Finless T-Belly

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:

Finless T-Belly

Unread post by nomastomas » Sat Mar 28, 2015 6:15 pm

Bob asked how I would shape a finless belly board, so here’s she is. I started with the common wide-point forward body board outline. This outline allows the rider to more easily keep the rail engaged with the wave face. Unlike the finned belly board, the finless Bodyboard needs a way to keep the rail engaged with the wave face. By placing some curve or hip forward of center, the wave-side rail can be driven into the wave face. Extra hold can be obtained by pulling up the beach-side rail. This changes/improves the angle of attack of the wave-side rail for even greater hold and forward speed. The finless Bodyboard is a tried-and-proven formula. So, my TBF is just a variation on this theme.

To the Bodyboard outline, I added my TB rocker, volume distribution (or foil), sloped rail, and concave deck. The bottom is a simple belly-to-single–concave-to-double-concave (sounds more complicated than it is). These are “open” concaves, and are used to create a rail shape designed to hook into the wave face. The rail has a tucked bottom edge but no hard edges. Round surfaces suck into the wave face creating hold but also drag. Edges encourage water to release, lessening drag. The tucked-edge rail is a compromise between the completely round rail of the 50’s and the hard down rail of the early 70’s. The concave(s) are about 5/8” deep at 12” up from the tail, and about ¼” deep at the tailblock. Open ended concaves also help to direct water flow, creating that “path of least resistance” which water always likes to follow. Only question is how deep to make the concaves for maximum speed and hold.

I’ve kept the dimensions pretty much unchanged at 48” x 22-1/2” x 2” (1-3/4”at centerline) and about 23L. EPS/Epoxy construction, with double 4oz deck and single 4oz bottom. (the drawings below are what the shape will look like after cutting. The hard edges on both ends will be rounded when I clean up the shape before glassing)

I'm sure this shape is not a lot different than other finless belly/paipos seen on this forum. It definitely has the look of a TB, and close inspection will reveal some nuances not previously seen in other finless belly boards.
Attachments
TBF_deck1_web.jpg
TBF_deck1_web.jpg (64.47 KiB) Viewed 3817 times
TBF_bot1_web.jpg
TBF_bot1_web.jpg (23.02 KiB) Viewed 3817 times
TBF_bot2_web.jpg
TBF_bot2_web.jpg (29.88 KiB) Viewed 3817 times
"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: Finless T-Belly

Unread post by bgreen » Sat Mar 28, 2015 6:46 pm

Thomas,

Thanks.

Aesthetically, a slightly more rounded nose would appeal to me, but that's just personal taste.

How much concave did you decide on and how long is the concave? My second last board had a double concave and I'd probably try another.

Do you think you'll make one?

Bob

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: Finless T-Belly

Unread post by nomastomas » Sat Mar 28, 2015 7:51 pm

For me, form follows function. More curve in the nose leaves less rail in the wave-face, which is a concern. With no fins, I want as much rail in contact with the wave as possible. The single concave starts just about where the centerline rocker starts to flatten. It doesn't stay single for very long as it becomes clearly a double concave by 12" from the tail. I admit that I had little interest in building a finless TB, until this exercise. Now my interest has really been piqued. I'm really enjoying my TBG4 right now. Rode it today at the Ventura Rivermouth and had a blast. Problem is I have a new longboard and a new speed egg quad that I want to get acquainted with. The TBF may have to wait a month or so. Too many surfcraft, not enough waves is an occupational hazzard :D
"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: Finless T-Belly

Unread post by bgreen » Sun Mar 29, 2015 12:40 am

Lots of boards and not enough surfing time - a familiar story.

I wouldn't have thought pulling the nose in a little would have made too much difference to rail in the water. The nose generally doesn't do a real lot.

If you do build one, post by all means.

Bob

User avatar
krusher74
Big Wave Charger
Posts: 774
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: Finless T-Belly

Unread post by krusher74 » Sun Mar 29, 2015 12:25 pm

On the rounded nose discussion.

I used my fav bodyboard to take the rail template from, and simply extended the rail line to a rounded nose. This meant that i did not have to curve the rail more and leave less rail in the face. It made a 41.5" bodyboard into a 44" paipo.

The main ergonomic advantage I found after the fact was that I now like to hold various positions on the extra nose part on the paipo that does not exist on the OG bodyboard. with a square blunt nose you a mainly forced to hold that front corner and that may not be the best place for comfort or performance.

I'm sure the nose of that design could easily be rounded with little extra length is the person so desired.

I would be very interested to try out the rounded rail with no hard edge.

Does the double concave at the rear cover the entire width of the board and flow into the rail?

Do you feel the straight tail is a design aspect? faster than as swallow tail , or a crescent with tail blocks like a bodyboard?

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: Finless T-Belly

Unread post by nomastomas » Sun Mar 29, 2015 11:35 pm

Krusher...Our thinking is pretty much the same on the round-nose issue, and I have a drawing to help illustrate. The drawing is a top-looking-down view, with the round-nose superimposed on the blunt-nose. The redline in the drawing is the wave face. Converting the existing 48” blunt-nose to a round-nose shape sacrifices 4”-6” of functional rail length. It also creates a blunter curve in the rail at the point of wave penetration. The existing blunt nose shape has the rail line of a round nose board approximately 4” longer, and presents a gentler curve at the point of penetration. I would argue that the blunter curve encounters more resistance and resulting drag at the point of penetration than the gentler curve. I would also argue that the increase in rail area at the point of wave penetration allowed by the blunt nose is important, given that the WP forward shape relies upon this area for control. I could, as you have done, increase the length to maintain the rail curve, but the object of my design is to maximize function and to minimize size. Granted, the blunt-nose shape is a minimalist shape, and may not have the aesthetic appeal of its curvier cousins (eye of the beholder). As for ergonomics, that to is left to the whim of the rider. I prefer the flat nose which allows a parallel, bi-dexterous grip. In fact I hadn't considered using the "corners" for better grip and will give it a try.

Yes, the double concave at the rear covers the entire width of the board and flows into the rail. As it exists in the drawing, the rail rocker is lower than the centerline rocker, but less so at the very tailblock. I'm thinking that I will essentially add some V, so that the rail rocker has more curve than the centerline. This will facilitate smaller turning radius. So, I'll probably try lowering the centerline rocker to zero, and then bring up the rail at the tail an 1/4" or so.

No, I don't think tailblock shape has a significant impact on speed, other than that is where you want a hard, down edge for water release. A crescent shape fits the body a little better, but I think that is its main advantage. Regardless of the shape, as long as there is a hard down edge for releasing water, your good. Its important to remember that unlike a surfboard, belly boards have body parts hanging off the tailblock which can interrupt water flow.

The rails on my G4 are pretty close to the concept I'm using for the finless, just not as exaggerated. The G4 holds into a steep wall like no other prone board I've ridden. The combination of rail shape and rail-fins is the reason for this. It will be interesting to see if a finless board can equal or surpass this performance.
Attachments
BluntVRndNose.jpg
"This is a paipo site...isn't it?"
www.tp4surf.com

User avatar
krusher74
Big Wave Charger
Posts: 774
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: Finless T-Belly

Unread post by krusher74 » Mon Mar 30, 2015 1:51 pm

That's very cool.

I bet Larry Goddard wished he had aku shaper instead of hours of drawing boards on squared paper.

The only time I have both hands on the nose is either if i am in very weak waves and trying to push weight onto the nose for more speed or force the board onto the face on a weak wave take off (kinda like a nose rider on a longboard) or in the middle of a cutback.

other wise I am wave rail hand on the front corner and outside rail back on the rail about halfway down the rail. I find this wouldmake me a goofy rider as i prefer lefts , as i am right handed and on a left i'm controlling rail with my strong hand

If you are going for a square nose i would say to radius that corner as they can be uncomfortable on the hand

I also find like a my weight over the back corner of a finless board, I dont think I could reach the nose happily if it was 48" long and keep my weight on the back corner, a 43" bodyboard if considered right for a 6ft rider, 44" is almost impossible to find, would be interesting to see if the long finless board is not as easy to work with as the long finned board.

jbw4600
Big Wave Charger
Posts: 289
Joined: Sat Nov 05, 2011 6:08 pm
City: Kentfield
State or Province: CA
Country: USA
Location: Fairfax, CA
Contact:

Re: Finless T-Belly

Unread post by jbw4600 » Mon Mar 30, 2015 5:16 pm

I have always thought that a squared nosed board was essentially a longer round nose board with the nose cut off. So a 48" square nose is the same as 51" (give or take an inch or so) long board. The main difference might be that the hand position would be different.

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: Finless T-Belly

Unread post by nomastomas » Mon Mar 30, 2015 9:53 pm

absolutely...
"This is a paipo site...isn't it?"
www.tp4surf.com

User avatar
rodndtube
Big Wave Charger
Posts: 1029
Joined: Thu Aug 18, 2011 10:34 pm
City: Arbutus Land
State or Province: Maryland
Country: USA
Interests: Waveriding, travel and the Paipo Research Project
Location: Maryland, USA & Where the Waves Are Breaking
Contact:

Re: Finless T-Belly

Unread post by rodndtube » Tue Mar 31, 2015 11:20 am

Adding a rounded handle up near the nose would also provide additional gripping options.
rodNDtube
"Prone to ride"
I love my papa li`ili`i

"The sea doth wash away all human ills."
-- Euripides.

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: Finless T-Belly

Unread post by bgreen » Fri May 06, 2016 7:49 am

Nomas,

Going back to your finless drawings/design.

What does the volume look like if you reduce width to 21"? 23 litres is a lot from my perspective.

From your description, I take it there is no chine between rail and bottom? Is this correct?

How much nose rocker does your design have? You'd lose your nose point forward but would more parallel rails be an option to add more nose rocker?

Bob

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: Finless T-Belly

Unread post by nomastomas » Fri May 06, 2016 12:58 pm

Its been over a year since the original post, and at that time I said I'd have one built "in a month". Best laid plans...but I'm now revisiting the concept, especially since my "edge-bottom" design begs for a finless approach. More on that later.

To answer your questions Bob: I've found that with the TB design and my body-weight-with-wetsuit of 200lb/91kg (my Patagucci R3 is a good 10lb wet), 23L is perfect for me for conditions up to 6ft face. My earlier p-boards were huge in comparison, and as the TB design evolved, it became smaller and smaller, volume-wise, at one point dropping to 21L. While ride-able, the 21L board felt slower to paddle and slower to rise up on plane, so 23L became my preferred volume. While the formula I use to determine board volume for a customer is based upon my preference, it seems to work for others as well. I do make concessions for experience, water-time and customer preference, and make adjustments accordingly. I have spent a lot of time riding this design, in a wide variety of conditions. I try to encourage my customers to "test drive" one of the TBs I have, whenever possible, to allow them the opportunity to get a "feel" for the design. I've built 10-15 of the G4s using this formula and haven't yet received a complaint that the board was too floaty or corky. With regard to volume, it important to consider the volume distribution and not just the raw number. Most prone-riders equate low volume with ease of duck-diving and rail-sensitivity. Typically (but not always) thinner boards are better in both categories than thicker boards. Looking at a side profile of the G4, you can see that most of the volume is in the rear-half of the board, with a very thin and narrow nose. That wedge-shaped profile is very easy to push under water. Likewise, a cross-section view reveals how the "sloped-rail" of the G4 minimizes rail thickness where the rail meets the water, allowing more penetration than a thick, 50/50 rail.

Correct, no chine on that design, rather the opposite. The use of a concave bottom and a 60/40 tucked-edge rail creates a bit of a hook, a downward angle. Again, when viewed in cross-section you can see how this shape would hold into a wave face better than flat (rail-to-rail) and way better than convex or "V". The double concave in the tail allows for a more extreme angle, while simultaneously managing water flow.

The 48" TBG4 has 2-3/4" of nose rocker and 3/4" tail-rocker, as measured in the traditional manner, i.e. placing a straight edge parallel to the centerline at a point on the bottom, equidistant from the nose and the tail. Typically, for any given design, rocker is increased as length is increased, and vice versa. This curve from nose to tail is commonly referred to as "centerline rocker". But there is also a curve from nose to tail out at the rail. This is called "rail-line rocker", and can be the same or different than the centerline rocker. For example, a flat-bottomed shape like the typical foam bodyboard has the same curve, both at the centerline and the rail-line. A shape with V or concave bottom (or both) will have a different curve at the rail than at the centerline. Outline shape doesn't affect rocker at the centerline, but it does alter the rail-line rocker as the board is rolled over on its rail. This is an important concept to grasp. Surfcraft are complex shapes with a plethora of compound curves. The rider can vary the shape of the surface presented to the water, and therefore its performance, by shifting his weight side to side or front to back. Bob, I'm not sure how to answer your question at this point other than to say I can increase the amount of curve at either end without changing outline curve.
"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: Finless T-Belly

Unread post by bgreen » Fri May 06, 2016 4:21 pm

Nomas,

Thanks.

I also started out with one of Larry Goddard's boards and have had four made based on the same design. The first one used Larry's specified thickness. It was a good board but I wanted thinner the latest versions range between 21-23 litre. My bonzer is almost 26.

However, the NoFin I rode for years in all sorts of conditions is 13 litres.
Bells_07_2.jpg
Bells_07_2.jpg (42.29 KiB) Viewed 2555 times
The third photo isn't this board but one similar
NoFin_profile_edited2.jpg
NoFin_profile_edited2.jpg (10.03 KiB) Viewed 2555 times
NoFin_profile_edited.jpg
NoFin_profile_edited.jpg (15.38 KiB) Viewed 2555 times
my board -

They are sturdy boards with solid glass jobs, mine survived a trip over some serious rocks with me attached (not going to use that jump off spot again in a hurry)
NoFin_survives.jpg
NoFin_survives.jpg (55.08 KiB) Viewed 2555 times
These are obviously a very different style of board to yours and those ridden by many others. Everytime you log onto the forum you see that photo of John Galera riding a board just like this. They ride solid, hollow waves. I'm thinking about a smaller wave version that will have more planning speed, without losing too much of that underwater glide that these boards allow. That quest continues.

Bob

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: Finless T-Belly

Unread post by nomastomas » Fri May 06, 2016 5:36 pm

Yes, very different: Planing hull (G4) vs displacement hull (NoFin). I bet that thing flies! Notice how flat the rear 3/4 of the bottom is. I'm guessing that shortening the length of a board like the NoFin would lessen the planing surface and reduce max speed. My Manta has a tri-plane bottom, and while its fast, it tends to drift more in turns (even with 4.6" fins) than the G4.

Out of curiosity, can that board take the path of the solid arrow in the photo below? I can make that turn on the G4, but not on the Manta.
Attachments
Bells2.jpg
Bells2.jpg (42.38 KiB) Viewed 2552 times
"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: Finless T-Belly

Unread post by nomastomas » Fri May 06, 2016 5:42 pm

Here's my take on how bottom contours work, based upon Dick Brewer's thinking.
Attachments
RailProfiles.pdf
(2.52 KiB) Downloaded 106 times
"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: Finless T-Belly

Unread post by bgreen » Sat May 07, 2016 3:44 am

Nomas,

The line that is possible is generally between the two but depends on the wave.

The wave is a lot of fun but not ideal for showing how either board typically rides (the NoFin looking for the hollows and the Goddard a long wall), The tide was lower when I took the Goddard board out, so the waves were a bit better lined up and there wasn't as much turbulence off the rocks.

The NoFin
https://www.youtube.com/watch?v=vTSsxx0CU6g

The first Goddard finless
https://www.youtube.com/watch?v=nbcseXmkYkA

Using fins would have made for more control but I did knock all of John's fins out when he loaned me his three finned board.

Generally, the NoFin gains speed (assisted by momentum) whereas the Goddard has speed off the mark. In waves with more power the waves power gives the NoFin added boost on take-off.

Thanks for the Railprofile doc. With the diagrams, what do the arrows in the wave face indicate?

Bob

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: Finless T-Belly

Unread post by nomastomas » Sat May 07, 2016 11:51 am

Great videos! Same rider, same spot, same day (I'm guessing), but different boards...amazing how subtle the differences between the two shapes "appear" vs. how they are experienced. All of our discussions/debates over intricacies of prone-board design would probably baffle the casual observer.

The arrows in my over-simplified drawing indicate the flow of water up the wave face, and the effect of bottom contours on that flow. I intended to add an explanatory caption to the drawing, but never got around to it. The drawing was inspired by a similar drawing in the book "The Surfboard Book: How design drives performance" by Sean McCagh, with input from Dick Brewer, Simon Anderson, Steve Lis and Bob McTavish. Anyone interested in surfcraft design should read this book.
"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: Finless T-Belly

Unread post by bgreen » Mon May 09, 2016 5:27 am

Nomas,

The NoFin & Larry's design vary in a lot of ways, but feel quite different. Here is another of my finless boards:

https://www.youtube.com/watch?v=WlvHCGMeh8U

I'm getting a finbox put in so will be able to ride it finned and finless. It will be board # 3 which I have the choice to ride either finned or finless.

Here is something else. Looks like one of Gus Acosta's boards - but finless: https://www.youtube.com/watch?v=LQzulsVOjII

Bob

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: Finless T-Belly

Unread post by nomastomas » Mon May 09, 2016 10:54 am

For me, convex and tri-plane bottoms don't offer the "bite" of a flat or concave bottom, with or without fins. Sure, they go fast and turn, but I don't make as many steep sections with them. And, by "make steep sections" I mean staying high on the face and actually crossing the section, instead of sliding down and then going around the whitewater and back onto the face. You end up in the same place, just a different path. I prefer the high-line, where the speed is found.
"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: Finless T-Belly

Unread post by bgreen » Mon May 09, 2016 4:06 pm

Interestingly some wooden boards handle whitewater better because they have less volume. my foam boards get stuck there because they can't project around it well and one just has no bite in such a situation (the 5 fin bonzer ploughs through). These boards generally don't have any real problems with a higher line, it is the flats that can see them lose speed. With a finless board, especially a wooden one I often am more surfing the wave's energy rather than surfing a board which carves a wave face. The surfing as an extension of bodysurfing comes to mind here.

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest