Lenticular centre-boss shields were common -- but harder to make (and therefore expensive). Regional "preferences" are an unlikely explaination. To state that lenticular shields "may have been" used is inaccurate -- they certainly were used from ancient times.
In addition, stuffing the leather or rawhide facing of a shield with grass or straw would have been unlikely in the extreme, as it would not have strengthened the shield in any way, and would have been quickly torn to shreds in combat against edged weaponry. The facing of the shield, whether rawhide or cuir bolli, would have been glued to the shield at all points, thus adding to the structural of the shield itself. Painted canvas covers may then have been added, if only because it was cheaper to replace a tattered canvas cover than strip the rawhide from the shield.
An excellent demonstration of this shield-making technique is in the fourth episode of the History Television documentary series "Weapons that Made Britain" -- definietely worth a watch, as it not only includes period shield-construction, but scientific tests of sheild strength between flat and lenticular centre-bosses -- the lenticular shield takes a full-strength blow from a daneaxe and doesn't fail. The flat centre-boss does.
The Tirksom Bog shield has just such a padding behind the leather and it and also bears the scars of combat. The Ballateare shield fragments bear the paint directly on the leather. There is no evidence for canvas covers to my knowledge.
I am tend to limit my interest in centre boss shields to the late Viking age I will not argue with your knowledge. I am however aware of a single plank from a shield that might be curved and some bosses with have flanges that may indicate that the shield that bore them was lenticular. To the best of my knowledge, their are no lenticular sheild extent today. I am happy to be corrected and would like to know more. --Paul Matisz
Making a lenticular shield boss is hardly more difficult than making a flat one. The dishing of the boss itself is a far more difficult task than a the slight dishing of a boss suited to a lenticular shield. A boss suited to a curved shield (such as a Norman kite) is more difficult as it involves curves in multiple directions and I had one made for me that fits perfectly from a guy who had made just 6 bosses in his life beforehand. --User 144 19:28, 25 Mar 2006 (CST)
And I guess I don't need to point out that lenticular shields negate some of the benefits of overlapping shields in a shield wall.--User 144 19:52, 25 Mar 2006 (CST)
The issue is not about making a lenticular boss -- the boss would be virtually identical in any case, but the curving of the wooden shield itself. (I intend on writing an article on period shield construction and contrasting it to SCA sheild construction -- keep your eyes peeled.)
In addition, whether or not a shield was lenticular has no impact on its usefulness in a shieldwall, so long as it covers the same total area -- remember, the edge of the shield is a uniform distance from the boss at all points. Lenticular shields were not very deeply dished, but dished nonetheless (i.e the shield carried by Boromir in the recent Lord of the Rings movie trilogy is a good example of a modern recreation.) The increase in structural strength would have only been an advantage. Curved shields (whether lenticular round or dished heater) provide distinct advantages to strength and body cover -- flat shields have the advantage of being much easier to create, which is why one sees so few curved shields of any type in SCA combat.
Canvas covers were from a later period than the Viking age -- typically only heater shields would have been so covered, and I suspect tourney shields at that. --Paul Matisz 21:07, 25 Mat (EST) If canvas covers were later than the Viking age they don't really have any bearing on centre boss shields.
Not having seen the show of which you speak, I would like to know if the scientific experiment was one just by hitting it or in a less subjective manner. I don't doubt that lenticular shields were stronger, the degree to which they were I would like to investigate further.
Flat shields provide better cover and support in a shield wall. It may be that the rank and file may have used flat in the wall and some higher ranked warriors who might have expected to fight in a more individual manner may have used them thus. It may also be that lenticular shields leant themselves more to duels. --User 144 23:25, 25 Mar 2006 (CST)