HULL HYDRODYNAMICS 101, DISCUSSION

[mark ricketts]

let's throw another issue into the bottom / rail combo mix.

Neil Luke's 'freak' design ( I can't do a hot link cause i'm not that bright but just follow the one to island kneeboards)- has a chine - that is there is a panel going from the bottom concave UP to the rail line which he claims lets the board rock over easier. Mitchell Rae used to do a similar thing and called it his "Twin Vee" design but doesn't seem to use it anymore.

any comments from the freak riders out there or those who have tried similar designs... does it work?

and, as frankfqr points out, does it make it easier to "pump" the speed up?

[KEL]

I agree with Masons............keep educating us with this topic!!! I have never been that involved with the bottom of my board. I have always told my shaper how I want my board to perform and the problems I had with the last board. Lift in the rails, double concave, vee....etc is very new to me and am loving the education . I have always just been happy with something that works, now that I have a flashpoint that is so different from my romo's, I am getting very much interested in this topic. I think part of hull design which I am not sure anybody has brought up is how well does the board paddle.....doesnt hull design have a big part in ease of paddling and catching waves???? Not just a longer board or more volume??? Just a thought. KEL

[strudle]

I too have been enjoying this post. I have only been knee boarding for about 5 years and have very little knowledge on the technical side, but would like to add my observations on my Island "Freak" for Mark Ricketts.
I find it very quick, and it turns on a dime. Never had a problem with the chine rails catching and I think it does exactly what Neil says it does. That is the bevels (Mark said panels) help get it off the concave very quickly and easily. However, it is quite slow to paddle. (compared to mate's Island pin and another's Flashpoint). I believe this is due to the huge concave and relatively wide nose pushing water. I use flippers so not such a problem. My flipperless friend found himself missing waves, or late dropping. Once up and running with the nose out of the water it is an extremely fun and effortless board to ride. I would definitely get another.

Forgot to add about pumping. I'm not the greatest at it, but I can definitely make it pickup speed without too much flapping around. and it loves the high line.

[Kev]

I too have a Freak and I also find it harder to paddle
... my newer boards are thick and perhaps a little flatter with less rocker in the middle

as such I have also found myself on a few late drops and the inevitable nose dive
I do have trouble with the nose catching on some cut backs and this prompted me to go for a softer more forgiving rail at the front on my newer boards

in the past I used 123 side fins with a very small centre but since riding my newer boards with a larger centre and further back I'll try 120's all round next time I get on the Freak
this may allow for a position slightly further back and may help me to control the nose

when in the pocket the Freak really does go
I just need to learn how to control it

on choppy and lumpy waves I do get thrown off
the relatively deep concave does lift and perhaps sometimes too much
again ... probably more about my skill than the board

[red]

I believe this is due to the huge concave and relatively wide nose pushing water

While these are probably contributing factors (the width, especially), it is likely the the rocker introduction that is causing a lot of the paddling issues.
I dropped an inch of rocker on my latest model, kept the rest of the rocker the same after the first 18" of introduction at the same time I took 1/2" out of the thickness.
Otherwise the board is almost identical to earlier versions of the model. It paddles really well, despite being significantly thinner than boards I've been using for the past few years.
Of course, the key is in having the right rocker in the tail to start with, otherwise the board will pearl.

[Headwax.]

Yes keep up the goode work.

[KEL]

ID: 14664 - Image Type: JPG - Size: 800 x 512 (45KB)

[KEL]

I want to show this pic for hulldesign water movement and such but not sure how to post it...it was from one of the latest pics posted, if anybody has any suggetions. (april 11th, I think..some guy in a drainout barrell with someone else standing in the shallows watching ) I have some questions............KEL

[Headwax.]

[albumimg]14664[/albumimg]


Hya Kel

you do this:


[albumimg]imagenumber[/albumimg]

cheers

[mark ricketts]

thanks guys for the views on the freak.
interesting point about the paddling - i also suspect there may be some other cause as my Flashie has what i call a deep nose concave and it feels like it almost get "sucked' onto and down a wave. it is a deep pin and I wear flippers so they are well into the water. those things certainly help with the initial momentum / acceleration until this forward tipping feeling takes over. like all concaves though, it prefers a glassy face.

[Casey Patelski]

CHECK OUT THESE PICS OF A 6-0 FLASHPOINT HULL; V NOSE INTO DOUBLE CONCAVE INTO SPIRAL V IN THE BOARDS ALBUM DATED 4/18/08. CASEY

[/img]

[balzig777]

True hull utilization and reference are items that are not touched on at all in these forums. :? How the water is channelled an directed thru the tail is not a discussion regarding hull in my minds eye. I see it as a leading bottom curve or contour directing water flow over a soft round rail creating lift and hold. Something totally different from the majority of shapers and riders mindset. Skip Frye and Steve Lis still embrace this basic concept, nearly all others incorporate a chine to some extent. As I ride a soft rail I can weight and unweight the forward rail to allow it to engage or not. Just part of my kneeriding arsenal. With chines and harder rails I feel a need to pump it or work to maintain the high line :x As GG declared,"Neutral Handling", the board naturally seeks the sweet line, maximum speed line. Parksey has it right, "surfer with most control."

Water never really channels off the end of the tail all water flow is at some angle depending on the turn and placement in the wave. concaves give lift, vee holds the tail in as vee sinks, channels don't direct the flow as much as they add rocker in the off the tail designs, or a flat spot in the centre of the board design. The rocker is very important in kneeboard designs, a concave or flat area has to flow into a specific amount of tail rocker ,vee or not in the tail, channels, tri hull designs all have their place but must flow from an area where the rider controls the board (sweet spot )Lots of designs are viable but all have a point of diminishing returns..... I'm just saying

[frankfqr]

Hello Mr. zig.....at least your post is following the true intent of this specific forum, a breakdown of the all emcompassing hull, nose to tail. I excitedly chimed in when presented with the forum headline "hull hydro's." I'm obsessed with the holding power of the rolled nose that GG laid down before us. Not the deep hull nose by any means, but a subtle roll leading into a soft rail to attain that lift and hold. Concave, tail rocker, tail beads, venturi, directional flow can all be dialed in for speed, but on a jacked up verticle face the forward rail entry becomes my focus, the high line, "fall line," maximum speed. If a shaper doesn't embrace that style of forward rail then it's not for me. Hence I shape 95% of my boards.THANKS HEAPS for joining in!!!!

[red]

or a flat spot in the centre of the board design

Zig, I know you by reputation and remmember a seeing a lot of your boards around when I lived in SD. It's good to see you on board.
I'm interested that you say the connie flattens rocker. I use the same stringer rocker in vee and concave boards because I believe that a good rocker is a good rocker. Of course the rail rockers are quite different.

I'm interested in your perspective.