PEARL Paleoecological Environmental Assessment and Research Laboratory
Department of Biology, Queen's University, Kingston ON, Canada, K7L 3N6
For instructions for using Glew corers and core extruding, click a button below
First things first. Learn to tie off the corer so you can't lose it at the bottom of the lake. See below.
Line Attachment Procedures for Glew Gravity Corers
By John R. Glew
All of the Glew-type gravity corers have been designed for a lightweight 6 mm braided nylon or Kevlar line. They are not designed for any composite / metallic-type of wire rope. If for any reason the line is removed from the corer, it must be relocated in the manner described below.
In replacing the line use only 6 mm diameter braided nylon or Kevlar line. The corer has been designed to operate only with the line attached in the configuration shown on the diagram. On no account use plow steel or stainless steel wire rope or other metallic line on the corer.
First, pass the line down through the messenger relay mechanism and pull approximately 30 cm of line out through one of the inspection ports on the tubular housing (Fig. 1A).
Next, reintroduce the end of the line into the housing and thread through the upper guide hole (“x” shown in Fig. 1A), from the inside out (Fig. 1B).
Finally, thread the end of the line down through the second guide hole in the upper plate and tie off with a reef knot and a thimble clamp if one is available (Fig. 1C).
The preceding is important because the clearance between the trigger mechanism and the line emerging from the lower end of the messenger relay is less than 1 cm. Attempting to tie off the line inside the tubular housing or by bringing it through one of the inspection ports will interfere with the release mechanism. In addition, other configurations will prevent easy inspection of the line, inspection of the knot used to secure it, and the effective use of a clamp.
It is important to occasionally check the free passage of the line through the messenger relay mechanism and tubular housing. To do this pull approximately 20 cm of the line through the corer housing to expose that portion of the line that is normally inside the messenger relay mechanism (Fig. 1C). Check for signs of abrasion to the outer braid. If the line shows signs of wear, inspect the upper portion of the line. If this is serviceable, cut the lower end of the line below the lower plate, discard the end portion, and re-tie. This will not necessitate the rethreading procedure. Melt the end of the nylon line to prevent fraying.