Good wooden shipwright's battens are really hard to find in large lengths now. The shop that I work in has switched over to fiberglass battens (It makes sense to us because we build fiberglass boats.) We have battens that are about 10 meters long. Since fiberglass is a pretty stable material the batten isn't affected by temperature or humidity. To make a fiberglass batten you'll need:

Once you've acquired the materials and found a good build area you can start to construct your future batten.

  1. Wax the surface of your mold until it is smooth and you are absolutely sure your batten will not stick to it
  2. Cut your fiberglass into strips a little wider than the finished batten will be
  3. Mix about a 2 L of resin and the correct amount of catalyst together in a bucket.
  4. Wet out the strips using a piece of mat then spread a bit of resin over it and place a piece of roving or cloth on top of the mat brush until the white color has left the fiberglass
  5. Lay that on your mold
  6. Repeat steps 4 and 5 overlapping the pieces of fiberglass
  7. Wet out a piece of mat and lay it on top of the previous ones
  8. Repeat for the remaining length of the batten
  9. Brush the fiberglass once it is in place in one direction to remove air bubbles
  10. Let the batten sit until it is firm and able to be cut by a sharp razor knife
  11. Cut the edges of the batten to the finished size making as long and straight a cut as possible (A straight edge will make this easier)
  12. Once you have done this remove the batten from the mold and sand the edges so that they are smooth and rounded.

Okay you now have a finished batten. this batten will last for decades and never lose it's fair or springiness.
please feel free to /msg with corrections and/or questions.