quad question?

[red]

Despite the excellent explanations about how quads work, and even a bit about when/why to ride one, I am going to challenge your mental models about how boards work, then we can try to relate it back to design concepts we know.

Consider a board without fins. Every characteristic then depends upon rocker. Before you get too excited, think of the board as a rectangular curved plane, from nose to tail.
Now put in a bit (or a lot, Headwax!) of concave- this changes the rocker (and water flow) through the centre of the board.
Put in V - this changes the rocker at the rails, relative to the centre of the board, again modifying water flow.

Now cut out the plane shape of the board and shape the rails. Notice how the rocker changes at the edges of the board. Rocker goes to infinity as you move around the rails to 90 degrees from the bottom plane.

Remember the water flow is generally parallel to the stringer, bar some speed up effects in some regions like the rails and edges of concave (remembering that the plane shape of the board gives virtual rocker when the board is on edge - the rails change the rocker from infinity to a smooth curve and back to infinity as you follow water flow front to back of the board).

Without having explained myself very well, I move to the point:
Why don't we have thruster shapes with 4 fins? Is it because we don't know where to put the fins (the 2 trailers gradually migrate to the stringer to make a single fin, as in a thruster) or because the drag is unacceptable when the rocker/area ratio falls below a critical value? Do 4 fins need relatively little rocker in the tail (to maintain lift), hence the v is spread over greater width?

If you've suffered this far, don't abuse me for trying to change the world. I'm trying to formulate an alternative model that will help me better understand why I should ride a 4 fin in 1' surf, rather than a purpose designed thruster, and how that thruster might be conceived.
Geez Steeno, you got me thinking....

[Steeno]

well red.....thats what these post are about.....making us think, its certainly done that to me. Isn't it great

[Bud]

More about Lee's board..........

Lee didn't have much / or any money and most times still owed me for a board by the time he broke it, which was fairly often.
He showed up at Pipe that morning with the 5'5 1/2" fish.
I think he also had a 5'8" like it at the time.
But Lee really loved his shorter ones and never hesitated to use them unless at a really big surf arena like Sunset or Laniakea / HUGE lineup , MASSIVE walls.

It was our standard everyday ride of the time.
Made for shoulder high to 12' face waves.

The fins were, as I said......roughly 3 1/2" high & 3 1/2" base.....each. They were set closer to the tail than modern boards.
Front fins about 12" up and all about 1 1/2" in from the rail. Back fins set base width apart.

We tuned them a little differently for less powerful types of surf than mid winter North Shore. Like a bit less V, sometimes short channels just ahead of the fins for a bit of extra lift, and more edge etc, etc.
The plan shape / outline pretty much stayed the same.
We rode them in most every type of surf other than tiny mush dribble.
Here's the same kind of board being ridden in average surf.
http://www.blasthawaii.com/photo_pg/Haw ... hawaii.jpg

[hart]

Hello again to all,

Kneeboarding to me is about surfing in all types of waves..so many variables, so often.. to which we all seem to qualify ourselves..and me included.

And this post is just that.

If we want to go in a straight line, purely because the waves we are riding demand it, I reckon that we would still be riding single fins..like, why wouldn't we?

Down the line..down the mine..almost too easy. Just design something to counteract the power of Nature. Simple. Go the keel fin Nat rode in 'Voyager' and you at least reduce the drag of 3 (or two) other fins..don't Dolphins do that? Just adjust the size, because we can.

But if we want to be Human (which we are) and do things that are beyond what we consider is purely tolerance and necessary for survival, then we will look beyond the boundary of simplicity of force and look to create our own dynamic..Hmmn

Mark Richards has done this..and so has Simon Anderson. We are now a part of the 21st Century..and we can learn more, if we choose.

Bottom turns in big waves are only one facet of the multiplicity of surfing..and that's what these posts are all about..they consider all the turns we strive to achieve..once we come off the bottom (if the wave allows) then what next?

Single fins (and the concept of bottom turn bite) suffer when we get to the top, or to the shoulder..or even to a wall.

I know this is a standup comment, but what have the last ten Pipe Masters actually ridden? And I know we don't stand up..but are we paying attention to what's happening around us? Or more to the point, do we care?

The post above shows another HOT pic of a kneeboarder doing a bullshit slash..heaps of spray. Imagine seeing it in the flesh?

But I can't get my head around the body postion or his eye contact..like he's had to do something to get the tail around and it doesn't look like he's in control of his equipment..it looks like it's controlling him.

I my opinion, you can never take your eye off the ball, so to speak.

Looks like hard work to me..yet whenever I see something natural (and when I'm not looking at me) it all looks too easy..like Andy Irons in a barrel and Farrer in a cutback or Nov in a roll..like how do they do it?

It all goes with the flow.

Regards forever, from OZ.

[Steeno]

Thanks Bud

I think that confirmed what I was tring to say

fins near the tail=rail tail drive=one stage carves-solid wave(more spray)
fins up the board=pivotal fin turns=more nursing-fat waves (less spray)

All through the 80's I rode thrusters with twins set at 12" from the tail with lotsa rake in em, and a full size third fin set at 4". They never surfed small waves well, and Parkesy was all over me about it ( I was not riding daves boards then). Majority of comps are held in crap waves, hence my growth in board change over the years, I still have my big wave boards with fins near the tail. As this discussion actually started about four fins, it should have been more about placement, not numbers.

sorry if I confused you drstarnge

[surfhorn]

I was able to handle one of Bud's Y2K quads at the November contest in Santa Cruz, although didn't get to ride it. I was interested in that he had set the rear set of fins inwards toward the stringer more than other quads
(3 1/2 inches off the rail on the leading edge; 2 1/2 inches off the rail on the trailing edge).

After riding singles/tri's/thrusters all my life, I've always found the flatter ride of a twin/fish/quad not exactly my cup of tea. But the new fin placement coupled with added board length is sure making my KBing life fun again.

I really think that there should be time set aside at our Gatherings to make various shapes available for others to ride. I will be bringing my new quad (and, hopefully, a newer thruster design) to Jalama. I will also find some other boards to share (new & museum pieces). Maybe we can hold some sort of design forum during that weekend.

Which shapers can make it to Jalama in May? And keep the dialog going - it is truly helpful to all.

-Dan

[stemple]

I ride both Parkes quads and Blast boards on weekly basis. In my simple understanding I must say that the fin set up on the boards makes big differences. Bud's template is very different and I think some the attributes of his boards are due to the position of those two back fins. Those trailing back fins seem to allow full on rail, driving bottoms turns. The parkes can do the same but the fin cluster being tighter and slightly farther up the board means you have to finesse the turn a bit more. Body position seems to be a bit more critical in the fin forward quad designs. I think when you have fins under your shins how you weight through the turns really can impact the position of the board through the turns and thus significantly change the response of the board.

I think the blast trailing fins really come into play as you start to initiate the turn. They give excellent holding power and really allow you to throw alot of weight into turn and get the board on its rail. The closer, fin forward, cluster of the Aussie quads needs to be initiated in a slightly more controlled fashion.

(In some of the videos of Don Harris riding his Parkes Quad watch how subtle and smooth he initiates those turns, especially off the bottom. No doubt this smooth "style" is derived through years of riding Parkes quads.)

Once the board is begining to get on its rail then you can crank through it. In short I have noticed if I try to surf the board (aussie quad) too hard it can slide a bit. I would agree with Steen that a good hard push with one cheek can get it moving about. You must ride the board instead of the board riding you if that makes sense. They are very subtle differences and I would think most kneelos can adapt to the characteristics of the board they ride often.

What effects of fin position are other people observing on other boards? I am sure this maybe overly simplistic but it is based on the day to day observations of your average kneelo.

[DrStrange]

sorry if I confused you drstarnge

Now that IS strange! This is a great thread. Feel like a fly on the wall at a convention of design meisters.

[Beeline2.0]

..

[stemple]

Beeline here you go;

The Parkes Quad has less rocker both in nose and tail. The Blast has slightly more tail rocker.

Fin area is close but the blasts are less by about 10%

Fin toe-in is about 3 degrees greater on the Parkes.

I will post a pict in the boards gallery of them side by side soon (technical issues)

[Beeline2.0]

..

[Steeno]

This has been a good discussion, with awesome valid points from the vast range of lifestyles within the kneeboard community. The strange thing is, we all come from different parts of the world and ride different vehicles and most importantly ride different waves of different size and power. This has everything to do with with our fin placement, amount of fins and the way we surf waves. For example, buds boards are made for consistent power and size and form, which in reality is different to say where I come from, and probably where you come from aswell. Dont get me wrong we all get big solid waves where we live, but defiantely not as consistent as say Buds backyard. At the start of this forum I was asked to explain why I was riding a four fin. I expressed it was for small waves to stay competitive, really against guys almost half my size (like albert), I am 6"4 and 105kg which I think is about 230pounds. As you could imagine, if your my size, small FAT waves are difficult to ride, let alone get some sort of speed on. Hence why Dave made me a board that would run as fast as possible with as least drag as possible, for me, this just happens to be a four finner, fins up the board. Making a board with flat bottom, forgiving rails and a board that when you do a jam wont drag the back fins/fin around or catch a rail, to basically keep the momentum of the board going down the line. In tiny waves, momentum and no drag is the key to being able to do multiple manourves without losing speed, great little comp board for crap waves. Now my boards that have there fins near the tail thruster or my other four, wont do this even if you make it flat and forgiving rails, to much drag and effort required to throw the board around, hence losing speed, you can do one big bang of a manourve on them and then the board slows down to much in crap waves, making it super hard to get another turn in. Not good in a comp, when the other guys get three or four manouevres in. You may have done the biggest manouevre in that heat, but there was no flow going on. I know I am talking about competition here, but that is how we got to where we are with board design-to stay competitive. My ignorance to this over the years, (everyone kept pointing it out to me) held me back in comp surfing, didn't worry me free surfing, I always enjoyed doing one big hit free surfing, but it held me back in the comp arena. With fins near the tail, I tend to surf of the tail, wich when you watch it on video in small waves, i was actually pushing water out the front of the board in small waves-making it harder on myself, once I broadend my view and actually rode fins up the board, till I felt comfortable on it, when I saw it on video-the water pushing had virtually stopped and I was going faster and doing alot more turns. The four fin also made it more pivotal, so on small waves I could just tweak that cheek and be on the 1ft lip in an instance, rather than trying to draw my up there. Now in crap waves i can actually link turn after turn, instead of turn, stop, pump up some speed, turn then try to pump up some speed again, just so i could drag the tail around.

thanks for reading my ramble, hope that makes sense, and this is what works for me.

cheers

[surfhorn]

The last KB I rode prior to my 4 year hiatus was a double wing swallow thruster - all the same size fins. This board was a culmination of riding Santa Cruz/ Monterey Bay waves since the beginning of foam KBs.

I had experimented with fin placement and that last 5'8" thruster had the rear fin in the normal (approx 4" off the tail) but I had bumped the side fins up so that they were just in front of where my ankle rested on the board. The KB had hard, off the bottom drive but I was still able to pop a verticle, under the lip snap and a powerful cutback. Needless to say, a great board.

After riding my 6'0" fin forward quad this winter, I'm really happy with the ease of paddle and flat out speed of the quad on big waves. Not many small waves to ride (wish we all had this problem, right?) But I miss the the square, off the bottom snap of the thruster.

I'm going to dig through the order forms (probably over 1,000 foam-dust-covered forms) and find the fin placement measurements for the old thruster. I'll then apply that to a new 6'0" and let you all know what comes of it. Hopefully, it will be ready for the Jalama Gathering.

-Dan