I call the back third of a board the business end. Rocker, fins, foil, and outline curve all work in harmony, ideally, to provide the rider with a desired feel.
Questions about tail shape seem to get asked most frequently. Understandably so, because in the last decade or so there has been a proliferation of "new" tail shapes. Tails are easy to separate and the visual differences are easy to identify.
To understand how tail shapes have evolved, I'll offer a little history. I don't profess to be a historian, but here is a little overview. At some point in time, thousands of years ago fishermen started standing up on their small hulls on the way in through the surf. Canoe? Kayak? Reed hull?
It's almost like speculating if there is life on other planets but it's safe to say that there were quite a few early fishing communities around the globe that were comfortable going out through surf and coming back in. Whimsical thought, children would play in the surf with small flat pieces of wood and some would stand on them.
A few hundred years ago, prone craft got supersized so adults could participate in the fun. Someone flew at a higher altitude and realized that the outline of a boat made sense but they didn't need all the volume. Once propelled by a wave's energy, volume becomes less relevant and early board shapers became intrigued with outline shape.
Eventually, the penny dropped and the importance of the planning aspect of a craft built specifically for wave riding clicked in and surface area became more important than volume -- a craft in motion.
How does a slab of indigenous wood (or flotsam from shipwreck for that matter) become a wave riding craft? If you look at the most primitive of shapes from early wave riding cultures you'll see that the shaper of the period has taken a rectangular plank and rounded the nose off a bit. As boards evolved, the rectangles became trapezoids of sorts: rounded nose, wide point was quite far forward. The board gradually tapered, on some designs almost imperceptible, to the tail section. Tails were wide and square with slightly rounded corners.
A designer's inner dialogue boils down to striking a balance between planning surface (area, lift) and control. Sometime in the early 1930s designers began cutting away area between the corners. Possibly to make it easier for the prone paddler to kick while still maintaining rail length for lift and control. These inverted arc tails may have been the precursor to a "fish" tail.
Tom Blake is credited with putting the first fin on a surfboard in 1935 to facilitate steering and is said to have built a two fin board in 1943. Simmons, quite possibly unaware of Blake's two fin board, built some two fin boards in 1948. Simmons built bigger, wide back, rounded square twins and a few shorter ones in the 50's. Tom Blake reshaped a Simmons square tail into a split tail, "The Makaha Wedge" around 1954.
An early Tom Blake design. Photo: Tom Blake\Surfing Heritage Foundation
This was most likely the inspiration for the Mirandons to build a single fin with a fairly wide split in 1967 called the Super Board and followed it with the Twin Pin: a double pin tail twin fin, in 1968. Arguably, the Twin Pin was the inspiration for Steve Lis to incorporate the fish tail and two fins into his very short kneeboards. Richard Kenvin has been working on a project, Hydrodynamica, that weaves all this rich history together.
Traditional fish have roughly a 10 to 12 inch split. Area and volume is removed between the corners. Maximizing rail length, enhances drive, adds traction, and releases quick. The further apart the corners, the less continuity there is in rail transition. The notion was to have a long, straight rail on a very short, wide board. Typically, the wider the gap, the deeper the cut. A round pin template can be used for the inside part of the curve so a deep cut doesn't lose too much area and the inverted pintails don't get too pointy. The deeper cut also allows the individual tail, the one in the water on a turn, to flex more readily.
Rewind just a bit: in the 1950s, with materials changing, boards becoming lighter, fins accepted and evolving, outline shapes and tails shapes were experimented with as well.
In 1954, Dale Velzy, bored with the same old outlines, used his nose template for the tail. This pulled the wide point well behind center and, while it may not have been the first round tail, "The Pig" popularized hips pulled back, and very curvy tails; rounded squash, round tails, and round pins. More curve equals tighter arcs and surfers found themselves accelerating out of turns. The era of angled takeoffs and straight line trimming was transitioning into the early days of modern, maneuver-based, performance surfing.
Velzy's "Bump" (1956/1957) featured an exaggerated hip which was arguably the precursor to the wing, or sting. In 1960, Velzy had a go with some ski inspired outlines, inverted parabolic midsections, and a version with an inverted midsection, with the wide point 2/3rds back, pulling into an almost nippled pin tail which he dubbed "The Stinger". Then in 1963, Velzy designed the Banjo/422 that featured possibly the first modern version of a step down type wing about 2/3rds back.
So this gets us into a period where experimentation with outline curves, hips, and tails is accelerating. With the short board revolution, single fins (and straighter tail rockers) arguably impacted tail widths and shapes. With shorter rail-lines, designers were searching for ways to build speed and drive back into the boards and still keep them from spinning out.
Tail widths and shapes in the late 1960s and up until the inception of the modern three fin were somewhat constrained by the limitations of a single fin.
With the Mirandons and Lis resurrecting interest in two fin boards, tail widths expanded. Also, in 1970 Hobie and Bing both marketed wide square tail twin fins. These incorporated totally different approach with fins.
In 1971, Brewer, Reno, McTavish and others start experimenting with three fins. These early versions were primarily two plus one setups: a single fin with small side-bites glassed on the rails, roughly about mid-base to the main fin. This allowed for a shorter main fin and wider tail blocks and experimentation with wider, "closed tail" designs, ie. squash tails and diamond tails. That same year Gary Goodrum won the US Surfing Championship at Huntington Beach riding a three fin.
The mid-1970s saw a lot of split tail design incorporated for small wave designs. While pin tails, and diamonds were left for larger surf. The fish, swallow, dove tail, allowed for wider tails on singles fin boards. Width, with the area removed between the corners, provided drive and hold with a quick release on tails. A more modern, split tail twin fin moved into dominance in the late-1970s.
In 1981, the modern three fin changed everything. Hot dog boards with wide squash tails took over. Squash tails maintain dominance for most small/medium wave designs. By mid-1980s more roundtail three fin boards were working their way into the mix.
Today, what I find fascinating is, most of the short, "performance" boards that I build, and other designers boards that I look at, have remarkably consistent width numbers the last 18" of the board. Width at 6", 12" and 18" up from the tail are very similar between shapers and designs for boards that are ridden in everyday conditions.
A few years ago someone came to me with a concept board that would allow the owner to change out the tail of the board. The width at approximately 18" up from the tail is around 16 ½" so the designer had interchangeable tail sections that joined the board at the 16 ½" width mark, wherever it fell, and allowed the owner to put in slightly shorter or longer and different tail shapes. He had some working prototypes and the thinking was sound. Depending on conditions or mood of the rider, the board could be modified to perform accordingly.
All things being equal here's kind of a basic breakdown on tail differences:
Square: Probably the grandfather of all tails, maximizes rail length and area in the last foot or so of the board. It adds stability, drive, more angular turns, quicker release, and less continuity in rail-to-rail transitions. They are used by some shapers as a small wave design and were used by some shapers in early big wave designs -- gun pioneers like Pat Curren used small square tails on guns.
Fish Tail, Swallow Tail, Dove Tail, Split Tail: A square tail with area removed between the corners, fish is a catchall name. Split tail is a name that doesn't initiate semantics debates. Fish used to be a wide (10" to 12") split with a fairly deep cut about half the width number. Quite often, shapers will use a round pin template to create the inner curve. Swallow was a used on more of a standard hotdog type board with a 5" to 7" split. The depth was an inch, give or take and the inside cut had curve. A Dove tail was similar width and a little shallower depth with a straight inner line. Width, depth of cut, and area (fullness of curve) of the inverted pins can be used to achieve different riding qualities.
An interesting sidebar on splits with deeper cuts is they promote flex. Plenty of shapers over the last few decades have experimented with thinning out the pins to the point where they are virtually just fiberglass.
Baby swallows or baby fish tail refers to a narrower tail on a gun with a split that maybe as small as 3" or 4".
Squash or Rounded Square: Here's where we start getting into semantics and hair splitting on the names. Maybe a squash tail is a round pin someone dropped and a rounded square is a square that had its corners sanded off. Basically, they are both shaped by rounding off the corners of a squaretail. In addition to the usual checkpoints, I track numbers 1" up from the tail and 6" up from the end of the board. An average squash tail is about 10 ½ wide 6" up. The 1" number reflects how much curve there is because it's difficult to measure the end of the board unless it has distinct corners, like a fish tail or a square. An average squash is somewhere in the 5 ½" to 6 ½" wide at 1" up.
This is probably the most common small/medium wave tail shape. It offers a nice blend of area and curve. It became the go-to tail shape when three fins took over the world in the early 1980s. There were wide squash tails built early in the shortboard era. The problem with wide tails on single fins was that the wider the tail (block) the deeper the fin needed to be. The deeper the fin, the more the frontal drag. With three fins, it really enabled designers to go wider and shorter, moving area aft because of the hold and drive three fins brought to the game. The tail shape provides lift, support, and drive.
The balance of release and smoothness or continuity depends on how rounded the corners are.
Diamond Tails: A blend of round pin and squash with the corners moved forward a bit maintaining area, shortening the rail, finishing with a subtle point, and a very clean exit for a board with some tail vee. Diamonds were used quite a bit in the early 1970s on a wide range of boards all the way up the ladder. A nice blend of aesthetically pleasing yet, still very functional.
Bat Tails: Take a squash or a diamond and invert the last inch of the tail. I did 'em in the early 1980s. They are all the rage for quads now. The area removed and little corners add some bite and help give the boards without a rear fin in the middle a little extra drive.
Round Tails: Uber-smooth turns. Make a clay model of a hollow wave, use a wire to slice it along the speed line in the barrel, and the cross section will probably look something like this. Or Google conic sections. This tail is a clean, natural curve that fits the pocket. It's a great tail for a performance shortboard, good in head-high to double-overhead waves. Also, a good option for next one-up type shapes.
Thumb Tails: Look like the tip of your thumb -- a blunted round tail with little less curve between front and back fins. Area in last few inches can vary compared to a roundtail; a little less than a squash tail. It's an excellent all around tail shape with the smooth transitional qualities of a round tail and a little bit of release that you might feel in a squash. Combined with a slight hip or subtle bump, it makes an excellent tail for everyday conditions and into the good stuff. Probably the second most popular tail, behind the squash, for performance shortboards.
Round Pins: Are typically used on longer boards for bigger waves. As the board gets longer, the curves get stretched out, it becomes a bit of a juggling act for the designer to maintain a balance of curve and area.
A tail that is too narrow sits too deep in the water, compromising the board by creating unnecessary drag. A tail too wide creates the opposite problem.
Once again, remember that rocker, fins and foil all come into play as well.
With 1970s style single fins, the wide points up, long rail lines in the back, and pinny pintails (low area) were necessary to keep the tail in the water in bigger surf. Tri-fins allowed designers to go a little wider and use more rocker because of the hold and drive created by the three fin setup.
With quads, it opens more doors.
Arc, Half Moon: I seem to do a lot of tow boards with this tail as well as some guns. Back to maximizing rail length, maintaining some width, and removing some area behind the fins.
Toad Tail: This is when the line starts to blur on "is it a wing or a tail?"
I worked with Will Jobson on Twinzers in the early 1990s. The Twinzer was a not really a four fin but a twin fin with little fins in front of the main fins that help feed the water onto the main fins to help them work more efficiently. Martin Potter charged to his world title riding a lot of these (Will's and Glenn Minami) designs. Will had a tail that looked similar to this but with the corners pushed even closer to the end of the board. He also had concaves running out through the corners. All these design elements he combined to make his visionary fin setup fly. The wings, or corners, step down the width, create release and hold. They're good for four fin boards. I've made three fin boards with this tail that have had great reviews.
Asymmetrical: Who says tails have to be symmetrical? My first board was an Ekstrom asymmetrical. I've built a few over the years and had a couple good riders swear by them. I made myself one last year and had a blast on it. Swallow wing on the frontside, roundtail on the backhand. Drive and release toe side, shorter, power arcs heelside.
In the mid-1970s, I shaped myself two swallow tails, identical in every way (as best I could do handshaping). When they were both finished, I sanded some of the curve out of the tail between the corner and the 12" mark. Some area removed, but more noticeable, a subtle hip or break in the curve. Any difference in the ride? Night and day. The one with the break in the curve won, hands down.
There were days back then when I was surfing solid winter Blacks on guns with the cleanest, smoothest curves I could make, and sometimes found myself wondering if an outline could be too clean. Beautiful, but vanilla.
Some things to remember:
Corners and aberrations break the line.
Smooth curves beget smooth turns.
Area affects lift and resistance.
Once again, it's the whole package; rocker, fins, foil, and entire outline curve that dictate the overall feel of the board. Tails are embellishments.
No right or wrong. Whatever flavor you are after, there's more choices than ever.