I use an old trick we used to apply with our Lark Dinghy back in the 70's. They had very large sealed buoyancy tanks which we used to fill with helium to provide a small amount of lift. We always felt it gave us an advantage in lighter conditions. Whilst it did not reduce the mass of the boat it did provide some lift and this was noticed by some of our more observant club members.
Helium, a by-product of natural gas production, has a lifting capacity of 1.02 kg/m3 (0.0640 lb/ft3). Methane is the main constituent of natural gas and is used throughout the world as fuel. It is also buoyant and provides about half the lift of hydrogen.
The weight of 1 litre of air, at atmospheric pressure, is 1.225 x 10^-2 N, and this gives the upthrust. The weight of 1 litre of helium, also at atmospheric pressure, is 0.166 x 10^-2 N, so the net upward force is 1.059 x 10^-2 N. This is ignoring the weight of the envelope. This force could lift a mass of 1.059 grams, including the mass of the envelope.
The volume of an IOM is about 10 litres so the lift provided will be over 10 gms. Small but maybe a significant difference when sailing. I have a small insert in the plug hole on the stern deck which allows for the entry of the helium and the exhaust is through the sheet fairleads. Of course when the boat is measured, a cover is off and the helium released so the boat will weight OK. Fill her up to go sailing and you get a bit of lift.
The helium comes from here and can be used for party balloons if you have any left over.
What day is it today?