Hi, I was wondering if anybody there is familiar the maths of how to calculate board volume given dimensions. Thinking of it in terms of where one can go further, regarding displacement and sizing issues.

Regards

Hi, I was wondering if anybody there is familiar the maths of how to calculate board volume given dimensions. Thinking of it in terms of where one can go further, regarding displacement and sizing issues.

Regards

aps3000 / aku-shaper calculates board volume in # of beers.

put it in a bathtub (totatlly submerged) and calculate the volume increase of the board+water (calculating the volume by multiplying the area of the bath tub surface times the height of the water increase… of course that is for a bathtub with walls that are perfectly vertical… that’s the most accurate way

The water displacement method was used by Clark Foam and the volume in cubic feet was listed with the blank info

in their catalog. You could make an educated guess at finished board volume from that.

Doing the measurements and the math to calculate volume from exterior dimensions of a finished board would be time consuming to say the least. Deck roll and rail contours complicate things considerably.

If you search the archives I’m pretty sure there’s a formula that will give you a rough but reasonable measure. Better for comparing board to board than for getting an exact volume on an individual.

Once a shape is scanned into a machine, it’s simple. As more shapers supply this data on their boards, we’ll get a feel for what (for example) .80 cubic feet looks like, and be able to estimate on our own for the boards that don’t have the info on them.

There’s another way also. I’ve been writing volume measures on all my handshaped Coil Construction stuff since last fall.

It’s a very useful tool to have as a shaper. I’m still collecting data points but about a half a cubic foot per 100 lbs of body weight seems to be a reasonable guideline for shortboards. Some guys like more, some less. I can quantify changes in volume on a new board or hit the same mark again for a given customer.

Mike

hmm, maybe paul bunyan’s bath tub

Quote:

aps3000 / aku-shaper calculates board volume in # of beers.

How do i know, how many beers or Liters will i need for my weight?

Is there any formula or table to get this info?

thanks

Quote:

Quote:aps3000 / aku-shaper calculates board volume in # of beers.

How do i know, how many beers or Liters will i need for my weight?

Is there any formula or table to get this info?

thanks

When I was bartending, we usually went with 12 oz. of beer per hour to keep the clients from being legally intoxicated (for liability purposes).

Personally, I tend to drink 3 or more for my weight of 195 lbs.

Hmmmm…there’s anoter thing that should get into consideration,

FOAM!

different foams contain different amounts of air in them

therefore , different floatation for different foams.

wow…how many “different” in such a short paragraph…

A graduated cylinder 24" wide 10’ long, that would be a heavy tall pipe. A livestock water trouph a board length long with vertical sides graduated. A slot trouph, home made, narrow width, board length long, 50" deep, graduated. Submerge board, measure water level/volume difference. Practice the displacement method and its related arithmetic with a chem lab graduated cylinder and various submerged objects. Boat builders have shop craftsman and drafts person methods of measuring displacements and volumes, library reading.

This has been covered ad nauseum (check the archives) but flotation or bouyancy is determined by the volume of the structure and the structure’s weight. What’s inside the board doesn’t affect flotation one way or the other. The water is just not smart enough to know what’s inside!

If two boards have equal volume and equal weight their bouyancy is also equal.

If two boards have equal volume but one is lighter, the lighter one will have an increase in bouyant force equal to the

difference in the weights.

The laws of physics are clear-cut and absolute. Ask an engineer.

You are correct that a lighter foam(by itself) is more bouyant than a more dense foam(by itself). One is lighter for a given volume. But we have to skin them to make them surfboards, and the lighter foam gets a heavier skin, while the heavy foam gets a light skin and the weights tend to equalize as you get to a finished product. Once the weights are equal, see above.

This may be the most misunderstood topic in surfboard construction. A lighter core changes the way a board feels in the water(by changing the center of mass,and other things) but it doesn’t make the board float higher unless it reduces the board’s weight. Again, see above.

Mike

checked it …and

you are 100% right!!!

thanks for the correction…

Glad to help. Thanks for being gracious.

Mike

Hi,

After reading all the posts till here, I’d like to add something that can’t be measured, but that is a reality to those who spend their lives making boards. Flotation is more than a relation between surfer/surfboard. It reaches the psychology area, once we can find individuals with very different approaches to this matter. For instance, two individuals with the same surfing skills and body features can show different preferences in relation to their boards’ flotation (even considering the same basic board’s features). Being so, I guess just working based on previous boards’ records, we can find the exact flotation which better fits to the especific surfer’s needs. Flotation tables as other tables like that ones which take in account weight, height, and wave size are just for reference, or as a starting point.

density=mass/volume

You could get a rough estimate by using this. Keep in mind it only works on homogenous substances (blanks where densities varies it won’t work for ie Clark style foam, TDI based as far as I know??) Density is usually known when you’re buying your foam, so just weigh your shaped blank and you can use this to figure out volume. It won’t account for stringer material, which can vary greatly in weight and density (balsa especially). If you keep this in mind you could still figure out the approx. volume to compare the volume of the boards you shape. For example, if you shape a retro fish and want to know how much foam it has compared to your standard thruster shapes. If you constantly err in one way, it should be okay for comparison reasons, but only when exact measurements aren’t important. Like when figuring out the volume of surboards :0) Accounting for glassing schedules would be more difficult.

Using APS3000 sound tempting now??

I have a great tool:

it comes in two variations, Right and Left. You need both, but I think you can get away with one if in a pinch. It has ten pieces, two of them reposable, the rest just as important. It sensitive to uncured epoxy though. . .

seriously though, the water displacement is a good technique. if I wanted to I’d take it to those medical weight / fat density calculators with their large water tank, and get the displacement numbers for my surfboard.

But they also have those laser scanner thingy’s that can scan an object and calculate the volume of it. . …

I just sit on the board, and see how high the waterline comes up on my body. I like a board where the water line is right at my belly button.

For boards in the planning stage, then APS3000 is definitely the easiest way to estimate volume. Take two pictures: one showing the top profile, and one showing the side profile. Import them into the software and move the lines around until the board matches the pictures. On the bottom right hand side of the screen you will see a volume calculation. You can have the volume diplayed in beers or liters.

Quote:

I have a great tool:

it comes in two variations, Right and Left. You need both, but I think you can get away with one if in a pinch. It has ten pieces, two of them reposable, the rest just as important. It sensitive to uncured epoxy though. . .

seriously though, the water displacement is a good technique. if I wanted to I’d take it to those medical weight / fat density calculators with their large water tank, and get the displacement numbers for my surfboard.

But they also have those laser scanner thingy’s that can scan an object and calculate the volume of it. . …

Very funny…That’s the tool I use too.

This guy sounded like he wanted more of an answer than “float to your belly button” or “use a water tank” that I’m sure he doesn’t have access to, so I gave him what I could…

I personally shape and surf whatever volume, whether it’s 5’10 x 18 1/2 x 2 1/4 to 10’ x 23 1/2 x 3 1/4 and everything in between…In my opinion this variety keeps surfing from stagnating and being able to take off on any board and rip is the mark of a great surfer (not saying I’m there yet :0p )

The downside is trying to find a place to store your entire quiver!!!

Volume is just another important measurement of a surfboard, like length or width or rocker. If you have the technology or methodology, it is a valuable piece of info to provide the customer, just like the other dimensions. I know my guys like it, and it helps me working across a quiver to be able to accurately quantify volume changes. And that’s just one example.

Mike

Would it be possible to estimate that the shape of a surf bord is similar to a triangle or a cone and say

Volume = 2/3 x Length x Breadth x Width

I’m sure this would not be accurate as it is just a guess, however after comparing the results of a range of boards maybe a table of constants could be developed to cover different board shapes, a mal may be 4/5 while a gun may be 2/3.

Armed with a table like this the average punter could easily calculate bouyancy with the dimentions given after weighing the board.

While this method is rough it could be refined to give close to accurate results. While all boards are different the general shape is fairly consistant.

In windsurfing the number to characterise a board is the volume (in liters)

It was length in the past (like surfboards)

Some day surfboards will follow just like the the compsand technology