I know there has been a lot of discussion on volume of boards but can anyone explain why a 2.4m modern board has the same volume as an old 2.7m or longer board. There a re several free ride boards that have high volume at a relatively short length and they are not that wide either, yet they have great flotation. Is it in the construction or what?

you're not thinking in 3D

You have come to the right place, Seabreeze is at the forefront of the Experimental Board Volume Theory.

Modern boards have more surface area, the more surface area a board has the better it will float*

How they do this is when you move volume to the rails you increase the surface area and therefore the volume of the board, think about a canoe*

Also, boards were once upon a time measured in 'Old School Volume' and now they are measured in 'New School Volume'. Which is why new boards float better. It takes many years of meditation and an Onion on your belt before this concept can be fully understood. When exactly the switch happened between OSV and NSV is not known, but it was a bloody battle and many brave shapers lost an Onions from their belts.*



* I pieced this all together from reading Seabreeze.

Things have length width and thickness

So if the boards are shorter and the same width they must be ........

They don't have a big pointy nose anymore, which artificially inflated the length figure compared to the volume figure.

Also they're a bit wider now. But the pointy nose is the main thing I think.

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barn said...



Modern boards have more surface area, the more surface area a board has the better it will float*

Wouldn't that be more volume the better it floats? Wide boards with lots of surface area will have better form stability making them more stable under foot and a better shape for supporting a load like a human, but a 120 liter board from 1995 and a 120 litre board from 2011 should have equal bouyancy.

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barn said...
Modern boards have more surface area, the more surface area a board has the better it will float*

* I pieced this all together from reading Seabreeze.

Maybe instead of piecing things together from Seabreeze you should have paid more attention in physics class.

2 people don't get it so far. lol

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swoosh said...

2 people don't get it so far. lol

Oh no! 1 post!

Big fat boards float big fat blokes. Question answered as I get older the board will continue to widen.

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ikw777 said...

>>>> but a 120 liter board from 1995 and a 120 litre board from 2011 should have equal bouyancy.

If they're the same weight they'll have the same buoyancy. but it's likely the newer board will be lighter, thus have more buoyancy.

And I think Neb's has put his finger on the length to volume ratio variation between old and new boards, it's in overall thickness and nose area.

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stehsegler said...

barn said...
Modern boards have more surface area, the more surface area a board has the better it will float*

* I pieced this all together from reading Seabreeze.

Maybe instead of piecing things together from Seabreeze you should have paid more attention in physics class.

Maybe you should have also

There is static bouyancy and dynamic bouyancy.

Static refers to how much weight you can put on an object at rest.

Dynamic refers to the fact that once the object is moving it will generate more upwards force due to water pressure - like a waterki lifting you before it starts to plane.
A short wide board will feel like it has more float as even at 2knots forward speed it has that little bit more bouyancy.
Plus a wider board is more stable laterally so it feels a bit bigger when you are not planing.
Think about a piece of wood the same volume as a solid door (probably about 3m x 30cm x 30cm) - which one would you want to lie on to float - especially in choppy conditions? Bet you'd pick the door.

So the O.P is correct - modern boards do seem to have more float than same volume in older boards.

Of course modern boards of same volume weigh less, and so does the rig, so they can have more weight placed on them (not supporting as much of their "own" weight).
Plus styro cores contain a lot more air and weigh less than the old Clark foam cores

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ikw777 said...

barn said...



Modern boards have more surface area, the more surface area a board has the better it will float*

Wouldn't that be more volume the better it floats? Wide boards with lots of surface area will have better form stability making them more stable under foot and a better shape for supporting a load like a human, but a 120 liter board from 1995 and a 120 litre board from 2011 should have equal bouyancy.

A larger surface area means better weight distribution... so it floats better...This is similar as Eskimos using tennis rackets to walk in deep snow

Its not just the volume of a board that determines its bouyancy you also need to consider its density, ie mass= volume x density. Another factor is relative density of the water so the saltier the water the better it will float.
I had access to a rectangular tank a while ago and submerged a few boards in it to calculate volume by multiplying the length x breadth x rise in water level. The production boards were pretty close but a couple of custom boards were nowhere near what the manufacturer claimed. just something to consider

OT: barn, Wed, alltime?

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Mark _australia said...

So the O.P is correct - modern boards do seem to have more float than same volume in older boards.

The key word is seem. Newer boards have enhanced form stability characteristics (like your door) which make them more stable and easier to sail, and a little bit more lift whilst underway, but they are not actually more bouyant or more floaty (if you like). 120 litres is 120 litres. (Small point I know but I though I'd make it - it seems like bad practice to confuse bouyancy with form stability).

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Mark _australia said...
Dynamic refers to the fact that once the object is moving it will generate more upwards force due to water pressure - like a waterki lifting you before it starts to plane.

Yup... aware of "dynamic buoyancy". Assuming the original poster was serious I guess we would have to get him/ her to clarify the question a bit further.

HHHmmm so to mix things up a bit , according to Starboard there is virtual volume as well. I think that's what we are talking about with wider board widths seeming to to have more float

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stehsegler said...

Mark _australia said...
Dynamic refers to the fact that once the object is moving it will generate more upwards force due to water pressure - like a waterki lifting you before it starts to plane.

Yup... aware of "dynamic buoyancy". Assuming the original poster was serious I guess we would have to get him/ her to clarify the question a bit further.

I doubt he was serious. More like a wind up. Sigh.

You are all wrong old and new boards float the same..... The difference is the era in which they were floated, global warming = warmer oceans = warmer water = water has lower density = water more easily displaced = less floaty boards.

The water was cooler and moe dense in the 80s so boards floatier in in the past (although, arguably the onion may have had some influence)

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nebbian said...

They don't have a big pointy nose anymore, which artificially inflated the length figure compared to the volume figure.

Also they're a bit wider now. But the pointy nose is the main thing I think.

Yep not that much volume in a pointy nose, nothing that a slightly fatter rail couldn't make up.

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ikw777 said...

Mark _australia said...

So the O.P is correct - modern boards do seem to have more float than same volume in older boards.

The key word is seem. Newer boards have enhanced form stability characteristics (like your door) which make them more stable and easier to sail, and a little bit more lift whilst underway, but they are not actually more bouyant or more floaty (if you like). 120 litres is 120 litres. (Small point I know but I though I'd make it - it seems like bad practice to confuse bouyancy with form stability).

Yes the first bit is right ("seem") but 120L is NOT 120L ( bolded part)

120L of Clark foam will float way different to 120L of styrofoam
..... just like 120L of lead will float way different.

New boards are more bouyant, but also have added dynamic buoyancy due to shape.

When Dr Karl is asked why steel ships float he always says "If an object is lighter than the volume of water it displaces, then it floats" so a lighter board should float more readily as it has to displace less water to do so???

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DrJ said...

You are all wrong old and new boards float the same..... The difference is the era in which they were floated, global warming = warmer oceans = warmer water = water has lower density = water more easily displaced = less floaty boards.

The water was cooler and moe dense in the 80s so boards floatier in in the past (although, arguably the onion may have had some influence)

Why the red thumb, this is a great theory

I don't know if anyone has mentioned it yet, but I think some of the modern boards are using more 'virtual volume'. In this case the volume seems to be related to marketing and not the displacment, and I think there have been cases of boards that are in theory 15 litres apart, but almost the same volume.

I think they argue it 'feels' like a 90L board.

I saw the red thumb .... Made me laugh.

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Mark _australia said...
Yes the first bit is right ("seem") but 120L is NOT 120L (bolded part)

120L of Clark foam will float way different to 120L of styrofoam
..... just like 120L of lead will float way different.

New boards are more bouyant, but also have added dynamic buoyancy due to shape.

Phew!! Someone got it at last. One slight correction though; 120L is 120L is 120L. The second part about the different materials is spot on. 120L of lead is the same volume as 120L of styrofoam, but their bouyancies are somewhat different.

As a Physicist, I'm offended by this thread. Please show some respect.

Fantastic responses (except the smartarse that thought I didnt understand volume=LxWxD). It seems that a few people out there might have been wondering about this. I have a new board that is as thick as my old board, a touch wider and heaps shorter but it is more buoyant. The comment about the core having more air is a good one. I guess a piece of styrofoam the same dimension as a piece of iron will float simply because it contains air. If this is the case then the new technology will float better since it is lighter (using lighter weight components). Volume is volume. My old board weighed much more yet has the same float as my new board which I can carry in one hand. Thanks for the responses. You have gotta love a sport that makes things easier as you get older!!!!

It's more a density thing...containing air doesn't sound as a reliable structure....

water has about 1kg/L density (salt water has a bit more weight than that), and styropore (EPS core) has 0,015kg/L ...this is why it floats... piece of iron is more dense than water this is why it doesn't float.
An avreage board has about 0,06kg/L density which is stil much less than water.

also you can try to imagine how much extra surface gains a 240cm and lets say 5cm wider board then your old one, which is about 30cm longer, has a pointy nose, which doesn't add much flotation benefits, because there isn't much weight added on the tip of the board and the rocker shape makes the nose high and thus it more or less points out of water... but on a 240cm board you get at least 190x5cm extra support all the time . surface area that gives you support is quite larger at new boards than the old ones...
then you have volume distribution...if the tail has more volume, you will get better flotation, because there is wher a great deal of weight is added on the board when you stand on it, so with thicker tail there is more resistance to sink and you can get planing earlier...

this is just my point of view.

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sideskirt said...

It's more a density thing...containing air doesn't sound as a reliable structure....

water has about 1kg/L density

(1) doesn't matter what it sounds like - styro has a lot of voids containing air. That is why modern boards have breather screws

(2) dunno about water having about 1kg/L. At STP is is exactly that

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Mark _australia said...

sideskirt said...

It's more a density thing...containing air doesn't sound as a reliable structure....

water has about 1kg/L density

(1) doesn't matter what it sounds like - styro has a lot of voids containing air. That is why modern boards have breather screws

(2) dunno about water having about 1kg/L. At STP is is exactly that

Water has 997.2995 kg/m^3 at 24°C (it is app. 1kg/L), ESP that a mate uses for his boards has 15kg/1000L a 110L blank that I cut at home weights 1,5kg