Quantifying board volume

[baliboy]

At the moment you get some idea of a board's volume from the thickness, width and length but the roll of the deck and rail thickness can change this significantly.

I was wondering why we don't just say how much volume in cc the board displaces. It could be quite easily measured by submersing the board in a tank of water and seeing how much the volume of water changes. With computer shapes you should be able to specify also exactly how much volume is under the chest area, back foot, front foot etc.

The benefit is:

1. I'd be able to have the same volume under my chest for every board so they paddle the same
2. I'd just adjust the other multitude of parameters to get what i want out of my new stick (one less thing to try and work out).
3. It would minimise wasted volume (and therefore weight) which should help with speed, aerials etc

What do you think?

[Bigpete]

Try to do a bit of reading on naval architecture. If you can somehow draw up three or four fairly accurate cross sections of your board and work out the cross sectional area ( draw them on graph paper and count up the squares), then you can draw a curve that represents the changeing volume of the board along it's length. I.E. you make a picture of a slab of even thickness.
Work out the area of this slab, multiply it by the thickness of your virtual slab and Bob's your uncle. Once you've done it a couple of times it's pretty easy. you don't need differential calclus, just some good sized sheets of graph paper and some ability to hold new concepts in your head.

[ian]

I'm with baliboy. Being new to surfing, and a composite yacht builder and designer, I've been trying to research design optimisation rules to bring to the design & manufacture of my own board(s). Please prove me wrong, but it seems that there exists NO stability graphs (or volumetric calcs) for differing thicknesses and beam sections over a defined vessel length with a 100% accuracy. Examining a BIT of NA is only going to deepen the problem unless the client understands what info they need.I also get the impression that commercial surfboard manufacturing is largely mired in the 60's tech era with a reliance on expanded polyurethane cores and polyester resins.
Times have dramatically changed!

1. I like the idea of 'same volume, different board', under the chest for paddling.
2. What's the list of parameters look like now?
3. Less weight is good. However, some shaped volumes provide tracking/stability/positive buoyancy with a minimum % of added weight. Perhaps the idea is to analyse and test

Like any floating vessel that carries a payload, the design is a blend of cubic spline equations to satisfy the rocker/rail/nose/tail combination of hydrostatic support. Different terms are used for a superyacht or supertanker, but the principles are the same. Go to the local TAFE that handles Master Mariner (M5, M4 Coxswain etc) and check out the study manuals on Stability. In Sydney it's at Ultimo or Brookvale.

[Boris]

With computer shapes you should be able to specify also exactly how much volume is under the chest area, back foot, front foot etc.

[/i]

g'day Baliboy

Check this out

http://members.ozemail.com.au/~cetsurf/pages/home.html

This guy, John Gillis, has put your theory into practice. In fact he's been doing it for a number of years and a number of leading shapers are using it even if they won't advertise the fact . The program is called DAT designer and can give you volumes down to the cc or ml. John was recently entered into the Surfing Hall of Fame for his work in this area and the design of the interface between software and shaping machine. Best thing is- it works.

[collnarra]

A couple of things to consider:

Most surfers wouldn't understand a volume measurement. 6'4 x 19" tells a surfer a lot about a board. A measurement in cubic cm would tell 'em nothing at all. Remember, we've had the metric system since '66, and boardriders would still have a hard time figuring what a 180cm board looks like.

( a brief aside. Steve Clements, a pro surfer, builds and sells boards using a laptop and machine. His label is CM3.)

Computer numerically controlled machines (CNC) can carve a board from solid foam using precise measurements but as far as I know (and Gillis' website, assuming it's still kept up to date, confirms this) most shaping machines can't do concaves and are, at best, rudimentary when it comes to vee.

They also have a hard time with tolerance. Blanks flex, and most machines can't compensate for flex. Still, 80% of boards are built using machines, so does that mean the average surfer doesn't notice poor tolerances?

It could be that, with current tech, a good manual shaper (assuming he's focussed and a great craftsman) can build a more accurate board than a machine but I'm not sure. What do you think?

[zzz]

I was wondering why we don't just say how much volume in cc the board displaces. It could be quite easily measured by submersing the board in a tank of water and seeing how much the volume of water changes. ...<snip>...
What do you think?

I think this is a great idea as well. I've got two 6'10" boards, both very similar dimensions:

6'10" x 2&7/16 * 19 3/4
6'10" x 2&1/2 * 19 1/2

But the volume difference is huge because one of them tapers heavily from the stringer to the rails and has a lot less volume along the stringer towards the front (so tapers more towards the front of the board as well) and is thinner under the tail.

To a large extent the thickness measurement of a board isn't very useful because the thickness of a board varies immensely from tail to nose and from stringer to rail.

I think board volume would be a useful figure when trying to compare different boards and when choosing a new board. And it wouldn't really matter what units it was measured in as long as it was consistent across manufacturers/shapers because you're using it as a relative figure between a new board and your current board.

It would also be interesting to know what volume boards different pro-surfers of different weights and heights ride.

[toot]

maybe of interest -

Jim Banks uses the Gillis gear. He reckons he can quite accurately scale up or down various tried and proven designs. Having one of his seven footers I have every reason to agree.

[dUg]

I have a theory on this some people may call a tad esoteric.

I believe a surfboard, or any hydrofoil, or airfoil for that matter, is comprised of a set of "perfect curves". I believe it's something a good shaper knows instictively ( therefore I don't! ), and is largely responsible for the asthetic appeal of a board. These curves can be derived from mathematical formulae, and can describe every curve on a surfboard from rails, to foils, to bottom curve. Be that as it may, calculating volume is then quite trivial... in fact summing up the entire displacement of a board in all planes ( x,y and z ) is also very simple.

All you need are some very basic input parameters - thickness, length, width at widest point, rail profile, and total volume. To model this on a computer would be so easy, similarly transfering this data to a profiler would also be a cinch.

Have a look at this website -
http://www-groups.dcs.st-andrews.ac.uk/ ... urves.html

Take particular note of the "Pursuit" and "Kappa" curves, The "Pearls of Sluze", and the "Folium". You'll notice these bear a spooky similarity to various curves you see on a surfboard - be it rails, plan or rocker. It may be entirely possible to have a set of "universal formulae", to enable a shaper to churn out perfect replicas of boards with perfect relative proportions.

As far as I know, not one shaper in the world has adopted this approach.

[buzzy]

I just had this idea to develop a "rule of thumb" calculation to determine flotation or displacement based on standard measurements of length, thickness and waist width. It assumes that the waist width represents approximately 2/3rds of the width of the board from tip to tail in that plane (in other words, it seeks to take account of the narrowing nose and tail).

The basic calculation is;

Length converted to inches x (waist width divided by 3, multiplied by 2) x Thickness.

So, a nugget with dimensions 6'8, 21 and 3 would have a cubic "rule of thunb" of 3360 inches, whereas a 6'10", 19.5 and 2.5 more standard board would displace 2665 cubic inches.

I recognise the calculation can;t tke account of the different outlines from board to board, and differing thickness across boards. It's just a rule of thumb to roughly determine displacement/flotation between two boards.

I guess you could also factor in only 80% of the thickness figure to take account foam thickness varies across the length of the board.

[mustkillmulloway]

Try to do a bit of reading on naval architecture. .

i've thought aboutn that but it doesn't seem translate well into surf design....the star fins a good example of a fail cross over

still....it makes a lot design sense on so many levels :?

[sandfly]

Hi Guys
I have been having the same thought over the last couple of years and would love shapers to be able to supply board volume measurements.

It would be particularly handy in the current envirnment with the new shorter shapes that are so popular.

When are just buying another basic hi-per thruster and going up or down a few inches it is easy to get the width and thickness to get approximately the same volume that you know works best for you.

The problem arises whern you want to get something that has a totally different shape.

This has happened to me recently when purchasing a new hi-per shorty, my normal thruster was 6'4" and I was looking at a shorter quad around 5'10" and wanting to keep ta similar volume. It took me 2 boards and a lot of talking to my shaper to get it just right. If I had volume measurements I feel it would have made my quest much easier and would have been able to get the right board in one go. Also saving me some money as well!

[mustkillmulloway]

^^ .35 litres of volume per kilo of body weight is what i've seen to be the suggested ratio..
http://www.diversesurf.com.au/boards/boards/volume2.php

Eg: 100kg = 35litre
Eg: 85kg = 29.749999999999996 litres

but i reckon it's an undersized ratio for most, especially considering 90% of the prevailing conditions..

very nice/interesting find iggy....



i need/like alot volume in my shortboard....but hate a heap foam on the rail....it's amazing how if u keep the same volume

but move it around....the massive difference that will make

quote the deverse site
If you can see the pics below of the 6'2" sprint shortboard, you can start to see the effects on your boards design. all 3 boards have the same pencil dimemnsions on the shape but quite different volume, floatation & most importantly performance characteristics. Regularly at our shop in Tugun we have people come in who have put on a few kilos (most of us do at some stage..) These surfers will want to go up an inch in length. Did you realize that going up longer by 1" on a 6'2"x18 1/2"x 2 1/4"=25.9l short board you will increase the volume by 300-400ml. Yet if you go thicker by 1/8" the volume jumps up approximately 1.2-1.5 litres. Going wider by 1/4" will give you a 700-800ml increase in volume.
Here is some more cool information. That 6'2"x 18 1/2"x 2 1/4" shortboard we have been using as an example with 25.9 litres floatation is very close to the same volume as a Magic mullet
fish 5'6"x 19 1/4"x 2 5/16" =25.7litres or a Twin fin at 5'0"x 19 1/2"x 5 5/16"= 25.9litres.




it's like we need a algebra formula fu.ck...shapers thinkin...wat next

[huie]

^^ .35 litres of volume per kilo of body weight is what i've seen to be the suggested ratio..
http://www.diversesurf.com.au/boards/boards/volume2.php

Eg: 100kg = 35litre
Eg: 85kg = 29.749999999999996 litres

but i reckon it's an undersized ratio for most, especially considering 90% of the prevailing conditions..

I am pretty sure it was Rusty P in a surfline article quoting 3.8Litres per kilo with a reasonable argument why. That seems a bit closer to the mark than Veral Daves

haaaa'' you relize what ya saying 30 od litres for ten kg haaaa''
ferels list is preety close to the mark.

tim i just checked my files the little blue board is 27 litres
it is quit easy to in crease the vol in that board to 32 litres
ie'' increase thickness spread it out in the right places

but hen i would rather shape it by hand & feel it up