thanks for the repys,

So far I think it's a good idea to use the trains we already have to
transport the passengers.

I was thinking to make sails the same width and half the height of the
train.

Put them in sets of 4 on their own set of wheels.

Then attach a row of such carts to the front and rear end of the train.

The amount of carts you take with you depends on how brutal the wind is
that day.

If there is non you bring non. :-)

I have no idea how often it would be useful.

But now that I've imaginated a size with the sail of the imaginary
apparatus maybe you could tell me how much carts we need to create an
interesting "wingspan" for our earth rotating windmill of sailnovation.
:-)