Why design a boat with prebend?

[Mac Smith]

The Hunter boats used the B&R Rig, with no backstay. My Hunter 31 also had the backswept stays which replaced the backstay needs. Proper tension on the stays will provide your mast with proper bend. Improper tension could allow your mast to invert or worse. See this link- http://sbo.sailboatowners.com/downloads/Hunter_gen_70432613.pdf

 

[mainesail]

Ok, so I've seen enough discussions here on sail trim, but not much about the purpose of prebend in the mast. Just if your sail is designed for it, you put some in. But why design a sail with mast prebend in the first place? What is gained?

Also note that a little prebend helps flatten the main. you set it using the lowers, forward ones if you have both, as you tune the rig. As a default, I usually put in a half to full inch, (gauged by looking up the mast track) depending on mast length. If you have twin lowers then you "lock in" the adjustment by tensioning the aft lowers which should be your last tuning step. Fair Winds.