Fishy Buttcrack Porn

[surfiber]

Short of theorizing on the science of buttcracks, this thread is to be devoted to the wide variety of fishtails and the buttcracks they feature. 

While how you ride your single-, twin-, quad- & multi-fin fishes is entirely an individual matter, there has got to be a definitive thread for swayfolks to refer to, so that those who intend to shape & fin their own fishes can have the confidence to take on such a dizzyingly stupendous endeavor. to simplify matters, rocker & board volume will be considered as an individual choice, and will not be covered here in detail. 

in this regard, tons of questions come to mind : at what point does a buttcrack on a board become a critical performance feature? at what point does it become a token slit that doesn’t really help a board ride better, but is really just an unnecessary adornment? at what point does it become a hindrance to turning, or cause a board to drag or stall? how is the buttcrack supposed to be shaped, in relation to the type of waves where they’re to be ridden and the fin cluster it goes with? is there really a science to shaping buttcracks, the way most tail shapes-- squared, rounded, pinned, stubbed, etc— play a minor but nonetheless important role in how a board performs, or is everything being done in shaping buttcracks purely a matter of artistic flair, imagination or speculation?

with your go-to buttcracked board you’ve shaped or bought for yourself, what tail-end attributes does it have that makes it ride better than the rest? tell us how it goes, show pics and provide dimensions when you can. this should be good, hmm !

[surfiber]

@$1

…Anyways here’s a previous fish with tasty buttcrack…and it’s got umm…a clitoris too!!!

JD

howdy jd,

is the leash loop some sort of wood or tinted resin? good job with that 2-toned, multi-strip tail panel too

cheers,

 

[kensurf]

I want to play

 

[speedneedle]

Surfiber - the leash loop is fin panel, set in the tailblock. Here’s the other side -

JD

[chippy61]

WOWWWWW !!!

SUPERB  , mate , as usual !!!

 

  And , oh , .....those FINS , Josh !

 

  any chance of a shot of THEM , please ? [if  not here , because it's "a buttcrack thread" haha  , maybe in a 'p.m.'  or over at 'Facebook' , please ?  or .... plan B .....you could always do "a fin photo thread"  , too, perhaps ?]

 

 ..... your wood and foam combo fins look GREAT ,  mate !!

 

  cheers

 

  ben  

[girvin]

I just trace a frisbee to get my fish tail then go at the crack with a round rasp till it looks pretty LOL

[scottkennedy]

[img_assist|nid=1064850|title=5'7" fish|desc=|link=none|align=left|width=67|height=100] I was taught that traditionally the trailing edge of your keels (parallel mounted, no toe/cant!) should be lined up with the start of the buttcrack and about 1 1/4" from the rail. works well for me… as i speculate, shallower buttcrack = more tail area = must be surfed more off the back foot…

[LeeV]

Before you discuss design nuances, I think you have to understand the function of the swallow tail/fish tail cutout.  While you will probably get a thousand theories, in my less than humble opinion, there is only one function; to reduce planing area in the tail to control the center of effort. The center of effort is the balancing of an object in motion so that it is stable.  If the center of effort is forward (in the direction of motion) of the center of the body, it is stable.  Try throwing a dart tail first.  The back wants to be the front and will spin around to achieve that balance. (There are a number of ways to adjust the center of balance; mostly weight and drag but that’s for another day)

On a surfboard, you usually want the front to be the front all the time.  To make a surfboard stable, you can keep the center of effort forward of middle by weight (you standing forward of center) and/or by controlling drag with the outline and fin(s).  If you have a wide tailed board and you stand on the tail, you will move the center of effort to the rear causing instability.  You can adjust for that by adding fin area or reducing the planing in the tail.

Lets ignore fins for now.  You can reduce the planing area by narrowing the tail.  Pintails are used on guns because they help stabilize the board if you have to stand on the tail during a steep take off.  (Pintails do other things too but that also is for another day). Or you can cut a wedge out of the tail to reduce the planing area.  Cutting the wedge will allow you to keep the outline of a wide tail and still let you stand there without spinning out.

Like all design features on a surfboard, there is a lot of give and take and many cat skinning methods…but in general, the wider the tail, the bigger the wedge that needs to be removed if you want to stand on or near the tail and still be stable.

The shape of the wedge-cut, in my opinion, is largely irrelevant.  No doubt, it may affect the feel of the ride, but I don’t think it affects the performance.  It’s the area removed, not the shape of the area that makes the difference.

A shapely butt-crack is a fashion statement or tool for production glassing.  The narrower the crack, the bigger pain in the ass it is to glass (oooh, that was a fun sentence).

Finally, to put a kabosh on the old Twin Pin theory of traction.  All they are feeling is the traction gained by keeping the center of effort up where it belongs…

 

PS I always use a keel fin for fish tail templates…it just seems right.

[nj_surfer]

[img_assist|nid=1064852|title=fish tail|desc=|link=none|align=left|width=385|height=288]

I figure it’s two important things… the geometery (no, I’m not going there), and the ratio.

The geometry has to do with the shape of the “cheeks,” for lack of a better term. The tips of the tails should be lobed… or fin shaped… while the crack should be relatively straight.

The ratio is the ratio of surface area removed to last foot of tail, as measured by tail width and tip-to-tip distance. I have a very mathmatical way of figuring out tip-to-tip and shape of crack/tails. I use it on all retro fish designs, and it’s a proven winner.

[thrailkill]

[quote="$1"]  ... purely a matter of artistic flair... [/quote]

An excellent description.    

[surfiber]

howdy BT,

if so, fishtail addicts might have to step off their boards, turn 'em over and do some headscratching to figure out where their stoke comes from, hmm ! 

cheers,

" )

[surfiber]

howdy girvin, any more scientific than that, you’ll probably have to use something with a tighter radius-- like a beer can!

hehe " )

cheers,

[surfiber]

finally we’re starting to get a bit of consensus here. while online resources on fishtail buttcracks come few and far between, these are the more common themes that keep popping up in discussion threads : sticking fins close to rails, ratio of removed tail-wedge section to the overall planing area within the last foot of the board, and matching fin choice (where there’s plenty of variety).

@$1

…traditionally the trailing edge of your keels (parallel mounted, no toe/cant!) should be lined up with the start of the buttcrack and about 1 1/4" from the rail… shallower buttcrack = more tail area = must be surfed more off the back foot…

@$1

… two important things… the geometery (no, I’m not going there), and the ratio. The geometry has to do with the shape of the “cheeks,” for lack of a better term. The tips of the tails should be lobed… or fin shaped… while the crack should be relatively straight. The ratio is the ratio of surface area removed to last foot of tail, as measured by tail width and tip-to-tip distance.

@$1

…to understand the function of the swallow tail/fish tail cutout… there is only one function; to reduce planing area in the tail to control the center of effort. If the center of effort is forward (in the direction of motion) of the center of the body, it is stable… If you have a wide tailed board and you stand on the tail, you will move the center of effort to the rear causing instability.  You can adjust for that by adding fin area or reducing the planing in the tail.

…Lets ignore fins for now.  You can reduce the planing area by narrowing the tail.  Or you can cut a wedge out of the tail to reduce the planing area.  Cutting the wedge will allow you to keep the outline of a wide tail and still let you stand there without spinning out.

…in general, the wider the tail, the bigger the wedge that needs to be removed if you want to stand on or near the tail and still be stable.

The shape of the wedge-cut, in my opinion, is largely irrelevant… it may affect the feel of the ride, but I don’t think it affects the performance.  It’s the area removed, not the shape of the area that makes the difference.

Finally, to put a kabosh on the old Twin Pin theory of traction.  All they are feeling is the traction gained by keeping the center of effort up where it belongs…

I always use a keel fin for fish tail templates…it just seems right.

any word from single-, quad- and other multi-fin fish surfers? how does the choice of fin setup make or break the fishtail design most common to fish-tailed boards? or is fishtail design largely a matter of aesthetics like girvin & BT mentioned?

@$1

I just trace a frisbee to get my fish tail then go at the crack with a round rasp till it looks pretty LOL

@$1

@$1

 … purely a matter of artistic flair…

An excellent description.

[nocean]

Heres some pics of mine, I quite often use a G5 Fin or similar and draw around that with the base of the fin at the stringer , seems a nice curve…

One traditional swallow tail, one shallow swallow tail which does not do much to reduce tail area ( Mini Simmons surfed further back off the tail).

Or Square it off as pictured which acheives the same thing :

[surfiber]

howdy nocean, how do they ride in comparison?

btw the scope of this thread naturally includes other types of tails with buttcracks going by different names-- swallow tail, bat tail, arc/crescent/moon tail, etc.

if there’s no consensus on the validity of this category of tail configuration, there should at least be a few good reasons why they persist " ) LOL

cheers,

[nj_surfer]

I would argue that it’s not all about aesthetics… the shape of the tails has EVERYTHING to do with the ride.

A swallow with more pointy tails, like the one in nocean’s second pic, relies on rail line and fin. The tail does nothing to add drive through turns. A more lobe shaped tail adds fin-like projection to turns, as the increased surface area at the tip adds leverage.

[sharkcountry]

Greg Griffin made my brother and I his version of a modern day fish back in 2005 or 2006. They have 5 fins and a variety of interesting design elements. My board is 6 my brother’s is 6-2. Every time I ride these boards I am amazed at how good they work. Doesn’t matter if it’s small waist high slop or double overhead barrels, the board is amazing. My friends were commenting on how well the board seemed to glide along in small surf a couple of weeks ago.

Here’s a link to a post Greg did when he finished my brother’s board. I think the serial number is either 0001 or 0002, mine is 0004. We were there when he went on his own and started Greg Griffin/Sunset Point Surfboards. Check out the crowning of the deck, the rails, tail and the fin setup. You stand pretty much on the buttcrack and these things just go like a ferrari F1 race car.

http://www2.swaylocks.com/node/1022231

[surfiber]

@$1

I would argue that…the shape of the tails has EVERYTHING to do with the ride. A swallow with more pointy tails, like the one in nocean’s second pic, relies on rail line and fin. The tail does nothing to add drive through turns. A more lobe shaped tail adds fin-like projection to turns, as the increased surface area at the tip adds leverage.

howdy NJS,

if a pointy swallow tail does nothing to add drive through turns, is the reverse valid too-- a wrong fishtail shape can mess up how a fish rides ?

also, you mentioned that a more lobe-shaped split tail’s surface area adds leverage-- to do what exactly ?

cheers,

[surfiber]

howdy sharkcountry,

compelling reference you got there, however oneula’s testimonial at the end of the thread got me a bit confused when he started referring to the shaper as chandler, whom the surf industry didn’t treat too well, while you mentioned greg griffin above as the shaper. care to clarify the back story? interesting stuff!

cheers,

 

[nocean]

Hi,
Good thread… yeah Surfiber, I cant do a very fair comparison of the three tails picured as they are on vastly different boards. Each one goes with the other parts of the boards, might picture the boards in their whole so you can see…

Nj, Im interested in The’ Lobe’ you refer to, by this you mean the end of the point of the swallow flattened off yes?

For me a pointier tail will draw longer lines in conjunction with tail outline and a more flattened off swallow will be a little more pivoty or as Nj described have more leverage…

Sharkcountry, Heres the pics for reference from the thread you put up, nice tail shape and the board looks fast( straight tail outline)… and the swallow is quite wide and shallow?