Testing The Dark Arts Of Carbon Nanotubes
The search for the better board continues. Sometimes it involves exploring less toxic materials, other times the motivation is improved performance or strength, but always the search involves rigorous testing.
The last time Swellnet spoke to John Dowse from Sanded was in 2020 and he was running tests on basalt fibreglass.
Sanded, for those that don't know, is a surfboard chemical and material retailer located on NSW's Central Coast. However, rather than merely stock and sell, John also likes to indulge his inner egghead, donning the scientist's white lab coat and testing the stuff he peddles.
Recently, John was put onto carbon nano resin, which is epoxy resin infused with carbon nanotubes and is a material that's become increasingly popular, used in everything from kitchen benchtops to big bore firearms.
When it's used in surfboards, carbon is usually either woven into the cloth or sometimes it's the whole cloth itself - see the work of Dick Van Straalen, Aviso, or what's coming out of the Dark Arts factory in San Diego. In contrast, carbon nano resin features tiny - hence the 'nano' - tubes of carbon that are mixed into resin and then applied to a cloth of choice.
So, rather than resin simply reinforcing the fibreglass, the carbon nanotubes reinforce the resin which then also reinforces the fibreglass.
Well it sounds good in theory, and it's being touted as wonder stuff, but, as he's done with many other materials, John wanted to run tests before jumping on the hype train.
There were two types of tests. The first was to make a surfboard using one layer of E-glass (standard fibreglass used in boards) laminated with epoxy resin mixed with carbon nanotubes, over an EPS core. This was to get a sense of performance and feel, those unquantifiable sensations that delight or detract when we're on a wave.
The second was what you might call the hard data. Various samples of E-glass laminated with and without carbon nanotubes, then compression tested till breaking point, with the results recorded. Every sample was tested twice to confirm the data.
When it was finished, the board, according to John, was "lighter by about 500 grams - taking a layer of 4oz off the board saves about 200 - 250 grams - and it feels solid." The extra 250 - 300 grams weight saving is possibly because less resin gets used when nanotubes are mixed in.
Also, while making the board John was asked about the possibility of the carbon conducting electricity and perhaps the sander getting zapped while working on it. "The only thing we noticed," said John in reply, "was that the sanding discs got a static charge that clogged them way quicker than normal. So that's maybe something to be aware of."
The laminating process was the same as normal, with John reporting his "first impression after curing was that it was hard to thumb so it feels light and strong, and would definitely pass the “pick up in the shop” test."
And the reason for that? "I think that the nanotubes fill the cloth weave so it makes a harder surface - though only slightly," says John.
When we spoke, John had surfed the board five times and it had "only very slight impressions in the deck" and that it rode well, feeling "slightly whippy" owing to the reduced weight.
The other tests, however, the ones conducted in a lab and hence free of human prejudice, were the ones that mattered.
These tests were done with 28kg3 EPS foam (the preferred foam core for machine cutters) using carefully measured epoxy resins, hand laminated, then left for seven days to cure without ovens. "In other words," says John, "we wanted to get as close as we can to how your surfboard manufacturer would do it in their factory."
Considering the board was made with one layer of E-glass, let's check the results of that test first:
Applied weight in kilograms up the Y-axis, movement in millimeters across the X, you can see the orange line - which is 4oz E-glass laminated with carbon nanotubes - survives breakage just that bit longer than the E-glass laminated with normal epoxy resin. They both get to approx 300 kgs, but the board with carbon nanotubes bends approx 15mm before failing.
"It's a very minimal improvement," says John.
On its own, this isn't hugely surprising, though it may make a case for pro boards - which are generally glassed with just one layer - using carbon nanotubes. They'd get a touch more strength and a touch less weight.
What did raise eyebrows was the comparison test using two layers of 4oz E-glass.
Sames axes, though the carbon is the grey line, standard epoxy the blue. As you can see, when using two layers the carbon nanotubes snapped first.
"My thoughts on this test," explains John, "would be that the carbon nano filling the weave gives it another substance to fail in between layers." Having two layers effectively reduces the board's necessary flex.
Considering most boards - pro boards notwithstanding - are built using two layers of cloth on the deck, this test was an important one.
While he was in testing mode, John applied the same procedure to basalt cloth in both one layer and two, plus another run of two layers of E-glass.
The light blue line is one layer of basalt laminated with carbon nanotubes, which lasted until the machine clocked out at 450kgs. The slight deviations around 350kg and 410kg are, according to John, "slight fractures in the fibre but not enough to fail."
The grey line is two layers of basalt laminated with carbon nanotubes, which also lasted until 450kgs, this time without any fracturing.
The dark blue line is another test of two layers of E-glass laminated with carbon nanotubes, which failed at 350kgs, exactly the same as the previous test.
So, the takeaways from all this tesing?
Firstly, carbon nanotubes 'may' have a place in manufacturing though it would be specialised - think shaping for Championship Tour surfers - or whenever one layer of cloth will suffice.
Secondly, basalt has once again flexed its might as a cloth with backbone.
The last words go to John: "I was hoping for better results to answer the hype and cost around carbon nanotubes, but it's good to get a result either way."
"In summary, for the cost of the resin, carbon nanotubes don't have enough performance advantages to make it viable."
The search for the better board continues...