Learn · Board science · Flotation
Does a wooden surfboard float differently?
Weight, volume and momentum: what really changes when a hollow wooden board weighs a little more than a foam one, and what does not.
Short answer: it floats practically the same. Volume is what makes a board float, not its material, and every extra kilo is offset by one litre. Where the weight does show is in motion: more momentum means more rail, more glide and more drive, and a little less snap in very tight turns.
Volume is what floats
A board floats by Archimedes’ principle: the water pushes up with a force equal to the weight of the water the board displaces. A litre of seawater weighs a little over a kilo (about 1.025 kg), so a 40-litre board fully submerged pushes up with about 41 kg.
That lift depends only on volume. Foam inside or air wrapped in wood makes no difference: 40 litres displace 40 litres of water. That’s why the air inside a hollow board doesn’t make it “float more”: what floats is the board’s total volume.
One kilo, one litre
What weight does change is how much of that lift is left to hold you up. The rule is simple: every extra kilo in the board takes away roughly one litre of flotation.
An example: a 75 kg surfer on a board that weighs one kilo more than its foam equivalent. That kilo is around 1% of the total weight the board has to hold up. A soaked wetsuit can add more than that, and nobody chooses a board by their wetsuit.
If you want to offset it completely, one extra litre of volume in the design is enough: a few millimetres of thickness or width.
Where it shows: momentum
Weight shows in motion, not while floating. A board with more mass needs more force to change speed or direction. In the water that translates into three things:
- Rail: the board holds its line and is less twitchy in chop.
- Glide: it keeps its speed through slow sections and between waves.
- Drive: it comes out of long turns with more push.
The trade-off: very short, quick turns take a little more effort. That’s why hollow wooden boards shine in fishes, midlengths and longboards, where glide is part of the design.
Swing weight: where the weight sits
Not all weight counts the same. In a turn the board rotates around a point near your feet, and mass far from that point weighs far more in the turn than mass at the centre. Shapers call it swing weight.
In a hollow board the inside is air and the weight sits in the skins, the rails and the solid nose and tail blocks. That’s why those blocks are kept as short and light as the build allows: taking weight off the ends pays more than taking it off the centre.
What it means when choosing a board
- Look at the litres on the spec sheet, not just the dimensions: volume is what holds you up.
- Coming from foam? One litre more than your usual volume more than covers the weight difference.
- Choose the family by the wave: in small to medium surf, the glide of a wooden board is an advantage, not a toll.
Want to see what yours would weigh? The calculator on How it is built estimates it from its dimensions.
FAQ
Does a wooden board float less than a foam board?
It floats practically the same if it has the same volume. Volume is what floats; the extra weight of the wood takes away roughly one litre of flotation per kilo.
Does the air inside a hollow board make it float more?
No. What floats is the board’s total volume, whether it is filled with foam or air. The air inside only explains why a hollow board weighs far less than a solid wooden one.
Why does a wooden board have more glide?
Because it has a little more mass: it takes more force to slow it down, so it carries speed better through slow sections and between waves.
Do I need more volume in a wooden board?
One litre more than your usual foam volume more than covers the weight difference. In most cases the same volume works well.
Build it with the wood already solved
Pick a shape and get the cut frame and Paulownia prepared for each part.
