not Aerotech sails, they do not have monofilm and are made of multiple panels like most modern sails, I think.

That does not say the sail is one piece of mono, it refers only to the luff. They are all made of multiple panels.

IF it was one piece and you tore one bit, you would only replace one panel by cutting along the batten seam, glue(tape) and sew new piece in.

I gather from all these questions you are wishing to try making sails? There is a LOT to it so I recommend going to a sailmaker and watching them repair a WS sail. The setup needed and the machine needed is quite a large undertaking. Maybe send a message here to the guy in Turkey (?) who makes his own. " Melih " I think........ ?

There is no such thing as a continuous panelled sail.

North sails 3DL are probably the nearest thing but they still use panels that are stuck together on a moulded surface, then a continuous fibre is laid from head to tack / clew etc, then more panels laid on top of that and then baked to set the glue.

Membrane sails still have panels, usually joined at the batten pockets, this is where the sails gets its shape.

Ben1973 said..
No and no.
and I don't know why some think the seams and joins are the weak points, if done right their stronger

You are Ben Severne?

No this again, the body of this sail is at lease 9 pieces of sail material.

This part of the add even tells you the body is made of different panels, and it the only way to do these batten pockets.

I think the breakdown photo of the panelling is quite interesting here.
A camber-induced sail is obviously more complex than a basic rotational sail design. Both sails still need to set with maximum sail fullness at some point one third back from the mast - although the upper sections of any windsurf sail tend to be flatter, and they set with twist.

In this case, the coloured (painted) section of the main panel could indeed be one flat piece, with the batten pockets then sewn over the top.
I would suspect however there is a seam between the window and that upper panel, with the seam covered by another batten pocket.

Sails do need some broadseaming to ensure reliable shape in the front sections of the sail but the seaming can be vertical as well as horizontal, and with a twin luff sail that shape can be added in the many vertical seams shown in that graphic. The twin luff structure itself does guarantee and front biased aerofoil shape.
And for the rear half or rear two thirds of the sail we do need the sail to set flat or flatter.


Our bigger light wind rigs are often made to set a lot fuller than the typical rotational sail, and they notably have double curvature* in the lower sections, whereas small rotational wave sails generally don't.
To get double curvature you definitely need seaming - in the same way that your jeans are cut to fit around your arse. (Whereas the legs of your trousers are just two tubes of material, cut with simpler seaming because we only need single curvature.)

*Single curvature means you can set a straight line along the panel in at least one direction. With double curvature, you can't.