Author Topic: Axis Downwind Boards - inverse relationship of length/volume and width  (Read 12700 times)

liv2surf

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Why do the new Axis downwinder boards get narrower as they get longer (with more volume): 21”, 20” and 19” wide for 100L_7’6, 110L_8’0” and 120L_ 8’6”, respectively. Is this a common strategy (for example, with Kalama Barracuda etc). I can imagine this keeps surface area down, thereby decreasing drag and increasing paddle speeds. My concern is that a 19” wide 120L board would be too tippy, side-to-side for a beginner? I’ve been told that the increased stability in the pitch axis (from extra length) allows rider to focus on yaw axis…. but in my SUP experience there is plenty of independence of these axes.
« Last Edit: February 09, 2023, 10:27:18 PM by liv2surf »
5'6 Quatro Wingdrifter Pro 105L; Cabrinha Mantis 3.1m, 4m, 5m and 6m; Axis 1000 (1150, 1020); Project Cedrus 91 cm carbon mast (68 cm fuse, 440/5000 rear); 9'6" CRUZ Surf foil SUP (152L); Chinook Thrust 92 Paddle -- fixed 78" length; 'prone' longboards on the rack, kites in the garage.

PonoBill

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Re: Axis Downwind Boards - inverse relationship of length/volume and width
« Reply #1 on: February 09, 2023, 10:19:37 PM »
Boards gain stability from length. They also, of course, gain volume. I'm useless on a 9' SUP board with 25" width, but I managed it just fine with a 14' downwind board. There's also a limit to how much volume you really want, a board floating high off the water is quite unstable and gets kicked around by every little bit of chop. And of course foil boards gain a lot of lateral stability from the foil and mast. But no, I wouldn't think a 19" wide board would be great for beginners.

There are lots of other possible reasons why designers choose dimensions.
« Last Edit: February 09, 2023, 10:23:20 PM by PonoBill »
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

Dontsink

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Re: Axis Downwind Boards - inverse relationship of length/volume and width
« Reply #2 on: February 10, 2023, 10:04:50 AM »
This is the way i see it:

When the board rolls the rail sinks,center of buoyancy moves to low side and resists the roll.

Longer board= longer rail= more resistance to roll.

So you can make a longer board narrower without loosing roll stability.

This means nothing when your shape is a perfect cylinder because rolling does not move the center of buoyancy at all...and this Kalama designs are closer to a cylinder than a trad surfboard shape.

19' is narrowish even for a surfboard... would love to try a few of these DW boards to see what width i could handle in chop etc.
Probably closer to 25' even Xtralong  :(

WHS

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Re: Axis Downwind Boards - inverse relationship of length/volume and width
« Reply #3 on: February 10, 2023, 10:31:00 AM »
I think the short answer is none of these sizes are designed are for beginner DWers. Armstrong also just released DW boards that don't have any obvious beginner sizes. It makes sense that they don't want to compromise performance in such a challenging sport and risk being labeled as inferior. It will be interesting to see what range of sizes are available when/if the Barracuda production boards are released. DK certainly has made enough customs to have a good idea of what sizes are needed. Wonder if the current E3 will be the default beginner DW model? Likewise Axis has the new hybrid which is a better compromise for beginners than their DW model.

Axis's inverse of length and width is pretty interesting. Could it be that they are more designed to cover a variety of conditions than user weight? Longer, narrower, and more volume could be better for faster bigger ocean conditions while smaller, slightly wider, with less volume could be better for steeper easier to catch wind chop/waves? I'm just speculating. Interested to hear what others think.

jondrums

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Re: Axis Downwind Boards - inverse relationship of length/volume and width
« Reply #4 on: February 10, 2023, 12:30:09 PM »
A birdie told me there will be a new series of Kalama production boards based on the barracuda in a month or two.  Three lengths and they are slightly wider as they get longer

PonoBill

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Re: Axis Downwind Boards - inverse relationship of length/volume and width
« Reply #5 on: February 10, 2023, 11:51:15 PM »
There's also the monkey on a rope version of stability if there's any rocker.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

peterp

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Re: Axis Downwind Boards - inverse relationship of length/volume and width
« Reply #6 on: February 15, 2023, 08:37:08 AM »
I've had a 8'2 x 20 110L sort of Barracuda design for about 2 months and I cannot fathom how stable it is - primary stabililty is as good as the 5'10 x 28.5 SUP foil board I normally use in surf. Secondary stability (when you roll past 30-40degrees) is a little less forgiving, but not by much.

I use it to paddle up on flat water and on dwds it's a gamechanger, gone are the days of being stuck in mud....

The length really adds a lot of stability as explained above. Is it for beginners, maybe not outright beginners, but it's pretty impressive. I have winged it as well - you get up in nothing.

SUPeter

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Re: Axis Downwind Boards - inverse relationship of length/volume and width
« Reply #7 on: February 20, 2023, 06:17:47 AM »
narrower boards have less edge leverage when small waves and bumps are encountered.  Wider boards have greater edge leverage, making them roll more.  The stabilizing influence of the mast and foil have a proportionately greater effect with narrower boards versus wider boards.  These narrow boards are far more stable than they would at first appear.  longer water lines also increase stability. 

PonoBill

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Re: Axis Downwind Boards - inverse relationship of length/volume and width
« Reply #8 on: February 20, 2023, 10:07:31 AM »
A billion years ago, when I was having trouble with roll stability downwinding SUP boards Dave told me "get your feet closer together". I thought "easy for you to say" but I tried it, and it was a lot better. The more I think about this the more I realize I should narrow the Kalama-style board I ordered from Mark that I might see by my 80th birthday. I'd just buy a board from Dave, but they are much too fragile for a clumsy, careless klutz like me.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

liv2surf

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A billion years ago, when I was having trouble with roll stability downwinding SUP boards Dave told me "get your feet closer together". I thought "easy for you to say" but I tried it, and it was a lot better. ....

narrower boards have less edge leverage when small waves and bumps are encountered.  Wider boards have greater edge leverage, making them roll more. .... longer water lines also increase stability. 

I have to believe that it is the narrow stance width of the rider more than narrow width of the board that PROMOTES roll resistance and stability in roll dimension. Of course, narrower board width does absolutely constrain the maximum rider stance width. Why would a narrow rider stance improve roll stability? I think narrow stance improves roll stability because a narrower stance width limits how far away from the board's centerline the rider can put their weight.... hence less roll. 
5'6 Quatro Wingdrifter Pro 105L; Cabrinha Mantis 3.1m, 4m, 5m and 6m; Axis 1000 (1150, 1020); Project Cedrus 91 cm carbon mast (68 cm fuse, 440/5000 rear); 9'6" CRUZ Surf foil SUP (152L); Chinook Thrust 92 Paddle -- fixed 78" length; 'prone' longboards on the rack, kites in the garage.

jondrums

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Re: Axis Downwind Boards - inverse relationship of length/volume and width
« Reply #10 on: March 27, 2023, 11:14:15 AM »
I think stance width of the rider changes the "sensitivity" to weight shifts as well as "reaction time". 

With a wide foot stance, when the board tilts, the rider compensates with the large upper leg muscles to stay balanced.  With a narrow enough stance, everything can be compensated with fast-twitch muscles in the lower leg.

Said a different way, if the board tilts XX degrees to one side, you have to make one leg longer than the other to keep your body in the right position.  With feet closer together, less movement is necessary in the body to do so.  If you get too close together there is not enough leverage to right the board when it starts rocking/tilting.

liv2surf

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Re: Axis Downwind Boards - inverse relationship of length/volume and width
« Reply #11 on: March 28, 2023, 06:59:12 PM »
With a narrow enough stance, everything can be compensated with fast-twitch muscles in the lower leg.

.....With feet closer together, less movement is necessary in the body to do so.  If you get too close together there is not enough leverage to right the board when it starts rocking/tilting.

This is interesting and illuminating for me (as someone with a SUP stance that is chronically too wide).

It seems you are saying a narrower stance width can allow more effective and efficient board roll corrections, while taking stance too narrow will diminish this ability and benefit. I wonder how to appreciate narrowing my stance.
5'6 Quatro Wingdrifter Pro 105L; Cabrinha Mantis 3.1m, 4m, 5m and 6m; Axis 1000 (1150, 1020); Project Cedrus 91 cm carbon mast (68 cm fuse, 440/5000 rear); 9'6" CRUZ Surf foil SUP (152L); Chinook Thrust 92 Paddle -- fixed 78" length; 'prone' longboards on the rack, kites in the garage.

surfcowboy

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Re: Axis Downwind Boards - inverse relationship of length/volume and width
« Reply #12 on: April 01, 2023, 08:19:20 AM »
Liv, this is 100% true. Just start trying it. It's often better to adjust once you're going but truthfully you can just force it when standing on the board.

A simple way to say it is, your toes are faster than your thighs or knees.

Solent Foiler

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Re: Axis Downwind Boards - inverse relationship of length/volume and width
« Reply #13 on: April 02, 2023, 01:07:44 AM »
Just to agree, and suggest a simple demonstration - a narrow stance on my balance board is way easier to manage than a wide one.
I'm 5'10", 66kg riding:
Swift Foil Boards custom 4'10 x 19.5" 35L
Gong Lethal 4'6 65L
Axis ART 799, 899, 1099, HPS 880 US & CS Adv fuse, 85cm mast
Gong Fluid L-S, XXL-S on 85cm and 65cm mast
Takuma RS 5.1, 4.3, 3.5

Califoilia

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Re: Axis Downwind Boards - inverse relationship of length/volume and width
« Reply #14 on: April 03, 2023, 12:49:49 PM »
With a narrow enough stance, everything can be compensated with fast-twitch muscles in the lower leg.

.....With feet closer together, less movement is necessary in the body to do so.  If you get too close together there is not enough leverage to right the board when it starts rocking/tilting.

This is interesting and illuminating for me (as someone with a SUP stance that is chronically too wide).

It seems you are saying a narrower stance width can allow more effective and efficient board roll corrections, while taking stance too narrow will diminish this ability and benefit. I wonder how to appreciate narrowing my stance.
This is a really good explanation from 10 years ago as to why narrow stances make sense wrt board stability, and not just width and liters that was the thought(s) years ago...

https://www.standupzone.com/forum/index.php/topic,19100.msg185179.html#msg185179
Me: 6'1"/185...(2) 5'1" Kings Foil/Wing Boards...7'10 Kings DW Board...9'6" Bob Pearson "Laird Noserider"...14' Lahui Kai "Manta"...8'0" WaveStorm if/when the proning urges still hit.

 


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