Board outline, with and without fins

[nomastomas]

Warning: If you have no interest in the “why” of surfcraft design, and would rather simply ride different boards until you find one you like (time honored tradition), please don’t waste your time reading this thread. Believe me, you’ll just be bored and may even get irritated.

Waiting for Delores to arrive, I’ve been mulling over board outline, as it relates to fin vs. finless designs. The act of riding a surfcraft (prone-ridden craft included) is a very dynamic endeavor. Determining what works and how, is not for the faint of heart. In looking at this question, I decided to start with what’s happening when the board and rider (B&R) are traversing the face of the wave. Sounds simple enough, but immediately I became stuck on defining the position of the B&R relative to the wave-face. So I started to nail down some of the variables: Wave height = 4ft, direction of rider = “going right”, location on the wave = upper-third . So far, so good. Then I began to define the position of the B&R in aeronautical terms; pitch, roll & yaw (see drawing). The pitch of B&R = slightly nose up (for the sake of argument), roll = slightly to the right (as rider counters upward flow of water by weighing the wave-side rail), and yaw =??? Yaw is a flat rotaton on a horizontal plane. Yeah, that’s where I got stuck. So I drew up a simple diagram (being a simplistic sort of guy) based upon my experience riding prone boards in the 41’ to 51” range. As a unit of measure, I’m using the degree of offset between an imaginary line representing the wave face and the centerline of the board, where the centerline of the board and the wave-face line intersect at the center of the tailblock. In reality, the exact point of this intersection maybe elsewhere at any given time, but just trying to keep it simple at this point. So below is the drawing I came up with, using my favorite bodyboard the Morey 7-7, as the outline. (Just about everyone who rides prone has ridden a Boogie board at one time or another, so it is a good frame of reference.)

My question is, to those still reading this thread, “what do you consider to be the typical “yaw” position while riding across the face of a wave?” I guessed a 12° but you may guess otherwise. (Hint: no right or wrong answer her, just trying to get a consensus opinion)

[kfitz +]

Fun and interesting read ,if it leads to fine tuning outline design and fin hold ,or finless function with less drag. Your disclaimer about relative position at any given point in the wave face makes sense, but multiplies the variables of optimum pitch roll and yaw not withstanding wave shape . I'm in ! This thread also validates my favorite mindsurf daydreams (work,home,etc.) . Now I can dwell on design and not the flat,gutless summer surf here in Ma. One thumbs up here

[krusher74]

Hi, well I read your post and had a look at some photos I have, I would regard this wave to be about a symmetrically perfect as your gonna get.

In all 3 pics I am just trimming to go straight along the wave, so not dropping down or turning up in anyway.

I would say we ride in the lower half of the wave mostly. I lost in your post what your trying to do, relate board outline to something?

I hope the pics will help you measure the angles your talking about.

[rodndtube]

As Keith's middle and bottom photos show there can be quite a different degree of angle for the Board and Rider when "going straight along the face" of the wave. That is the case for me as well. And I find myself turning in all angles along the face of the wave. This is a tough nut to crack, Tomas.

[SJB]

Nomas and I had a sterling outing at C St. in Ventura this morning and discussed this very question. I am inclined to agree with Nomas that if you are going to generalize 12% seems about right....but to Krusher and Rod's observations there are a lot of variables involved here given the many shapes and sizes of the playing field. Stating the obvious this is not like stepping out onto a never changing tennis court. Lousy analogy....but best I can do. So I am going with 12% plus or minus 5% depending on too many variables to list here.
The purpose of our outing this morning was to test drive a 46 inch TBG4. I have been incredibly happy with my 43 inch TBG2....but Nomas got me seriously thinking about leg and swim fin drag....not a problem on a larger juicy wave but I have noticed drag on smaller waves. The extra float and length of the 46 did help (hits me mid thigh on the plane rather than at the hip joint) so I ordered up. For the record in my old age I have shrunk to 5'8" inches tall and 167 pounds and the surf today was in the head high range. Right now with the remnants of Hurricane Dolores it feels like the tropics. A very sweet outing.
P.S. Rod...my Austin is languishing in the garage....and forget that center fin old school. You need to come out here and test drive one of these T Bellys.

[krusher74]

Nomas and I had a sterling outing at C St. in Ventura this morning and discussed this very question. I am inclined to agree with Nomas that if you are going to generalize 12% seems about right....but to Krusher and Rod's observations there are a lot of variables involved here given the many shapes and sizes of the playing field. Stating the obvious this is not like stepping out onto a never changing tennis court. Lousy analogy....but best I can do. So I am going with 12% plus or minus 5% depending on too many variables to list here.
The purpose of our outing this morning was to test drive a 46 inch TBG4. I have been incredibly happy with my 43 inch TBG2....but Nomas got me seriously thinking about leg and swim fin drag....not a problem on a larger juicy wave but I have noticed drag on smaller waves. The extra float and length of the 46 did help (hits me mid thigh on the plane rather than at the hip joint) so I ordered up. For the record in my old age I have shrunk to 5'8" inches tall and 167 pounds and the surf today was in the head high range. Right now with the remnants of Hurricane Dolores it feels like the tropics. A very sweet outing.
P.S. Rod...my Austin is languishing in the garage....and forget that center fin old school. You need to come out here and test drive one of these T Bellys.

Do you know how much more volume the 46 has over the 43?

The last board I had was 25L to attempt to match what I though was a previous 25L board, the new one had loads more float so I guesstimate the old one was only 23L, The 2L difference feels huge, makes the 25L board feellike a minimal and a handfull!

[SJB]

Old one 21.5L....new one 23L.

[Poobah]

I tried looking for some Bodyboard video that was shot by helicopter or aerial photography. But I ran into problems, because helicopter and aerial have other meanings in the bodyboard universe. Can any of you recall any bodyboard vids filmed from above?

Meanwhile...here's something for the quadfin guys to laugh about.

[rodndtube]

Camo shark proof?

Pondering what board to take to the Pacific Northwest next week... the Bonzer Paipo or the Orange Matter (Baseline Austin). Thinking the baseline Austin since it has more float than my bonzer. All that rubber stuff adds up in tonnage! Gives me more time to contemplate my slide angles. I do like the drive from the center fin on those PNW waves

P.S. Those look like very skeggy rails on that camo board.

[nomastomas]

Wow! After viewing Keith’s photos, feedback from Rod, watching SJB ride waves today (where was my camera?) and my own experience today, my mind is just buzzing. First off, C St waves are nothing like the waves in Keith’s photos. Even at head-high and above, the wave never really throws-out. “Spills over” is a more apt description (see photo below). For that reason the wave is only “steep” in the upper third, which is where you have to stay or risk stalling. Nonetheless, I would say that there is a lot to be learned here.

To clarify, I’m interested in defining the relationship between a belly board’s outline (mostly defined by the location of the wide-point) and its performance, with and without fins. Are some outlines more efficient, i.e less drag, than others? How do fins change the performance dynamic?

So I started by looking at the interaction between the B&R and the wave face. After looking at Keith's pictures and watching SJB in action, I think the angle is more like 15deg. As has been already stated, this action is very dynamic, changing as the steepness of the wave changes, and as the rider's intended direction changes. Looking at Keith's first two photos, it can be seen that the forward rail intersects the wave face about where his elbow is on the deck. Plotting an imaginary line from that point to the center of the tailblock should represent the wave-face line. (although, the vertical curve of the wave face presents a problem. Nearly the entire tailblock is in the wave!) A second line drawn longitudinally along the center of the deck appears to deviate about 15deg from the wave-face line. This is very close to what I observed today, and is consistent with what I I have seen in other photos. Now we all know that waves are curved, both vertically and horizontally, but at any given moment, the segment of the wave occupied by the rider and board is essentially straight, horizontally. The curvature of the face and how the B&R fit into that curvature is another matter. More to think about....

[nomastomas]

Camo shark proof?

Pondering what board to take to the Pacific Northwest next week... the Bonzer Paipo or the Orange Matter (Baseline Austin). Thinking the baseline Austin since it has more float than my bonzer. All that rubber stuff adds up in tonnage! Gives me more time to contemplate my slide angles. I do like the drive from the center fin on those PNW waves

Here's one of my customers riding a "full-bodied" 51" TB1 at the 49th parallel in the summer. Float is a good idea....

[rodndtube]

C Street can be a very nice break. Only have ridden it a couple of times but the best was actually about 33 years and one month ago (late June 1982). From the peaks all the way down towards the pier. Like you said it wasn't a Pipeline type wave but I do like those long walls for carving, turning, coming off the top, blah blah blah. Looks kind of crowded in the photo above and the other couple of times I have seen it.

Simple is straight rails should be the fastest? Tear drop shape is technically slower but also holds into the wave better. Wide tails (guitar pic HPD style) can be fast but also very loose. Where would you put the fins on a board with nearly parallel rails with no discernible hip in the board. Of course, it is all a series of compromises because I probably would not like the "fastest going straight shape" as one can generate speed off of maneuvers and use of the skegs.

[JJJ]

Was watching a Greg Daniels video on youtube; he takes water shots/video at various spots on Oahu. Mostly shorebreak. The following link is a video of a fun day at Makapu'u: https://www.youtube.com/watch?v=OQfv0x-4nqU

There are a couple of underwater shots of body boards going down the line that gives a clear view of the boards planing surface in contact with the face of the wave. One in particular stood out at 4:18.

If anything, it's a cool video to check out.

[bgreen]

Nomatomas,

I asked Larry Goddard about his thoughts on your questions. He liked the analytical approach adopted and his comments follow:

"I think the Yaw angle of a board on a wave depends on the steepness and breaking or Peeling Speed of the wave a lot, in addition to the outline shape of the board, and
the speed of the board across the wave face. All the boards I designed for myself to ride in big, fast Point Break surf had skegs, so had a minimal Slip Angle, or Yaw.
I started out on the flat-bottomed Paipo Nui, which had a tail that was much wider than the nose area, giving the outline of the board at the rails a sort of
triangular outline profile. That makes the centerline of the board point inwards toward the wave face when you are in full trim going across a wave, BUT, when you
lift the rail up in the air to carve a turn, the centerline of the board then points in the OPPOSITE direction of your intended curved path! It's dynamically UNSTABLE!
It fights you when you want to change direction, as in a cutback. That's why most paipo riders just prefer going fast, in a more or less straight line. But, that's
all right; they're all 'SPEED FREAKS', anyway! That's why I started designing and shaping my own belly boards: I wanted to find a shape that would make it easier to turn, yet still be FAST enough to make most waves.

I decided on the best 'slip angle' to design my board for, and made the nose wider, but with the tail only slightly narrower than the width at the Wide Point. The
result of testing my designs in fast Point Break Makaha surf (10-15'+, mostly) was that the tail width was about 3 inches less than the width at the widest point, with
the Wide Point a couple inches forward of the Center Point location. The slip angle of my boards (with the skeg or skegs installed) was only about 6 degrees, at most.
The mathematical curve that best fit those requirements was the Exponential Curve. That is what I used on all my High Speed boards. 'Hot dog board' shapes use a more Elliptical outline (or Plan Form).

I don't care for the skegless 'slip-'n-slide' feeling of bodyboards, or even wide-tailed 'Guitar-Pick' style paipo boards. Oh well... it's all relative."

Swaylocks might have some interesting stuff:

http://www.swaylocks.com/groups/theory-balance

From a pronish perspective Rod saved a lot of Terry Hendrick's stuff.
Bob

[bgreen]

Poobah,

boydboard + drone footage

Lots of hits.

Bib

[krusher74]

I have also surfed Cstreet on my travels an would put that wave in the middle ground of waves for shape and power.

Today I was on in uninspiring 2/3ft onshore beach break conditions. I took out my BZ retro boogie board (retro is the model name) it very wide nosed and tailed with a very straight template the wide point is forward of middle http://www.wireplanet.com/ecom/stores_a ... 0large.gif

This is the boar I use in less than powerful conditions. I notice today on awave that went very flat on me that to keep speed I move very far forward on the board at one point till my knee caps are on the back corners of the board. I fellthis is to move up till weight is over the wide point. This board in its straight template is very fast ,but slow an hard to turn with its lack of rail curve.

I put this board forward as about as straight railed/wide and wide point forward as anyone would need (unless they just wanted to just straight line a wave.

I took it on a trip to G-land one year as an experiment and once the wave was over shouler high it was out of control,I see it as my minimal paipo. (I call it "the log")

How do you think its angles fall in your study nomas?

[SJB]

Krusher wrote: "I have also surfed Cstreet on my travels an would put that wave in the middle ground of waves for shape and power."

Here we go again with a "generalization". Since C St. is 30 minutes from my door to shore I look at it daily on the web cam....and some days it is weak and I don't bother. Medium days can be lots of fun.....and on power days I typically don't go. It can run the gambit....again....depending on too many variables to list here.

Rincon is 20 minutes from my door to shore.....I would also rate that as somedays too weak....somedays just right....and somedays too powerful FOR THESE 69 YEAR OLD BONES. Send me some youth!

This time of year C St will get some south swell action....Rincon seldom. Winter north swells will typically get into both but here is the deal....Rincon can be a cluster F given the crowd and demographic. C St. has more take off locations which can make it less agro and more fun.

Having said all of this....when both spots are too powerful for my old bones....there are several less traveled spots that give me all the action I can handle with a smile on my face.

All of this is to say I thank my lucky stars each and every day that I live where I do. Come on out....but don't stay too long.

[krusher74]

Krusher wrote: "I have also surfed Cstreet on my travels an would put that wave in the middle ground of waves for shape and power."

Here we go again with a "generalization". Since C St. is 30 minutes from my door to shore I look at it daily on the web cam....and some days it is weak and I don't bother. Medium days can be lots of fun.....and on power days I typically don't go. It can run the gambit....again....depending on too many variables to list here.

Rincon is 20 minutes from my door to shore.....I would also rate that as somedays too weak....somedays just right....and somedays too powerful FOR THESE 69 YEAR OLD BONES. Send me some youth!

This time of year C St will get some south swell action....Rincon seldom. Winter north swells will typically get into both but here is the deal....Rincon can be a cluster F given the crowd and demographic. C St. has more take off locations which can make it less agro and more fun.

Having said all of this....when both spots are too powerful for my old bones....there are several less traveled spots that give me all the action I can handle with a smile on my face.

All of this is to say I thank my lucky stars each and every day that I live where I do. Come on out....but don't stay too long.

For the sake of the topic of this thread its runs the "gambit" of on its average day a medium wave in my opinion, so I will stick to that "generalization"

How about your opinion on board outline compared to wave shape? (sending you some youth )

[SJB]

Apologies for my uncalled for outburst Krusher. Thanks for taking it in good humor and sending me some youth. As a generalization I will accept your C St. observation. I have 55 years time in grade in these waters and I love them and I got a bit defensive. Fact remains....on some days C St. can be powerful.
Now...as to the angle of the dangle....look back and you will find I already put my two cents in on that subject earlier in this thread. You will see I have the "generalization" theme on the brain. Not very technical but with a playing field that is constantly in motion and flux how can there be an exact answer to such a question?

[rodndtube]

<snip snip>
...You will see I have the "generalization" theme on the brain. Not very technical but with a playing field that is constantly in motion and flux how can there be an exact answer to such a question?

Yup, that is the biggest challenge. Not only the playing field being in constant motion but in many cases the rider as well. The danger is maximizing one board attribute with the unintended consequences of diminishing other board attributes. Nonetheless, it is fun and can be rewarding to walk/ride down this path.

Off-topic for this thread: The old brain does numbers on me at times, too, oh, all too frequently! Sometimes, if it is weaker at a given break it forces me to say something stupid like it is only 2-3 ft instead of 4-6 ft. But on-average, Rincon (Calif.) and Fairgrounds/C-St, break rather well with their nice stable point break qualities, even on less favorable surf condition days. The crowds and behaviors... that is a whole different story in "rating" wave/spots.