T-Belly G3

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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T-Belly G3

Unread post by nomastomas » Fri Aug 22, 2014 1:57 am

This is actually the second G3, but its more representative of the typical shape. The intended rider is 5'10" 170# lifetime surfer from Australia. His local break is occasionally OH to 2xOH, with rare 3xOH days. After a great deal of discussion, we selected the following dimensions: 44" x 22" x 2-1/8" 23.8L. The extra volume (via more length and more thickness) will serve to widen the wave range of the original design. Notice that the wide point has been moved further behind center. I believe that most prone riders turn and trim off the rear third of the board. Moving the wide-point back provides a pivot point for shorter-radius turns. This bulge or "hip" in the outline is where the rail has maximum contact with and penetration into the wave face. I locate the front-fin (of a quad set-up) adjacent to this point to leverage the pivot point, but also to maximizes hold in the wave face. The deck concave of the G2 has been removed in the interest of more efficient volume distribution. Also notice that the sloped rail keeps volume in the center of the board and the rail "knifey" thin. The bottom "belly-to-flat-to-down-rail" remains from the G2, as does the tail exit concave.
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IMG_1159.JPG
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G3Bottom.JPG
G3Bottom.JPG (53.92 KiB) Viewed 3180 times
IMG_1158.JPG
IMG_1162.JPG
Slope-rail viewed from tail
Last edited by nomastomas on Wed Sep 10, 2014 10:35 am, edited 1 time in total.
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Re: T-Belly G3

Unread post by krusher74 » Fri Aug 22, 2014 9:11 am

The evolution continues!

Nice to hear you have rider interest from as far away as Australia. :D

I wish my local was OH once in a while :cry:

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Re: T-Belly G3

Unread post by Canyon » Fri Aug 22, 2014 12:49 pm

What is the purpose of the stepped tail bottom concave, as opposed to a more traditional smooth concave transition?

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Re: T-Belly G3

Unread post by nomastomas » Fri Aug 22, 2014 1:51 pm

When the board is planing, pressure is created the area in the rear third of the bottom. The concave, which is not closed but open, allows water to freely escape out the back, reducing this pressure and decreasing the drag associated with it.

Water is very "sticky". It wants to cling to surfaces. Hold any curved surface in a faucet stream and observe how water clings to the surface and wants to flow around the object. Then hold an object with a hard edge in the faucet stream and notice how the water flow clings to the surface until a hard edge is encountered, at which point it breaks away. The hard edge on the concave is there to enhance the release of water off the bottom and out the tail. Of course, any time you get water to detach you reduce drag, and less drag means more speed.

As a side note - There is a popular misconception among surfers that the hard edge seen on the tail of most modern surfboard shapes is there to facilitate turning. In fact, the hard edge is put there by the shaper to encourage water release off the tail.
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Re: T-Belly G3

Unread post by rodndtube » Fri Aug 22, 2014 10:46 pm

Is that what we would call a Paipo Pig shape?

I might be the exception to the norm as my riding is more forward on the board. However, I do notice a lot of West Coast guys hanging on to their boards way back.
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Re: T-Belly G3

Unread post by krusher74 » Sat Aug 23, 2014 2:31 am

rodndtube wrote:Is that what we would call a Paipo Pig shape?

I might be the exception to the norm as my riding is more forward on the board. However, I do notice a lot of West Coast guys hanging on to their boards way back.
I'm with you rod as a weight forward rider, this generates more forward speed (especially in weak waves), In the bodyboard world prone boards have wide point forward of centre, dropknee boards (where the rider sits on the tail) have the wide point rear of center.

There is a lot of control from riding "way back" but on my boards it also acts as a constant stall.

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Re: T-Belly G3

Unread post by bgreen » Sat Aug 23, 2014 5:25 pm

Rather than hi-jack the thread I'm going to start a forward position thread on the 'Your Wave' section.

A T-belly interview is in the works (don't think I mentioned this Rod).

Bob

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Re: T-Belly G3

Unread post by nomastomas » Wed Sep 10, 2014 10:48 am

One of the advantages of the G3 design is that it can be easily extrapolated to accommodate riders of all sizes. This G3 was built for a rider who was 5-9/240lbs. The board has the same length, but was widened to 23" and thickened throughout (2-3/4" at thickest part). Volume was increased to 30L. Same eps/epoxy construction.
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Re: T-Belly G3

Unread post by nomastomas » Sat Sep 20, 2014 1:47 am

We've had some pretty good swell this week, with SW groundswell and NW windswell at my local point. A little peaky and downright crossed-up at times, but with 5'-6' faces on set waves. I paddled out on the G3 using the twin-fin set-up that I've come to love in the small stuff, and had difficulty holding a high line. Paddled back in and added the rear fins, and that's all she needed. This afternoon the waves were surprisingly good. Typically, it gets pretty blown-out by noon, and the kite-boarders are out in force. TodayThis afternoon, it was the cleanest I've seen in weeks, and the crowd was light, with most people expecting the usual victory-at-sea conditions. I started my session on my 8-6 mini-longboard, but I just couldn't compete with the shortboarders in the zippy, low-tide conditions. After struggling for over an hour, I caught a wave in and immediately switched out the 8-6 for the G3 and a pair of swim fins. By the time I returned, the crowd had thinned even more and set waves were rolling through with no riders!! I spent the next hour trading set waves with an SUPer. Nothing real big, but solid 5'ers, peeling cleanly for close to 80 yds. What a blast! I continue to be amazed at the G3's speed and agility. A couple of times, the direction change was so abrupt that I slipped off the deck. I'm still learning to modulate the pressure needed to carve turns. There's literally no drift as long as your weight is not too far forward. Below are pictures of the two different fin set-ups I'm using. I have another quad set that I eager to try. Hopefully, the good waves will continue.
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DVS Quad Keel, Fronts Only
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DVS Quad Keel
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Re: T-Belly G3

Unread post by nomastomas » Thu Oct 09, 2014 3:27 pm

Finally had a chance to get the TBG3 out in some 6'-7' waves at my local break thanks to Hurricane Simon. I used an S-5 quad set from Shapers (Front Fins = 4.44” Base, 4.55” Depth, Rears = 3.89” Base, 4.37” Depth). The board performed really well, with the exception of some take-offs. On these larger waves, the "air-drop" was a little more pronounced, with a harder landing. On a couple of occasions, I was thrown partially off the board, on the beach side, as the fins grabbed the face and held, while my momentum continued. This also stalled the board momentarily, just enough to put me in the whitewater. Of course, getting out of the whitewater on a belly board is complicated by the fact that you typically have water in your face and are unable to see very well. I would just hold on until I eventually popped-out onto the face.

I believe the problem is that, in anticipation of a late drop on a steep walling face, I'm applying too much pressure on the inside rail (a carry-over from my finless boogie boarding days) and not allowing the fins to do their work, And/or I'm using too much fin. The first WNW of the season is due this Sunday, so the point-breaks from Ventura to Santa Barbara should all have good waves. More testing to come…
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Re: T-Belly G3

Unread post by bgreen » Thu Oct 09, 2014 4:09 pm

Thomas,

Sounds like the fins to me. Did you try easing the pressure off on the inside rail during the surf or is this your reflection after the surf? The bigger wave also generates more speed so you have a speed x fin interaction you mightn't have on smaller waves.

Bob

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Re: T-Belly G3

Unread post by nomastomas » Thu Oct 09, 2014 4:48 pm

No, it was all hindsight. To be honest, I was caught completely off guard by the event. My biggest worry has been lack of hold in larger waves. Never occurred to be that the board could be over-finned. I think fin size is the most likely suspect, but I really want to see what will happen with these fins and a less aggressive rail-set.

Another reality check was negotiating the heavy whitewater. I believe I can duck-dive the G3 about 3', maybe a little more, but in heavier surf there is whitewater turbulence much deeper than that, especially if the lip explodes 10' in front of you. I also noticed that while the G3 paddles pretty darn well, its not as fast as a shortboard, which kept me in the impact zone longer than I would have liked. In those ominous situations, when the sets are stacked in front of you, I soon learned to make a quick check for traffic behind me, and then simply dive for the bottom. Wearing a leg leash attached to the rear corner was really helpful in these situation, keeping my arms free to stroke downward. I found this to be the best technique for not losing ground on the paddle out.
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Re: T-Belly G3

Unread post by flojo » Fri Oct 10, 2014 10:03 pm

So Thomas and Bob, do you mean that the extra speed increases the effect of the fins and so in this circumstance, smaller could be better?

During my knee boarding phase, I too found the best way to get thru when caught inside on big sets was to abandon ship (after making sure nobody was behind me) and let the leg rope do its job.

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Re: T-Belly G3

Unread post by nomastomas » Fri Oct 10, 2014 11:15 pm

Typically, fin area is increased as wave size increases. Likewise, fin rake also is increased to produce the drive and projection needed out of turns to keep up with larger, more powerful waves. Additionally, fin stiffness should be increased as wave size increases, and/or as rider size increases. If your fins are too small, to flexy and/or too upright for the wave size, you will lack drive/projections out of turns, you will lack hold into the wave face, and your turns will wash out. The problem comes, when the board is finned for larger waves, and the rider uses an air drop take-off. When the larger, stiffer fins release and then suddenly engage, there can be too much sudden hold, sudden grip, causing the rider to loose control, momentarily. I'm trying to work out rider input strategies to minimize the impact of the air-drop, reducing fin size maybe one of those strategies.
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Re: T-Belly G3

Unread post by flojo » Fri Oct 10, 2014 11:50 pm

Thanks!

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Re: T-Belly G3

Unread post by rodndtube » Sat Oct 11, 2014 1:45 am

From your description of the free fall/late take-off and partial air drop, it seems to me that straightening out on the drop and turning once on the wave again is the solution. And maybe a slightly smaller sized mix of fins. That is a TON of fin for a relatively short board.

Think of the small boards and small fins on the boards being ridden by tow-in surfers. They are not using 10" tall x 8" base and super raked fins (my guess is the fins are stiff).
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Re: T-Belly G3

Unread post by nomastomas » Sat Oct 11, 2014 10:05 pm

"They are not using 10" tall x 8" base and super raked fins (my guess is the fins are stiff)."
I'm not, either...?? Front Fins = 4.44” Base, 4.55” Depth, Rears = 3.89” Base, 4.37” Depth
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Re: T-Belly G3

Unread post by rodndtube » Sat Oct 11, 2014 10:59 pm

LOL... I know you are not using the 10-inchers, Tomás! My guess it that you can safely go smaller and still maintain good control and not have steering tendencies. P.S. Photos can also be misleading... your last one makes it look like the fins are dwarfing your small board.
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Re: T-Belly G3

Unread post by nomastomas » Thu Oct 16, 2014 6:48 pm

Caught some clean, shoulder-high beach-break action at the tail-end of the last swell. Reduced fin size to 3.7" side-bites x 4, and altered technique. I realized a week ago that I'd been falling back on old boogie board technique, e.g. setting the rail too hard and putting too much pressure with the forearm on the front part of the rail. Necessary with the fin-less, wide-point forward body boards, but totally unnecessary with the G3. In fact, it spoils the ride. I've learned to trust the wide-point back outline of the G3 and my 4 fins. With just slight weighing of the back-third rail, there was no stumbling out of the gate, just smooth acceleration on the drop-turn, plenty of hold across the face, and snappy cutback turns off the top. But then, shoulder-high is not head-high +. I'll have to wait for another swell to fully test out my new approach.
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