This is the pattern I've drawn. I measured my arm at several places. I measured the distances between them and put this all on the fabric.
The rectangle at the left is for the velcro and the ones at the upper part are for the gathering.
I serged the piece except the lower third.
I cut out a rectangle from canvas, pressed the edges inwards and sewed on the bracer pattern into the upper part rectangles. The short sides are not sewn on.
I cut out bias tape, ironed its upper edge and sewed on the lower edge of the bracer piece.
I turned it over and sewed on.
I ironed the upper edge to the wrong side and the lower third's edges for the velcro.
Now I could sew one part of the velcro to the right side of the bracer.
I used a twill tape to gather the elbow area. I threaded it through the tunnel, sewed on one side, pulled the other end to a measured mark and sewed on this end as well.
I pinned the elbow seam and sewed from the velcro level to the upper edge. At the elbow part I decreased the width of the seam allowance to provide freedom of move.
I sewed the other part of velcro to the wrong side of the bracer.
I pressed the seam allowances flat and sewed the upper hem on.
I put each bracer on the sleeve board and evened up the chaotic gathers to neat lines.
