The Crux of Sectional beams

The essence of a "sectional beam" is not the mechanical structure on the loom, but how the weaver uses it.

Any warp beam that rotates can be used as a sectional beam. And, any culture that understands carts, can construct beams that rotate.   For vertical, warp-weighted loom, all that is required is to scribe lines on the beam to delineate the sections of the beam.  The the warp can be wound on the beam, stored, and wound off as needed.   Looms designed for weaving long bolts of cloth do require pegs or pins in the beam to support the sections of warp as they are wound on, but it it is very easy to insert such pegs in a beam. Little "L" brackets held in place with duct tape work.  Nails work. These approaches will not satisfy some prissy recreational weaver, but they will allow winding wool singles onto the loom at hand, right now.  And, a very good tension box can be improvised from a bit of plywood and some wooden dowels from the hardware store. Two thousand years ago, making a tension box was no harder than making little stool - a easy morning's work.  I could drive to Jackson, buy any one of Stephenie's little looms, convert it to a sectional beam, and be winding warp on it, section by section, by night fall.  (Or I could use the sectional beam on my AVL as a warping mill, prepare a warp under tension and then wind it on the little loom.)  The crux of the idea is keeping wool singles (each and every one) under tension at all times as the loom is warped.

A sectional beam on a modern loom has additional features for recreational weavers, but these were not required for industrial weavers of the late Roman Era and Middle Ages. They would weave to the end of their warp, wind on another warp (section by section) tie the two warps together, and weave on with minimum waste, and very little effort. There is no reason why the 2-beam, horizontal loom of  the late Roman and early Middle Ages could not have used sectional warp beams.   The difference between an "ordinary" beam and a sectional beam is a hand full of wooden pegs that can be inserted or removed as the kind of cloth being made changes. (And, minor differences in how the warp is tied to the beam.)  Once you have thought about it the concept is easy and logical.  It is only hard if you think about a sectional beam as a device, rather than as a way of using a beam that rotates.  For the real weaver, "sectional beam" is a way of warping rather than a mechanical device.  It is a set of procedures and techniques for keeping warp singles under tension and under control at all times.

A second approach that works for industrial weaving  is to have a sectional warping mill that is warped section by section, and then the entire warp is wound on to the warp beam of the loom as required.  One such mill can support several looms and avoid down time of the looms and their weavers. It is the same concept, just moved off the loom to separate operation. For details see the old texts on industrial weaving.

Do I see such mills in modern weaving classrooms?  No. And, I bought the only loom with a sectional beam from the largest local weaving classroom.  50 weavers (many very advanced) and nobody was using sectional warping.) They gave me a good price on that loom, because nobody was using it. Sectional beams are not needed for mill spun (2-ply) wool warps, or silk, or linen, and few people weave with fine hand spun wool singles these days.  On the other hand, there is a large class of traditional  wool fabrics that can only be woven from the fine wool singles that are easier to handle when warped under tension (e.g., section by section).

The evidence for sectional beam looms is in the fabrics produce in the Late Roman and Early Middle Ages. To understand the evidence, one must understand working with fine wool singles. That means getting out your spinning wheel and spinning "fines".