Building a raft for irrigation systems can be a very useful way to hold equipment above water level or at a certain depth beneath the water.

For example: you may have suction baskets you want to keep away from the riverbed or hold maintenance equipment in the middle of a river you pump from.

Raft Buoyancy

Suction Baskets


There are many cool instructions on how to build one like this.

I like the idea of building one from the materials you have already and repurposing items that would otherwise become trash in our environment. Plastic barrels were the first thing I had in mind and actually it’s probably because I saw that as the most common buoy used in irrigation projects we design for developed countries.

Building a raft isn’t difficult but calculation for buoyancy might be a pain in the #@!# for some, so we created a buoyancy calculator especially for this purpose. The calculator defaults to dimensions of a typical 200-liter barrel made from plastic but these may differ a little between manufacturers. You can always google to find the appropriate barrel and change dimension accordingly. (Remember to get the info for the barrel weight, as it will affect the buoyancy of course.)

Beside making sure the raft will float, you need to know how deep the barrels will be submersed in water and how much additional weight you can have on the raft. We built a very cool slider that you can play with water level on the barrel.

The frame of the raft will have its own weight that can be added too, and the calculator assumes that it will be above the water level or at least does not contribute any additional buoyancy if submerged, so the worst case is covered! You can add as many barrels as you want.

Note: This buoyancy calculator built on responsive template so it will fit on your mobile device without downloading additional apps 🙂 


Buoyancy Calculator
Water Level Slider

Written By : Noam Kompano