A Closer Look at Updates to Tensor™
We sat down with NEMO's Director of Engineering to get the lowdown on how our best-selling sleeping pad is now even better.
Before we get into it, can you introduce yourself?
My name is Patrick McCluskey and I’m the Director of Engineering at NEMO.
How'd you end up with this gig?
I got my Bachelor's in science for Mechanical Engineering from CU Boulder, and while I was in school there, I also worked a bit at the La Sportiva warehouse, shipping shoes and boots. During the same time, I spent a couple summers guiding rock climbing trips for Eastern Mountain Sports.
Then I got my Master's in science and Ph.D. in Engineering Sciences (with a focus on Mechanics of Materials) from Harvard. While at Harvard, I also worked as a climbing instructor at a nearby gym.
My first job after school was as a Materials Scientist for GE at the Global Research Center, where I worked on coatings for jet engines, electrical submersible pumps, and additive manufacturing. I came straight to NEMO from GE and have been here for a little over 6 years, working on various aspects of everything we make.
What exactly does a Director of Engineering do at an outdoor gear company?
Basically, I do all the technical stuff that other people can’t figure out! [laughs] Stuff like thermal modeling, mechanical modeling, materials research, manufacturing research, and more.
Why did we decide to update our Tensor Sleeping Pad?
The Tensor is our best-selling series of sleeping pads and we wanted to make it even warmer. It now has the perfect balance of comfort, weight, warmth, and durability for ultralight backpacking. We’re constantly looking for ways to improve this pad to maintain its industry-leading performance.
We made the Tensor 20% warmer without adding any weight or bulk. We did this by removing a very thin layer of polyester non-woven fabric from the top of the pads. The insulated version then received an additional layer of TPU on the inside that undulates between baffles along the length of the pad. The uninsulated version was also updated with a layer of mylar (metallized film) added to the inside. The result is the same stable and quiet ultralight pad, just warmer.
Thermoplastic polyurethane. Thermoplastic means that it can be heated to a malleable state and then solidifies again when cooled — and in the process, it becomes sticky, so it’s often used to laminate weldable fabrics. TPU is traditionally used as welding layers in our pads, but this time we included a layer that was free-floating, weaving in and out of the baffles from head to foot.
Can you remind me what R-value actually means?
R-value is shorthand for thermal resistance. It’s a measure of a sleeping pad’s ability to resist the flow of heat through the pad. Generally, the heat moves from the warm body on top of the pad to the cold ground beneath the pad, and the cold air at the edges of the pad.
Why would you want to have a sleeping pad with a higher R-value?
A higher R-value means a warmer pad and a warmer sleep system. If you’re not warm enough at night you’ll struggle to stay asleep and won’t be well rested for the next day’s adventure. And even if you’re not planning on camping in colder conditions, an uninsulated pad with an extended R-value range is versatile enough to use in the shoulder seasons or unexpectedly cold evenings.
How can you make a sleeping pad warmer without adding any weight to the product?
We used materials more efficiently. The thin layer of polyester that we removed didn’t provide much additional warmth. The undulating TPU layer, however, works very well to reduce convective heat losses. The two layers weigh about the same, so the swap adds no weight but makes the pad warmer — increasing the R-value from 3.5 to 4.2 for the insulated version. The TPU layer also improved the durability of the pad by reinforcing the welds of the pad.
What’s the difference between convective heat loss and radiant heat loss?
Convective heat loss involves the movement of atoms. These atoms gain heat energy from a warm source (your body) then physically move to another location where the atoms lose thermal energy to a heat sink (the ground). Radiant heat loss operates by electromagnetic wave, like visible light but at a longer wavelength. Radiant heat transmits readily through lightweight fabrics and air gaps, but it can be reflected using metallized films.
How long did it take to get this update right?
From concept and thermal modeling to final design and sampling, then refinement and testing, it probably took about two years, which is pretty fast for this type of update.
The new Tensor is also made with 100% bluesign® APPROVED, recycled fabric. Why is that important?
We’re proud to be partnering with bluesign®. They help us identify suppliers that are as concerned about chemicals management as we are. Through restricted substances lists and preferred chemistry guidance, bluesign® helps us choose materials that are better for the environment, workers, and consumers.
Tensor’s known for being especially quiet — no annoying crinkling! Do the updates affect that at all?
It’s still just as quiet as ever. Our mylar layer has cutouts to allow the baffles to pass through and is essentially free-floating inside the pad, so it’s not disturbed as easily when you shift or move around throughout the night. With other pads, when mylar film is used for insulation, it’s welded in place, so any time you disturb the surface of the pad, the mylar is jostled — and makes a lot of noise. The TPU layer that was added to the insulated Tensor is a soft film layer, so it won’t contribute to any noise.
How does Tensor manage to avoid feeling like a waterbed?
The reason it feels stable is because of something called “point deflection resistance.” Our baffles are made from fabric laminated with TPU, and this construction prevents them from stretching and ballooning when pressure is exerted elsewhere on the pad. If you push down with a palm or elbow on one area of Tensor, it doesn’t cause the rest of the pad to expand or adjust because there just isn’t enough stretch in the material. This is what makes the Tensor sleeping experience feel more stable and secure.
Learn more about the Tensor here.