Plan shapes: do you know your long and thin from your short and fat?

Published in Wavelength ISSUE 216

This one’s super simple. Remember all the talk of foils and aeroplane wings in the previous articles? Well, fluid dynamics state that matter travels faster across a straight line than a curve. This is down to resistance due to surface area. If you need a diagram, take a í10 note, roll it into a tube so that one edge touches the other edge. That has the same surface area as it does when it’s flattened out. ‘Alright... alright... I get it, but how does this relate to my board?’ I hear you ask. Simple; the straighter the plan shape, the faster the board will be, but at a sacrifice to turning. The more curved an outline is, then the slower but more manoeuvrable the board will be. Fact.

The other important factor is length. Check out all the fastest freestyle swimmers; they are tall, lean, but powerful. They also shave their legs and body, but that’s beside the point, the main thing to focus on for now is their height. It’s the same basic principle with powerboats, Oxford and Cambridge rowing boats, very fast fish and, of course, big wave guns. They are all long, and straight in their outline, not short and curvy. Adele would not make the Olympic swim team, yeah?

Guns and step up boards handle high speeds thanks to their straight and long outline. They tend to be a little longer than your average stick, but also a little narrower. My Indo gun is 6’10 x 18” wide; it looks sexy and fast, but has the turning circle of a cruise ship. That’s ok though because big waves and hollow waves require little turns or at least have more face to turn on. In contrast, my small wave boards are all like Adele - short and dumpy. They’re 5’9ish x 19 ó”, so they are more curved in their outline. In big waves they’d skip out and get too wiggly underfoot. However, in small waves you need to utilise every little steep part of the wave, so you need something that turns on a dime. Imagine how much tighter all your turns have to be to hit the top and bottom on a waist high wave.

Usually a board has a fine blend between the two, custom made or at the very least chosen to suit your style of surfing. If you’re surfing properly then generally you gain speed off your front foot, but turn off your back foot. This is called ‘trimming’, probably the first thing you learn, but it also seems to be the first thing forgotten too. Plan shapes of boards are sometimes shaped and designed to make allowances for someone’s surfing being ‘front-footed’ or ‘back-footed’, but the reality is that if you are front-footed or back-footed, you need to change your surfing, not your board.

So a typical board will have a straight outline from nose through to the mid-point, and then gradually increase in curve through to the tail. Some wider template boards, such as fish styles, may even have stingers or wings in the last 18 inches of the tail. These are steps into the rail to reduce tail width and therefore volume, without the shaper losing their envisaged plan shape and tail curve. The tail has the last say on how the board harnesses its plan shape properties… but more on that next month…