"There are two tails, and only two tails..."



Was browsing surfline and checking out this segment on Stretch.  Curious to see what people have to say about his statement made on tails.  He starts off by saying one of the two he is talking about is a rounded pin but never quite brings it home.


Your thoughts?



He doesn't get around to saying what the other tail is.  Likely they edited out that info.

Nice clip, thanks.

It's an interesting quote... the fellow is a successful builder, so giving him the benefit of the doubt seems reasonable. Here's a little more of his comment.


There are two tails, and only two tails: there are round pins; a round pin will shorten the rail-line of a board over all the other rails and all the other tails … and if it is shaped the same, meaning it has the same tail width, the same curve, and the same tail block that ends in the same place, all other tails ride the same...”  William “Stretch” Riedel (09/18/09), Surfline.com, Shaper's Bay


Regarding rail length, my guess is that the quote has a context which is likely clear to Riedel. Geometrically though, if you interpret his comment literally, it's not true.

When you think about it, at least in functional terms - a rail is simply where the bottom ends. Also, the distinction between rail and tail can get a little arbitrary, especially when you're referring to pins. But I'm not sure Riedel is thinking in such pure terms. Again, he likely has his own view, but given time/space constraints of the interview, I guess we'll just have to guess what that was (or is.)


However, his opinion about the comparative value of a lot of the tail designs currently in use is sort of interesting. I think the impact of the tail design is greater for slower/mushier conditions, though even then, his point is well taken.



Pretty sure what he says is this:


Round Pin = one tail.


Every other tail shape = the ‘other’ tail

So a competent rider will feel a difference between a round tail and something else, but not between the something elses? Then something else is a signature, or nom de plume???

Same tail rocker and width @12", can you really tell the difference between a square, rounded square, swallow, diamond and fish tail? Theoretically they all work differently, but maybe it's all style at the end of the day.

Trad fish is really two pins, so that would be different.



Context! It's is the interpetation of what Stretch Quoted. Two tails. I made a one minute diagram to show basically there is little difference in a tail preformance under the context of the way it was presented. 

Unless you vary the width at the end, but who's going notice, 45 to 55, or 45 to 60 for that matter?? 

Rails basically demarcate bottom surface. Of course their design -i.e. profile, can also make a difference  However, ultimately they set the amount of bottom surface that can be in play. But exactly how a given design will impact a board’s riding characteristics will depend on both how that bottom surface is being deployed, and under what conditions.

In the context of your diagram, its sort of clear how you’ve decided to interpret Riedel’s comment, and it’s not that unreasonable (given the context etc.) Yet, for example consider nocean’s Ride Report 5’10" “Split Tail” … . Sure it’s pretty extreme, but surely it suggests that there are (functional) limits to the swallow tail design (which are also likely to depend on flow,etc.)  Not all swallow tails are alike, even if we hold all the parameters suggest by Riedel constant. Surface area isn’t necessarily conserved when changing from one tail design to the next. But there are also other factors here,  like  flow conditions.

Your point in the context in which you’ve presented it, the two respective surface areas being damn close, is understood. But even if they weren’t the same, you could still  make something that is, and it that wouldn’t look that different. So again, you’re point is understood. But even then, flow considerations have to be taken into account.Though admittedly, like the case you’ve presented, dynamically the difference is likely small.

But whatever the case, Riedel’s success does say something about his approach with the market he’s serving.


NJ…more fodder…good assessment of tail attributes. Esp. the ROUND aka thumb tail. I concur.

P.S. If you look closely, you will see the cup and inserts still have cloth over them (just a hotcoat).

Right on this sheds some light on it.   Honestly I thought he was going to say that the other tail was a regular pin.  And I only came to this conclusion because he talks about the rail line.

Sorry… but I couldn’t DISagree more…

Here’s something I wrote on the topic…

“There is a sort of simplistic “conventional wisdom”
and general consensus among shapers, about board tail shapes and how they
effect performance - square tails facilitate square turns, and rounded tails
facilitate round turns. The reason for this general statement has to do with
the fact that the straighter outlines in the tail and the added surface area at
the corners of a square or squash tail’s pod or block – the very
end of the board, measured corner-to-corner perpendicular to the stringer -
create more lift, thereby deflecting more water when the board is turned. The
more water deflected, the faster and harder the turn, but the more force
required to initiate the turn. Rounded tails, by contrast, have curvier
outlines in the tail and no corners, allowing water to release from under the
tail sooner and in a more diffused fashion, and therefore deflect much less
water. Because water is shed from under the board earlier and more evenly along
the rail of the rounded tail, turns become less snappy and more fluid, and
require less force. While this “rule of thumb” is helpful, a more detailed look
at what’s going on along the board’s last foot or so can give a better
understanding of why tails work the way they do…”

Later, I say…

“…three tail shapes can be discussed together, as they
are generally straighter in rail template along the last foot of board. In
terms of lift, the square tail, with its maximized surface area and hard
corners, creates the most lift, followed by the rounded square, then the
squash. With each progressive loss in lift, there is an increase in
release. Square tails, of course, are simply…square. Used mostly on long boards
and high performance short boards, the large square corners give the rider a
lot of leverage and lift to pivot off of. The rounded square tail is basically
a softened square tail with the corners rounded off. The feeling is very
similar to the square tail. The squash is similar to the rounded square tail,
except for the fact that the rounded square tail retains its flat, straight
pod, while most squash tails have pods that are very slightly arched. By far
the most popular tail, the squash provides what many feel is the ideal balance
between lift and release - the shape produces sharp but fluid turns. The
difference between these three tails, particularly the last two, can be subtle,
and often only a matter of degree”


“Full round tails, sometimes referred to as “thumb
tails, provide the most lift out of the curved tail designs. Release is smooth
and diffuse along the rail, but the rail template is straighter  in the full round tail than the next tail
down the line – the rounded pin tail. Full round tails have curves that
accelerate greatly near the pod, as the fuller outline and soft curves leading
into the tail are rapidly pulled together into the arc of the completely
rounded, “would-be” pod. The feeling can be very similar to the squash tail,
but tends to produce smoother, more open turns. The rounded pin, however, pulls
the tail template in much sooner, feeding into a pulled but curved tail shape
with less curve acceleration where the rails converge. Due to the reduced
planing surface of rounded pins, the back foot is placed further forward than
would be placed on a squash or rounded square tail, making these tail shapes
better suited for large, steep, hollow surf. The more parabolic curves of the
rounded pin produce a soft rounded point, rather than a sharp point, found in
true pin tails. True pin tails are reserved for big wave guns, as surface
area and lift are severely minimized in an effort to focus on control and easy
rail-to-rail transfer at top speeds.”

More fodder later.

I just woke up to find Surfding shot this over to me…without pulling up Bill’s comment on Surfline, I will say this…then come back. KCasey has got a pretty good grip on it.

Surface area

Demarcation of rail

Flow characteristics

Heady thoughts indeed but to paraphrase some of these comments, let’s put it into practical application. Even if we retain the same design elements at one foot up from the tail, rocker, thickness flow and ‘end the tail’ at the same place, you still have differentiation that exists by the choice of tail design. Surfding’s diagrams displaying a roundtail with a small butt crack is probably the closest to the board **appearing **to be virtually unchanged- at least noticeably by the vast majority of surfers.

That doesn’t mean that sensitive instruments couldn’t measure and record subtle differences in dynamic flow characteristics between the two configurations. The “practical applications” that I personally experienced can be demonstrated by hopping on your choice of tail designs and getting towed behind a boat. On numerous flat days I would go ‘free boarding’, and one day I started to notice the difference in release from tail to tail. You can experience this yourself. Just take out a rounded pin and watch the line that is apparent off the tail opposed to two lines releasing off a dove or swallowtail. To extend that further, watch the FOUR disstinct lines releasing off a swallow winger.

If you wish to extend this observation further, try a diamond tail, a double winger and even the differences on a bump versus a definitive wing. Take a square tail out and see if you notice any significant difference between the two release lines of a 5" wide square tail and a 5" wide swallow tail. Is there a void in the wake of the square tails width?

Long time friend and co-shaper for my 80’s company, Bob Krause, once quipped to me “wanna cruise? Make a canoe. Wanna go fast? Chop it in half.” True to that thinking, when we designed race boards for the “California Speedcheck” held in the 80’s at the San Luis Reservior, our design, a square tail, achieved the 2nd fastest peak speed as recorded by radar. The winning board was ridden by speed czar Fred Haywood, on a Jimmy Lewis design. Both Lewis, and our design then achieved the fastest times in the world for a wind driven hull…

Since I haven’t read Stretch’s comments yet, I don’t mean to take anything out of context. However, I will state that if there are only two tails with all things remaining equal…and IF Swaylockians are ready to take this as truth, then I suggest you delve further into the subject.

Bat Tail = three distinct (fine) lines from tail

Diamond Tail = three distinct lines from tail…different ‘void’ from bat tail (significant shortening of rail length)

Round Pin = One line from tail slight rooster tail

Sharp Pintail = One line less rooster tail (specific singular pivot point esp. off top of wave)

Round Tail =  One line from tail - non distinct rooster tail due to increased outline curve/allows subtle direction changes

Square Tail = Two distinct lines from hard corners

One set (pair) wings = add two distinct lines to appropriate tail design

Double set wings = add four distinct lines to appropriate tail design

Triple and multiples = just times by two…you get the picture…

Conclusion: ANYONE supporting the supposition that there are only two tails (whoever that person might be) is subscribing to a design reality that I do not adhere to.

jeez... I started by giving Riedel the benefit of the doubt (for

good reason)… I then implied we probably weren’t getting the whole
story because the clip was short,etc. … I then wrote that he seems
to be successfully serving his market, so chances are he’s doing
something right…and with respect to your diagrams, I indicated
that I got the point… in fact my posts were so hedged, it’s kind of
amazing I was able to get any point across at all (that’s assuming I
actually did.)

This is Swaylock’s, it’s a forum, an exchange. I don’t remember
who suggested first or if it was only expressed once, but it’s a
notion that basically amounts to that, here on Swaylock’s (an open
forum), the kind of (throw it out there) statement made by Riedel in
the video (and, admittedly it was likely edited) without a lot more
qualification would be pretty polemic…and result in numerous
assholes being ripped anew … in all parties… in the resulting

The neat thing though, is that it introduced, somewhat indirectly, a pretty interesting
topic, at least for me, that given that a tail (or any design
element) may function one way under one set of conditions, can you
really then extrapolate to all conditions. For example flow matters,
conditions matter, they impact the dynamics and therefore the
response of a given design element. There isn’t anything really new
in that statement, but given some of the chimera like boards that
you occasionally see, here or elsewhere, you’ve just got to wonder
what the designer had in mind when he build the thing.
Designing/building boards ain’t always “plug-in and play” with
respect design features,… like tails, contours, fins, etc.

I’ll definitely give Riedel the benefit of the doubt on what works
(for his market), but that’s a long way from buying into a ‘universal

Maybe I’ve misinterpreted your post- apologies if I did. But I do
believe I got your point. I just don’t think I’ll be voting to add his
[Riedel’s] comments, as they stand, to surfing’s gospel, if such a thing could
be said to actually exist…and assuming I’d have a vote.

Also, I guess it’s pretty obvious that we didn’t go away with the same interpretation as to what Riedel said. It’s too bad he didn’t make the comment in an open forum, like here on Swaylock’s. My first guess would be that he’d have a little more to say on the matter.


I think the title is the culprit if it incites a Sway’s riot…

Context is all important regarding this subject matter. One would have to agree on the actual parameters in order to have an “equal” conversation. Otherwise we are all pissing in the wind, some of us with the insight to position ourselves upwind of the resulting stream! :slight_smile:



I’ve got nothing but respect for both Riedel’s and your

On that note, (and my recent change to a high fiber diet) perhaps it’s best I go shape a few myself…


…okay, maybe “pinch a few" would be more accurate


Good to know you have a sense of humor!


Dead your work is so outstanding!



I’ll throw this out there… and I’m referring to Stretch’s ideas here, too…


“It has been said that there are only two basic types
of tails – square tails and pintails – and all other tail shapes are just
variations of these two. If the designer considers how a tail shape relates to
rail line and surface area, there is a great deal of truth to this concept.
Square tails maximize surface area at the end of the board, while pintails
minimize it. All other tail types – squash, round, swallow, etc. make critical
adjustments in surface area, while allowing the shaper to maintain the desired
rail line…”

Later I add…


“…the tail shape that most naturally complements the
rail line (should be) chosen. The purpose of matching tails and template has to do with
how water along the rail moves. The curves of a board’s planshape through the
middle are designed to provide adequate width for the intended conditions, but
also to allow the template outline to flow smoothly as to minimize transitions
along the curve. In other words, the chosen tail shape should be an extension
of that smooth, flowing curve, so that the appropriate tail width can be
accommodated without creating unintended release points along the rail.”

I also say…


"Another aspect of rail line has to do with the length of effective rail – the length of rail that has the primary function of providing hold and directional stability, rather than release. Simply put, shorter effective rail lengths result in shorter turning radii, all other design elements being the same. It is clear to see how diamond tail, for example, provides a shorter effective rail length than a square tail, as the point of the diamond extends beyond the corner of the rail. The same is true, but to a lesser degree, with squash tails and rounded tails when compared to swallows, crescent, or bat tails. The latter three extend and straighten the rail line compared to the rounded off corners of the squash, thumb and round tails. It his helpful to understand that any rail behind the back foot becomes a lever, with the foot acting as the fulcrum of effort force. The longer the lever, the more water it will push when turning on a rail. Shortening the rail allows water to release from under the board sooner, reducing resistance, and allowing the board to flow around a tighter arc. While this may sound complicated, chances are you’ve known this all along… which way do you move your back foot right before you do a snap, forward or back?"