Photos courtesy Blackstick
A Carbon-Fiber Sunshade Solution
Nanette Hultgren lives in Palmetto, Florida these days and runs a thriving business there that sells an array of innovative carbon-fiber sunshade support poles. She calls the business BLACKSTICK and, over the past decade, the burgeoning little company has gradually supplanted and indeed eclipsed her original, awning and upholstery operation, Shellback Canvas. A Shellback, of course, is an honorific given to a salty soul who’s crossed the equator by boat. Hultgren earned the designation in her more youthful years after a stint at Cal Maritime got her a job on a large, oceangoing tugboat. The long, bluewater voyages ultimately took their toll, however, and Hultgren decided that making biminis, cushions, boom tents, awnings, sunshades and other canvas products—and essentially being home every night—was a heck of a lot more fun than spending months on end plunging across the high seas.
Eventually, however, a niggling little problem bobbed to the surface. The only supports she could find for her biminis and sunshades, it seemed, were inferior to the craftsmanship she was putting into her Shellback products. The only stainless-steel poles she could find were too heavy, aluminum (even if it was fairly heavy-gauge stuff) tended to bend and PVC was too flexible to offer even reasonable wind resistance.
“So, I finally decided that carbon fiber was the best bet,” she says. “It’s light, strong and doesn’t rust. But when I priced out the carbon-fiber poles from the mainstream manufacturers, the cost was prohibitive. So, I decided to make my own carbon-fiber poles. Little did I know, back then, that I’d be spending the next ten years developing a new approach to creating carbon-fiber composite tubes.”
Today, most carbon-fiber composite poles for sunshades, awnings and biminis are created via a rather complicated, expensive but long-standing industrial process. Typically, the whole thing starts off with woven fabrics that have been pre-impregnated with epoxy. Until these “pre-preg” materials are actually used, though, they must be transported and stored at very low temperatures to forestall a premature cure. The next step entails applying a release agent to a mandrel and then tightly winding on a swathe or swathes of pre-preg fabric until the desired tube thickness is achieved. Following the application of a form of shrink-wrap tape that tends to compress the rolled or wrapped fabric, baking the part in an oven or autoclave at a high temperature comes next. Then finally, extracting the mandrel with a dedicated machine completes the process.
The technology that Hultgren’s invented and patented over the past few years is, she thinks, superior to the technology that’s currently used to create most of the mandrel-wrapped, pre-preg shade and awning poles on the market. For one thing, it’s comparatively less complicated and less expensive, in large part because pricey, difficult to store and handle pre-preg fabrics are not necessary and neither is a large oven or autoclave. And then she takes an entirely different approach to the composition of the carbon-fiber fabric that she employs .
“Instead of winding pre-preg onto a mandrel,” she says, “I use a braided sleeve that goes over the mandrel very much like a sock goes over your foot. This creates a support pole that is extremely tough and flexible thanks to the multi-directionality of the fabric in the sleeve. It’ll better handle the ever-changing stresses put on the pole, like wind and boat speed. By comparison, the pre-preg products are strong vertically, due to the orientation of the weave of the fabric, but not so strong laterally. This makes it hard for them to stand up to the wind and other sideways stresses without eventually failing. Some manufacturers even specify the use of support straps to keep their products from breaking.”
Seriously detailed aspects of Hultgren’s methodology are proprietary. But suffice to say that, in general, factoring in a two-part compression mold and a novel approach to releasing agents makes it possible for her to create a variety of support poles (thanks to a patented bell-shaped receiver, some can be broken down into two pieces for easy storage) that are basically made up of very resilient, wind-resistant, boat-speed-resistant braided carbon fiber that’s been thoroughly infused with conventional epoxy resin.
“Because the BLACKSTICK products are so popular these days,” she says, “I’ve had to get out of the canvas business altogether, although I do recommend Serge Ferrari Solstis 86 fabric to my customers since it’s so dimensionally stable and doesn’t stretch and sag over time. Otherwise, I’m barely able to keep up with demand.”
