SUP Volume a easy guide...

[Absolutetrip]

I field alot of questions about volume and after testing foam bouyancy and building several hundred of these things in the 3 years I have a good grasp on it. Now I have built prone surfboards for over 18 years some 10k+ of them and have been building custom surf and flat water SUPs for 3 years. Mostly surf models.
 Well me like everyone else got a SUP when they started coming out in my case it was a godsend because a injury to my chest made it to where I could no longer prone surf. So here I am SUPs and sup surfing is all I do. When I decided to start building these things I did alot of tests because I hate guessing about anything I want to know exactly how it works and why. SO here are some of my results I will share.

 1 cubic foot of foam is listed to have a bouyancy of 68lbs. Well it will support 68lbs but only just at the waters surface I mean right at or a 1" below. The real world number I found from testing a 1'x2'x6"thick piece of 2.2lb EPS foam in 78 degree saltwater is 36lbs of wieght positivly floated about 1/2" above the water surface.
 With this simple test we can figure within a 10% aspect ratio the amount of foam we need in a SUP for our weight.
Here is how. We know a cubiic foot of foam positively floats 36lbs so I weigh 215 just divide 36 into 215 and get the cubic feet of foam needed. The answer is 5.97 cubic foot of foam converted to liters x by 28.3168=169.05L
How about a average sized person of 170lbs.
170/36=4.72cfx28.3168=133.65L
Now the +or- 10% aspect ratio comes into play when you factor in rider ability, and choppy conditions and length of board.
a Novice SUP surfer or choppier condition SUP, 170lb rider +10%=146L
A 170lb intermediate level SUP surfer no ratio 133L
A 170lb expert rider -10%= 120L (expert rider can deal with -20% but its a good starting point)
I use this equasion to figure volume for a rider for any size surf SUP from 11' down to 6'. I personally ride 160-172L of volume in my personal boards any size.
Peace,
Ron Neff

[jdmotes]

 Thanks Ron. I appreciate people who take the time to research this stuff. Having been involved in surfing (and wave-sailing) the last 47+ years, I pay a lot of attention to volume. I ride a 127 liter board in the surf and I'm (usually) in the 175 lb range. It's not the easiest thing to paddle but I do like the dividends it pays. Plus: when I get on anything larger, it's a cake-walk to paddle... Later,     JD

[RainWaves]

 Thanks for sharing that! I've been looking (via internet) at lots of board specs out there, and volume is one that I appreciate seeing in the Dims. Always figured you wanted around 20 Liters less than your weight in LBS as a Minimum, but good to see you can go quite a bit lower. 

[Admin]

You will find a bunch of alternate suggetions for getting at Volume by searching here as well.  

You start getting near minimum comfortable volume for an experienced rider at something like:

Clothed rider weight + board weight + paddle weight + 20 L = minimum volume (all in Metric, of course).  

[colas]

Absolutetrip, as admin says your formula is wrong as you do not take into account the "dead weight" of the wetsuit+paddle+board, that you must add, not multiply.

+20l is confortable for experienced
+10l is realistic minimum
+0 is Archimedes theoretical absolute minimum :-)

beginners should be in the 50+ range

Also, do not forget one VERY important factor: most manufacturer quited volumes are somewhat off... not an issue with +80l margin, but VERY sensitive in the +20l range...

Also, the shape adds a lot to the stability factor. Wide at extremities, of course, but high rockered boards are more stable also, as the board sits deeper in the water.

[Absolutetrip]

How far off am I?
I am trying to help equate volume to weight for proper floatation as a starting point. The factors you speak of + about 50 other factors are considered but not mentioned just understand this is a starting point for proper floatation.

Amins says rider weight+board weight+paddle+20L= comfortable start for good rider. ok I am 98kg+9+1+20=128L

By my formula for a expert rider starting with what I figured out for myself 169L-20%=136L
  I am 8L on the positive side comparing the 2 ways of estimating volume for weight.

[Admin]

Yup. We went for a comfortable minimum.  too much less and its clean conditions only, and constant balancing.  You can go more for sure and in some cases gain stability and paddle speed, but we were looking to get at a comfortable minimum when we put that together.  I still think it is pretty good.