't allow newbies like me to respond to PMs until I've made enough posts. So, I'll answer it here.
Here's the question: The part we haven't figured out yet is what to do when we go off road. Nothing crazy, but more like bikepacking down some singletrack. I've seen videos of tandem downhill racing and the captain seems to be calling out the turns to the stoker so they can do...something. Lean in anticipation of the turn maybe? It almost seems like the stoker is doing the turning and the captain is just moving the bars to keep up. I haven't found anything that explains how this properly works...do you know of any YouTubers or anything that explain how this or do you have any words of wisdom?
Riding a tandem on technical trails is definitely challenging--and really fun & rewarding when it all comes together. Here are some thoughts:
1. A lot depends on the skill of the team. My wife and I both rode mountain bikes a lot before buying a tandem, so we both understood how to move our weight around. The goal is to translate this knowledge to the tandem. If you or your stoker don't have much single-bike experience, it's going to be a much bigger learning curve to successfully ride technical terrain.
2. As the pilot (our preferred term for the rider in the front), I didn't require that much adjustment, especially since I had experience riding a loaded bikepacking rig. But I had to learn where the back wheel is (WAY back there!), so that I could get it to track around rocks, roots, and follow the correct line. I also had to learn how to not set up my stoker for pedal strikes, since she can't easily position her pedals to avoid rocks.
3. One of the things that my wife figured out pretty quickly was to watch my hands, and to essentially pretend that she was steering. This was HUGE, since it allowed her muscle memory to kick in from riding a single bike. I think that this was probably the most crucial factor of riding smoothly--whether moving slowly or quickly. Once she discovered this, we practiced on the road by making quick turns.
4. Feeling the bike is a great way to determine whether you're in sync. On our first few rides, I couldn't understand why our bike felt so bendy. After all, it just didn't seem plausible that a Cannondale 29er tandem (with that HUGE boom tube) would ride like a limp noodle. Well, we quickly learned that noodling was a sign that we were basically "steering" in opposite directions or trying to compensate for each other's movements too much. Pay attention to this feeling, and figure out why it's happening so that you can get on the same page.
5. As a more aggressive rider, I was used to leaning my bike harder in turns than my wife. She was actually really excited to learn that it was possible--and it's actually helped her be a better single-bike rider. The lesson here is that riding a tandem has the potential to help teach each other new skills. But there's a really important caveat here (see next point).
6. I learned very quickly not to make my wife feel vulnerable, EVER. A scared or uncomfortable stoker will do all the wrong things with their body weight. As a pilot, you need to give your stoker every reason in the world to trust you--and trust is hard-earned but easily squandered. If you push too hard, or crash, it's not fun for your stoker. While I'm generally happy to crash my single bike by pushing limits, this is never a good idea on a tandem. My goal is to never crash. Take your time to build your skills together, since you will both need to learn to be loose and strong at the same time (never tense).
7. Learn to crash together. Yes, we've crashed a handful of times. But we developed a protocol ahead of time, so all but one crash was pain-free for my stoker. Basically, if the bike is out of control, your stoker should feel 100% comfortable bailing off the back. The pilot needs to go down with the ship, but the stoker should practice quickly getting off the back of the bike--which is actually pretty easy, especially of the pilot sacrifices themselves to keep things upright as long as possible.
8. The only hard crash that we've ever had was due to my error and inattention. We were cutting across a grassy field, and I tried to bring the bike onto a paved path at a stupid angle--especially considering that the grass was wet. We went down so quickly that neither of us had much time to think. The lesson here is to NEVER let your guard down as the pilot. Unanticipated crashes are truly the worst!
9. When necessary, the pilot should announce their intentions. This will change over time as you get in tune with each other. I used to call out damn near everything, but I don't need to as much anymore as she's learned my piloting style, and I've learned what she can see & anticipate. But I still call out bumps, technical areas, or anything that she can't see that will require cooperation to navigate.
10. Once you achieve blissful flow, you'll really start to realize how much a good stoker is actually steering the bike. Not that long ago, my wife and I had a very revealing moment. We decided to stop at a picnic table for a break. The only thing is, there were several tables ahead of us, and we didn't confirm which table we were heading for. She steered left, and I steered right--and hilarity ensued. The takeaway is that she can basically steer the bike herself, which demonstrates how useful it is to work together.
11. Last, but not least, I really hate the term "captain." It just implies too much authority and hierarchy. I'm the pilot because I have to point the bike and stop it. My stoker isn't subordinate. We're a team, so we work together. But I realize that not everyone is the same. A really imbalanced team, with a strong & experienced pilot pared with newbie stoker, might require a more defined "chain of command."
12. OK, this is really the final point: Everyone is different, so find what works for you! While my wife and I are solid our bike with each other, we might totally suck if paired with other riders. Most tandeming advice that I've read is pretty biased towards one team's experience (including mine!), so take the time to figure out what works for you.