Hopefully you’ve all seen our “Lake CO2 Flux Estimates Using Floating eosFD’s” blog post where we show photos and eosFD CO2 flux data from 2 floating platforms in Lochaber Lake, near Antigonish, NS.
An eosFD floating calmly on Lochaber Lake continuously measuring water-atmosphere CO2 fluxes.
Recently, Spafford & Risk published the full data set from the lake also using the Forced Diffusion technique for monitoring, which earned them an EOS Editors Highlight.
Here, we’ve picked the brains of the StFX FluxLab (special thanks to Renee McDonald) to let us know how they designed and built their floating platform.
Materials for the Platform
What you’ll need to get started is as follows:
- Sheet of 1/2″ thick plywood
- Sheet of 1″ thick styrofoam insulation
- 15-20 2″ long stainless steel bolts, nuts and washers (Make sure to get nice wide washers)
- Waterproof glue (marine epoxy or similar)
And of course, you’ll need a few tools:
- Measuring devices (ruler, tape measure, etc.)
- Drill & Drill Bits
- Jigsaw
- Sockets/wrenches
- Box cutter
- Twine
- A Pencil
IMPORTANT: Eosense assumes you know what you’re doing with the tools and materials listed above and that you’re wearing appropriate PPE. Please take appropriate safety precautions and learn to use the tools listed above before moving on.
Building the Platform
If you want to replicate the platform that was used to float our eosFD units in the “Lake CO2 Flux Estimates Using Floating eosFD’s” blog post you’ll need to cut a 122 cm diameter circle from the plywood first. Mark this out by tying your pencil to your twine, measuring out 61 cm of twine and nailing the other end to the plywood. Now use it like a geometry compass to mark out the circle. Remove the twine and use the jig saw to cut along the line.
Next you’ll want to remove some of the material around the outside edges of the platform. The team at the FluxLab did this to ensure that the platform was minimally blocking factors like wind and solar input that have a big effect on lake CO2 dynamics. In the photo below, Renee has cut out bean shaped portions of the platform (A) with a width of about 20 cm and a length of around 60 cm each. Make sure to leave at least 10 cm (B) between the edge of the platform and the edge of the “bean” to ensure the platform remains rigid.
Once you’ve traced out your “beans” (you can do this freehand, if you’re feeling lucky), use the drill to make an initial hole along the traced line and then insert the jigsaw blade. Now use the jigsaw to cut along the line.
Finally, you’ll need to cut a small hole in the centre of the platform to insert the eosFD collar. This diameter of this hole should be around 2.875 inches, so use your pencil and twine trick again to trace out the circle and use the drill and jigsaw to cut the hole. Try to cut a bit small on this one as the more space you have between the collar and the platform, the more glue you’re going to need to use.
Now that you’ve got all of your holes cut, take the platform and trace out the appropriate holes on the styrofoam insulation and cut them out with the box cutter. Line up your styrofoam and platform, toss some of the marine epoxy onto the styrofoam surface, and mate the plywood and styrofoam portions of the platform. Once the epoxy has dried enough to be sticky, you should be able to drill 15-20 holes in the platform, around the circumference and on the thicker portions of the interior of the platform, to insert the 2″ bolts, washers and nuts. This will provide a mechanical hold of the styrofoam to the plywood, incase the glue breaks down.
Finally, insert the eosFD collar into the platform and glue it in place using the epoxy (make sure to fill in all the cracks, we don’t want your CO2 flux coming out around the collar).
Researchers from St. FX University carrying the floating platform from the truck to the lake
What’s next?
That’s really it for now – depending on how you plan to power the unit you can mount solar and battery to the platform, but the design and tools needed to do that are on a case by case basis. Renee did mention that because they were using a relatively heavy battery, they needed to add another small piece of styrofoam under the battery to ensure the platform floated roughly level. We’d love to see your platforms and hear about your floating flux measurements – get a hold of us at info@eosense.com or on Twitter @eosense.
