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D-Flex Triangular Fly Rods

D-Flex Triangular Fly Rods: Changing the shape of fly rod performance.

Fly fishing guide and England International Nick Dunn reports on a new profile of fly rod to hit the market in 2021…

There’s a new kid on the block. “D-Flex” Triangular profile fly rods have been many years in the making and finally it looks like they will become available to fly anglers in 2021.

More than 10 years ago, Dr Chris Underwood, a Doctor of Physics and very keen Salmon angler, wondered how he could make a fly rod that had a dual action. He originally wanted to make a rod that had a more powerful “snappy” forward casting action along with a slower action for a smooth back-cast, initially for Spey casting with a longer rod.

Having made some prototypes during D-Flex’s development, it turned out that the shape the good Doctor deployed, the Reuleaux Triangle, led to some other valuable angling benefits that he had not initially planned for.

The team at D-Flex say, “this is the fishing rod reinvented and it has never been commercially offered before.” In summary, the patented D-Flex triangular profile reduces weight and flexes differently in opposite planes for universally improved performance and a better fishing experience. Of course, there’s much more to it than that though:

Dual Action
D-Flex rods flex differently. More flexible one way and more rigid the other. This is scientifically termed “Differential Flex” and is at the heart of the name “D-Flex.”

Compared with conventional circular rods which flex evenly in any direction, the “Differential Flex” innovation creates a Dual-Action rod. Stiffer in the forward casting stroke and softer, with better feedback for playing fish. Or vice-versa, according to rod type; for example, Lure rods for throwing smaller baits intended for big fish would benefit from D-Flex, offering softness in the casting plane for light lures and stiffness in the opposite plane for when a big fish is in play.

Lighter & Stronger
Triangular geometry is inherently stronger than circular. So, a D-Flex rod needs less material than any circular rod for the same power rating. Less material equals lighter weight, which is especially important for the likes of fly and lure anglers who are making hundreds of casts per day. D-Flex uniquely has the opportunity to make the lightest carbon fibre fishing rod blanks ever made.

Optimized Energy Transfer
The Dual-Action of a D-Flex rod transitions energy perfectly through the casting cycle for a pure, heightened synergy between angler, rod & line. For a single-handed fly rod, the softer action loads optimally and presents true, tactile line feel while the stiffer forward action delivers maximum power and pinpoint control.

Point & Shoot Tactical Accuracy
The D-Flex shape eradicates the unwanted spine effect of conventional rods, and instead naturally generates a performance-boosting Triple Spine Effect, which self-stabilizes and resists ovalisation for perfect straight-line tracking. Result; the line launches precisely where you aim it.

D-Flex Dampens Oscillation
D-Flex’s Dual-Action dampens oscillation in the final moment of a cast more rapidly, generating a superior energy transfer into the line for greater accuracy and control. The result is a supremely crisp, snappy recovery that’s unmatched by any circular rod, and an incredible payoff of smooth power and precision.

It’s also worth mentioning, that the D-Flex triangular cross section means D-Flex joints can’t inadvertently twist and slip.

Why hasn’t this been done before?

Non-circular shapes including triangular, were widely used with old bamboo or split cane rods. The performance attributes are game-changing. But it’s never been done before with the superior modern material: carbon fibre. Why?

This is because of the industry standard “Roll-Wrap” manufacturing process. To manufacture carbon fibre fishing rods in volume, carbon fibre sheets are rolled (between two parallel surfaces of a rolling table) around steel mandrels (which are later removed). Rolling is critical to the process to ensure pressure is applied uniformly. There’s a lot more to it than that of course – but that’s the gist.

Until now, manufacturing triangular rods this way was considered impossible, because triangles don’t roll as needed. But here’s the thing, actually they do – although most people wouldn’t realize or even believe it.

More than 10 years ago now, the inventor of D-Flex and lifelong angler Dr. Chris Underwood invented and patented the process to use a Reuleaux Triangle cross section instead of a circle.

He knew from his scientific work in medical device manufacturing, that a Reuleaux Triangle is a Curve of Constant Width. Meaning it would roll perfectly between two parallel surfaces, just like a circle and with uniform pressure.

It’s actually perfectly possible (and we’re doing it) to manufacture triangular carbon fibre fishing rods using the industry standard Roll-Wrap process. And we’ve got high-performance, ultra-lightweight prototypes to prove it.

It’s taken a while to get there as back then it was an on/off side-project balanced around a full-time scientific career, and it’s a mightily difficult (and expensive) endeavour, self-funded and without any background or contacts in the fishing industry.

But with bucket loads of determination, years of testing and refinement, and eventually a proper team in place, D-Flex is finally here. The team today consists of engineering, commercial, and marketing specialists along with a resident professional angler. Proudly crafting a supremely accomplished, game-changing fly rod that we can’t wait to get into your hands.

“Nothing else out there feels and performs like a D-Flex rod.”




If this innovative new concept has grabbed your interest, you can click here to sign up for regular updates. The D-Flex team will keep you in the loop on the development of this intriguing new rod building innovation and let you know when they are available.

Social media feedback –

“I look forward to hearing more, I’m a custom rod builder so always interested in new products”


“As an engineer I have argued for at least 20 years someone should do this. I am glad it is finally here. Where do I send my money when a 4-weight and a 6-weight are finally ready?”



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