hello,
i've never worked with bend sensors, but i'm a little afraid, that amplifying an analog signal to pump up sensitivity might not be ideal. if the signal you're getting now is not distinct enough you'll probably might just end up amplifying unwanted noise... but i don't want to discourage you, as i said i've never worked with bend sensors.
maybe you can solve your problem mechanically, by adding a lever to your sail/sensor design?
you could also try using a temp sensor , or a classical windmill (plus a photo-diode and LED) to get your information.
sorry that i can't help you with the op amp.
kuk