BOTTOM LINE: PART TWO

Rusty offers more history: bottom contours from the '80s-present day

07/12/10 | Visits: 9,507 | Comments: 27 | View Comments Posted:| Visits:| Comments:

Kelly Slater's tight surfing was the catalyst for the single-to-double concave, rockered-out banana chips of the early nineties. Photo: Joli/A Frame.

Tom Curren's infamous Backdoor cutback on a reverse Vee. Photo: Tom Servais

Venturi concave.

PT and a Bonzer bottom. Photo: Surfresearch.com.au.

Single con with a split off the tail.

Deep single.

Pointbreak board: double barrel (domed) vee.

Reefbreak board.

Note: the rail and stringer are flush, not a vee, but a double concave

Big-wave board.

steve king 07/15/2010 07:50 PM take a good look at jeef alexanders surfboard bottoms inverted vee from nose to tail nobody can touch jeefs talent.

don 07/15/2010 01:57 PM Hi Rusty - it has been many years since you made boards for me - in fact my first board was a canyon back in '82. As I've gotten older my boards have gotten shorter and returned to a fuller outline, much like you shaped for me as a teenager. I really like what you're talking about here and would love to reconnect with you - anything in the bottom curve to advance the performance is great. As I recall - TC had written in your old factory "less rocker, more V" - Take care. Don

Dan-NSB 07/15/2010 04:50 AM I think Rusty should write an a-z book on shaping. If he did I would buy it.

Roberto Baquerizo 07/14/2010 01:21 PM * PREMIUM MEMBER - Real Name Hello Rusty, thank you very much for your great articles. A couple questions, what were the draw backs on those really thin boards that Kelly and the new school pros were riding in the early 90's? Where did they evolve to, and why? Thanks once again.

fishfood 07/14/2010 11:57 AM Very "user-friendly" article. Thanks, Rusty, I appreciate it!

Samson Agonistes 07/14/2010 11:20 AM my next board will be a rusty !

Gary Coccaro 07/14/2010 11:05 AM I have been riding concave boards since the 70's and you hit the dynamics right on the head.I love the way they allow a little bit earlier entry as well as late entry release.They seem to be a lot looser overall as well.Thanks for the tech-insight,I appreciate your breakdown on the mechanics as well...G

jimmy conn 07/14/2010 08:17 AM wow very well done tremendous mount of effort and time!!keep it sutle michael and miton willis once told me that their phazer bottms only helped a well shaped board. so that tells you that you have to have complete and full understanding of the basics in shaping- before experimenting with larger bottom changes--at least 10-20 years of hard work!!very well done rusty!!long live da soul and jimmy fuller and redman!!

Charles Williams 07/14/2010 04:56 AM I spent alot of time on the North Shore in the 90's, were i was reunited with a old friend Davy Miller.He was rideing Cambell Bros bonzers, he introduced me to bonzers and the brothers.I made a few for me and my brother, also twins, took them to our stompin ground Puerto Escondido Mexico.The desgin worked insane !!,the next summer Davy came down put on a clinic, end of that summer everyone there had to have one, even made a few there with Miguel stripped old boards and reshaped. 'BONZER'work

Mik 07/13/2010 10:21 PM Excellent article, but I no like single concaves. They only work in clean surf. In NorCal power with lots of water moving around I prefer very slight vee up front, becoming almost flat in middle for speed, and vee out the tail. 6'3" round pin / 18.25 x 2.25 thin. EPS. Lightening fast rail to rail transitions, and full power carving round-houses anywhere on the face, not just out on the shoulder. Concaves tend to hang up or displace of the faces aren't clean... But obviously, the Pros love em.

Mark 07/13/2010 08:22 PM Cool photo of a bonzer. Talk about underground surfboards, those guys were from Hollywood by The Sea, which made the whole thing more intriguing.

Luke Dorrington 07/13/2010 05:45 PM thanks for inspiration!!

Edward Arikian 07/13/2010 11:21 AM * PREMIUM MEMBER - Real Name Rusty...you definately tell it the way it is...I teach highschool and college physics (not alot of hydrodynamics, admittedly)....but every single thing that you talk about makes perfect,logical sense, from my perspective...I've surfed many places around the world for 42 yrs. and I enthusiastically read all that you write...Peter Benjamin shapes my boards and I get ideas from you...he will hear about them for my next order.!!! Keep up the good work. E. A. :)

EZ 07/13/2010 11:01 AM This was the best blog yet. Feels like the problem was diagnosed, and I'm out the door with my prescription. Thank you Doctor Preisendorfer.

Ismail Gunal 07/13/2010 10:44 AM * PREMIUM MEMBER - Real Name I guess it was around 1990 when I was heading to Tavarua for 2 weeks in August and I needed 1 more board. I got a Rusty 7' channel bottom from Chris Fro that filled the void. Surfed solid 20'+ faces at cloud break with 4 of us and that board was f'n magic. S turns down the face into the bottom turn and thru the pit. Like a magic carpet. Made every wave except 1! Memorable Day! Broke it 3'crap. Wish I had another.

And with the changing of the competitive guard around 1990, board design took an incremental jump. Boards got narrower -- very narrow -- for rail-to-rail sensitivity and quickness. A byproduct of the narrowing, the outlines got straighter and the boards actually crept up a little in length.In order to compensate for the loss of outline curve, the bottom curve increased. Younger, quicker surfers were demanding more sensitive equipment that would draw tighter arcs. How to build drive back into these narrow, heavily bent boards? Straighten the centerline on the bottom. The concave wasn't conceived, but taken to new extremes.Some history: In 1991, Shane Herring was ranked 33rd on the ASP World Tour. Kelly Slater was 43rd. In late April of 1992, at the Coca Cola Classic North Narrabeen, the second event of the '92 world tour, this changed. Shane Herring and Kelly were both in their first ASP final together. Shane won, riding a Greg Webber-shaped deep single concave "Banana Board." Webber had been building deep singles since 1986, but didn't really gain any traction with the design until this event. Reportedly the board was specifically designed to help Herro take on Slater. Kelly went on to win his first world title in 1992. Shane finished 4th. That was his best finish and only win. The deep concave movement was on, full tilt.I built a few 'nothing' bottoms for Taylor Knox in the early nineties. He was pushing for sub-18" (17.75") 6'2" boards. At 175 lbs, it was challenging to design him boards that would work outside of the pocket. In a nice hollow section, everything clicked. The second he was on the flats, challenging. We took a stab at flat bottoms on heavily-rockered, narrow boards: pretty vanilla. Had to put the drive back in them somehow. Concaves.A perfectly neutral bottom is just that. It seems that there needs to be some deviation in surface and curve to help initiate release .Imagine a skimboard, sliding effortlessly across a two-dimensional playground. Next, try to imagine riding that greased pig in a three-dimensional venue, a wave. Sure, there are certain things a gifted surfer can pull off -- but the tendency would be for it to want to suck flat down onto the water at any opportunity.Picture two pieces of glass stuck together with a little water between them. Surface tension. Introduce longitudinal curve and the line is interrupted: rocker. Introduce lateral aberrations and instability is a by-product. Wide boards generally do better with convex bottoms and narrower boards are good candidates for concave bottoms.1991, Tom Curren is reigning world champ, living in France. Aussie ex-pat, Maurice Cole is shaping Tom's boards. MC received a container load of blanks from Oz that had distorted in transit from OZ and ended up with excess rocker. So the story goes. He tried to shape out the excess rail curve through the center of the blank. The railline looked familiar, but the finished blank had vee running through the midsection and was flat in the tail. At any rate, one of the first boards finished out of the tweaked foam was for Tom, and EEV (Reverse vee or Forward vee) was born.Pat Rawson had introduced me to Maurice. Pat and I both spent some time in France during this period, shaping out of Maurice's place. As the reverse-vee gained acceptance, springboarding off Curren's popularity, the demand for Maurice's boards grew.I've been getting some interest in forward vees again.Forward vees are not to be confused with a vee that starts a few feet in front of the fins and peaks under the back fin. Since the late '60s, it's been a common practice for shapers to "peak" the vee under the (back) fin and flatten last few inches of vee, which would lift and thin the tail. This would reduce drag and make the board looser.In an EEV board, vee starts early in the nose entry......and gradually increases into the midsection, deepest under the front foot......sometimes transitions into a double coming into the fins......and blends to zero or concave in tail.Ironically, Maurice is now a proponent of very deep single concaves in his tow boards and more notably, his regular paddle-in surfboards.Who might like the ride of a forward vee? Front-footed surfers riding a lined-up wave with some power and surface issues, like offshore winds, seem to enjoy the ride. The forward vee moves through the textured water like a butter knife. Speed banks off the front foot and nice tight gaffs off the top are almost autopilot. Cutbacks are a joy; with a well-designed EEV, when pressure is applied to the outside rail, it will bank and drive in a smooth arc back towards the energy center.The aft portion of the board is flat or even light concave, heavily bent and thin. The geometry through the fin area puts the top skin and bottom skin close together so it flexes more readily as well. These design elements all combined makes for a board that drives exceptionally well off the front foot and has potential for tight, smooth direction changes off the back foot.Back in the day when glossed and polished was the standard finish, there would be conditions when the waves were so glassy, I could feel my board sticking to the wave face (surface adhesion or tension) like two flat pieces of glass with a little water between them. In different parts of the wave, the front rail would slide and lack traction at inopportune times -- like driving a car with bald front tires. In the early '70s, Skip Frye introduced me to sanded finishes. For me, the first time I rode a board with a fine-sanded finish as opposed to a polished gloss, the difference was very apparent.Every once and awhile we get treated to a light offshore from the right angle that creates the perfect texture on the wave face. It's a session when the wind causes a ball bearing-like effect on the wave face surface. The board seems to ride simultaneously on a cushion of air while still remaining in contact and control in the water. It's a magical feeling. Loose, free, fast, and in control. Nature's contribution to an ideal surfing boundary layer. I'm not even going to get into laminar flow, boundary layers, and different types of drag -- that's all on the Internet if you're interested.Why not try and create a bottom that has that feeling? Willis Brothers did. They borrowed from the golf world and put dimples in the bottom of their boards...PhaZer bottoms. Good idea, but a nightmare to glass!Over the years there have been countless debates about the ideal performance (not cosmetic) finish. A directional, longitudinal 400-grit finish seems to get the nod.There may be zones on the bottom and rails that are candidates for alternative sanding patterns, like fine crosshatching to promote neutrality and other zones with deeper, directional grooves like micro-channels (Peter St. Pierre, Micro Grooves) to manage flow and increase traction.Speed-coating products from the boating and aircraft world have been repackaged and offered up to surfers many times over the last few decades. On the grand scale of things like yacht racing and fuel efficiency on planes and jets, fractions of a percent makes a difference. Surfboards...? Flat out speed efficiency isn't always the main objective. Overall handling and feel in a variety of conditions is far more important. Keep your bottom and rails clean with a Scotch Brite pad or something similar works fine. There are plenty of surfboard specific cleaning products on the market.While not part of your board, leashes add a lot of drag. If you have never gone unleashed, you might enjoy the sensation of taking off the handbrake.I've covered these in earlier blogs. Think about a spray nozzle on a garden hose. The wider the pattern, the less you feel push back. Tighten the cluster so the spray coming out of the end of the hose is more focused; the more focused the stream of water is coming out of the nozzle in relation to the diameter of the hose, the more the nozzle feels like it is moving away from the directed flow.Technically, venturis need a closed environment. But the basic principle seems to work on a surfboard bottom. The water isn't really being compressed so much as it is being redirected and focused.With Bonzers, the longer side fins contribute to the process. In addition, they add more drive and hold. On a regular three-fin setup, with a venturi type concave, you will probably feel a fair bit of lift but a little less hold or bite than you would with a double concave that extended out to the rails. On the upside, the rails will probably feel a little less grabby in weaker surf.Taylor Knox is a fan of the venturi.The Campbell Brothers definitely deserve kudos for contributing to the foundation of modern bottoms.With variations and deviations on the bottom of a surfboard, waterflow is changed. The idea is to do it in a productive way. Design the bottom to direct the flow based on individual needs. I'm a big fan of subtle. The greater the deviation or change in curve, the more opportunity there is to incur drag and inconsistency in performance.Bottoms that have a strong degree of influence on waterflow (i.e. 6 channels, Venturi) tend to be specialty boards, unless other design elements are brought into play to offset the big personality. Smaller fins, breaks in the outline, going shorter, more rocker, etc are examples of ways to offset the directional tendencies of these types of bottoms.The basic thinking on how or why single concaves work is that the flow of water is directed through the center of the board, through the fins and out the back of the board. Less water is spilled out the sides, more lift created. The rail has more curve than the center. The water travels with less resistance down the straighter path. Put the board on rail and the arc tightens.At lower speeds, the single concave is a relatively free and unfettered bottom that provides a lot of lateral forgiveness. The steepness of the concave wall out towards the rail contributes to a faster reaction time, a more sensitive feel. It will allow the rider to do a series of quicker, flatter turns to generate speed. At higher speeds, the walls of the concave adds bite to the turns on the inboard rail and the water sheeting off the bottom is deflected off the outboard concave wall and is directed aft.Is there anything else that that the concave does to increase performance? Does the concave add area? Yes, but it is negligible. All things being the same, take a stock 6'2" with a typical 3/16" concave running through the bottom and increase the concave to ½". Area added? Approximately 5 square centimeters or about .78 square inches on a board that has a total of 3355 sq centimeters or 520 square inches: less than one 10th of a percent. Make it 1" deep (that's deep!) and the increase is about 10 cm sq or 1.55 square inches: 1/3 of 1 percent more area.With a deep enough concave, the argument can be made there is actually less wetted area, less drag, because it is acting more like a catamaran than a mono-hull.Singles are good for relatively low volume, low area boards. The amount of lift and speed the single concave generates is more easily managed on these types of boards. Put a deep concave in a longer, wider, thicker board and it will fight back. Too much lift, too hard to control.Conversely, higher volume, bigger boards can be made a little more user-friendly when certain types of convex features are incorporated. A little release on the forward part of the rail, a light vee between the feet -- features that help initiate turns and keep the front part of the board from catching.In other words: The power and the shape of the wave dictates the bottom shape -- depending on your approach.For average surf, which usually lacks in power and line, we're looking for a board that is short, responsive, and makes the most of the weak wave energy. Wide (planing area) and thin (sensitive, increased flex) boards with concave (lift and hold) bottoms are a common solution. The concave will typically start in the entry or somewhere roughly 12 to 18 inches from the nose and gradually increase through the center and reach its deepest point between the feet or just in front of the fins. It will transition fairly rapidly into a flat or light vee in the last few inches of the board.Most small wave designs typically incorporate a fair bit of tail area. To keep the wider tail free from sticking on tight turns, slides, or launches, a little tail release or vee seems to help."Single Con" is a catch-all name...most actually have the single splitting subtly going past the front fins with either a light spine under and through the rear fin(s) or flattening and lifting off the last few inches.To create tail vee, the rail-line must accelerate more quickly than the centerline off the back end of the board. This helps to tighten the turn arc as the water moves past the fins.Small, weak, lined-up surf opens the menu on equipment: short, long, everything in between, and a variety of bottoms -- whatever suits the palette.But in a clean, hollow, compressive beachbreak, a shortboard (fit and reaction time) with a deep single concave running right through the tail offers full tilt carve, linking tight radius turns. More carve and less slide but the board curve needs to fit the wave curve.A long, running pointbreak with some nice hollow bits? The lines on the board can stretch out a bit, the concave not as deep, smooth transitions, longer lines, a little release in the tail to bleed speed when needed. A double barrel (concave) vee: the stringer is above the rail, subtle but slightly elevated. Rounding the spine of the vee lends to smoother feeling transitions rail-to-rail.Off to the tropics? Shallow, clean, double concaves are usually a good solution. Still get the lift and the bite from the concaves but with some directional enhancement from the spine of the vee. High-speed rail-to-rail transitions are made easier because of the lateral break in the bottom.Ready to tackle some big waves? You're looking at a longer, drawn-out board designed to deal with dispersing energy -- managing it in a different way, 'cause there is a surplus of power. For decades, entry usually incorporated vee and/or roll to part the not-usually-smooth water on the way down the face. The mid-section of the board usually is flat or slight concave for planing speed. The last third typically has a light vee that flattens behind the back fin. In recent years, more gunsmiths seem to be running vee the front 2/3rds of the board and going flat or double concave through the fin area. This type of bottom helps the board to penetrate and drive down a windy, bumpy face and commit the inside rail to a long steep wall, minimizing drag out the back.For roughly 20 years, the single concave has been a go-to bottom for most board builders. Easy to build. Easy to ride.After all is said and done, there many more options than just a "single con" for the everyday stuff. It comes down to understanding the whole package. If there is a certain bottom or feel you're interested in; if you're looking for something new and fresh to challenge you or add some fun back into your surfing, an experienced shaper can help you by combining all the elements needed so that the sum of the parts yields the performance you are after.Happy surfing.-R.(27) Add Your Comment View All Comments (27 comments)