Society for the Promotion of Traditional Archery
For UK societies, the English longbow generally conforms to the specification set out by the British Long-Bow Society, that is, the cross section must be in the ratio of 1(width) to 5/8 (depth), this producing the deep, narrow section which differentiates it from flatbows. The BL-BS also requires that the length between nocks is no less than 60inches for drawlengths up to 26inch, and 66in for over that.
Horn nocks for BL-BS shoots are mandatory, but not for SPTA events.
SPTA allows recurved longbows, unlike the British Long-Bow Society. There is no limit regarding draw-weight. It is advisable to ask the shoot organiser before using bows over 70lb draw weight.
No artificial materials to form the laminations, which are restricted to 4. Artificial glues are allowed.
A few of the bows from the 'Mary Rose'
A yew bow which 'comes compass' ie forms an arc at full draw