Public Lab Research note

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First prototype of kayak towable thermal fishing bob rig

by kgrevera | May 04, 2015 20:39 04 May 20:39 | #11782 | #11782

First prototype of kayak towable thermal fishing bob rig


I am working on a project with Sara Wylie at Northeastern University further developing the thermal fishing bob. Preliminary testing last summer showed that the fishing bobs submerged and suffered water damage when towed behind a kayak. The submerging made it hard to see the light and caused increased water damage. So, we are working on a rig to float the thermal fishing bobs above the water that can be towed behind the kayak. We hope this will make the lights easier to see and reduce water damage.

Research Questions

  • What is the best way to rig the thermal fishing bobs so they can be towed behind a kayak? We are looking at multiple floatation devices: the first which I am discussing here is a child's pool floatie. We are also going to try a foam sled/boogie board and a toy boat.

Pool Floatie Prototype

  • What is the best way to reinforce the thermal fishing bobs so they don't fall out? The leg holes in the pool floatie are slightly too big so my first question is how to make those holes smaller.

  • How do I prevent the fishing bobs from getting wet while still keeping the light visible? My second question is how to make sure the light is still visible inside the pool floaties.


In this first prototype, two thermal fishing bobs have been nestled into the leg holes of a child's floatie toy with a piece of foam wrapped around each like a coffee cup (about 2.5-3 inches high). The "coffee cup holder" needs to be just large enough to hold the fishing bob, but not so large that it obscures the bob's translucent body. The foam is then reinforced on the top and bottom of the floatie with duct tape. A small circle of tape loosely attaches the cardboard around the thermal bobs to each other and to the walls of the float to keep them from rattling around. The thermistors are different lengths so that they can measure temperatures at different depths. The thermal fishing bobs are constructed with the instructions from thermal fishing bob barnraising.


  • 2 thermal fishing bobs
  • duct tape
  • foam
  • child's floatie with open leg holes in the bottom
  • kayak/canoe
  • kayak tether
  • scissors





First Try

The first attempt was pretty successful. The lights were visible, nothing leaked, and it stayed afloat. In my next try I will definitely have to test it out later at night so that the lights are easier to see. In addition, a new rig to pull it with my need to be devised. This try used reinforced duct tape stuck on to the front of the float with a simple string fishing/kite reel attached to it. I will try a rig with two loops next time to see if this helps to keep the float steadier.

Next Steps

Another try!


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