Research into Designing a Walnut Specific Spile

In this study, we worked with 4 partnering farmers tapping black walnut trees to trial a new walnut specific spile and assess tapping methods to increase walnut sap production. The walnut specific spile was designed and built by the Robert C. Byrd institute of advanced manufacturing. It incorporated a longer barrel to accommodate the thick walnut bark, more taper to seat better, and a larger 7/16-inch tap hole. The modified tapping procedures called for drilling a deeper tap hole, cutting through the entire depth of the sapwood of the tree. The 2006 study by Gary Naughton found that sapwood thickness correlated most highly with sap yield. In three of the four partner studies the walnut specific spile and new tapping guidelines significantly outperformed the practices the farmers had used in past years.