Preface


The wooden turtle drifter was originally designed with “cold-stunned” sea turtles in mind. Each year as winter approaches many sea turtles in Cape Cod Bay, for example, begin to head south for warmer water, but end up being trapped. Before long they become stunned by the bay’s cold water, and their fate, whether that be washing ashore or leaving the bay to warmer waters, depends on Cape Cod Bay’s ocean currents, wind, and waves. The turtle drifter was designed to mimic cold-stunned turtles that are moved by these forces. As of July 2015, a few turtle drifters have been built and tested but there is much more to be learned about their water following behavior. Most of the instructions and dimensions below are approximations for an adult Loggerhead turtle but, with the help of James Melvin, a Falmouth Academy High School student in Nov 2015, we have also built and deployed at least one Kemp Ridley-sized turtle as shown in the pictures here.



Experimentation with design is still taking place to modify turtles to be self-righting. During the summer of 2015, Tim Anderson (West Washington State University) began a project to better understand the water following qualities of the turtle drifter. Bianca Santos (Virginia Institute of Marine Science) is also making more turtles in 2015 and fitting a loggerhead carcass with a transmitter.

While the turtle drifter is technically a surface drifter, the fact that a large portion of it protrudes from the water makes it’s path greatly wind and wave affected. With that said if you are interested in a drifter that more accurately follows ocean surface currents, the surface drifter may be a better option.

Tools



tools

Materials for Loggerhead Wooden Turtle


Assembly Instructions for Loggerhead Wooden Turtle


  1. Outline Cuts
    • On plywood, outline oval turtle shell shaped cuts with the following major and minor diameters:
      • 71 cm x 60 cm
      • 60 cm x 50 cm
      • 50 cm x 40 cm
      • 40 cm x 30 cm
      • 30 cm x 20 cm
      • 20 cm x 8 cm (2)
    • On styrofoam, outline oval turtle shell shaped cuts with the following major and minor diameters:
      • 65 cm x 55 cm
      • 55 cm x 45 cm
    • On 2"x4" wood:
      • At one end, outline a rounded cut of similar shape to the largest plywood outline.
      • 71 cm from this end, outline a neck and face shape (take caution not to make the neck too thin, reducing the wood’s strength).

  2. Make cuts
    • Make cuts outlined on the 2”x4” and for the flippers with the jig saw.
    • After adjusting the jigsaw to cut at an angle (about 45°), make the rest of your cuts in the plywood and styrofoam, with the jigsaw blade pointing outward.
    • Stack your turtle body with the styrofoam layers below and above the second largest plywood piece. Make any minor adjustments with a non-electric saw and mark each piece with “front” on one end.

    turtle cutouts
    Turtle body pieces cut from 2” x 4” and plywood

  3. Make bolt holes
    • From bottom, push bolts through bolt holes of bottom turtle body layer.
    • Flip bottom layer and stack turtle layers and foam, putting bolts through every piece (these bolts will fit tightly, and you may need to use a hammer or force pieces onto bolts with body weight).
    • Place a washer on protruding end of bolt and tighten nut to secure layers together.

    bolt guide

  4. Attach "backbone" and flippers
    • Remove bottom layer of turtle body and flip upside down.
    • Using the ⅛” drill bit, drill pilot holes in 2”x4” backbone and in 1”x1” posts (see below picture for approximate spacing).
    • Screw backbone and posts to bottom turtle body layer with 2 ¼” screws and 2” screws, respectively.
    • After flipping turtle base to be right side up, drill pilot holes in flippers and attach flippers to upper side with 1 ¼” screws (see photo above for guidance).

    bolt guide
    Attaching backbone and flippers (screw placement isn’t all that important)

  5. Bolt body layers and attach transmitter
    • From bottom, push bolts through bolt holes of bottom turtle body layer.
    • Flip bottom layer and stack turtle layers and foam, putting bolts through every piece (these bolts will fit tightly, and you may need to use a hammer or force pieces onto bolts with body weight).
    • Place a washer on protruding end of bolt and tighten nut to secure layers together.

  6. Attaching ballast
    • While we’re still experimenting with what the right ballast weight is ballast, we noticed that the turtle drifter likely needs some extra weight to reduce its buoyancy
    • For this drifter, we attached about 40 pounds of brick ballast with 2”x2” wooden posts
      • other materials can also be used for ballast, and having fewer flotation layers in the turtle would reduce the ballast needed
      • less ballast will be necessary if using this guide to make a smaller turtle, such and a Kemp Ridley
bolt guide