Square Tail Rails?

General Discussion
1

Why do most shortboards have square tail rails?

Is it just a practical issue with regard to having enough thickness for leash plugs and fin boxes, or is there some other performance issue?

I ask because I just made a shortboard, and the blank didn’t have enough tail rocker for my liking so I compromised tail thickness for rocker. I made it so thin that I wasn’t able to put a lokbox plug in the center, so I made it a quad. The board goes pretty good… tail flexes too.

2

the square rails makes the flex response quicker and the shape sheds water sooner…

3

A certain amount of why is because a sharp bottom edge works best as well as a thin tail.

In order to keep the sharp bottom edge and keep the tail as strong as possible the rail is kept square on top to retain the most foam.

Back in the 60s and 70’s when tails were thicker they often rolled the rail in the tail.

my 2c worth.

Brett.

4

I believe this thread occured back around september

5

http://www.swaylocks.com/forum/gforum.cgi?post=345284;search_string=square%20tail%20rails;#345284

6
Quote:

the square rails makes the flex response quicker and the shape sheds water sooner…

Hey G-star,

I understand how having glass in the vertical direction of the flex reduces flex, kind of like how channels reduce flex. But how does it change the quickness flex response? Doesn’t it just flex less?

Also, I understand how a sharp bottom rail edge sheds water faster, but how does having a sharp top rail edge factor into shedding water?

Thanks,

Ian

7

Hi Ian (you’ve got a good memory, ha!),

Yes, a stiffer tail is also quicker, a bit like a short fishing pole versus a long one.

The short one “twangs” back to position sooner (for us, at a better time) than the

longer fishing pole. The short one also takes more energy to flex the same amount.

The flex actually gets put further into the board too, or distributed through

the board a bit more and not just off the very tail end.

We tend to make our vert rails only in the last 8 or 10 inches or so.

The shedding of water concept came from years of building sailboards (you

can literally just look straight down at your board and see how water interacts

for minutes at a time in good trim).

At low speeds (and with thinner tails) there is quite a bit of water to be

shed until full planing speed is attained. This water is on the sides and top

of the hull.

While generating speed (pumping the board) the little vert area at the very

rear of the board acts as a spot the surfer “pushes” against. This is especially

true at lower speeds, but even at high speeds (30+ on a sailboard) I can slide/kick

the tail slightly sideways and find some water to push against.

Even when surfing at planing speed, there are decent amounts

of water the sides of the rails come into contact with by either hitting or

sliding into, and this water tends to stick until a curvature is so tight

(ie. and edge) it cannot continue to wrap and cling.

The easiest spot to shed water is in the tail region as there is enough

flow direction pulling away, thus trailing, the outline.

(edit: I should also add that NOT all boards must obsess with shedding of water,

I make plenty of displacement hulls which require water contact to work properly)

8
Quote:

We tend to make our vert rails only in the last 8 or 10 inches or so.

thanks for the informative reply. What happens if you keep the rail square further up?

9

This might be OT, but I saw Greg Sauritch do a vert band almost through the entire board

about 15 years ago. I heard the board traveled through sections and kept its’ speed. The

rail did not penetrate well whilst on edge however…