Thursday, October 13, 2011

Bottom configurations by Len Barrow

What’s Up With Bottom Configurations?

If you are a beginner surfer or surf SUPer bottom configurations may seem most perplexing.  They seem complex yet the basics are quite simple.  For our purposes here the bottom refers to the entire bottom plane of the board.  If you want to examine what type of bottom you have just flip your board over wax or track, side down.  Run you had horizontally from one tip of the rail to the other at the midsection of your board.  Does the board express a V shape or does the board express a concave shape?  Make a careful mental note of this.  Repeat this process every twelve inches as you move to the nose.  Go back to the center of your board and do this again except move toward your tail.  Presto!  You have just mapped out your bottom configuration.

You may find that at some areas of your board are almost flat while other areas are heavily veed.   Some of you may surprisingly find two double concaves dug out of this plane in your board.  The question arises: what does this all mean to your surfboard or SUP’s performance characteristics?  The following article will answer these questions.

V Bottom Configuration

Vees were the first in bottom variation and were innovated by the indigenous Hawaiians.  It was often thought that early Americans such as Tom Blake in the 1940’s created the vee configuration but in fact it was the native Hawaiians.  There are examples of 150 year old boards with veed bottoms in the Bishop Museum of Hawaii.  This is an interesting subject yet it shall be left for another article   

How does the vee function?  Imagine a see-saw with to children on them.  If the lower child applies force via his legs to lift off the ground, this child rapidly and efficiently rises;  conversely  the higher child quickly drops.  With a see-saw force is rapidly shifted in a predictable manner.   This see –saw effect is crucial to modern surfing in which requires precise and efficient redirections of energy.  This effect allows Kelly Slater to do his rapid direction changes.  If you watch professional -surfers closely, they are tipping the board from side to side in a see-saw motion to create momentum and utilizing the vee for quick direction changes.   Vee is literally the reason that modern surfboards are able to do what they do today.

 To put it simplistically, bottom Vees allow you to tip the board on the rail to “cut”  in one direction or another.  One may also use the vee to “bottom turn” off your rail to do an off the lip.  Vee also functions  to tip the board from side to side.  Again, this enhances the boards maneuverability and speed by allowing rapid directions changes.  Next up are concave bottoms!


Bottom Concaves have revolutionized surfboard design.  When I was growing up we were restricted to veed bottoms.   Concaves suddenly became mainstreamed in the late eighties.   When we jumped on concaves we were surprised at how maneuverable and fast they were.   We were pretty bummed out that we were missing out on so much fun for so long.

Concaves seem complex but they are actually based on a very simple principle.  A concave allows a small air pocket to form under the board.  This contributes to the board’s ability to lift out of the water very much like a hydro-plane.  A concave theoretically uses the Venturi effect.  This phenomena can be roughly explained as follows.  When a wide river reaches a narrow bottleneck in its form, the water speeds up.  Shapers use this to good effect.   Often in modern surfboard design, a wide single broad concave in the nose is channeled into two narrow concaves in the rear third of the board.  The water flow is thus speeded up under the board and translated into speed. This can be used to great advantage by the surfer.   Most modern concaves today are a variation of this theme.  The extreme version of a concave bottom is a “Bonzer”.   In this design a deep broad concave is dug in then formed into a narrow channel in the tail of the board in a direct emulation of the Venturi effect.
Lastly, vee can actually be incorporated into concave bottoms.  How is this done one may ask?  The shaper will initially carve a vee into the bottom of the board.  He will then dig two concaves into each side of the stringer keeping the center higher than the rail edge thus retaining the vee despite the concave.   This is the standard for high performance boards today.  In the end equation, you can create an excellent board with the qualities of both a vee and concave. 

Experimental Bottom Designs and SUPs

I hope the SUP surfing community starts to experiment more with bottoms configurations.  So far I have seen only single to double concaves, vees and nose concaves.  As creativity is part of our sport, it would be wonderful to see SUP shapers experiment.  I have yet to see an extreme Bonzer-bottom on a SUP surfboard.  That would be really cool and probably very functional.  Another unorthodox bottom that I hope that shapers experiment with is the reverse vee.  Tom Curran did his best surfing on this bizarre design.  The Reverse Vee was innovated by the French shaper Maurice Cole.  The vee which is usually in the tail is completely reversed and moved to the front 2/3 of the board.  The tail is completely flat, with no vee.  This configuration seems totally illogical but they are amazingly manouverable.

The world is the SUPers oyster.  These alternative bottom configurations have never been (to my knowledge) applied to a SUP surfer.  We know how they work on surfboard but the SUP has the extra element of the paddle which allows the surfers to modify the performance envelope of the design.  When the paddle is added into the performance equation these experimental bottom types may blossom, in fact I am sure they will.  So, until next time, keep your minds open and I hope to see some weird boards out there!

Aloha Len Barrow


  1. This is fascinating. I've heard many of these terms before but never knew what they really meant. Thanks for taking the time to explain. Your passion is clearly on display. Thank you!

  2. Robert,

    Love your blog! I need to get back in the water and if I lived in Hi I would. Too damn cold in central Cali anymore for me old connective tissues!

    You might devise a test to see if a concave actually produced lift or an increase in speed. Perhaps two identical boards on with, one without. I would guess that flat would actually be faster. I would love to know!

    Venturi and Bernoulli principle would imply that as the water sped up the pressure would go down. It's what creates the *lift* on a wing right? If the concave was 'sealed' against the water side to side along it's length. The actual effect might be more like a ground effect tunnel on a F-1 race car. Suction. This might actually enhance tracking and directional stability more than lift. If the channel ended in a flat section then maybe the result would be lift? Heck I don't know! LOL! But I have been suspicious about this concave channel thing since I rode one of Al Merrick's "Tri Hulls" in good point surf in Baja 30 years ago.

    Love you scientific approach with the Zen spirit and spin. My way as well!


  3. Hi Buzz,
    Thanks for the comment, I'm glad you enjoy the blog and feedback is always appreciated. This post on bottom configurations was actually written by my friend Len Barrow, so I can't take credit for it. I will just give you my 2 cents: my first SUP race board, the C4 Vortice XP (14') had a pronounced double concave bottom. The board was pretty fast but after trying many other boards I have come to the conclusion that for (downwind) SUP race boards, I prefer mostly flat bottoms (with only very subtle contours, if any) as they seem to be the most stable, provide good lift and are easy to control (steer in the bumps). I'll ask Len to see if he has any input.
    Aloha, Robert

  4. Aloha Buzz (from Len),

    Thanks for comment Buzz. Your analysis is spot on. I think that the unusual thing about surfboards and surfing SUPS is that sometimes, if surfed properly, they are put at 80 to 90 degree angles to the wave (as in hard cutbacks and bottom turns). Somehow their is a calculus between wave energy, vee, and concaves thaat is almost mysterious. Somehow shapers have figured it out. You are right though. I would love to see a experiment.

    Mahalo BUZZ!!


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