T-Belly G6

What works and what doesn't. Share design ideas, references and contacts for paipo board builders.
User avatar
nomastomas
Big Wave Charger
Posts: 515
Joined: Thu Nov 17, 2011 2:30 am
City: Ojai
State or Province: CA
Country: USA
Interests: Surfing, cycling and fishing
Location: Ojai, CA
Contact:

T-Belly G6

Unread post by nomastomas » Sat Apr 20, 2019 3:25 pm

I spent the past week refining designs for surfcraft at the extremes of the length continuum: a 12’ “glider” style surfboard and a 52” prone board. The prone board, dubbed the “G6”, is the latest iteration in the T-Belly line. As I’ve discussed elsewhere on this forum, the previous TBs were designed to maximize performance in waves under 6’. I have found that the G5 shape needs to be de-tuned for waves over 6’ by increasing fin area in order to reduce speed and the accompanying excessive lift generated by the shape. With the G6, I started with the foil of the G5, and then made changes which I believe will reduce lift, and thereby enhance control in waves over 6’.
To begin with, I changed the outline by increasing the length from my personal standard 49” to 52”, and switching from a diamond nose to a pulled-in, semi-pointed nose. Simultaneously, I decreased the width from 22.5” to 21.75”. Finally, I added a wing to the outline in the tail, with the intended purpose of improving turning performance. These changes reduced planing area, and produced a longer, but thinner shape which can still be held in an effective kick-paddling position with hands on the rail and elbows on the deck. The G5 has a much wider nose, and I’ve had experiences where the “corner” of the diamond gets caught in the wave face, creating unwanted drag. The pulled-in nose should correct that.
After the outline, I focused on the bottom contours. I reduced the depth of the middle concave, another lift-producing feature of the G5, keeping the belly in the nose and the dual-exit concaves in the tail. I also eliminated the beveled/concave rail. On the G5, this feature was designed primarily to maintain a low rail cross-section in a relatively thick shape. Increasing the length while reducing the volume of the G5 (23.7L) served to thin-out the overall shape, eliminating the need for the beveled rail. Overall, these changes created a much more simplified bottom contour, and a nice thin rail cross-section.
The shape is being cut and should be in my hands by next Thurs. I’m using EPS 2.0PCF with no stringer. I’ll finish the shape, smoothing out the transitions and marking the fin placements for the FCS Fusion boxes. I’ll use the 5⁰ cant boxes in the front and the 9⁰ cant boxes in the rear. The additional cant in the rear will compensate for concave in the tail. Then the shape will take its place in the line at my glasser’s. I haven’t decided on the finish, but I have a week or two to decide.
Attachments
TBG6_Deck.jpg
G6 Deck
TBG6_Deck.jpg (20.36 KiB) Viewed 2474 times
TBG6_Bot.jpg
G6 Bottom
TBG6_Bot.jpg (21.35 KiB) Viewed 2474 times
TBG6_Overlay.jpg
Comparison: G5 to G6
TBG6_Overlay.jpg (25.84 KiB) Viewed 2474 times
"This is a paipo site...isn't it?"
www.tp4surf.com

SJB
Big Wave Charger
Posts: 221
Joined: Fri Sep 30, 2011 12:39 am
City: Santa Barbara
State or Province: CAL
Country: USA
Location: Santa Barbara

Re: T-Belly G6

Unread post by SJB » Mon Apr 22, 2019 11:22 am

The Elon Musk of the body board world. :D Still a die hard fan of my G2 and G4. Let me know if you are seeking a test pilot.

User avatar
nomastomas
Big Wave Charger
Posts: 515
Joined: Thu Nov 17, 2011 2:30 am
City: Ojai
State or Province: CA
Country: USA
Interests: Surfing, cycling and fishing
Location: Ojai, CA
Contact:

Re: T-Belly G6

Unread post by nomastomas » Mon Apr 22, 2019 11:40 am

Ha! Could definitely use your feedback. I have a couple of lefts in mind that only need a solid summer Southy to light up.
"This is a paipo site...isn't it?"
www.tp4surf.com

User avatar
krusher74
Big Wave Charger
Posts: 773
Joined: Wed Nov 07, 2012 3:53 pm
City: easkey
State or Province: co sligo
Country: Ireland
Interests: Surfing, vintage cars and motorbikes
Location: Easky, Co sligo , ireland
Contact:

Re: T-Belly G6

Unread post by krusher74 » Fri Apr 26, 2019 4:31 am

How do you find the concave deck for positioning? I really like to have my hip and elbow way over on the engaged rail (but maybe that's a finless thing) although I see stand up surfers foot position also goes over towards the engaged rail.
Do you lie in the central position for both lefts and rights?

User avatar
nomastomas
Big Wave Charger
Posts: 515
Joined: Thu Nov 17, 2011 2:30 am
City: Ojai
State or Province: CA
Country: USA
Interests: Surfing, cycling and fishing
Location: Ojai, CA
Contact:

Re: T-Belly G6

Unread post by nomastomas » Fri Apr 26, 2019 6:37 am

When I stand up surf, my feet are pretty much on the stringer, with maybe my lead foot a little more towards the wave and my trailing foot a little more towards the beach side. If I stood on the rail, the board would roll over. Its enough to just put my weight on my toes or back on my heels. That's because all of my weight is focused on my feet. When I ride prone, only half my body weight is on the board, and that half is spread out, over a wider area than just my feet. But even so, I tend to be on my elbows, with most of my upper body mass focused in the general area of my hips. Turns and/or setting an edge is done by rolling on to one hip or the other. I find that with the traction of fins on the board, one can make extremely abrupt direction changes, with little or no drift. Making abrupt direction changes at speed introduces centrifugal forces that can pull the rider in a direction which is counter to the turn. Early on in my designs, I found that I would be literally pulled off the deck when making a hard turn, especially if I didn't overtly "bank" into the turn. My solution was to add some concave to the deck to help keep me centered. The deck concave also helps keep me centered when I'm arm paddling and not holding on to the board. I try to avoid dragging anything besides my legs in the water, unless I want to slow down. In fact I size the TB to keep an inch or two of real estate all around the rider, especially at the hips. The majority of the time my fins give me all the hold I need. Of course, there are those ultra steep take-offs where I'll fall back on my rail-grab technique to set the rail and hold a line. This may just be a learned behavior from years of riding a boogie.
"This is a paipo site...isn't it?"
www.tp4surf.com

User avatar
bgreen
Big Wave Charger
Posts: 1051
Joined: Fri Aug 19, 2011 5:17 pm
City: Brisbane
State or Province: Qld
Country: Oz
Contact:

Re: T-Belly G6

Unread post by bgreen » Sun Apr 28, 2019 3:41 am

I do the rail grab instinctively (my background is stand-up only) on certain waves, probably more on my backhand (going left). Dropping down a steep face and turning into a tube seem to be when I do it most.

asier esnal
Big Wave Charger
Posts: 184
Joined: Tue Apr 24, 2018 4:56 am
City: Astigarraga
State or Province: Gipuzkoa
Country: spain

Re: T-Belly G6

Unread post by asier esnal » Sun Apr 28, 2019 8:51 am

I'm very curious about the narrowness of your boards, in what improvement compared to a more oval design? with nose wider? thank you very much, you are an inspiration for me
Attachments
TBG6_Overlay.jpg
TBG6_Overlay.jpg (35.2 KiB) Viewed 2400 times

User avatar
krusher74
Big Wave Charger
Posts: 773
Joined: Wed Nov 07, 2012 3:53 pm
City: easkey
State or Province: co sligo
Country: Ireland
Interests: Surfing, vintage cars and motorbikes
Location: Easky, Co sligo , ireland
Contact:

Re: T-Belly G6

Unread post by krusher74 » Mon Apr 29, 2019 5:12 am

asier esnal wrote:I'm very curious about the narrowness of your boards, in what improvement compared to a more oval design? with nose wider? thank you very much, you are an inspiration for me
have you seen the Goddard sketches? Asier. Good notes on them.

http://mypaipoboards.org/interviews/Lar ... humb.shtml

asier esnal
Big Wave Charger
Posts: 184
Joined: Tue Apr 24, 2018 4:56 am
City: Astigarraga
State or Province: Gipuzkoa
Country: spain

Re: T-Belly G6

Unread post by asier esnal » Mon Apr 29, 2019 6:33 am

If I have read it and the reason for the question, the design of nomastomas is very far below the measures recommended by Larry and this is precisely my curiosity
I see in the designs very much like board rails contact with the water due to the narrowing of the nose


http://mypaipoboards.org/interviews/Lar ... dard.shtml

Surfboard designers measure the nose width 12" back from the nose, which may be very pointy. But, since a pointed nose on a short bellyboard is useless and non-functional, I use a round-nose design, and measure the nose width at 6 " back from the tip of the nose. Then, the 'shoulders' would be measured at a point 12" back from the nose. I thought that the nose widths looked best when they were about 60% to 80% of the board's maximum width, and a nice compromise is about 70% of the width.
Attachments
TBG6_Overlay.jpg
TBG6_Overlay.jpg (40.41 KiB) Viewed 2388 times

User avatar
krusher74
Big Wave Charger
Posts: 773
Joined: Wed Nov 07, 2012 3:53 pm
City: easkey
State or Province: co sligo
Country: Ireland
Interests: Surfing, vintage cars and motorbikes
Location: Easky, Co sligo , ireland
Contact:

Re: T-Belly G6

Unread post by krusher74 » Mon Apr 29, 2019 9:20 am

asier esnal wrote:If I have read it and the reason for the question, the design of nomastomas is very far below the measures recommended by Larry and this is precisely my curiosity
I see in the designs very much like board rails contact with the water due to the narrowing of the nose


http://mypaipoboards.org/interviews/Lar ... dard.shtml

Surfboard designers measure the nose width 12" back from the nose, which may be very pointy. But, since a pointed nose on a short bellyboard is useless and non-functional, I use a round-nose design, and measure the nose width at 6 " back from the tip of the nose. Then, the 'shoulders' would be measured at a point 12" back from the nose. I thought that the nose widths looked best when they were about 60% to 80% of the board's maximum width, and a nice compromise is about 70% of the width.
Yes, I too found this interesting when he first showed off the first Tbellys, From my bodyboard world the only boards with a wide point/template close to this are extreme DK specific boards, and those guys ride with their weight over the back corner all the time. With it being for over 6ft waves you would expect waves with power so your harnessing that power off the back of the board not leaning forward and planing on the front 3rd of the board to generate speed. I have experienced what Goddard did on board with thin noses. But Tomas and the guys that ride his board seem to find its working well for them. I guess its also putting the pivot point on the rail closer to the fins

User avatar
nomastomas
Big Wave Charger
Posts: 515
Joined: Thu Nov 17, 2011 2:30 am
City: Ojai
State or Province: CA
Country: USA
Interests: Surfing, cycling and fishing
Location: Ojai, CA
Contact:

Re: T-Belly G6

Unread post by nomastomas » Wed May 01, 2019 1:39 pm

Good questions...The outline of TB needs to be considered relative to all of its other design features, which includes the use of fins. The outline shape of the finned TBs speaks to the difference between finned and finless prone-board shapes. The TB designs are driven by the use of fins for primary control, as opposed to the use of the rail. Not that the rail doesn't contribute to control, but more that the rail is used secondarily in this effort. The opposite is true for finless boards that rely heavily on the rail for control on the wave face. While all prone-boards (finned/unfinned) are turned off the rear corner, maintaining position on the wave face is accomplish by using the rail on finless boards. And, the steeper the face, the more rail that is required to hold the position. So, it makes sense to have as much "available" rail line as possible, even at the sacrifice of ultimate speed. On the other hand, relying primarily upon fins for control allows for the use of a more curvy outline, which is not only faster and easier to turn, but also, due to the narrow nose shape, more forgiving on late drops. It was for this exact reason the the wide-point forward outline of the mid-70s single-fins was abandoned in favor of the wide-point behind center outline of the early-80s multi-finned shapes.
"This is a paipo site...isn't it?"
www.tp4surf.com

User avatar
krusher74
Big Wave Charger
Posts: 773
Joined: Wed Nov 07, 2012 3:53 pm
City: easkey
State or Province: co sligo
Country: Ireland
Interests: Surfing, vintage cars and motorbikes
Location: Easky, Co sligo , ireland
Contact:

Re: T-Belly G6

Unread post by krusher74 » Thu May 02, 2019 1:55 pm

nomastomas wrote:Good questions...The outline of TB needs to be considered relative to all of its other design features, which includes the use of fins. The outline shape of the finned TBs speaks to the difference between finned and finless prone-board shapes. The TB designs are driven by the use of fins for primary control, as opposed to the use of the rail. Not that the rail doesn't contribute to control, but more that the rail is used secondarily in this effort. The opposite is true for finless boards that rely heavily on the rail for control on the wave face. While all prone-boards (finned/unfinned) are turned off the rear corner, maintaining position on the wave face is accomplish by using the rail on finless boards. And, the steeper the face, the more rail that is required to hold the position. So, it makes sense to have as much "available" rail line as possible, even at the sacrifice of ultimate speed. On the other hand, relying primarily upon fins for control allows for the use of a more curvy outline, which is not only faster and easier to turn, but also, due to the narrow nose shape, more forgiving on late drops. It was for this exact reason the the wide-point forward outline of the mid-70s single-fins was abandoned in favor of the wide-point behind center outline of the early-80s multi-finned shapes.
I thought the straight the outline/rail the faster the board, but the curvier the better its turned.

User avatar
nomastomas
Big Wave Charger
Posts: 515
Joined: Thu Nov 17, 2011 2:30 am
City: Ojai
State or Province: CA
Country: USA
Interests: Surfing, cycling and fishing
Location: Ojai, CA
Contact:

Re: T-Belly G6

Unread post by nomastomas » Thu May 02, 2019 3:16 pm

All things being equal, e.g. rocker, volume, rail shape, bottom contours, fin set up, etc, straighter rail line = more rail in wave face = more drag = less speed
Drawing shows a comparison of a G5 with a Mach 7-7. The G5 is 49" in length and the Mach 7-7 is 42". The yaw angle for each relative to the wave face(green line) is the same. Notice that despite its longer overall length, the G5 has less area and rail line exposed to the wave face (red outline) than the Mach 7-7 (black outline).
Attachments
YawAngleVsWP.jpg
"This is a paipo site...isn't it?"
www.tp4surf.com

User avatar
krusher74
Big Wave Charger
Posts: 773
Joined: Wed Nov 07, 2012 3:53 pm
City: easkey
State or Province: co sligo
Country: Ireland
Interests: Surfing, vintage cars and motorbikes
Location: Easky, Co sligo , ireland
Contact:

Re: T-Belly G6

Unread post by krusher74 » Fri May 03, 2019 2:47 am

But does more curve not equal more drag in the same way as more toe on a fin does?

User avatar
nomastomas
Big Wave Charger
Posts: 515
Joined: Thu Nov 17, 2011 2:30 am
City: Ojai
State or Province: CA
Country: USA
Interests: Surfing, cycling and fishing
Location: Ojai, CA
Contact:

Re: T-Belly G6

Unread post by nomastomas » Fri May 03, 2019 10:03 am

More bottom curve, yes...more outline curve, no.
"This is a paipo site...isn't it?"
www.tp4surf.com

User avatar
nomastomas
Big Wave Charger
Posts: 515
Joined: Thu Nov 17, 2011 2:30 am
City: Ojai
State or Province: CA
Country: USA
Interests: Surfing, cycling and fishing
Location: Ojai, CA
Contact:

Re: T-Belly G6

Unread post by nomastomas » Sat May 04, 2019 1:22 pm

“I find it is the opposite of surfboards. So, the bigger and heavier the wave the smaller the board you can ride. Since those waves give so much more speed you just increase your control by using a smaller board which is super helpful when making crucial late drops or bottom turns on slabby waves. For small waves foam is your friend, whether that means using a thicker, wider or longer board or even a different tail type like a bat tail.” Jeff Hubbard, three-time bodyboarding World Champ, 4/30/19 https://www.surfline.com/surf-news/ask- ... rder/50492

Always good to get validation of an idea...still waiting on Marko for my blank...
"This is a paipo site...isn't it?"
www.tp4surf.com

CHRISPI
Big Wave Charger
Posts: 301
Joined: Sun Dec 28, 2014 2:48 pm
City: Durban
State or Province: Natals
Country: South Africa

Re: T-Belly G6

Unread post by CHRISPI » Sun May 05, 2019 1:21 pm

That explains exactly what I am trying to do with my board, getting a thin foil rail in that high lift area, but retaining inboard volume.

User avatar
krusher74
Big Wave Charger
Posts: 773
Joined: Wed Nov 07, 2012 3:53 pm
City: easkey
State or Province: co sligo
Country: Ireland
Interests: Surfing, vintage cars and motorbikes
Location: Easky, Co sligo , ireland
Contact:

Re: T-Belly G6

Unread post by krusher74 » Sun May 05, 2019 2:30 pm

nomastomas wrote:“I find it is the opposite of surfboards. So, the bigger and heavier the wave the smaller the board you can ride. Since those waves give so much more speed you just increase your control by using a smaller board which is super helpful when making crucial late drops or bottom turns on slabby waves. For small waves foam is your friend, whether that means using a thicker, wider or longer board or even a different tail type like a bat tail.” Jeff Hubbard, three-time bodyboarding World Champ, 4/30/19 https://www.surfline.com/surf-news/ask- ... rder/50492

Always good to get validation of an idea...still waiting on Marko for my blank...
I can also say I use a smaller bodyboard in bigger waves, I think part of it is also being able to sink the rail of a smaller board to get more hold.

I think more though than seeing it as a surfer in big waves mught right a 6.6 and in smaller waves a 5.11.

in bodyboard terms, I think it's more we ride a groveler in normal waves, 5.6/20.5 (42" bodyboard) and in good waves ride a performance board, 5.11 by 19 (41/41.5") bodyboard.

I think that where bodyboards could evolve (although maybe the manufacturing process holds them back) their rails are very basic and same thickness front to rear, you cant get a bodyboard with a nice foiled knifey rail, so you just buy a smaller one with a thinner rail

asier esnal
Big Wave Charger
Posts: 184
Joined: Tue Apr 24, 2018 4:56 am
City: Astigarraga
State or Province: Gipuzkoa
Country: spain

Re: T-Belly G6

Unread post by asier esnal » Sun May 05, 2019 3:46 pm

according to those bodyboard measurements, I do not understand why the paipos are made as big, 49 and 52 as you comment in the first post?
What is the overdose that is compared to 42 of the bodyboard?
my paipos are 43/44 x 18.5... 20 max inch and I measure 1.75cm weight 75kg

User avatar
nomastomas
Big Wave Charger
Posts: 515
Joined: Thu Nov 17, 2011 2:30 am
City: Ojai
State or Province: CA
Country: USA
Interests: Surfing, cycling and fishing
Location: Ojai, CA
Contact:

Re: T-Belly G6

Unread post by nomastomas » Sun May 05, 2019 5:21 pm

Asier, Have you read all of the threads I've posted on this forum? You'll find the answer there...
"This is a paipo site...isn't it?"
www.tp4surf.com

Post Reply

Who is online

Users browsing this forum: Bing [Bot] and 10 guests