Ive been crunching numbers, which hurts Damook's head, but it makes it a bit more understandable when i approach new board purchases.
By comparing what i already ride to whats out there, i get a rule of thumb of how low in volume I can go. Interestingly, My smallest volume board is actually my longest. Its a 6'8x19x2 3/8=3610(volume) step up squash that i have not used in along time (not since my last costa rica trip) but i can throw it around like my 6'2x20x2 1/2=3700(volume) swallow firewire.
Anyone else obsess over this type of thing? It just puts it in a clearer perspective for me when board shopping. I am 6'0 190 btw. I want the CI MBM, which is 6'4x19 1/8 x 2 1/2 = 3633.75 (volume) which is similar to the 6'8.
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Thread: Calculating Volume
Apr 6, 2011, 04:56 PM #2
Apr 6, 2011, 05:05 PM #3Senior Member
- Join Date
- Nov 2008
You can get a rough estimate from modeling with BoardCAD are AKUshaper software or put the board in the bathtub (of it fits), submerge it, and measure the difference in water height. With a little simple math you can figure out the displaced volume. It helps to have someone sink the board and another to measure the water heights with a tape measure or yard stick.
Tubs taper a bit but you'll get a 'good enough' volume calculation assuming it's a square cube.
Shape Your Surfing Experience
Apr 6, 2011, 05:43 PM #4
thinking about it a little deeper, i think you can get decent results this using l*w*d method.
Get out a sharpie or piece of chalk and break the board up into sections. Like..
1. the top two feet or so (of a short board) would be a triangle. Pretty thin. Use the center of the area in question for its thickness, not its thickest or thinnest point. calculate volume of a triangle.
volume1= 1/2(base*height) * Length. (length is your thickness, in this case)
2. Take the tail section next. its a trapezoid (probably) determine the thickness the same way as part one. Calculate the volume of the trapezoid.
volume2 = (((long side + short side)/2) * rail side length) * thickness.
3. Whats left is the meat. This one you can treat as a square/ rectangle
volume3= length of the section * width of the board * thickness of board.
Total volume = Volume1 + Volume2 + Volume3
I don’t obsess over volume but I do try to calculate approximate volumes of my boards- it is helpful as another data point, like width – thickness etc
I followed how you calculated your #’s, but think there might be a little better method so you can compare to the volumes calculated by guys like Coil, Firewire etc who publish the volumes of their boards.
I got this from Swaylocks, and I realize it is not EXACT but it provides a close enough number for comparisons. I have compared volumes calculated this way with volumes supplied by shapers and it is usually within 5% (on the high side) and it works better for shorter boards
Approx Volume Calculation
½ L x W x T + (10 for each inch over 6’) divide by 60.02 for liters.
Liters divided by 28.32 = cu ft
Modeling the board in Board CAD or AKU Shaper would obviously provide a better estimate.
wow, i thought i was being obsessive!!
lee, i got the spins now, i need to puke.
Greenlight, I don't think my bathtub is big enough, but is Board CAD free?
JTS, ½ L x W x T + (10 for each inch over 6’) divide by 60.02 for liters., sounds a bit easier to get an idea. I don't need exact measurements of volume because all i am doing is comparing boards that i have ridden to ones I would like to ride.
do the math for me on this example so i can know for sure how to calculate.
6'8 x 19 x 2.375
I get 31 .4 liters or 1.109 (call it 1.11) cu ft
There is also some interesting estimates by guys like Mike Daniels at Coil and an Aussie named Dave - (Diverse surfboards) which talk to appropriate vol for weights and styles of boards. I will see if I can dig them up
IIRC MD says .5 Cu Ft per 100 lbs for shortboards (adjust for age/fitness/personal pref)
.75 Cu Ft per 100 lbs for hybrids/Fish (adjust for age/fitness/personal pref)
You young rippers use less, old bastds like me, like more
Found the piece I was referring to
On one of those 2007 threads I laid out my general guidelines for different types of boards. For shortboards, it's about .50 cubic feet per 100 lbs of rider weight, fishes and hybrids about .75 cubic feet/100 lbs, eggs and mid-lengths 1.00/100 lbs, hp long 1.25/100 lbs, and classic long 1.5+/100 lbs.
edit to add that 1 cubic foot = 28.32 liters, I like using cubic feet more because it's easier to see percentage changes. (most shortboard #s run between .70 and .90) Mike Daniels of Coil
Last edited by JTS; Apr 6, 2011 at 07:16 PM. Reason: Add MD vol "s
Apr 6, 2011, 07:29 PM #8Senior Member
- Join Date
- Jul 2007
- MonCo NJ
Mook, easiest way to dial in your volume is to stick with the same shaper who calculates volume from the start.
The Coil guys were really the ones who perfected this process and quite honestly their boards are by far one of the best options available so that is two reasons to order from them.
You can order a Coil and Mike and or Kirk will shape it for you. Then they weigh it before glassing. They can calculate the volume based on the known density of the foam used and the weight. But in reality the value they are calculating for you is FLOAT or BUOYANCY not volume because the same volume can be occupied by two different density foams and the float or buoyancy will be completely different.
Next time you order you can then tell them to go up or down in volume and you know 100% that is what you are getting because they know what density foam they used on the last board.
The same technique applies to shapers who use a CNC machine. They can add or subtract volume to change the float and use the same foam as they did on the last board.
There is no other technique that will assure you that your numbers are proportional. One shaper can shape two 6'2" x 18 3/4" x 2 1/4" shortboards and the volume and float can be wildly different.
Brian (Greenlight) is a good friend of mine, but sorry man, I don't know any bath tubs that will fit a surfboard. If they make a super big tub like that, I want one, cause it will make bath time action with the lady a lot more manageable.
Even AkuShaper or BoardCAD will not guaranty a proper measure of float unless you know the density of the foam used and take A LOT of measurements. However, they will give the best idea of volume you can at home, and they are free.
But, keep in mind paddling is NOT proportional to volume. Rocker, bottom contours, planing surface area and foam distribution can play a HUGE part in determining the paddle-ability of a board. Again the best way to dial in what works for you is working with one shaper on that. He will know how to adjust the volume for decreased planing area (ie wider boards) or increased rocker.
I may have given you more info than you want, but the basic answer is if you want to look at volume number AkuShaper and BoardCAD are your best bet, but there are enough other factors involved that you are not guaranteed to get it right. Hope all that helps.
Basically, if you really want to dial in your boards to work perfectly for you, order a few boards in a row from a shaper like Coil, that is mathematical about design with you. It will make a world of difference in your surfing.
Last edited by rDJ; Apr 6, 2011 at 07:32 PM.
Apr 6, 2011, 09:10 PM #10Senior Member
- Join Date
- Feb 2008
lost boards all have the volume posted next to the off the rack dimensions you can buy them in on their website, i love when shapers post volume.