How much yarn will I need to knit a gansey?

Obviously a lot depends on your desired fit.  Ganseys were traditionally meant to have 2-4 inches of ease, but there can be a lot of yarn encapsulated in the 2 inch difference.  That said, 2000 yards for a men's small/woman's medium is a good place to start.  Gansey yarn is also great for gloves and mittens, should you find yourself with a few extra skeins.

How do I go about designing a gansey?

Ganseys are gloriously easy to design.  To figure out the structure of a gansey, my favorite book is Beth Brown Reinsel's Knitting Ganseys which contains, among many other helpful construction techniques, a really useful percentage system to help one figure out basic gansey proportions and how to apply them to one's own shape.  Beth's book includes several traditional design motifs and stitch patterns, but I often find myself turning to Gladys Thompson's Knitting Jerseys Guernsey's and Arans for a wider range of traditional stitch patterns.  Ms. Thompson does not really write knitting patterns as modern knitters are accustomed to, and some of her graphs slipped through the editing process tilted on their sides, so I find that I use her book (with a little caution) as a stitch dictionary, and Beth's book for construction advice.   Ganseys as we think of them were traditionally a male garment, so there isn't any waist shaping (nor any particularly good advice on how to add waist shaping).   The women who followed the herring fleet and processed the fish - sometimes called "gutter girls" or "herring girls", often wore their own ganseys.  I have been looking for patterns for herring girl ganseys, but so far have been unable to find anything equivalent to the relative wealth of patterns we have for men's ganseys.  If anyone has any information about herring girl ganseys, please get in touch. 

When will gansey yarn next be available? 

As of this writing (February 2018) I have the 2017 yarn back from the mill and will be focusing on listing it properly on my website.  I prefer to dye to order, so please feel free to get in touch about your gansey hopes/plans.