I'm on a canal with no tunnels and best of all, no locks. And, it's a
ship canal so it's very wide and has plenty of room to pass other
boats so I don't think that is a problem. And you're right, it would
be unwise to try to cruise with the thing up. I'm not going to do
that. I'll only erect it when moored up.

Don't think I need an A frame. I can lift 21 kg on a pole myself. It
would be on a pole and you just lift if into the upright position and
hook on support ropes when it gets to upright. That's how I handle my
present, not very powerful Rutland 913 which weighs 10 kgs. I do
cruise with that up, unless the wind is high.

So, I return to my original question - if this is such a good idea,
why doesn't everybody do it? And, why are all commercial wind
turbines for boats the same size - around 1.2 metres diameter?

Thank you for your comments.

Peter