Kneeboard Surfing USA Community Forum

Of my last two boards, one was for small waves (2.5 foot or fattish waves), one was for 4 to 7 foot waves.

The small wave board is thickest. Consequently the rails (think late 70's Hot Buttered and you're almost but not quite close) because of the taper are less boxy than the larger wave board.

Now the small wave board happens to fly upto six foot, even though it shouldn't (theoretically).

While riding it I happened to watch the rails in front of my knees. Because of their shape they bury nicely, but because of this "ease of buryness" they are also harder to manipulate rail to rail -ie there is more water travelling across the top of the rail - therefore rail to rail transitions are slightly harder.

The boxy rail, though thinner, is slightly harder to bury and thus has an easier rail transition.

This leads to question one: does anyone change your rail shapes depending on the wave size to be ridden because of the wave size rather than as an epiphenomena of the different thickness? .

Both boards have square rails at the tail. The shaper, for who I have the greatest respect, tells me it is for "gouge" and also the possibility that the board might plane slightly on this part of the rail. I didn't understand that at first till I thought about the rail having a hard edge both top and bottom - now I know exactly what he means.

Recently I read that Mctavish has been experimenting with ways of improving rail to rail transfer by limiting the amount of water travelling over the top of the rail. He has been doing this with a squarer rail profile (in the tail??)

Question 2: Anyone experimenting with a square (I mean square!) rail profile further up the board, perhaps even as far as where the nose lift ends, for use with small wave boards? - idea being to keep water off the top of the rail to keep the transitions tighter.

Having the clean edge on the top of the rail as well as the bottom appears to have interesting possibilities. Think of a 90 degree edge on the deck end, with the bottom of the rail slightly chamfered to eliminate catch.

Last December I made myself a board and ended up with boxy rails right at the widest planshape point. This was slightly behind centre. Iv've noticed that this becomes a pivot point because it is the hardest part of the rail to bury. Because of this pivot point the board goes vertical much easier than any board I've owned. (the rest of the time it goes shithouse)

Anyone else working on this idea of pivot point by changing rail shape? rather than depending on planshape or bottom contours?



Any comments welcome.

uh??? my board goes... and i hold on so i dont drown ... lol!

...

HW

Too many questions.
I dont know what you mean by boxy rails. Are those the 70's down rail/ tucked under rails or do you simply mean fatter, semicircular rails?

For small waves I believe in flattening the domed top deck and carrying more thickness to the rails. This gives a thicker rail (say 2" at 2" in, rather than 1.5" at 2" in). I'm then less inclined to bury the rail (and my inside knee) in slow/small surf so I flow better. The key here is more in compensating for my own style, rather than specific small-wave board designs (which may tend towards wider, flatter).

Standup shapers always go for those square rails in the tail because they have don't undertand that kneeboarders simply cannot bring 80% of their weight to bear down on the tail the way standup surfers can. In my opinion those square rails won't ever work on a kneeboard that you want to put on rail - they inhibit the kind of rail transitions we initiate (from the centre of the board). I suspect they cause the tail to 'hop out' of the water (as you 'click' onto the flat edge) so you have to sit back on your heels and stall the board in order to get it to turn.

There are a ton of brilliant standup shapers who understand hydrodynamics, but only handful have the insight to understand that kneeboarding is all about burying the rail from nose to tail - they still work with the standup paradigm of the 'vital last 18" '

Square rails? Watch footage of landing craft!

Mr. Wax
I shape a boxier rail for some of the reasons you posted. I like the fuller rail for weaker waves. The floatation in the rail helps compensate the lack of power the wave has. I like a more foiled rail for thicker walls. Now as you noticed the board buries a little deeper into the face and follows the rocker profile through the turn. If you set up the rocker for the power turns you like then the sleeker rail should work better in big surf. At least that is how I fine tune my boards for the size and power. But there are many stradigies and design options that can be used.

this was ment to posted after beeline but the server crashed


gosh wax

a red faced man shooting

and

a culture club fan man seemingly being impolite (no so i assume he is being serious) sorry if your not Beeline

yet

a short answer from me due to lack of time

I am finding that my thick railed full volume square tailed and wider nose quad suits the smaller stuff but does surf well in bigger

my thin railed lighter less volume pointed nose thruster is definately my bigger wave board - though they are both the same length and width - the thruster has rounded pin tail

of course the above is pure luck rather than design as theyare both pre loved boards - now im in a love triangle that makes it hard to choose in the car park unless its pretty big or pretty small


wax - it is interesting to note an increase in posts when your around - and interest - such a refreshing breeze


wax on

lyrically

dorje

..

Aargh I feel a bout of zealotry coming on, as I spring to the defence of HW.

Mr Beeline how can we take you seriously, I'd sooner be seen mounting an inflatable lady than one of those bloody surfmats you refer to. Things may have moved on since my 1976 twin fin Balin surfmat but I’d hazard a guess that these new fangled ones just offer just a better class of tit rash and side slipping than their predecessors.

As for HW’s query, well I’m still digesting the technical aspects of it and despite my ability to sink/submerge a rail don’t feel qualified to value add to the discussion.

..

its your bed you sleep in it

Hi Beeline,

Headwax you always seem to be full of hot air
maybe you should get a mat too.

You're right about me being full of hot air I'm afraid. I was trying to be succinct (see John's example) but just came out being verbose! Apologies. I have a mat at home but my second wife won't let me use it on account of the overdue alimony I never paid.

Red Dorje Shelfbreak John Kava Beeline et al. Thanks for your quick response!

My questions (too many!) arise from my experience with quads over tris.
Basic history: I've always surfed tri fins with small rocekr and biggish fins. I guess I'm the equivalent of an 18 inch rail man Red cause I surfed the tail of the board!.

But with quads, as you know, that doesn't work because they don't have a centre fin. Consequently I've just spent 18 months relearning how to surf by using my rails as the main driving force.

In doing this I have come to appreciate more the design of rails. It also gives me an insight as to why a high proportion of kneelos are so undynamic in their surfing - because they cannot utilise their main leg muscles etc to propgate kinetic energy (how's that for hot air Beeline ) because pushing off a rail deosn't give you half the energy (hyperbole too!) of pushing against a big raked fin.

My version of a boxy rail Red is take a vertical rail face and bevel it top and bottom then round it out slightly with sand paper.

The trouble I've found with the not-boxy rail is tracking - because of the water flow over the rail.

A hard edge on the top of the rail might fix this by allowing you to break the meniscus tension more easily.

How about another question?

Why are rails rounded off??

But with quads, as you know, that doesn't work because they don't have a centre fin. Consequently I've just spent 18 months relearning how to surf by using my rails as the main driving force.

You should try one of my many 4 fin designs.
Outrageous drive and plenty loose.
I've got combinations for all kinds of surf. Fun play waves and even those death defying places.
see....
viewtopic.php?p=20395#20395

You really can't generalize on them.
When you have 4 fins there's heaps of combinations to get the feel and drive you are after. Change the locations and angles and templates till you find the set up you like. We've gone through hundreds. What we use now is great fun but what we used in the 80's then the 90's was equally so.
There's nearly always a fin holding in to drive off of when you want it.
Unweight to break them free if you like.

Hi Bud

Nice pic.

You're right, I've been caught generalising.

But I stand by the generalisation about the difference between tris with large fins and quads - as far as my own experience and a few of the Aussie guys I know. Not putting shite on quads - after all, they're presently my board of choice.

But I'd be honoured hear how you feel they are different in their dynamics and how a rider needs to change his style between the types.

And I'd like to hear your ideas on rail design, especially in gutless waves.


HW

Sorry lost my way on why I actually posted the thread

One of the original ideas was related to the fulcrum - associated with your Red's thread on rider longer boards on small waves. As far as I can see you can vary the fulcrum point by abrupt changes in outline (most obvious in Aipa's stingers, and wings), by changes in bottom contours (Spiral Vee could be a contender here) and most obviously, changes in fin position.

It ocurred to me that you could also introduce a fulcrum point in the rail by making one part of the rail less easy to bury. It would mean that everything behind that point would mimic equivalent rail length of a smaller board.

John Manss wrote:

But there are many stradigies and design options that can be used.

John: very interested in your design philosphy on small wave boards - not just width, planshape planing area but also the subtleties. Care to explain? EG: Not only do you prefer a fishtail or a diamond tail, but where do you end the hard edge on your rail?

Shelfbreak:

Sorry to make something sound complicated.

Concepts: some rails easyier to bury than others. Easy rails can track - good for longer turns but can cause problems going frrm rail to rail because of the water on top of the rail. Conclusion is that we need different shaped rails for different size (and types) of waves. Another concept: big boards go better in small surf (eg Mals) but have longer turning circle. Can we shorten the turning circle with rail design? Third concept: can we increae ease of rail to rail transfer by decreasing the amount of water sitting on top of the rail by usuing a flat rail - as in boogie boards.

Why do we have rounded rails?

Because "form follows function" or because "form follows tradition."?

Is it all give and take?
I suppose you could make a board that popped rail to rail like a cork, but would it 'move' well with a variety of waves?
I'm wary of boards with overriding tendncies. They are a bit of work to 'learn' and can be a letdown when you least desire.
There's only so much you can do with gutless surf, I know, I surf it all the time. you indicate it might be an equipment flaw. I think its just a 'power' flaw. Little stand-ups can rip in gutless surf (skateboard effect) but anyone over 175lbs isn't moving at all unless they're on a log, and they're not turning, just trimming.
I have the 'gutless threshold'. Buoy has to be 3 feet and at least 8sec for me to even think of bothering, and then I don't expect much, maybe a little cover-up so you look shrink-wrapped in the wave. It's amazing what another foot of size can do for your surfing.
You may have to check "Y" and his (Tom Morey) ideas on board design. I believe he proposed the bodyboard rail system (check 'swizzle').