filed under: trail amenities & structures
Carroll Vogel showed us that in the world of suspension bridges we are still looking for the boundaries, we are still finding new structures, applications, and uses of materials.
By Gerry Wilbour, Professional Trailbuilders Association
If, as trailbuilders and advocates, we believe that trails form a critical piece of our green infrastructure, an essential component in the fabric of American life, then suspension bridges make a unique contribution to that fabric and infrastructure. They carry us over rivers, valleys and through treetops. They link together important destinations and communities. They can span much greater lengths than more rigid structures and they make crossings possible that no other structure can. Without them, many of our important trails would not be possible, many of our destinations unreachable.
Being visually appealing and providing access to otherwise unreachable heights, they often become a major trail feature in their own right. Their symmetry is demanded by the structural needs of the bridge itself. From a distance they appear as thin ribbons of steel that push and pull against each other in a symphony of loads and stresses that work together to form a completed whole--whole that is dramatically greater than the sum of its individual parts. In form they are two gentle parabolas, strung together and arching towards each other in a discordant harmony and perpetual tug-of-war, neither one able to move when bound to the other. Each piece contributes to the overall strength and stability of the structure. There is no waste. Even the deck that we walk on contributes significantly to its stability.
It’s only by the skill and dedication of the engineer and builder that they stand at all. Today’s builders stand on the shoulders of bridge builders of the past. We’ve perhaps learned as much from Galloping Gertie--the infamous Tacoma Narrows bridge that failed dramatically in 1940--as we have from the spectacular success of the Golden Gate. It’s only by making and taking note of all the mistakes that we can get it right on a consistent basis.
There are many rigid bridge types that are used on trails including log stringer, gadbury, steel I-beam, steel truss, aluminum truss, prestressed concrete, fiberglass truss, sawn timber, and glue-lam timber and truss. Each style has an appropriate application. Some create a simple functional crossing, and all too often an unsightly distraction from the overall trail experience. In the hands of a skillful builder they can be works of art that carry us over spectacular natural features and inspire our appreciation of the natural world. However, as their lengths grow, all of these rigid bridge types grow exponentially in size, weight and cost. Somewhere between 50 and 150 feet in clear-span length, the structural members required to hold up these styles become so large, they cease to become a practical solution. In contrast, we have yet to find how long a span we can make with a suspension bridge.
Those initiated into the craft can discuss for hours the nuances of suspension versus cable-stay versus hybrid cable bridges. The optimal solution for any given site is determined by a variety of factors and site conditions as well as the skill of the builder.
Scott Groenier, a US Forest Service Structural Engineer who has studied trail bridges across the continent has said that we have trail bridge structures figured out, we know what is possible and have largely defined what can be built and how to build it. We simply have to choose the most appropriate type of structure for the given application. He points out, however, that bridge site selection and site design remains a complex task for each individual bridge, with a variety of site-specific factors to consider.
Carroll Vogel showed us that in the world of suspension bridges we
are still looking for the boundaries, we are still finding new
structures, applications and uses of materials.
After more than a decade of building and repairing trails and bridges in the backcountry for the National Park Service and the Student Conservation Association and training others to do the same, in 1990 Carroll started a private business “Sahale LLC” that eventually would become the dominant national design/builder of recreational cable bridges.
The U.S. Forest Service has long had a substantial inventory of
suspension bridges on its extensive backcountry trail system. Carroll’s
early measured efforts on suspension bridges focused on building and
rebuilding some of these. After working on and learning others designs,
and rebuilding older bridges in need of repair, he began to make his own
adjustments, his own alterations that would reduce cost and make longer
spans with more effective use of materials. Of the more than 200 trail
bridges he built, all of the longest ones were some form of cable
Suspension bridges on trails are a specialty that not many of us, as trailbuilders, try and few are competent to build. It’s a craft that takes a decade or more to really learn and longer to excel at. In making improvements in fittings, fasteners and anchors and developing precise and complex prefabrication made possible by sophisticated engineering and computer-aided design, Sahale was able to build longer, more stable structures and push the boundaries of the art beyond where anyone else had taken it. An active internet presence allowed a nationwide marketing of the product. A "Sahale Bridge or equal" has become a common specification in many public contracts. Truth is, there is no equal. The Sahale standard represents an unusual combination of mountain man, earth-bound savy and high-tech sophistication.
I have known Carroll for almost two decades as a friend, competitor, collaborator and veteran trail and bridge builder. In the past thirty-plus years in business, my company has designed and/or built well over 100 trail bridges and way too many trails and trail systems to count. Because of our common background, many of my conversations with Carroll dealt with details of specific projects, what worked, what didn’t; the challenges of running your own business; problem clients, suppliers and bureaucracies and how to deal with them. How to maneuver a project through the endless conundrum of red tape that too often drives up costs and conspires against individual initiative and creative expression. How to balance family and work life when work is spread far and wide. Few can understand the complexities of running your own construction business, especially in an unusual trade such as this. I always valued the wisdom of his insight and had tremendous respect for the depth of his business acumen – a very necessary ingredient in pulling people and institutions together to accomplish significant tasks.
Carroll had an unusual ability to see the big picture, to envision grand undertakings and how they fit into broad workable concepts and at the same time, the laser focus on detail to pull it off. He knew the beauty of a hand-crafted bridge and the often intricate art of trailbuilding. Both affected how he envisioned and built his structures. He also had the nerves of steel required to spend days at a time assembling a bridge from a bosun’s chair suspended from a cable far from a valley floor on a project on the other side of the continent from home.
Talking story with Carroll a couple of years ago we both expressed that our fondest memories of trail work were deep in the back country in our youth -- his in the vast backcountry of Yellowstone. Years of living and working deep in the wilderness under the tutelage of those who had mastered the art before us leaves an indelible mark, it puts you in touch with the natural world in a way that nothing else can. It teaches you to work, live and build as if you’re always yearning for that deep connection. It strongly affected how Carroll approached his craft.
Like Carroll, Scott Paul touched many with his passion for trail work and wildlands, and left a legacy of excellent trails that continues to keep people in touch with wilderness. Scott also left us with poetry that captures that connection; the poem at right Carroll posted on his company website. Scott was a neighbor and friend of mine, his passing a deep shock to all who knew him. After Scott was killed in a very tragic construction accident on the Drift Creek Suspension Bridge on the Oregon Coast, Carroll’s firm took over the project and completed it. Carroll’s moving tribute to Scott at the Drift Creek Bridge dedication gives us insight into the passion that drove both of them and drives many who take up this line of work. These are Carroll's words:
“Bridges and trails are a metaphor for the human experience. They carry us across seemingly impossible terrain and bring worlds together. Trails, like the continuum of our lives, carry us to and through the great diversity of the earth. Old growth forest, sub-alpine meadow, storm-lashed shore; all linked by trails that rest on the landscape like pathways through time. And the bridges, especially backcountry bridges, allow us to vault chasms that divide, permitting us to experience worlds that seem near enough to touch, but impossible to attain. Simple in form and function, with a singleness of purpose unchanged since the dawn of human history when primitive humans opportunistically traversed a fallen log to reach new land, fresh opportunity. It is no wonder that bridges have come to symbolize human aspirations and folly, and a few to represent some of the greatest achievements of human engineering endeavor.
"Bridges remind us of what it means to be human, to be perpetually reaching out for unachievable objectives, to dream, but to dream our dreams in the reality of the present, while fully awake. Great bridges are grand engineering and architectural masterpieces and building them is amongst the most challenging of construction endeavors.“
If sustainable trails take us lightly over the land, then well-designed canopy walks and towers allow us intimate access to the unique ecosystem of tree canopies. As our knowledge of the natural world grows, the contribution of the part of the forest between the ground and the sky becomes more apparent. Suspension Bridges can carry us over sensitive landscapes and through treetops to create access for observation, study and personal appreciation of that often-unseen part of the natural world. Several Sahale projects in different parts of the country focused on making that access possible.
Carroll left us here this past 5th of July to carry on building trails and bridges without him. The cruel cancer that he had quietly battled off and on for six years claimed his life. He was 56 years old. He leaves behind a loving wife and their 3 wonderful children, a brother, two sisters, mother and his step father, who was also his business partner and structural engineer.
The larger trails community owes his family a huge debt of gratitude that they shared so much of him with us.
In many respects Carroll was several people rolled into one. Some remember him as a musician and fierce conservation activist that had put himself into harm's way many times to protect whales and seals. Others knew him for his years of teaching traditional backcountry work skills to legions of trail builders. He is credited as being one of the five most influential people in the founding of the Student Conservation Association, the nation's largest youth conservation organization. He was recipient of President Bush’s Point of Light Award in 1989 for his work coordinating the restoration of the Yellowstone National Park trail system after the devastating fires of 1988.
In measuring the impact of his contribution in trails, this much can be said: he was the most accomplished trail bridge builder of his generation. He didn’t just build a whole bunch of bridges; many of them inspiring works of art, he raised the bar to a new level and gave us a new vision of what is possible. He built with the passion and the artistry of a master backcountry craftsman, and created an effective system for building suspension bridges that is unequaled.
There is a 360-foot wide gorge that creates a missing connection on a major regional trail not far from my home. On several occasions, I’ve glanced over and seen a Sahale Bridge arching though the trees. It would be a three-fer; a canopy walk that gives us an intimate view into the upper forest ecosystem; a viewing platform for the salmon bearing stream and wetland below; and a major regional trail connection. Unfortunately, it’s still a mirage that quickly vanishes. When I envision more conventional structures built by less artful means at the same site, they largely destroy the first two values to accomplish the third.
Many recent Sahale projects began this way, by someone seeing Carroll's other structures, and then imagining a new important crossing. By developing an effective system for creating them, and showing us that it can be done, Carroll remains a bridge between our hopes and our dreams and their realization in the physical world--just as he was often the bridge that brought people together to accomplish some very significant tasks, including a lasting legacy of spectacular bridges.
Published July 2010
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