What make a board unstable and/or tippy?

[CB1]

What bottom shape characteristics make a board unstable or "wobbly"?  Vee, concaves, rocker???  I have the Naish 11'6" and everyone who has ridden my board says it is "tippy" and not as stable as say something like the JL 11'er.

For those of you guys riding what I would consider narrow boards 28" or less, how does your boards handle in non-glassy conditions?  What about ridding in choppier conditions when the wind is blowing?

Just curious if someone could shed some light on the bottom shapes and how they are making these sub-10'ers easy to paddle.

Thanks!

[boots]

Practice makes them easy to paddle.

[CB1]

Practice makes them easy to paddle.

Understood.  I should clarify my last sentence.  Instead of "easy to paddle", I should have asked what makes those boards more stable than others.  Ive read several posts in the forum, talking about how stable and etc some of these shorter boards as compared to their bigger brothers.  I could be wrong and maybe read too much in-between the lines? 

Do these boards have flat spots where the rider stands and then the vee kicks in towards the tail?   Are there slight concaves and how do the affect stability?

Thanks!

[boots]

Yep. Flatter or concave bottoms will be much stabler than rounder bottoms. Some boards have concaves most the length of the board, that probably helps quite a bit with stability also. Just because a board is big doesn't always make it stable; the foil and the bottom contour does a lot.

[paddlesurf.net]

funny- I hopped on that same Naish board and found it to be very tippy too- there are definitely other board makers out there who's boards are more unstable then others.

[MichaelF]

I have found that adjusting the middle fin forward and back can make a difference.  FOrward appears to be more tippy and back more stable.

Obviously, a longer single fin also makes a difference.

[StandUpPaddleSurf.net]

I'm not a shaper but I find that a pulled nose and tail make my boards more tippy.  I also notice that a tucked, downturned or sharper bottom part of the rail makes it more stable.

[Allan Cheateaux]

I'm not a shaper but I find that a pulled nose and tail make my boards more tippy.  I also notice that a tucked, downturned or sharper bottom part of the rail makes it more stable.

Which is funny, because ALL of my boards are more pulled in, but tend to more stable or the volume than most.

[river]

Yes ALlan that is true.  After riding 26 different boards I have found that spec alone dont tell you shit until get on it and try it.  I have found that Tapered or step rails have a huge affect on stability because in cross chop the edge is Feathering through the bumps in the water and the wind.  I noticed yesterday that the wind was knocking me off the board as much as the chop.

[Dwight (DW)]

Yes ALlan that is true.  After riding 26 different boards I have found that spec alone dont tell you shit until get on it and try it.  I have found that Tapered or step rails have a huge affect on stability because in cross chop the edge is Feathering through the bumps in the water and the wind.  I noticed yesterday that the wind was knocking me off the board as much as the chop.

You lost me. Are you saying a vertical rail is more or less stable in wind chop?

[Rand]

My 2 cents says that full, boxy rails (especially when carried up towards the nose like on many of the current pop outs) really suffer in wind and chop.  Being able to submerge the upwind rail a bit and let chop pass over the deck smoothes things out a lot.

[srfnff]

A friend is in process of adding a performance SUP to his quiver and this question is key for him right now as he moves down in size from an 11'9" X 31 X 4.24 cruiser. It seems to me that there are at least three design elements that will make a board unstable or tippy. 1) Thickness (or lack of it) 2) Width (28 inches or less), and 3) Vee. Vee is a bottom configuration design element that adds to instability, especially when compared to a flat bottom, concave bottom etc.

Tail shape can add to instability also, an example of which might be a large square tail compared to a rounded pin or pintail. My friends decision is to find out what will make his new performance SUP more maneuverable and surfable without taking it too far beyond his skill level for now.

I'm thinking something like 10' X 29.5 X 4.24 with slightly pulled nose and square tail. Tri-fin set-up so he can put that giant center fin in for stability and work his way to smaller fin sizes as he gets better. No vee, rather something like concave into flat into double concave or He's about 5'9" and 180 lbs. or so. Intermediate skill level.

I'd love to hear your thoughts.

Mahalo.

[Dwight (DW)]

A friend is in process of adding a performance SUP to his quiver and this question is key for him right now as he moves down in size from an 11'9" X 31 X 4.24 cruiser. It seems to me that there are at least three design elements that will make a board unstable or tippy. 1) Thickness (or lack of it) 2) Width (28 inches or less), and 3) Vee. Vee is a bottom configuration design element that adds to instability, especially when compared to a flat bottom, concave bottom etc.

Tail shape can add to instability also, an example of which might be a large square tail compared to a rounded pin or pintail. My friends decision is to find out what will make his new performance SUP more maneuverable and surfable without taking it too far beyond his skill level for now.

I'm thinking something like 10' X 29.5 X 4.24 with slightly pulled nose and square tail. Tri-fin set-up so he can put that giant center fin in for stability and work his way to smaller fin sizes as he gets better. No vee, rather something like concave into flat into double concave or He's about 5'9" and 180 lbs. or so. Intermediate skill level.

I'd love to hear your thoughts.

Mahalo.

I have ridden super thick boards that were very unstable.

My dislikes are chine and vee in the paddle stance area. My new (oops, the wife's new) PSH is dead flat rail to rail, with vee only at the tail. The board is thick in the middle, but hidden well by the excellent rail shaping. The board is thinned out nicely at each end. I am super stoked by it. Not only is the stabilty amazing, but the volume distribution and feel in the water under my feet is spot on.

My advice would be to follow this concept. It sure works brilliant for me 

[srfnff]

DW,

Thanks for your comments, they are well taken. I searched around a bit more and found some good stuff on Sways. I was thinking specifically about bottom contour and stability, without considering maneuverability. But rail shape, bottom config, foil, thickness and rocker all really work together.

Here's a couple of the comments I thought were interesting:

From Blane: "Whatever you do make a stand up board stable by carrying the wide point farther up and keep the bottom fairly flat till you get good at it. I'd say minimum 28" to start if not wider... Its not easy to stand on these things!"

From Honolulu: "Stability is created when you lean to one side, and the displaced water increases on that side. Thus, the stability of a board that is just barely submerged at rest will not improve when you lean it over - it's already fully submerged.

Now that assumes zero rocker. In reality, if the board has a little "banana" or rocker, there will almost always be a little more volume to submerge, usually in the nose. This is a static effect and when you start to move there will be lift forces which depend on speed and rocker. Then it's different, and I think once you move past paddle speed, your stability problems are over (highlights mine). A slightly large assumption, but let's work with the static or slow-moving (paddle speed) case.

Ergo, you want a board that has some reserve volume. The needed reserve depends on the amount of rocker. A naval architect will discuss this in terms of metacentric height, which you can calculate with the help of aps3000. Doesn't the program give you the center of mass? Assume this is also the center of buoyancy. It will be along the stringer near the center of the board...

The thing isn't approachable directly without experience. As an engineer that's where I live. Stability is going to be a trade-off between width, rail thickness, and displacement (thickness and volume). Other things equal, thicker rails will help, since slight lean angles give relatively larger displacements, increasing buoyancy.

In short, I think your assessment is insightful.

[PonoBill]

I thought I had some idea where stability comes from until I rode the Jimmy Lewis 10'6" X 28 3/4 (shaped like a downsized 11er) and the 10'8" X 28" JL Pintail yesterday. Now I'm completely confused. these boards are too small for me--I sink them until only the nose and tail are clear of the water--the deck goes awash with every little bit of chop--and they are almost as stable as the 11er. I could paddle them fast and they had good coast (!?!), they caught waves great, they're super maneuverable, and they were relatively easy to stand on. Diane called them both "jesus boards" since it looked like I was standing on water.

I don't get it.

there's some pictures on www.kenalu.com and an article on www.ponohouse.com/ponoblog and i did some video which I'll share as soon as I get it edited. Here's one picture. The green one is the little 10'6" micro 11er. The blue one is even smaller, probably great for someone about 175#


I think everyone is getting really smart about what makes a standup work, and we're starting to see the benefit that.