Necessity Leads to Hoop House Invention
During my tenure with the Noble Foundation as a horticulture consultant, I've had the opportunity to meet many innovative growers. I met one such person this past September on the farm of Tod and Jamie Hanley at a hoop house conference sponsored by the Kerr Center for Sustainable Agriculture. More than 100 participants had gathered to erect a 17-foot by 102-foot hoop house (aka high tunnel). Many hands made quick work. Under Tod's direction, we were able to assemble the structure in what could be a world record time - two hours. Material cost for this 1,700-square-foot house was less than $1,000 or about $0.60/square foot.
For Tod, the process of designing such an inexpensive structure began two years ago when he attended a hoop house workshop conducted at the Noble Foundation. It was here that he was introduced to a no-frills hoop house that uses rope as an alternative to wiggle wire or lath to secure the poly covering to the frame. Tod liked what he saw, but had issues with the cost of the structure. Using his training in mechanical engineering, he quickly began a quest to improve the design while making it less expensive and quicker to assemble.
To cut the cost of the hoops, he fabricated a hoop bender. Instead of the standard round tubing, he chose square steel tubing to eliminate the twisting that can occur when using a homemade bender to bend round tubing. Tod realized a 50 percent savings on the cost of hoops by bending his own.
Tod has also devised an innovative method of anchoring any house using rope straps. Most ground posts consist of steel pipe driven into the ground 20 to 30 inches. When pounded into dry ground, the top of the pipe has a tendency to flare, which can present a problem when the hoops are installed. To avoid this problem, Tod uses 17-inch pieces of 5/8-inch rebar to anchor his houses. The rebar stakes are driven to a depth of only 11 inches and at an angle of 15 degrees. The top of the stakes are slanted towards the house interior. Tod's experience has shown stakes installed at an angle are more resistant to being pulled out of the ground.
On structures that utilize rope straps, the rope is typically attached to the ground posts via an eye bolt or holes drilled in the pipe. Tod has devised a less expensive and faster method of attaching the rope. The process involves forming a loop in the rope using a knot, placing the loop over the rebar stake on top of which a ¾-inch washer is placed followed by the hoop. The washer prevents the attached end of the rope strap from riding up over the stake while the hoop keeps the washer stationary. When the rope straps are cinched tight, the hoops and poly covering are secured firmly to the rebar stakes.
In Tod's case, necessity truly was the mother of invention. Since learning about hoop houses, he has always appreciated their usefulness; he just hasn't always appreciated their cost. He decided to do something about it, and his design innovations will benefit other hoop house growers and the local foods movement as a whole. Good job, Tod!
To view drawings and learn more about the "Hanley" hoop house, visit the Kerr Center Web site.