Whilst a lenticular shape may add to the strength of a shield, I am unsure as to how we could justify a curved shield doing the same job. Thinking about it one would imagine that strikes to the side edges would cause glued planks to fail more readily. ie strikes falling perpendicular to the face rather than at a more obligue angle.
Curved shapes do however allow better protection for an individual than a flat shape does. This is probably why they became so popular for knights etc. --User 144 16:32, 27 Mar 2006 (EST)
Trust me, as a fighter you get strikes all over the shield, particularly on the edges when you try to parry a wrap-shot away. This one of the reasons why SCA shields are edged in hose (and why medieval shields were edged in iron or rawhide) -- it's easier on the shield and less likely to break rattan (or bone on a poorly-controlled parry). Curved kites and heaters not only protect the body and add structural strength to the shield, but redirect the energy of a blow, making it more likely to glance away and expends it's energy somewhere other than the shield itself.
Also, this is a purely subjective observation, but a flat shield doesn't feel as good as a curved one. Flats feel like a pier tied to your arm -- they do the job, but there's no liveliness to them. A curved or lenticular shield feels like its protecting you better, and are easier to handle. Also, they tend to protect the "blind spot" behind the left shoulder from wrap-shots. User:Paul Matisz 11:19 EST, 27 March
I am aware of shields being hit all over the place although the standard 'rage cut' angle falls most on a shield thus chopping that section up pretty well.
I guess it's all a matter of what you are used to. I find curved kite shields to be a liability (mainly as I don't fight with them very much) and much prefer a flat centre boss shield. I have not fought with a lenticular shield. I also prefer to face someone wielding a kite or heater as they are easily suckered into exposing a leg for a thrust.
I still feel that a flat shields are better for a wall. As you yourself said, a lenticular shield doesn't curve very much it doesn't really give you that much of an edge, and I was specifically refering to the joined edges of the planks when refering to a possible weakness. All shields have that weakness but a curved shield tends to let the blow fall more often perpendicular to the face edge and thus more forcefully. Curved edges remove more edge blows extending the life of a shield.--User 144 15:38, 28 Mar 2006 (EST)