TBXL

What works and what doesn't. Share design ideas, references and contacts for paipo board builders.
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nomastomas
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TBXL

Unread post by nomastomas » Sat Feb 24, 2018 11:53 pm

After discussions on the G5 thread, I decided to start another post specifically documenting my attempts to design a better “big wave” belly board. “Big wave” is a relative term, and for me it means waves with face heights in excess of 6 feet, more typically in the 8’-10’ range, which I occasionally see at my local break. On rare occasions, my local surf heights will push into the triple-overhead range, but I’m always content to watch from the beach on these days. I’m hoping that this thread will generate more discussion, and to that end I would invite everyone’s opinion.

The key design concerns I have gleaned from the G5 thread is the need to mange the impact of less than ideal surface conditions, and the need to control the speed and consequent lift that comes into play when surfing larger, more powerful waves. To this end my first attempt has a spear-like outline, with peaked nose, wide-point forward of center about 2”, and a winged square tail. In laying out the dimensions, I wanted only enough deck area to keep my body from contacting the water. Essential, I wanted the deck to mirror the outline of my body, but with roughly an inch margin all the way around. The intended deep V bottom entry made my preferred diamond nose shape impossible. A peaked nose was just more suitable. My new goal dimensions reduced the the size of the outline as compared to the G5, but it is still a wide tail. Tail width impacts turning radius. A wide tail is harder to turn than a narrow tail. One way to compensate for a wide tail is to increase tail rocker (conversely, flat rockered boards are made more responsive by narrowing the tail, e.g. big wave guns). Another way is by adding “bumps” or “wings” in the outline to rapidly reduce tail width. With this shape I did both, increasing tail rocker from zero to ¾” and by adding the wing 10” up from the tail (which is also where the trailing edge of the front quad fins will be located) The combination of the toed-in fin and the bump in the outline serves as a pivot point for turns when on rail. The tail was left square to maintain efficient water flow along the bottom for as long as possible (which is when it encounters my trailing legs) The width of the tail at the wing is almost 17” while the tailblock is 13.5”. Wide point is 20” and the nose at 6” down is 13.5”. I increased the length from 49” to 52” primarily to compensate for the loss of volume when I narrowed the outline. The pulled-in nose will allow me to grab the rail 2-3” below the nose but still have my elbows on the deck.

The shape incorporates an extreme “V” nose-to-flat bottom design, with wide-point forward and thickness flow (or foil) skewed towards the front. I want the front of the board to cut through chop and to resist lifting. At the same time, I don’t want the nose to be prone to pearling, so I have set the nose rocker to 3.25”. The bottom transition from deep V to essentially flat is in about the middle of the board, with a corresponding change in the rail shape from a tightly pinched (almost up-rail) shape in the nose to a softer, 70/30 rail mid-section and then an almost hard down-rail in the last couple of inches. Gone are the concaves to minimize lift and speed; the flat bottom will be fast enough.

Questions? Comments?
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Re: TBXL

Unread post by jbw4600 » Sun Feb 25, 2018 2:04 am

Looks good. I'll take 5. Can you show a better outline shot?

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Re: TBXL

Unread post by nomastomas » Sun Feb 25, 2018 2:48 am

Outline looking down on deck.
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Re: TBXL

Unread post by krusher74 » Sun Feb 25, 2018 6:52 am

The one thing I found from bodyboarding over the years is the the bigger the wave the smaller the board I prefer.

In smaller waves the extra planing area and rail volume of the board helps both catch waves and generate speed on them, in big waves these attributes are a hindrance. Too much rail volume and the board wants to pop out of the face and loose traction, you cant sink it in the face and get it to bit hard.

I'm lucky that the magic board you CNC modeled for me works better than another board I've have in good waves from 1ft to 12ft. The only time any other board i have performs better is in very soft small waves and that just the fact that the fat bodyboard I would use had a large gain in volume.

I really enjoy the up-rail at the front of my board.

Lots of interesting ideas on your design.

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Re: TBXL

Unread post by nomastomas » Sun Feb 25, 2018 8:06 am

I agree with you Keith about the up-rail nose. I think I started going full up-rail nose on the G3. Its very forgiving and adds a little more rocker out at the rail. What's been your experience with the" skipping stone" phenomenom?

Here's a head-on view of the nose:
TBX1e.jpg
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Re: TBXL

Unread post by rodndtube » Sun Feb 25, 2018 2:00 pm

nomastomas wrote:After discussions on the G5 thread, <snip, snip>
Questions? Comments?
Nice discipline and articulation in trying to pull together many of the theories and comments in the 6-12 ft. mitigating chop hop discussion.

My only comments as I mull things around the wetwear is that the diagrams present very sharp rails throughout the board. The "V" also appears to extend half way through the board. Challenging to visualize some of this stuff!

Looking forward :)
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Re: TBXL

Unread post by nomastomas » Sun Feb 25, 2018 8:27 pm

You need to keep in mind that what you see is what the blank will look like after machining. The process of finish-sanding the blank will dull the sharp edges in the nose, as will the lamination. The rails are pinched but soft until the last 6" of the tail. Here the edge turns down but with a slight tucked edge. Edges release water, but down hard rails with sharp edges don't offer enough hold. I always want a little water to wrap around the rail before it releases, even at the tail. But, I always want the tailblock to have a firm, down edge so that the water is forced to let go. Water is actually very sticky, and wants to adhere to smooth surfaces. In the "Slices" view below, notice how there is no hard edge after the first 4"-6" in the nose.
TBX1f.jpg
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I have the extreme V deepest where the bottom enters the water when in a normal, planing position. It becomes progressively less deep and more flat as it moves rearward from the "entry" location, and becomes completely flat in the last third of the bottom where most of the action takes place. When paddling or moving down the wave face at less than planing speed, most of the bottom is in contact with the water. But at a certain speed, the board begins to lift out of the water, typically the nose first and then the rest of the bottom. Very much like a power boat, at planing speed the front third or more of the hull is out of the water and the rear third remains at or close to the water surface, which is why I say that is where the hydrodynamic action occurs. Of course, shifting over onto the rail completely changes this dynamic due to the loss of planing surface. As speed increases lift increases but much faster. Rough water or chop can act as a ramp, which also increases lift. Deep V entry serves to slice through this ramp instead of riding up it. So, I'm hoping that the shape, with speed, will lift and ride on the rear flat, and that the entry V will come into play whenever the water surface becomes uneven. (It occurs to me that the analogy to power boats is weak, in that power boats rarely go "downhill". At least not typically)
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Re: TBXL

Unread post by bgreen » Tue Feb 27, 2018 6:01 am

Nomas,

A couple of comments.

Regarding wide tails - my boards have tails varying from 20" to 15". I've never had trouble turning these.

One potential issue with the new board, is that so many variables are being changed it may be difficult to know what aspects of the new design make a difference.

I had a wave today where there was a significant skipping. When we talk about skipping, there probably are a few varieties - high speed propelled skipping and the bumpy, less forward propelled bounce. The type of chop is probably a variable. Today, it was more the bumpy, less forward propelled type, where just hanging on is an issue. The difficulty dealing with this is that the focus becomes hanging on, making it difficult to get too fancy in trying things to reduce bounce.

Then there is the issue of big waves versus choppy big waves.

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Re: TBXL

Unread post by nomastomas » Tue Feb 27, 2018 3:06 pm

“Regarding wide tails - my boards have tails varying from 20" to 15". I've never had trouble turning these. “
Just to clarify, I’m not saying that wide-tailed boards can’t be turned or even that they are difficult to turn. I’m only saying that with all other things being equal, e.g. rocker, volume, fins, length, etc, a narrow-tail board will have a shorter turning radius and will be experienced as more responsive (quicker turning) than a wide-tail board, an admitted generalization widely accepted by most shapers and riders. The same is true for board length; in general, shorter boards turn easier/quicker than longer boards. And finally, one of my favorites, fins offer more directional control than no fins.

“One potential issue with the new board, is that so many variables are being changed it may be difficult to know what aspects of the new design make a difference. “

A surfcraft’s performance is more than the sum of its parts. It’s difficult if not impossible to determine the contribution of any one particular design feature outside the context of the integrated whole. Surfcraft designers are accustomed to considering the integrative impacts of multiple design features. For example, how tail width, outline curve, fin placement and rocker all combine to impact turning. The proposed design is purposely quite simple; deep-V-to-flat bottom, relatively narrow, wide-point-forward outline. Volume has been maintained at 23L. The simplicity of the new design will help to identify those features that have an impact. My money is on the deep-V.

Lots of wave condition possibilities to be sure. My local point break is relatively slow and sloping, even at size. And yes, there is speed-generated lift, and lift caused by “ramping”, which can be due to surface anomalies (chop) or from striking the surface at a less than optimal angle, typically on take-off. And of course, a combination of the two, which is what I usually encounter and will be the conditions I’ll be testing in.
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Re: TBXL

Unread post by krusher74 » Wed Feb 28, 2018 12:36 pm

[quote="nomastomas"]. What's been your experience with the" skipping stone" phenomenom?

I think i've missed if some other thread what were talking about here :?

If were talking about what I think we are, then my design does not do it unless there is a lot of chop on the water, with a smooth to fair wave surface (and wales clean waves are what I think you guys would call choppy) then either it does not happen with my board or i dont notice it.

I think coming from bodyboarding I am always putting weight through my elbow into the rail, I think maybe use my shoulder as a shock absorbed to cushion shock/skipping.

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Re: TBXL

Unread post by bgreen » Wed Feb 28, 2018 4:38 pm

Nomas,

Maybe we are using language differently. I would have thought a square tail would turn easier than a pintail, the latter able to draw a longer line.

My series of 7 boards on the same design, has focussed on changing 1 or 2 variables at a time. For me this was a useful way to learn, how certain changes affected the boards ride.

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Re: TBXL

Unread post by rodndtube » Wed Feb 28, 2018 4:48 pm

bgreen wrote:Nomas,

Maybe we are using language differently. I would have thought a square tail would turn easier than a pintail, the latter able to draw a longer line.

My series of 7 boards on the same design, has focussed on changing 1 or 2 variables at a time. For me this was a useful way to learn, how certain changes affected the boards ride.
On the tail and turning: it is a matter of degree and also has something to do with lines (plan shape) of the board. At a certain point a very wide tail is hard to turn (unless rocker, tail kick are changed, rail changed, etc.). Likewise, an extreme pin tail is hard to turn.

I agree that Nomas is making several changes at one time -- I sort of did that as well in my Bonzer paipo design, while also maintaining several design features constant, and figured I would be able to sort out a couple of things with the fin (skeg) mix. It worked out very well for me. But, yes, in the past I have been extremely incremental (and still don't make many quantum leaps, e.g., no skegs, twin-fins, super-wides...).
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Re: TBXL

Unread post by nomastomas » Wed Feb 28, 2018 6:49 pm

Once I have a workable shape, I believe incremental changes are useful for fine-tuning that shape. But when designing a prototype, a shape that deviates dramatically (in terms of either performance and/or design) from an established shape, a different approach is indicated. I find that a "clean slate" is the best approach. It helps to minimize design biases that are built into an existing shape. In these cases, my process is to start with a basic notion of how the shape is intended to perform. This notion will dictate certain basic design elements. Once I have assembled those elements into a cohesive shape, I scrutinize the shape, looking for obvious incompatibilities between design elements. Here, I'm relying not only upon my knowledge and experience in creating surfcraft, but the knowledge of others as well. Once I'm satisfied with the new design, I shape it, have it laminated and take it out for a test drive. Testing is a very important part of this process, and will usually lead to the small, incremental design changes necessary for fine tuning.

So, for some concrete examples. Many people have asked me how the TBGs would ride finless. I know from riding them with minimal fin size that they ride better with fins. That's because the outline isn't conducive to finless riding. The finless design I'm working on has the familiar outline of a Morey Boogie board. There's simply no denying the efficacy of this outline. Rocker and bottom contours are a different matter. My bottom contours for the TBF(inless) are very different than those of the TBGs. It would have taken me numerous iterations to take the TBG4 to TBF as now designed. This was just not necessary.

The Manta, a tri-hull bottom with full-length concaves, centered-wide point and fork nose, was the product of the "clean slate" approach.

The TBH(ull), was a hull-shaped prone-board that again, was radically different from the TBGs. Single-fin, pointed nose, convex bottom and centered outline, couldn't be much different. That too was the product of the "clean slate" approach.
So, for me, design iteration has its place, but not when prototyping.
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Re: TBXL

Unread post by bgreen » Thu Mar 01, 2018 5:19 am

Nomas,

If you can afford and build your own prototypes, why not. An expensive option for the average punter. One day, I hope to complete an interview with the late Peter Berry, creator of radical kneeboards, he described working from a concept, which would then be pushed in different directions, looking for something a "bit wilder".

When I've made some big departures in design, they have usually been into well trodden territory (Rod's bonzer is an established design), a big change for him, but a new BB design.

Is anyone riding your finless boards?

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Re: TBXL

Unread post by nomastomas » Thu Mar 01, 2018 1:07 pm

"An expensive option for the average punter"…perhaps. Every first shape is a “prototype” be it from a shaping newbie, a backyarder or a seasoned vet. Expense is relative. Indeed, some would say surfing with the need to by boards, wetsuit, etc is too expensive. Likewise, golf or fishing or bowling or cycling; each has its price of admission. It really comes down to the individual’s willingness to make the sacrifices required to follow their passion. And, of course, that’s different for everyone. But it doesn’t mean that the “average punter” can’t make that commitment. It’s a personal choice, not an externally imposed limitation…

As for a finless T-Belly, it remains a concept that is still undergoing tinkering. Not quite ready for “prime time”, although I have a very interested client, in addition to myself, so a rideable prototype should happen sometime this year.
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Re: TBXL

Unread post by Nels » Thu Mar 01, 2018 1:56 pm

I hope to complete an interview with the late Peter Berry, creator of radical kneeboards
Dang, Bob, I know you're good...but that seems like a superhuman challenge...

Would like to see it though.

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Re: TBXL

Unread post by bgreen » Thu Mar 01, 2018 4:25 pm

My latest nine boards aren't in this photo
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Pete Berry -a man who was fond of experimenting. I'll let you know how the channelling is going.
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Re: TBXL

Unread post by nomastomas » Tue Aug 07, 2018 8:53 am

krusher74 wrote:The one thing I found from bodyboarding over the years is the the bigger the wave the smaller the board I prefer.
I haven't had the time to devote to the XL design and testing, but I think Keith is on to something here. Going smaller as wave size increases reduces planing area, which in turn reduces speed potential. I would argue that "speed" on a prone board is a function of "wave size" and "planing area". As wave size increases, less planing area is required to maintain the same given speed. The ideal speed would be something less than the speed required by the shape to lift completely off the surface, where the rider loses directional control due to insufficient drag. Of course another compensatory maneuver would be to use leg drag as a way of modulating speed, the traditional and time-tested technique used to stall for the barrel.

So, with these new insights, I'm officially abandoning the XL design, which I now consider to be "barking up the wrong tree" vis a vis the "skipping stone" issue. Better to focus on reducing planing area, and rider technique when surfing waves of consequence...oh, and fins, of course.
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Re: TBXL

Unread post by asier esnal » Tue Aug 07, 2018 10:04 am

I encourage you to keep working on this idea. I am also in it. I saw your design a long time ago, it is interesting, but the nose of the paipo practically never touches the water, so putting a boat nose is not a good solution.

I think the work has to focus on the middle part of the tail, there is where the water pressure works, the jumps are generated ... I keep making designs in the solidworks looking for that answer, catamaran type designs, making a design in shape of V, T-shape ... there are many baristas to contolar and little time to be able to manufacture

encourage and fight that in a long or short time we get it

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