Volume mystery

[mrbig]

No worries mdsurf. You clearly have had a lot more personal experience with the Cannibal  line. Our local cannibal shop had Assassins, Surf Hybrids, and one Bomb!

I sent AJ an email and will post his response if I get a response. I was shocked that the Bomb was completely flat from the points on the swallow tail to area a foot or so in front of the fins. No v, no concave, no spine  flat like Kansas! And then the belly like a very subtle single concave in reverse going to wide flat areas several inches wide all along the rails.

If I had not owned the crazy quad with the hull bottom by MTB I would not have had immediate deju vu on an unusual bottom contour!

[55NSup]

Come guys, use your noggins. 160 L vs 147 L.  Those 13 l could be all above waterline. Very very small changes in outline, rail thickness could also influence sunmerged volume.

[The Kernel]

You'd think that with all the CAD and CNC technology out there we'd have the volume issue down pat.  I use advertised volume as a rough estimate and focus more on how a board feels and how well it meshes with and enhances what little style I have.

Getting the volume answer is sort of like sitting around at a party with your buddies and their wives and having everyone declare how may people they've slept with before getting married.  The collective answers would be self serving, general ballpark at best with the more important issue being whether everyone is happy with their current situation.

Of course, boards ARE easier to swap out than spouses....

[kayadogg]

Matt, stoked for you and your new order, I think you're going to love it.  I'm skeptical about most advertised volumes.  Mrs. kayadogg-to-be had a 8'0 Naish Hokua that had 95L stamped on the bottom of it - no way.  I found an article online of someone saying it was mislabeled and was closer to 82L.  That 13L difference is a lot more critical when you are dealing with volume under 100L, in my opinion.  I can paddle most boards that are around 92L and higher (some with more ease than others) but when I tried to paddle that Hokua, I literally sank it to my thighs.  The board that I have been on for the past 6 months is a custom 8'2 x 27 Rogue, very thinned out and pulled in nose and tail.  It can be very challenging to stand on it in rough conditions but doable (very tiring though).  Based on my experience with boards that I've owned, I guesstimated that board to have a volume of around 93-96L, somewhere in that range.  I was over the owner of Rogue's house a couple weeks ago and he pulled up the cad file of that board and it had the volume listed at 106L which I really find hard to believe.  Now I use volume as a starting point to get in a ballpark and then from there, I think board design has much more to do with stability.  SoCalSupper has a V3 Phoenix that I believe is 92L but is stable for the volume.  Still a workout but I'd take that shape compared to a shortboard design with the same volume.  What does this all mean?  I don't think anything, I'm not even sure why I replied.  Slow day at work...

[mdsurf]

the bomb is it like this?

[freetobeme]

the bomb is it like this?

Bingo

[mrbig]

Now if we could just flip it over...

[mdsurf]

Fun board.  That is called the Rocket here in Florida.  It is probably more volume than the Assassin of the same size.  The tail on the other hand is pulled in and thinned out.  There is also a Fat Rocket.  Little more volume in it.  That tail is a little less stable waiting for the wave but fun on the wave, turns easy.  I am going to stick with my guesstimate of 130 liters of float.

[mdsurf]

Rocket bottom

[freetobeme]

Fun board. That tail is a little less stable waiting for the wave but fun on the wave, turns easy.

That is my experience. Def has more volume in center and a smallish sweet spot to stand on. I still need to keep my paddle near/in the water at a stand still. Construction is top notch and swing weight feels nice. Pushes through and over whitewater with ease. I'm hanging with the long boarders with it and able to get on a wave with 3 or 4 strokes. Board makes me feel like I'm surfing vs riding the wave.

[mdsurf]

Here is one of my favorite Cannibals lately the tear drop.  Big sweet spot and stable for me.  Nice rides on the nose from this latest swell left overs.  It also turns real easy with the pin tail.  like this board.

[14 West]

Got a small pool handy? Only real accurate way is to measure displaced water.

Or weight. Attach some weights to the leash plug until it is neutrally buoyant. Weight that sinks it in KG is equal to Volume in L assuming you are in Fresh Water.

[OUTSIDEWAVE]

DO YOU  LIKE IT? THEN SURF IT.... IF YOU REALLY WANT TO KNOW, SHORT OF A POOL TO MEASURE IT JUST TAKE, THE MEASUREMENTS AND FIND A SHPER WITH A PROGRAM FEED HIM TH MEASUREMENTS IT'LL BE CLOSE/

[Califoilia]

Here's something that was written by an old poster, very good SUSer, and board shaper.....

More volume = more stable... (in the traditional sense of course). Add volume and width and its even more stable. Instability comes from a rail diving down, the board sinking and then you loosing balance and falling off. Volume, and volume away from the center line, increases stability.

It takes 8lbs of pressure to sink one gallon of air. Lets assume for this purpose that your board is pure air (no material to make the foam as its close enough for this). If you weigh 200lbs, you need a MINIMUM of 100ltr in your board to have neutral floatation. This is just to float you with the very top of the board right at water level.

Now, stability is not the same as float, but they are related. Stability comes from the ability of the board to "push back" at you when you push down on it. at 100ltr, 50lts is on each side of the stringer. So it takes 100lbs of pressure (weight if you like) to push the right rail into the water. If you're standing centered on the board you're good. As you loose balance (lets say to the right) so you transfer more than 50% of your weight to that rail. Now you have more weight on the rail than the volume is able to push back against, and so it sinks. The more it sinks, the more you loose your balance, and the more weight you transfer onto that already sunk rail, and it sinks more... and more... until you either fall over, OR the "center" of the boards volume passes the 'tilt" point and it flips over (and then you fall).

However, its not that simple. Its not just about how much volume is on each side of the stringer. its also about how FAR it is from the stringer (moment arm), and how much of it is how far from the stringer.

If 70% of my right sides volume is within the first 6" of the board (measured away from the stringer) and only 30% is 15" from the stringer (on a 30" wide board), and I'm standing 10" away from the stringer, then my foot is already outside of the area that has the most foam/floatation. Therefore less pressure (weight) is required to sink the rail.

So... a board that has a lot of rocker, or a lot of outline curve, is going to have less volume out away from the stringer to push back at me than a board with wide ends, low rocker (low rocker engages that volume sooner as its already on the waters surface - rockered boards have a certain amount of the volume lifted out of the water and it only engages after the board starts to lean over). Boards with pinched rails and deck crown are going to have less volume to push back at you.

So... what does this mean?

A 25" wide 9' board that has wide ends and a flat deck with full rails and is 100ltr will be more stable than a 30" wide 9' board with dramatically pulled in ends and pinched rails that has 120ltrs.

But this is overly simplistic... standing height affects stability. For every 1/2" you move up, you need to add on average about 1" per side of width )this is dependent on rocker, width, outline and so on, but its about this) to have the same overall stability, so you get quickly reducing returns on increased volume from increased thickness. Also, as your board gets shorter, so you introduce a new dimension of instability  -end to end sinking which compounds the side to side instability. As you get closer to the "critical" volume for your weight (you and board combined) so reduction in length has an exponential affect on overall stability, and thus moving more volume towards the ends of the board becomes paramount to maintaining that stability.

One solution is to stand closer to the stringer. While this puts you in a position of feeling like you're always "slightly wobbly", its also harder for you to put the kind of pressure on the rails that causes them to sink, as your weight is centered.  Closer feet, kung fu style, will allow you to have much less instability as you're not pushing out on the rails. Pulled in ends, more rocker, pinched rails are all benefits of a tight standing stance as YOU loose YOUR moment-arm of pressure to push on the rails, and thus the board needs less of that moment-arm to push back.

Wide boards, wide ends, flat decks, full rails, low rocker ALL increase stability if you stand with a wide flat stance. The downside is a massive reduction in board performance. As your stance narrows, so you can quickly reduce volume, and more significantly, reduce how far that volume is located away from the central part of the board, and thus shape the board, with a view of more surfing in mind rather than paddling (stability) in mind.

IOWs, knowing the volume is all well and good I suppose, but actually having the foam distributed in getting that volume is much more important....

And why at 220# I've paddled and surfed boards at 8'2"x29"x4" and 102Ltrs when shaped correctly, yet struggled on another board that's 9'x28"x3-3/4" and 120Ltrs....not to mention my 7'8"x30"x4-3/8" and 119Ltrs "Lil Red Wagon" feels like a big ol' boat to stand on, and surfs like a "Lil Red Rocket".....

So IMO, volume itself isn't all that it's cracked up to be.....

[TallDude]

So it remains a mystery......