Author Topic: Advice on Volume for those on low volume boards  (Read 3549 times)

adamrod

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Advice on Volume for those on low volume boards
« on: April 04, 2018, 01:26:11 AM »
Hey all, looking for some advice on volume for all those riding at or near their buoyancy limit (e.g. riding a board that won't float them)

How difference is the stability in riding a board slightly above your weight, exactly neutrally buoyant vs below?

i.e. I'm 77 kg.

Comparing the stability of say, a 90L, a 78L and a 73L board...

Standard philosophy would say higher volume = more stable, but I've also heard people say that once you go down to say, neutrally buoyant, you get more stability as the board is under water and thus not affected by chop.

Assuming all other dimensions are the same...does being under water actually help?

Thoughts?

surfinJ

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Re: Advice on Volume for those on low volume boards
« Reply #1 on: April 04, 2018, 07:07:02 AM »
Im 195# and standing on my 120l shortboard shape feels more stable then on my 200l log. Thats standing still or light paddling.  The log feels wobbly and the shortboard sits just underwater and is solid.

But once I dig in with the paddle that changes with yaw and unbalancing of the shortboard.

And taking off on the wave requires a spread legd surfers stance.  Ya gotta force the drop-in.

SanoSlatchSup

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Re: Advice on Volume for those on low volume boards
« Reply #2 on: April 04, 2018, 08:42:41 AM »
This post from a few years back really helped me understand volume, and that just in how we stand on a board can effect or determine the stability of it, and not so much just its volume...

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.

Make sense?

Corran

Narrow stance lets you have a smaller, narrower more progressive shape overall.

Hope that helps.
Me: 6'1"/200...5'11" & 6'0" Chelu Foil Boards...9'6" Bob Pearson "Laird Noserider"...9'6" Costa Azul Wide Body...14' Lahui Kai "Manta"...8'0" WaveStorm for when proning urges still hit, and 7'3" Chuck Glynn foil board backup.

adamrod

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Re: Advice on Volume for those on low volume boards
« Reply #3 on: April 04, 2018, 06:01:51 PM »
SanoSup and SurfinJ thanks!

surfinJ- at 195lbs=88kg,  120L is still positively buoyant though. My question is more, say you have a board with the same dimensions, but it was <88L, is that more or less stable than your 120L? or does being slightly underwater (i.e. <88L) actually make standing stability better?

SanoSup, yeah, makes a ton of sense. But lets assume width, shape, rocker etc is all the same. As you go through the transition from positively buoyant to neutrally buoyant to sinking, how does stability change? 

When you're riding a board that doesn't float you, is stability better or worse than one that barely floats you? I've heard a bunch of folks claim that being underwater slightly is actually better for stability (you're lower, and less affected by chop).

SanoSlatchSup

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Re: Advice on Volume for those on low volume boards
« Reply #4 on: April 04, 2018, 06:39:30 PM »
adam, I personally find it to be sort of a diminishing returns thing when it comes to how low you want to sit in the water.

IMO yes, it is easier to balance a lower volume board (to a point) that a majority of it is just below the waterline, than it is one with more volume where the majority of the board is sitting on top of the water like a bobber twitching all over with any surface bump at all.

For myself, I'm like having the feet just barely under water, or at least one of them at a time as the board tips from side to side.

As just another personal preference, I find myself a little further forward on the board than many, as I like the feel of using the volume in the nose by sinking it a little more to get more of the "rocker foam" in the water...just feels more stable to me.

The only problem one might find with that (I don't), is that many of my initial part of paddle strokes stuffs the nose underwater by a couple inches, but as the stroke continues, the nose does come up, and planes fine.

So this does get the board a little more underwater, and does seem a little more stable to me, but again...that's just personal preference, and what's become comfortable for me over the years once I learned how to use the "float" of the board, and allow it to come up on it's own if/when I do happen to sink it more than I planned or because I lost my balance momentarily. If I just brace with my paddle when the entire board gets 5-6" underwater (mid shins), and don't panic...it will come back up slowly, and when the nose just breaks the water, and strong pull will get it up and out of the water, and on our way we go again.

My latest challenge will be a 7'4"x28x"4.25" foil board at ~105 liters for my ~97 kgs. But I have found as others have said that the foil acts as a nice ballast, so it is fairly stable, even though it sits lower than any of my other boards...I've been on it once which went OK, but I think the jury's still out on how stable it's going to be to paddle over extended sessions. I'll let you know...
« Last Edit: April 04, 2018, 06:41:40 PM by SanoSup »
Me: 6'1"/200...5'11" & 6'0" Chelu Foil Boards...9'6" Bob Pearson "Laird Noserider"...9'6" Costa Azul Wide Body...14' Lahui Kai "Manta"...8'0" WaveStorm for when proning urges still hit, and 7'3" Chuck Glynn foil board backup.

supthecreek

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Re: Advice on Volume for those on low volume boards
« Reply #5 on: April 04, 2018, 09:10:40 PM »
Adam.... I had a very interesting experience right at neutral buoyancy.

Because I'll try to paddle or surf everything I see, I had to try my buddys new board.

Weighed myself 1 hour before
242 lbs  - 110 kg

The board:
8'6 x  29.5" at 112 L
pointy nose - pointy pintail Pro signature model.
I had no real expectations.... but was blown away by how easy it was.
I was doing buoy turns, spinning circles and paddling around at will..... no struggle at all.

When I stopped paddling it settled below the surface... and I stepped off.

BUT.... and this is the interesting part:

Another friend was there with his new board

8'4 x 32" at 107 liters
Wide nose, full outline.... only 5 liters less..... but a full 32" wide!
Side by side, ALL of us would have bet our paycheck that the 32" wide board would be easier

4 solid shots at it.... never came even close.... thrown off instantly because it sank so fast that even the wide outline couldn't help.
I went over sideways and backwards... nothing worked

Bottom line

I found a HUGE difference between being 2 liters OVER neutral  and 3 liters UNDER neutral... even a much friendlier shape couldn't change the outcome.

I want to stress..... I never surfed these boards.... no way I could, but I thought you might find this interesting, from a buoyancy standpoint

Without pictures, it didn't happen  ;D

adamrod

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Re: Advice on Volume for those on low volume boards
« Reply #6 on: April 05, 2018, 05:31:13 PM »
that's actually really interesting! thanks for posting!!

impressed that you had no issues at neutrally buoyant actually...

APPST_Paddle

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Re: Advice on Volume for those on low volume boards
« Reply #7 on: April 06, 2018, 06:54:03 AM »
Adam.... I had a very interesting experience right at neutral buoyancy.

Because I'll try to paddle or surf everything I see, I had to try my buddys new board.

Weighed myself 1 hour before
242 lbs  - 110 kg

The board:
8'6 x  29.5" at 112 L
pointy nose - pointy pintail Pro signature model.
I had no real expectations.... but was blown away by how easy it was.
I was doing buoy turns, spinning circles and paddling around at will..... no struggle at all.

When I stopped paddling it settled below the surface... and I stepped off.

BUT.... and this is the interesting part:

Another friend was there with his new board

8'4 x 32" at 107 liters
Wide nose, full outline.... only 5 liters less..... but a full 32" wide!
Side by side, ALL of us would have bet our paycheck that the 32" wide board would be easier

4 solid shots at it.... never came even close.... thrown off instantly because it sank so fast that even the wide outline couldn't help.
I went over sideways and backwards... nothing worked

Bottom line

I found a HUGE difference between being 2 liters OVER neutral  and 3 liters UNDER neutral... even a much friendlier shape couldn't change the outcome.

I want to stress..... I never surfed these boards.... no way I could, but I thought you might find this interesting, from a buoyancy standpoint

Without pictures, it didn't happen  ;D

Interesting conversation - I'll say I have bounced around boards looking at volume more than the design, and in my instance, the design matters more than the volume. I'm 170 lbs (77kg) and my beginner boards were an Allwave and then a Naish X32, when I decided to step down, I made a big jump from 140L to 108L.

It was too much of a jump and I was frustrated, so I jumped back to 127L (8'6" x 30"), it floated me too much and was corky, so I decided to thin out rails/volume but keep some length, 8'8" x 29" - 112L, and it is under just enough with a wetsuit on so that it's not bouncy, and very comfortable.

My next drop down will be into the 105L range, but I will echo what creek said, I think the wider boards can be a bit more difficult because you tend to spread your legs out horizontally a bit more.



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anonsurfer

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Re: Advice on Volume for those on low volume boards
« Reply #8 on: April 06, 2018, 07:30:03 AM »
Bottom line

I found a HUGE difference between being 2 liters OVER neutral  and 3 liters UNDER neutral... even a much friendlier shape couldn't change the outcome.


I have found this to be true.   I am about 73kg (160lb).  At a Guild Factor of 1.0 (my weight / board volume) I don't find too much issue popping up, balancing and paddling.   Once you go below a GF of 1.0 it becomes exponentially more difficult to pop up, balance and paddle.   

My 7-0 x 24 Greedy Beaver is about 75L and is very stable (GF=1.04).   If I add 3kg weight (I use a back pack with weights in it) I can still pop up fairly easily and paddle around without too much problem.  This is a GF of 0.99.  If I add another 2kg weight it becomes a lot harder to pop up and requires a lot more effort to paddle.

My 7-0 x 22 LOG is a GF of about 0.95.  It takes a LOT of focus to pop up.  Once up it takes a lot of work to keep it going but is stable as long as you keep moving. 
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MDG

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Re: Advice on Volume for those on low volume boards
« Reply #9 on: April 06, 2018, 09:22:02 AM »
As the owner of the 112 L board Creek was paddling on (Sunova 8'6" Flash), I can attest to how surprised we all were with the result. I certainly expected Creek to have better luck on the wider/fuller outline board despite having just 5 L less volume. The small difference between being just over vs just under neutral buoyancy was huge, and the difference between the boards' outlines seemed to have little impact.

For me, however, it was an entirely different experience. I am no where near neutral buoyancy on these boards. At ~80kg, my 112 L board floats me just fine - but it felt a bit more tippy paddling around vs the wider 107 L board. So for me the difference in board outlines had a significant difference. At least for this flat water paddle. The real test would be in the surf - which unfortunately I can't comment on as I have not been on 107 L board other than this one flat water episode.



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adamrod

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Re: Advice on Volume for those on low volume boards
« Reply #10 on: April 07, 2018, 04:30:24 AM »
interesting...so, anonsurfer, imagine your 75L board was the exact same dimensions, but now say, 85L. do you feel like it'd be more stable? less stable? the same?  Seems like, once it floats you, there's not much benefit to the extra volume...right?

surfafrica

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Re: Advice on Volume for those on low volume boards
« Reply #11 on: April 07, 2018, 08:08:47 AM »
Great thread!  Creek & Anon, those test results are really interesting. I'm only 145 lbs (66 kg). Your experiences suggest I could potentially "handle" a board in the 66-70 L range (which seems crazy to me by the numbers).  I'm currently on 81 L (v/w ratio of 1.23) and I really like it's level of float. I'd love to try something in the low/mid 70s to see how it feels.
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surfinJ

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Re: Advice on Volume for those on low volume boards
« Reply #12 on: April 07, 2018, 08:12:02 AM »
  Seems like, once it floats you, there's not much benefit to the extra volume...right?
Only paddling mobility, for whatever that might be worth to you.

And I misspoke about my weight 210#. My 120l board is pretty sunk though not under.

SanoSlatchSup

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Re: Advice on Volume for those on low volume boards
« Reply #13 on: April 07, 2018, 09:50:16 AM »
interesting...so, anonsurfer, imagine your 75L board was the exact same dimensions, but now say, 85L. do you feel like it'd be more stable? less stable? the same?  Seems like, once it floats you, there's not much benefit to the extra volume...right?

I believe that what creek said here is possibly the most important to take note of also IMO....
Weighed myself 1 hour before
242 lbs  - 110 kg

The board:
8'6 x  29.5" at 112 L
pointy nose - pointy pintail Pro signature model.
I had no real expectations.... but was blown away by how easy it was.
I was doing buoy turns, spinning circles and paddling around at will..... no struggle at all.

When I stopped paddling it settled below the surface... and I stepped off.
This is my experience as well, must be taken into consideration when taking about usable volume.

When I talk with folks about volume limits, it's with the idea of also being able to stand in one place, and balance "somewhat" comfortably in the line up to yak with your buddies (I use my paddle a lot compared to others just standing there), and not having to keep paddling in circles around them just to stay afloat while you do it.  :)

But yes, IMO once you find a comfortable "standing volume" (for no better term), than I don't see much additional benefit to any additional volume.

Me: 6'1"/200...5'11" & 6'0" Chelu Foil Boards...9'6" Bob Pearson "Laird Noserider"...9'6" Costa Azul Wide Body...14' Lahui Kai "Manta"...8'0" WaveStorm for when proning urges still hit, and 7'3" Chuck Glynn foil board backup.

surfafrica

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Re: Advice on Volume for those on low volume boards
« Reply #14 on: April 07, 2018, 11:51:51 AM »
But yes, IMO once you find a comfortable "standing volume" (for no better term), than I don't see much additional benefit to any additional volume.

What ratio do you guys think makes for comfortable "standing volume"?  I'm comfortable at 1.23 -- 145 lbs/66 kg on 81 L.   Think there is a sweet spot between 1.0-1.2 for an intermediate?
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