I’m seeing mostly squared off tail rails these days, and I don’t understand what affect this would have on performance. I have always kept in mind that the pod area of the tail is still a rail, and making the bottom edge hard or soft, thick or thin, was the most important thing outside of tail shape.
What’s with the square top rail?
Something about tail flex, tracking and breaking lines.
Think release. On rail, tail rails sees a lot of water wrapping around. A square rail has release both on the bottom and off the top of the rail for maximum water shedding and speed. DHD boards are a good referrence.
It’s a myth…water does not wrap around a rail to the deck unless you are groveling or stalling to the point the board is not planing efficiently. Try watching your rails while you surf sometime…
Square tail rails are faster and easier to shape/reproduce and take less finishing if they are cut from a machine. Miniscule effect on performance if any. Same reason most swallows have a flat wedgy looking rail shape (see Griffen’s boards)with no buttcrack nowadays. A breeze to shape and glass with no adverse effect on performance.
What craftee’s talking about is not water wrapping from the bottom up over the rail to the deck ‘‘edge’’.
You’re right , if you look down at your tail at speed you’ll see water releasing off the rail ahead of any
square area. In really tight top turns, however, water does come across the deckside at high velocity.
Probably some of the highests velocities attained in surfboards. The thin, sqare rail seems to be the best
thing us shapers can come up with to strike that perfect balance between resistance and release. Luckily
it’s really tricky to get right, and the glasser and sander have to be highly skilled to replicate what the shaper
intended.
Plenty of pics of this phenomana in any standard surf mag. Look for water going diagonally across the outside
corner of a squash mid-off-the-lip.
Mike
Mike, all due respect and based on my personal observations…
Nope…still don’t buy it. If you are planing, everything is being pushed away, displaced. If you are coming to a stop and swiveling, yes water can come onto the deck. Watch some of the old movies with the camera pointed off the tail in the tube…no water on the deck. If you are stalling, then water on the deck. Nose riding is stalling; water on the deck. A swiveled off the top is stalling. So water on the deck. A carve is planing, no water on the deck.
It all goes back to the theory (or is it a law…help me now janklow) of planing, wake, root spray, etc. But I promised a lot of people I would never go there again and I won’t.
If you think that a square topped tail rail “releases” better when you stall, great. I think the only thing a square topped tail rail does let you hide a little foam in the tail without hurting anything.
I understand what you’re saying and don’t disagree except for the fact that in the moment
of WHACK off the top the water does flow just as I described. Look at the pictures. It’s not
hard to find examples.
I’m deep into dynamics theory (as janklow will tell you) but there are moments in surfing,
especially in the lip of the wave, that have their own set of parameters that don’t quite fit
boat or aero wisdom. Some of that is what we’re discussing here.
Respectfully submitted also,
Mike
The double edged tail rail thingy…I first noticed it waaaay back in the very early nineties when Damien Hardman’s Bells quiver came in for repairs.
These ones had something similar happeing in the nose, and at the time I figured old man Greg Clough was just sleepy that day!
This point of design has slipped into vogue with very few shapers having ever verbalised what it’s function is.
My thought is that it maintains some rail volume through thin tails, allowing a buried rail to pop out more easily in skippy-flippy maneuvres, where a heavily downturned rail would catch and bog.
While I’m not a “new-school” ripper, I use the double edged tail rail in my personal boards and I find it very responsive to weight and unweighting in direction changes.
Its also my experience that its a serious liability in powerful waves…
Speedy
I have used soft rails on the deck in the tail of a couple of boards. I notice the turns are smoother. My intention was increase rail penetration in step up boards. I take the view that the rail/bottom around the tail is a fin. So I ask myself how I want the water to flow around that foil for the type of board I’m shaping. I have never thought about it in terms of its effect when stalled. I mainly consider it in relation to changes in the angle of attack, and how such a foil would retain or release water and therefore energy.
The 7’6" gun on the racks will have a foiled topside rail in the tail.
speedneedle has it. I have only seen it in smaller wae boards. All boards for bigger waves have it rounded down like skimboard rails.
Lee, I dunno, I’ve seen a lot of pics of the forward rail of Lbs in forward trim that had what looked like water wrapping over the curve of a (much softer than what you guys were talking about I guess) rail–just like Tom W says on his rail article on his website–he calls it suction–refer to the spoon experiment–it also follows Coanda’s law of attachment–from the point where a water molecule first encounters the rail, it will stay more attached to a curve–a bladey rail, a hard down rail, a fully boxed rail will all release it in a Newtonian way like youre talking about, where a longboard’s softer rail will hang onto it–it explains “the glide” and why the ride is so critical on the Liddles, like you said in the TSJ piece, and why trim speed is so much faster. Essence of the hull ride, iddenit?
EDIT: Also the sorta parallel profile allows more flex up to a certain point I think than a more domed treatment, lets a shaper keep volume in if he wants to, and is easier to shape…
http://www.revolt.it/PHOTOS/ITALIAN%20TOP%20LONGBOARDERS%2005/images/RUBEGNI.jpg
The square rail releases quicker and slides are more controlable.
eg. Better for lift-off and re-entry on airs and floaters.
The rounder or knivey jobs are to catchy in this area of surfing and as a result takes more time to recover thru the manuver.If not just catching and pitching you off.
As far as faster ?..You only can go so fast… and the wave vs. rider makes most of that up.Herb
True 'nuff–the point is how much slower you can go with the other,
and getting enough lift from your rail and minimizing drag(s) that you can get to “so fast”
G,
Again,
Depends on the wave vs. user…
…traditionally, a boxy
(squarer) rail is king for speed.
If you want more lift …use a concave or tunnel fin,but it’s not nessesarily faster.
Bob McTavish wrote extensively about this tail rail phenomena in a Surfers Journal article called “Kicking Over the Traces”, where he analysed some design elements from the shortboard revolution and what happened in design up to modern shortboards particularly wrt to rails.
His conclusion was basically the squared off tail rail releases and doesn’t drag during fully rail buried high speed arcs.
looking closely at modern shortboarding manoevres you can see quite clearly where water flow is “up and over” the tailrail and how critical it is that the water release cleanly and not drag the tail under and stall the manouvre.
He credits greg Clough with “inventing” it and Al Merrick with perfecting it.
It is de rigeur on modern small wave shortboards.
I don’t know where in history I fit in ,but I’ve been doing them square since the late 70s.I pretty much did it all on my own.
If I had any influence on this subject ,I’d have to say, Jeff Ho(Zephyr),Lance Collins, and McCoy.All three used squaretailrails back in the day.Not as square as todays stix, but alot more than the boards of it’s time.
That’s one reason I loved the Stinger design. The shape easily allowed me to square the back third of the rail out while maintaining a hi-grab rail in the forward 2/3.Herb
