Was in the local shop the other day picking up some soft racks for MaMa’s Suburban. Made the customary rounds to look at all the board offerings. I noticed a design detail that was fairly re-occuring. The rails in the tail block area(shortboards) was fairly squared off. Most boards were in the 3/8 to 1/2 inch thick range at the tail but gone was the slight roll from the deck to the hardedge. Deck edge was almost as sharp as hardedge(bottom). I can see where this would increase release as the water would not wrap the edge up onto the deck as easily, but release off the top. I still have a tendancy to roll my rail all the way back to the tail. How does this squaring off of the top edge affect performance?? I liked the look but I’m curious about the mechanics and feel in the water of it.
I don’t know but maybe they were computer shaped then finished off by some lazy wanna be shaper??? or maybe it’s a top secret rail design to get your board to do really big airs?. ???
Next time you are riding a softer wave with no problems in front of you, twist around or look between your legs and check out the tail…high and dry. The whole “water on the deck” thing is just not happening most of the time. The board and particularly the tail is planing on not in the water. The shape of the deck on the tail (in my opinion anyway) is meaningless.
Square means a little more float and a lot less time in the shaping room (if you are cranking out 5 or 6 a day) more than hydrodynamics.
Look for an article in Surfers Journal on Bob McTavish (sorry, don’t remember how old it is - a couple of years). There’s a lot of interesting stuff about symmetrical rails in the tail.
All the boards I’ve ridden that have felt real good have that squared-off rail in common.
Sure, all those hard, turned down rails of the bunker board era can’t be all wrong!
Who would have thought that a blocky, squared rail actually works really good, provided you have the weight/strength/leverage to sink it for a second on your bottom turns at speed.
Width control solves that, maybe a little V in the tail bottom, and less surface area aka rounded pins.
The rails are not thick. They are probably 3/8" for at least 6" up from the tail then gradually thicken and pick up the deck roll. I can see that it would allow some flex. Mostly I can see the release potential. These are flat bottom to a slight “V”. Interesting…I am going to try one on my next shape just to see what it feels like.
I hate squared off rails in the tail. They feel herky-jerky as compared to a more turned-down edge- just don’t flow that well IMO.
I get where LeeV is going with his comment, but when skating over “softer waves with no problems ahead”, chances are you are skating neutral-rail and relying upon the planing abilities of the board to keep you going, with a lot of pressure on the front foot and little pressure on the back (which would sink the tail lower and cause water to wrap over the rails along the tail). When you get on a hollower, more vertical wall, chances are your rails are going to be engaged and you are creating drive with the fin cluster and rails along the general tail area of your board- hence they are engaged and water is flowing up and over them. Not a time for your boards to get herky-jerky and your rail to attempt to release due to a big flat area along the rail.
I paddle a 16’ paddleboard with a boxy (edge) but rounded (top and bottom margins) rail along the tail- on long distance paddles one’s neck cramps up, and to allieve this problem, I wind up looking through my legs (I am knee-paddling at this point) and watching the water flow over the rails along the last foot or so of the tail. Water definitely flows over and wraps around the rails in the back end.
Flowing water hates flat surfaces- leads to ventillation and boundary-layer seperation. No flat areas for me, please.
In a hollow wave it seems as if the water would not wrap around the rails anyway,water sucking off the bar/rock/reef going vertical at a rapid rate…driving the board forward off the bottom ,side rail and fin…no? I mean of course some water will get over the rail/tail…but is it doing anything? Water may hate flat surfaces but flat = fast (bottom…) ,seems like a rail like that would hold and drive fine…peace and waves…
Man, I wish I did not have a real job so I could wax poetic about this as it is something that is always in my head when I examine boards.
I think you have to think smaller than in the water moving up the face of the wave scale. Yes, water (actually, it is transmittence of energy more than a flow of water) is moving up the face, but you are also progressing forward (down the line) and rapidly traveling within and between infinite “parcels” (a term used by ocenographers and other marine scientists to describe indeterminite scalable units of water- it is not a quantitative term, but a qualitative one) of water during your journey. I wish I could elaborate on this better, but boards generally glide over masses of water (ok, they do displace a little water) when neutral-rail, and slice through water when on-rail… othewise you could make a board with 4" thick rails and have it ride and precisely as a typical high-performance shortboard, no?
Nothing remains constant during a surfboard’s journey- paths meander, a myriad of pressures are experienced (from both the water and the rider), angles are changed, momentum is transferred, etc.
As for the flatter=faster rocker thing, none of the boards that are surf-able have truly flat rockers, all have curves of some kind, whether in the profile rocker itself or the concaves running along and side to side on the bottom surface- the flat vs. curved rocker thing is really a misapplication of terms as they are relative to each other and not to absolute-flat surfaces (a 2D plane) and an absolute curve (I guess that would be a sphere?).
As long as there is some sort of curve, it is better than having no curve at all (regarding boundary layer seperation issue). And of course too much curve can cause said curve to plow water ahead and suck it behind. The problem with large flat areas of the rocker (I’m thinking of boards with broad flat sections in the middle, and rocker is used to compensate in the front and tail sections of the board) is that flow is lost to seperation and instability is created- like a skipping rock, a very flat board is fast but relatively erratic and unstable as compared to a constant (but subtle) curved rocker. Of course, these are all generalizations, but I like to learn the theory and then see it applied.
I agree that water will flow over rails and across the deck if you are going slow enough (paddleing speed) or nose riding (where I still haven’t a clue as to what is going on) or at the apex of a snap where the board is momentarily slowed almost to a stop…but when you are up and going, dropping, trimming, turning, the deck is essentially dry. Proof? Look at any photo in the surfmags, especially the photos of surfers in the tube.
Say I’m all wet, I don’t see how water flowing across the deck would affect the performance as it leaves the top of the board. The bottom of the board, yes. But the top? Maybe the stickiness you feel is the result of something else; the slight change in balance point due to a more buoyant tail, for instance.
Not flat rocker…bottom shape (flat…) …with the “square” rails seem like they would hold in trim yet release well when on rail…anyone? Loehr,Phillips,Cleanlines, Olsen…
Here’s a quote from the website of Pipedream surfboards:
The Box Tail Rail
Many surfers may have noticed the latest in tail rail shapes when tend to be very square but thin.
The reason for this is that due to the release nature of edges having on top as well as the bottom gives you a double release. The trend is toward thinner tails i.e. the last 12” at least which allows a surfer to plant his tail easily in order to make quick direction changes. If the tail was thin and knifed out at the tail it would bury too deeply and draw more rail up forward thus slowing down the quick rail-to-rail exchanges we see pro surfers executing in small waves The double-edge effect allows a thin tail, which can be submerged quickly, to be released almost as quickly. This is why we are seeing hotties ripping up 2’ waves like they never would before
This is a good debate, I hear it all the time. First of all, in reference to Ocean23’s comment about flat bottoms, I think he was referring to the bottom shape rail to rail. I just sold a shortboard that I built with a ruler flat bottom rail to rail, from nose to tail. In 3-6’ glassy conditions, it was one of the fastest boards I’ve owned. But in choppy conditions the board was a nightmare. The all time fastest board I’ve ever surfed had about 3.5 feet of flat in the tail rocker and was ruler flat from rail to rail also. It had a super hard edge in the tail, I believe it was a late 70’s G&S board. Super fast down the line, but turning was out of the question. So in my opinion, flat=fast in optimum conditions. But in reality the conditions are rarely perfect. So various bottom contours (V, dbl concave, rocker changes, etc…) are needed for control, tailored to each surfers personal preferences. As for the boxy tail debate, the Surfers Journal Article by McTavish mentioned above is spectacular, I wish I could dig it up right now, maybe later. Any of you guys ever jump up to you feet, go to do a bottom turn and stall out because your foot was hanging over the rail a little? Didn’t quite get your foot placement right? That shows you just how much water is actually flowing over the rail on the deck of the board. Little water on the actual deck, but along the rail, sure every time you roll the board through a turn, you are going to get lots of wetted rail… “Aye mate, he buried the whole rail through that turn ehh?” …watch Occy surf, sometimes he’s got the whole board under the water. hehheh. Any ways, I have experimented with boxy rails with and edge on the top and bottom in the tail, and rounded on top edge on bottom, many many times. I never really notice a difference, I think having a boxy rail compared to a foiled rail is what makes more of a difference. The thicker (boxier) the rail is in the tail, the more the board is going to push back when pressure is applied… usually good for larger guys, and bad for the flyweights. But if you want to look at it in a simpler sense, where water is flowing directly off the end of the tail, top and bottom, then a foiled rail would have a more streamlined shape, and the boxy rail would create massive amounts of drag, especially with a hard edge top and bottom, sort like not bothering with foiling the trailing edge of your fins. Of course though, so much more stuff is in play when the board is actually being surfed, that I think that hard or soft edges on the top of a boxy rail simply adds up to cosmetic preferences. -Carl
I’m looking at some pictures of guys in the tube…The water is definitely wrapping onto the top of the boards. On longboards(noseriders) this wrapping is desireable as it holds the tail down to help support the rider on the nose using the board as a lever, the rocker/wave as a fulcrum. On a shortboard this affect would rob some speed from the drag of the water being deflected around the roll but gain some stability. The sqared rail does not deflect water in two different planes and this lack of deflection would seem to equate to speed. As with all aspects of board design I think it is yet another compromise. Speed/release vs. stability. The cross section of a squared rail is usually thinner than a rolled rail so the feeling of “bouyancy” on a rail turn would be reduced for sure. Good thoughts by all…