SHAPESHIFTER CURVES, FLATS & EDGES

The hard work­ing trio of surf­board de­sign

New Zealand Surfing - - News - With Roger Hall

As in­no­cent as these three words sound, they pretty much sum up what makes a surf­board ride and feel the way it does and why one board goes dif­fer­ently from an­other. It’s fas­ci­nat­ing how these three com­po­nents present them­selves in so many dif­fer­ent parts of a surf­board and how they af­fect the in­ter­ac­tion of the water flow from a break­ing wave when coupled with the ap­pli­ca­tion and place­ment of weight through the rider’s feet. These three facets are largely re­spon­si­ble for why your surf­board goes great in some waves and not so great in oth­ers!

The mod­ern short­board is made up al­most en­tirely of curves with a small amount of edge. The edge is easy to spot, start­ing on the rail around the front fins and run­ning back around the tail. More al­ter­na­tive mod­ern shapes will likely feature flats in ad­di­tion to curves and edges. It’s fair to say that edges al­ways oc­cur be­tween two or more curves or be­tween a flat and a curve. It’s these edges that mostly de­fine the mod­ern surf­board. The pres­ence of edges to­gether with the amount of curve used is of­ten what sets the mod­ern surf­board apart from its older coun­ter­part. Prior to the mid 1970’s you would have to look much harder to find a surf­board with an edge, not so these days.

When it comes to curves, the most ap­par­ent to the eye also hap­pens to be the long­est; this curve forms the perime­ter or plan shape of the board, also known as the out­line curve. The out­line curve is also the curve with the most vari­a­tion in its form. The width of the surf­board at given points to­gether with the tail shape de­ter­mine what form this curve will take. Some­times it un­du­lates through melted wings, some­times the out­line curve will be in­ter­sected by an edge as is the case of a more de­fined wing. Some surf­boards have re­verse curves known as side cuts con­tained as part of their plan shape.

Next long­est is the rocker curve with it’s nose lift, flow­ing into a flat­ter curve through­out the body of the surf­board and then lift­ing again as it sweeps off the tail.

The third curve that runs from nose to tail is the deck curve and the shape of this curve is of­ten hid­den un­der lay­ers of wax and deck grip yet pro­vides an in­cred­i­bly im­por­tant func­tion. This nose to tail deck curve works mostly as a vol­ume distrib­u­tor. Run­ning across the deck from rail to rail are also curves which dis­trib­ute vol­ume as well as forming the rail shape.

All in all, curves are ei­ther blend­ing into other curves and flats or stop­ping at an edge. Therein lays the key: curves give a board its char­ac­ter­is­tic per­son­al­ity while edges give the board its at­ti­tude! As dif­fer­ent in con­cept as curves and edges are, they work to­gether.

"Curves tend to hold onto water and con­trol speed and di­rec­tion while edges break water, re­leas­ing it from the board. If its curve that al­lows a board to turn into an arc, then its edges that give a clean crisp feel to the en­try and exit from that arc."

Curves tend to hold onto water and con­trol speed and di­rec­tion while edges break water, re­leas­ing it from the board. If its curve that al­lows a board to turn into an arc, then its edges that give a clean crisp feel to the en­try and exit from that arc. Edges en­hance the speed and pro­vide the spark, ac­cen­tu­at­ing the power in a turn by in­creas­ing the drive from it. Shapers may increase the amount of curve in var­i­ous parts of a surf­board to de­sign in per­son­al­ity to a board and then off set the ex­ag­ger­a­tion by adding in an edge to coun­ter­act or re­duce any neg­a­tives or resid­ual lag af­fects. Edges give the ZING!

A big chunk of what we feel com­ing back to us through the soles of our feet has to do with the con­tours of the bot­tom sur­face of your board. While these can be iso­lated and de­fined at any point along the length of the board these curves are usu­ally chang­ing and blend­ing into dif­fer­ing amounts of curve to per­form dif­fer­ent func­tions ahead of, di­rectly un­der, or be­hind a rider’s foot. We can only re­ally de­scribe these curves when we mea­sure them at a cer­tain point or as an iso­lated feature: we may see a con­cave for ex­am­ple or we may see a rolled bot­tom or a Vee con­tain­ing dou­ble con­caves. Now here’s an in­ter­est­ing point: curves are curves even though they may look com­pletely dif­fer­ent, say for ex­am­ple the dif­fer­ence be­tween a roll con­tour and a con­cave con­tour, these con­tours are both made up of curves its just that their re­spec­tive high or low points are re­versed. A stock in trade mod­ern short­board is likely to have a con­cave which has it’s low­est points where it dis­si­pates hence defin­ing it’s po­si­tion rail to rail and fore and aft. With a sin­gle con­cave its low­est points are out to­wards the rail while its high­est point is at the stringer line. This high point de­fines the depth of the con­cave and also has the func­tion of flat­ten­ing out the rocker curve adding plan­ning speed un­der foot.

An in­ter­est­ing point about con­caves is that even though they are in them­selves a curve, they can have the af­fect of flat­ten­ing out the curve that they are shaped into i.e. the rocker curve. So in this case adding the curve of the con­cave into the curve of the rocker cre­ates speed. In the op­po­site sce­nario where a roll con­tour is used the op­po­site will oc­cur. . . . .

Think of the curve in your surf­board a bit like the curve in the waves you ride. If your wave is steep and bowl­ing it will have more energy and be faster mov­ing, there will be a curve in the face more like a con­cave shape. Waves like this can pro­pel a board with more curves like roll con­tours and over­all rocker curve. This is why boards with ac­cel­er­ated tail rock­ers light up in steeper waves and take on a lively feel they may lack in waves that are slow mov­ing and fuller faced. A board that’s de- signed for waves like this may feel slug­gish in weaker flat­ter faced waves.

The “sweet spot” in a surf­board is gov­erned by the make up of curves un­der the rider’s feet: rocker curve plus con­tour curve equals longer or shorter sweet spot.

What you see when look­ing at a surf­board is not so much curves, flats or edges in iso­la­tion but rather a con­tin­u­ous seam­less skin. You are look­ing at com­plex com­pound curves blend­ing and chang­ing to form the surf­board shape as a whole. We shapers how­ever tend to dis­sect the board at cho­sen in­ter­vals into a se­ries of one di­men­sional com­po­nents that we can more eas­ily de­fine. Once as­sem­bled the surf­board shape takes on its com­pleted form. You can de-con­struct your surf­board us­ing a straight edge and your eye to dis­cover curves, flats and edges over the sur­face of your board. Even in a board made up en­tirely of curves you will likely find flats that oc­cur at the in­ter­sec­tion or over­lay of curves run­ning in dif­fer­ent di­rec­tions as they blend to­gether. When a surfer tilts their board into the face of a wave these “se­cret” flats come into play adding sen­sa­tions of speed and drive. So, next time you surf, have a think about what you feel and how that re­lates to what you saw with the straight edge. It may help you to un­der­stand and con­nect with your surf­board in a more mean­ing­ful way.

Rail tuck meets rail edge meets con­caved curve blend­ing into the bot­tom curve at the stringer line. The far right side of the level re­veals a few mil­lime­tres of Vee is also present.

A straight edge re­veals more than the eye can de­tect as the curves, flats and edges blend, meet and morph along the length of this Mod­ern Quad shape.

Search­ing for "se­cret" flats cre­ated by the in­ter­ac­tion of mul­ti­ple curves.

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