Surf Science: Chasing Tail

Chasing Tail
What do the last few inches of your board actually do?

Words: Casey Koteen
John King

Swallow, square, squash, diamond, rounded pin, half moon, elliptical … the list of possible shapes that describe the tail of a surfboard goes on and on. But what do these different tail shapes actually do? It’s common knowledge that a pintail is typical of a big-wave board and 95 percent of 6’2” shortboards are squashtails, but why? Is there really a huge difference between getting a rounded pin, squash, swallow, or something else on your shortboard, and could the average surfer even tell the difference?

“I think so,” says master shaper Rusty Preisendorfer. “You start splitting hairs when you’re talking about a rounded squash versus a squash, but I like to tell people that basically an angular tail creates a more angular turn.”

It makes sense when you visualize how water flows off the back of a board as it goes through a turn. The smoother the rail line is, as on a pin or rounded pin, the smoother the turn will tend to be. “Water is kind of a sticky substance,” says Todd Proctor of Proctor Surfboards. “It’s touching your board at the entry point, grabbing the rails, and the last thing it does before leaving the board is bending around the tail shape. It can bend around the tail and hold on to it the whole way, like on a rounded pin, which keeps things stable. On a squash, square, or any tail where you have some flat area, water jumps off the flat areas. That creates a pivot point and makes the board skatier.”

For shortboards, the squashtail is the undisputed king of tails. The reason they’re so popular is that the wider tail shape creates more volume back there, which translates to more stability and lift, so they’re good for mushy sections, but they fair well in hollow surf, too. In a word, they’re versatile.

“The water wraps around enough so it can carve,” says Proctor, “but with the flat space at the end of the tail, the water can release and you can make the board pop off the lip. You’ve got the best of both worlds; it’ll draw a nice, clean arcing turn, but it’ll still release.”

Okay, so rounded pins are smoother, and squashtails have lift and release. What about the wily and weird swallowtail? “Depending on the depth of the cut, you’ll get a bitier tail. Swallowtails sink and bite a little better,” explains Rusty.

That, too, makes sense, especially when you consider that most fish-type shapes have swallowtails. The thinking is that you want to have as loose a tail as possible on a fish, because their typically straight outlines make them quick down the line but harder to turn, and a bitier tail shape compensates for that.

If you’re still having trouble processing some of the subtleties of tail design, Rusty describes it this way: “Just imagine you have three squashtails that are all the same: What happens if you cut a notch out of the tail and turn it into a swallow? Well, you lose area and volume, and that corner goes into the water and it becomes bitier. What happens if you sanded the corners off a squash? You lose some area, but you gain curve so the tail sinks a little easier and the board will be smoother feeling.” Apply that thinking to the rest of your questions about tail shapes, and you start to get an idea about the cause-and-effect relationship each design has.

But ultimately, you have to actually ride each one of these different tails to really know how they differ. So get out there and start filling out an order form and experiment a little. You can stay conservative and order that swallowtail or rounded pin you’ve always thought about, or just go hog wild and order up some crazy asymmetrical tail—either way, you’ll end up knowing more about surfboards.

Originally published in the June, 2006 issue of Transworld SURF.