We set out to build a simple heat box to help saturate the skis with wax after stone grinding. Little did we know that we would end up with sun tans, scorched fingers and the largest ski oven in the world.
Building a heat box has to be the number two summer DIY project for cross-country ski nerds right behind rollerboard construction. After a summer of sitting in front of the computer dealing with the planning, accounting and worrying required to start up a business that involves retail sales, on-line sales, stone-grinding service, ski camps and coaching, I was excited to roll up my sleeves and tackle something physical and real.
I had a lot of design ideas in my head based on seeing countless examples of them all across the country. A heat box is almost like a ski enthusiast’s badge of honor – a public way to show you are serious about the sport. In my travels I think I’ve seen the full range – from dusty crawl-spaces with scary old space heaters to crazy space-ship designs that look like clean rooms and have infrared heating. My goal was to create something simple and reliable that would work well in a production environment. Capacity had to be around 50 pairs of skis, the temperature control had to be very precise and it needed to be easy to load and unload. It also had to be somewhat portable because we will be moving our whole stone grinding operation to West Yellowstone for the Fall Camp.
My trusty assistant Peter and I sat down to work out the design. I wanted to use rigid foam insulation panels placed in 2x4 frames. Peter liked the idea of the insulation, but suggested we make it out of steel or aluminum. Peter headed off to the Home Despot and discovered that the metal options added approximately $8000 to the cost, so we bought $20 worth of 2x4’s and a fire extinguisher.
I spec’d out a whole bunch of industrial components for the heating element and temperature control. I have seen a lot of heat boxes with cheap space heaters and they probably work just fine, but that approach scared me. I would be absolutely mortified if I ruined one pair of skis, let alone 50 because a cheap space heater fried them, so it was an easy decision to go with quality parts.
A few days later, an industrial stainless steel heat element, NIST-traceable temperature controller and two high-quality 230cfm fans arrived in a big box with some other fancy electrical gadgets we are using to build our ski testing fixtures. We pulled everything out, ignoring the instructions as usual, and were immediately impressed at how quickly the heating element scalded our fingers.
A less severe occupational hazard was the glare of the sun off of the reflective skin on the insulation. Sunglasses and lemonade were required during assembly of the panels and as I ripped grooves into the 2x4’s, Pete slid the panels in and nailed them together to form the back, top, bottom, sides and double door for the front. The panels were great: strong and light, although perhaps a bit too bright for full-sun installations. With all of the panels complete we assembled the box and installed the shelving and electrical components.
The final product is massive. Internal space is 4 feet high, 2 feet deep and 7 feet long. I was overly conservative estimating the spacing between shelves, so instead of being able to fit 7 rows of skis, we can do 11-12. Each shelf holds 7-8 pairs, so instead of the goal of 50 pairs, we have room for 80-90. Oops, I better get on that marketing stuff.
We created a panel to divide the top and bottom since most of the batches we run will not require full capacity. It allows us to run about 30 pairs in the lower compartment without heating up the entire box, but we can quickly yank the divider if we need more space.
The next step was checking the heating consistency. The box needs to be heated evenly throughout and the temperature needs to be precisely controlled. It takes about 10-12 minutes to raise the entire box to 60C from 20C when empty, so it should take a load of skis up to temperature pretty quickly. We took temperature readings from locations all around the interior and adjusted the fans so that our air flow created a very consistent temperature throughout. Our maximum temperature difference was 1.5 degrees C between the hottest and coldest spots, and once up to temperature, it did not fluctuate more than 1.5 degrees C from the set point.
Next up is to run more testing with the box full of old skis to measure temperature differences and verify that we are not getting hot or cold spots. Our stone grinding machine is arriving here in less than two weeks, so it is great to have the Behemoth up and running. While the capacity is way beyond what we need, it will be helpful to be able to put large batches in overnight. It will allow us to run one batch of skis at a lower temperature for longer instead of having to run multiple batches shorter at higher temperatures.
If you are interested in the parts list that we used for the behemoth, we will be happy to email it to you. Just send an inquiry using the feedback form on the contact page.
The Behemoth in full glory