TBG5

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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Re: TBG5

#101

Unread post by nomastomas »

Its been almost a year since my last G5 post, so I thought I would provide an update. First off, I continue to enjoy riding the G5, and always leave the water with a smile. I've pretty much settled on the old FCS "H2" Quad fin set as the best choice for all-around California waves. Since the loss of my ability to produce EPS/Epoxy boards, I have been focussing on converting the G5 design to standard PU/PE construction, and have used the opportunity to make some design tweaks. First, the beveled/concave bottom rail has been eliminated, as has the concave deck, in favor of a more simplistic design (so as not to scare off the new CNC machinist and the new glasser). The key purpose of both features was to keep the rail profile thin, which I have been able to manage by moving to a slightly crowned deck. I also realized the with PU foam being less buoyant than EPS, I would have to adjust my formula for volume. So, now instead of 23L, I'm targeting 25L for my personal board. Again, the crowned deck provided a place to stash the extra volume while keeping the rails thin. I'll probably return to using a stringer, not out of concern for stiffness, but again to make the blank easier to set-up on the CNC machine. I tweaked the location on the bottom for the fin boxes to provide a flat, albeit slightly slanted surface to mount the fin-box jig. (Mounting fin boxes adjacent to bottom concaves is tricky at best.) I kept everything else the same. Waiting to hear from my new glasser to see if he is up to laminating a super short blank. Glassers rarely laminate anything less than 5'4" and have their laminating and sanding racks set up accordingly.
TBG5PU.jpg
TBG5PU.jpg (148.81 KiB) Viewed 1302 times
The other thing I would add is that, thanks to Belly Rider, I have found a new interest in kneeboarding and kneeboard design over the past year which has competed with prone-board riding and design for my attention. While many of the design concepts are transferable, prone riding is of course very different than knee riding and both are very different than stand-up riding. Each form of surfing presents a specific set of requirements to the shaper that can best be understood through direct experience.
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Re: TBG5

#102

Unread post by flojo »

Hey Thomas, what length are you making yourTBG5 ?
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nomastomas
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Re: TBG5

#103

Unread post by nomastomas »

Length based totally on intended rider height. I’m 5-10 and ride a 49”.
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Re: TBG5

#104

Unread post by krusher74 »

nomastomas wrote: Fri Oct 23, 2020 6:20 pm I also realized the with PU foam being less buoyant than EPS, I would have to adjust my formula for volume. So, now instead of 23L, I'm targeting 25L


from my understanding of physics two items of 23L will have the same buoyancy, the only differing factor will be weight. So is the PU board going to have that much more weight to make it need 2L more volume to float the same?
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Re: TBG5

#105

Unread post by GeoffreyLevens »

krusher74 wrote: Wed Oct 28, 2020 3:57 pm
nomastomas wrote: Fri Oct 23, 2020 6:20 pm I also realized the with PU foam being less buoyant than EPS, I would have to adjust my formula for volume. So, now instead of 23L, I'm targeting 25L
Yes, density is key. Think liter of feathers vs liter of lead to cite an extreme example. Even same material, 2 lb EPS at same volume will float a lot more than 3 lb EPS


from my understanding of physics two items of 23L will have the same buoyancy, the only differing factor will be weight. So is the PU board going to have that much more weight to make it need 2L more volume to float the same?
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Re: TBG5

#106

Unread post by nomastomas »

krusher74 wrote: Wed Oct 28, 2020 3:57 pm
from my understanding of physics two items of 23L will have the same buoyancy, the only differing factor will be weight. So is the PU board going to have that much more weight to make it need 2L more volume to float the same?
Actually, weight or "mass" is a critical factor in determining buoyancy. Much of the confusion about buoyancy comes from the two different uses of the term “buoyancy”. In the traditional/scientific use of the term, two objects of equal volume and equal mass(weight) will have equal buoyancy. That is, when placed in a liquid, the objects will displace equal amounts of that liquid. The objects will sink down to a point where the buoyant force of the liquid counters the force of gravity acting on the mass of that object. (“Buoyant force” is a function of the density of the liquid, e.g. Oil is less dense than water.) Two objects of equal volume but unequal mass will have different buoyancy. A 5gal bucket filled with sand will be less buoyant than a 5gal bucket filled with feathers. A surfboard with a polyurethane foam (PU) core will be less buoyant than an identical surfboard with an EPS foam core. (PU weighs approx 3lbs per cubic foot, while EPS weighs anywhere from 2.2lb PCF to 1lb PCF.) As surfers, we can recognize this difference in what we refer to as "float". EPS boards feel more "floaty" than identical PU boards. (Note: When EPS was initially used as a core material, shapers were using the same dimensions as their PU-core boards. The complaint received from surfers was that these EPS boards were too "floaty" compared to their identical PU-core cousins. Shapers responded by reducing volume of the EPS boards.)

Shapers/surfers use the term “float” in a more general sense that includes not only the traditional definition of buoyancy, but also incorporates consideration of board surface area and rider load. Shaper’s have come to rely on board volume as a crude indicator of buoyancy when foam density is held constant. A 30L shortboard is considered more buoyant than a 27L shortboard, but it also has a greater mass and is greater in one or more physical dimensions. Shapers consider the mass of the rider as it relates to the volume of the intended board. Trial-and-error has shown that there seems to be a relationship between the weight of the rider, the volume (buoyancy) of his board and optimum board performance. Boards can be too buoyant for a rider's weight/mass, or not buoyant enough. A problem arises when the buoyancy needs of the rider require a volume that distorts the dimensions of the board to a size that is less than optimal for that particular shape's performance. This is especially the case when one or more of the dimensions are restricted. As an example, “shortboards” are generally limited to less than 7ft in length and 20in in width. At a certain point, the only way to increase volume is to increase thickness. Increasing thickness can lead to increasing the thickness of the rails, and generally, shortboard performance suffers when rail thickness begins to exceed 2” at 1” in from the rail apex. One solution is to use a core material which is more buoyant per liter of volume. In that way, a SB with 1-3/4” EPS rail can provide the same buoyancy as a SB with a 2-1/8” PU rail.

My initial T-Belly shapes had PU cores and were 2-1/2” or more thick. Switching to EPS core allowed me to reduce thickness (at the same 48”x22” dimension) and thereby, reduce volume while maintaining the same “float”. Now, returning to a less buoyant PU core necessitates increasing volume (adding width, length and/or thickness) to achieve the same “float”.
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Re: TBG5

#107

Unread post by bgreen »

Nomas,

Good to hear that you may have a glasser.

The flat area where you allowed for finboxes reminded me of this board.
Wings_finished.jpg
H2_bottom.jpg
I have been very content with my current board, but with the world situation, I was looking at this board that I added the wings to and thinking of a refinement - mostly thicker through the nose.

Bob
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Re: TBG5

#108

Unread post by krusher74 »

I have seen in some articles them ay that some pros can't tell the difference between eps and PU and then dont feel more boyant, but i guess if you used a 3.3pcf PU blank and a 3.3pcf EPS blank then they would be the same.

I suppose the EPS boards can shave off enough weight to make that much of a buoyancy difference.

Is there a buoyancy measurement? for example, if an eps board was 10% lighter than a PU board and they are exactly the same shape how much more buoyancy is the eps and what's the metric you measure than in?
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Re: TBG5

#109

Unread post by nomastomas »

Bob...I prefer a relatively thin nose and a thin tail, with max thickness at or just above center. thin nose for lighter swingweight and easier duck diving; thin tail to sink into wave face when taking off and making turns.

Keith...If it was 10% lighter (less mass) it would be by definition 10% more buoyant, assuming equal volume. "Metrics" are sorely missing from surfcraft design. Most of the data is of the 'experiential/anecdotal" variety. I've ridden and shaped a variety board shapes, from prone-boards to LB gliders using both PU and EPS. In my experience, EPS shapes float higher in the water and feel lighter under-foot, than PU boards of equal volume. And, they also have a hollow ring to them, which some find disturbing (especially on a choppy day).

(Note: hand-laminated EPS shapes differ greatly from molded and/or vacuum-bagged, multi-laminate shapes. This was especially the case in the early days of Surftech and Boardworks, before they had dialed-in the best combination of materials to provide ideal flex pattern. Those early eps shapes had the dimensions of the PU shapes that they copied. The complaint was that they were too "corky" or "floaty"', words used to describe the increase in buoyancy experienced by the rider.)



Like much of surfboard design
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Re: TBG5

#110

Unread post by rodndtube »

Bob, I might be confused on whether you are speaking of a wider, fuller nose plan shape or a thinner, less thick nose area. Photographs and angles can trick the eye... the nose appears narrow with nose kick. I would likely keep the thickness as it appears but go with a fuller plan shape in the nose area a bit less nose kick/rocker, mainly because I believe that you and I ride more forward than back on our boards. Then again, with those suggestions I might add a tad more thickness for the wider nose doesn't dig into the wave during forward turns.
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Re: TBG5

#111

Unread post by bgreen »

The style of board I mostly ride was based on one of Larry Goddard's shapes, as were some of Nomas' early BBs.

Larry favoured a thin nose, because he said the nose didn't do anything. I found these boards, nose-dived at speed, something Larry also found, at times.

My current boards have more thickness in the nose area. A photo will have to wait. I find these boards do a great bottom turn. Obviously it is not just about nose thickness, but I have had a number of boards, with similar shapes, and have been happy with the thicker style nose. Surprisingly, I find them easier to duck dive.

Bob
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Re: TBG5

#112

Unread post by rodndtube »

On the nose thickness it is also the rail shape. I always shoot for the airplane wing leading edge which tends to lift out of the water during minor pearls and through shop. Nose kick doesn't really help much in a nose pearl other than slow and slosh the board down. Some nose kick does help in steep takeoffs and re-entries and too keep the high speed glide moving. We're talking minor nose kick here relative to the typical short board.
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Re: TBG5

#113

Unread post by bgreen »

I'll start a new thread on nose thickness, so as to avoid the hijack.
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Re: TBG5

#114

Unread post by belly rider »

"(so as not to scare off the new CNC machinist and the new glasser)"
Thomas I am still puzzled by the "Glassers/laminating" world and now you through a new curve ball to me when you mention that
CNC machinist are basically fussy and can create problems when dealing with a shapers design made out of a EPS core verses a PU
If CNC machines are programmed to suit the design of the shapers CAD Paipo/kneeboard/surfboad design why can't they just
do it regardless of the core material used (PU, EPS, Wood, etc and any other core on the market)
Furthermore it discomforts me to find out that you basically had to modify a successful and proven hull design (applied both in your Paipo's
and the kneeboards models we worked on) to accomodate the industries CNC machinists
Business is business I guess it does not always apply and the surfing industry might be an exception to the rule
Keep in contact with me should you find another Epoxy laminator in your area and or if the PU / Polyester shop you are working with
can make a board as strong as my Epoxy ones. Innegra Fiber, Carbon/Kevlar, and God knows what else is out there
The boards you made for me are all super and work great-- all Epoxy and EPS based
its all about the ride
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Re: TBG5

#115

Unread post by nomastomas »

David, let me try to clarify...most surfboard CNC machinist are experienced with machining molded surfboard blanks. Occasionally, they will machine a "slab cut" of eps, which is a rectangular shaped blank, with a rocker already cut (imagine a block of eps 4'Hx4'Wx8'-12'L. A hot wire is used like a cheese slicer to cut slices of EPS foam according to the desired rocker curve. The slice is split in half lengthwise, and a center stringer added. This is referred to as a "slab cut".) The molded blanks can be either polyurethane or EPS. My unordinary prone board shapes present a challenge and slow their production. On the other hand, Marko Foam is a well established manufacturer of architectural EPS foam products like fluted columns, ornate window trim, etc. Their machinist are experienced and skilled in machining complicated objects from blocks and/or slabs of EPS foam, as well as molded surfboard blanks. My out of the ordinary shapes were no problem for them. The good news is that I have just recently discovered that Millennium Foam has recently developed a a new blank (5'0"WS) that is a much better fit for my prone shapes.I just need to acquire an Aku file for the blank (the CNC process requires 2 Aku files; a file for the blank and a file for the shape to be cut from that blank). Stay tuned...
As you know, EPS requires the use of epoxy resin. Epoxy resin requires a longer time to harden or "kick" than polyester (PE) resin. Epoxy is also more sensitive to ambient temperature, which can extend or shorten kick time. Conversely, the kick time for PE resin can be modulated by simply altering the catalyst-to-resin ratio. The longer time to kick is not a problem in a one-off, non-production environment, where a laminated blank can rest on a rack for several hours. In a production environment, time is of the essence. This is less of an issue in a large shop, with multiple laminating racks. My previous glasser had over 10 laminating racks, 3 devoted to epoxy lams, while my new glasser has only 2. Slowing production to service epoxy laminations is just not economical for a smaller shop. My new glasser did an excellent job of my recent kneeboard (see below) and is willing to accept the technical challenges presented by G5. Again, stay tuned...
4534FD42-9C52-4D8A-B917-F45E505B18CD.JPG
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Re: TBG5

#116

Unread post by belly rider »

Thanks Thomas for your elaborate explanation. This helps us common folks understand better the complications of building, shaping, glassing boards
I started researching UK shapers and found one out of Jersey on which I am taking a gamble on my next two boards
He is using a new foam (not PU nor EPS) and I am interested to see what's going to come out from his shop
Unfortunately due to Covid Shutdowns and the fact that in this current year I had to make the US trip twice-- Carla and I decided it best to skip out the traditional Jan and Feb trip and opt out for the following year-- 2022
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Re: TBG5

#117

Unread post by nomastomas »

G5-PU Progress Note:

Customer Order for G5 twin received
Shape Aku File created
Blank Aku File created
Machinist buy in obtained
Glasser buy-in obtained
PU Blank ordered from Millennium Foam and maybe delivered today
Probably 5 wks out from completion.

This particular customer has been riding one of Malcolm Campbells Bonzer belly boards for several years. He demo-ed both the quad-fin G5 and a twin-fin G6, and was very impressed with the increased responsiveness. He also preferred the twin-fin set-up to the quad-fin set-up, and thought the quad felt stiffer than the twin.
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Re: TBG5

#118

Unread post by bgreen »

Gday Nomas,

Would the customer be someone I've done a paipo interview with? No need to name names., but that would narrow the field.

Bob
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nomastomas
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Re: TBG5

#119

Unread post by nomastomas »

I don't think so, he's a local Ventura guy, lifelong surfer. While riding the G5, he was having trouble over-turning and doing inadvertent 360s and kick-outs as a result of muscle memory related to turning his Bonzer. The combination of the curvy outline and the location of the fins make the G5/G6 turn on the proverbial dime. His comment was, "I just have to think where I want to go and it goes there".
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Re: TBG5

#120

Unread post by bgreen »

Thanks. I didn't Malcolm had made a lot of BBs. I know 3 suspects who ride them, but obviously not your customer.
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