Kayak design is a combination of many things. Flared sides are used in newer East Greenland models and in there the flare gives narrow waterline, which gives good speed and low initial stability. The flare also gives wideish deck, which gives good secondary stability. Flared sides will also lead to good displacement while having low deck. Low deck is clearly desired in usual Greenland kayaks.

So you could say the flare gives more speed while keeping the secondary stability well. In other side the flared sides might not work well in tight lake chop and paddling a wider kayak is a bit more difficult. However the East Greenland ones and still quite narrow, having under 50cm beam (19 1/2 inch)

I would personally assume the low deck and flared sides could work very well on sea where waves are long enough.

Here's two newer shape East Greenland kayak made by Harvey Golden.

http://www.traditionalkayaks.com/Kayakreplicas/L19157.html
http://www.traditionalkayaks.com/Kayakreplicas/MUS48057.html

btw. If you just take a usual design and add some flare to cockpit area it can turn the model quite bad...

Toni.

: Anybody care to discuss the various attributtes of flare on the sides?

: I see all boats have flare fore and aft of the cockpit....some boats
: have pretty flat sides at the cockpit..some have flare.

: My Petrel has flat sides at the cockpit..has very good initial stablility
: and i'm not experienced with enough boats to say how good the secondary
: is..seems good.

: What will flare at the cockpit add? (besides drag)