Quad Concave Body Board Study

What works and what doesn't. Share design ideas, references and contacts for paipo board builders.
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Uncle Grumpy
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Re: Quad Concave Body Board Study

#81

Unread post by Uncle Grumpy »

The first alaia I built was slightly oversize. Over time I slowly paired it down little by little eventually thinning it out to to where it was thin enough to flex enough to really give some spring back when it was pushed. Less than 3/8ths"
It was the best thing ever. It felt alive and was such a blast to ride; Until the day I lost my grip on it and it came up in two pieces after we both got pummeled. Been trying to get that feeling ever since.
Paipo surfer in repose,
Nose on the nose,
No grunting he-man pose.
See how fast he goes!
What is it he knows?
CHRISPI
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Re: Quad Concave Body Board Study

#82

Unread post by CHRISPI »

Flat laminates have very good twisting flex but bad bending flex or rocker flex ,I run 5mm x about 50 mm foam strip along the bottom centreline .Blended into the bottom surface making a lengthwise domed rib and the stiffness is control by how many layers off clothe laminated , good twist flex around a stiffer rocker flex
PhillyViking
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Re: Quad Concave Body Board Study

#83

Unread post by PhillyViking »

Good idea to go a bit big on a design that can be refined down to get right sized flex. You can always add material but it seems easier to incrementally remove. I have been putting cork on the deck so I can do the same on the bottom.

Somewhat like Crispi's approach, I notice that using Carbon Fiber tape or similar materials are used on short-boards etc. in a very targeted manner to get the right kind of stiffness where needed. Since we ride prone we do not have to concern ourselves with the concentrated weight of our feet. But there might be an argument for only taping under the bulk of our weight to control rocker flex allowing the flat laminate to be looser so the board can shape shift more like a mat or store energy for recoil in a turn. However, on such a short paipo don't we end up taping the entire length in which case we might just as well use a wood stringer.

Likewise, if I use a 2 lb EPS core and thin out the nose and tail thickness and make the area under my weight thicker then doesn't that thickness give me some extra rocker control where I need it most.

The 48x19x1" board I discussed in this thread only had one layer of cloth on the bottom (7.9 oz Basalt/Innegra Weave) and none on the top. I glued cork directly to the EPS core. However, It did have a stringer. I had it in some 7' dumpers this season and it did not break. The Basalt has strength somewhere between carbon fiber and S-glass but has better damping characteristics than carbon. The innegra will take compression hits and bend rather than break. I generally liked the flex (it has a good bit as you can imagine) but I might focus on whether it could use even more rocker control and I was actually surprised it did not break. I really intended it for small shore breaks and not 7' dumpers. Ironically. I eventually just went to my beloved mat when it got small.

I noticed that Tom Wegener put some wood strips inside some of his EPS Alaia but not necessarily for the length of the board. It looked liked he routed out a channel and glued in the strip of wood. By putting the strips inside he could have a wood skin that could be shaved down until the desired flex was obtained. That approach allows more targeted rocker control then a stringer built into the entire blank. The downside is that once you do it your done .. Chrispi's approach allows you to add/subtract on the outside after experience although doing so also changes your bottom contour.

BBs have internal rods as well and some can accommodate swapping for conditions.

If I was to add targeted tape I would use Basalt rather carbon fiber or fiberglass and go internal. I could keep the layers even by shaving enough off the core for the tape thickness. Or would the resin just smooth that out? If I went easy on the internal tape I could always add a bit more to the exterior without impacting shape too much.
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krusher74
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Re: Quad Concave Body Board Study

#84

Unread post by krusher74 »

Bodyboards have no rocker, just a nose kick in the front 6", other than that they are flat, I guess in a quad concave you could say that it gives the tail 1/4" rocker.

Did you see the chambered wood board i already made? https://mypaipoboards.org/forum3/viewto ... ?f=4&t=544
PhillyViking
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Re: Quad Concave Body Board Study

#85

Unread post by PhillyViking »

Just reviewed your chambered board. Very cool. How does it ride compared to your SDF boards?
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krusher74
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Re: Quad Concave Body Board Study

#86

Unread post by krusher74 »

PhillyViking wrote: Mon Nov 02, 2020 6:05 pm Just reviewed your chambered board. Very cool. How does it ride compared to your SDF boards?
I got the shape of it wrong, to much belly in the nose, so it needed a powerful wave to be planing on the back, if the wave went soft and i needing to move forward to speed up then the belly pushed to much water. It certainly had a different feel being wood. sfiff i think But ultimately getting the hand shaping wrong did not let me compare like for like.

I swapped it for a surfmat to try one of those out.

here is an interesting pic for fluid dynamics i saw today
Attachments
water shed.jpg
CHRISPI
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Re: Quad Concave Body Board Study

#87

Unread post by CHRISPI »

Fluid mechanics love it I spend a lot time watching wakes, vortexes on clips like this but this one has stumped me .
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Uncle Grumpy
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Re: Quad Concave Body Board Study

#88

Unread post by Uncle Grumpy »

Looks like a stall from here.
Bodyboard version of a tail stomp.
Paipo surfer in repose,
Nose on the nose,
No grunting he-man pose.
See how fast he goes!
What is it he knows?
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krusher74
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Re: Quad Concave Body Board Study

#89

Unread post by krusher74 »

These popped up the other day, shows how little of a board is in the water.
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quad2.jpg
quad.jpg
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