Scouting founder Robert Baden-Powell believed every Scout should know how to build bridges. From designing the structure to gathering materials and putting it all together, bridge construction combines technology, teamwork and enthusiasm to complete a span that is memorable and useful.
A bridge on a hiking trail can be as simple as a log across a narrow gap. A more serious one relies on sturdier materials like rope and poles. A rope bridge Baden-Powell described in his 1908 manual, Scouting for Boys, is what today’s Scouts would call a monkey bridge.
This is a classic pioneering project, and a variety of styles and instructions have been shared many times, from a 1965 Boys’ Life article penned by Scouting leader and author William “Green Bar Bill” Hillcourt to various editions of the Pioneering merit badge pamphlet.
If Scouts don’t have a stream or small gully to cross, they can build the bridge in a meadow or backyard. Follow safety rules, ensuring the foot rope is no higher than 6 feet off the ground and no longer than 25 feet between A-frames. Using a 50-foot rope, the maximum span between A-frames should be 20 feet, with the extra length being used for anchoring the bridge.
Before building any pioneering structure, it’s necessary to first acquire the wherewithal to experience success. The skills, along with the lashing ropes and poles required to build a monkey bridge using double A-frames for better stability, can be used time and again, for a variety of pioneering projects and troop meeting activities. Here’s how to build a monkey bridge.
- Eight 8-foot-by-4-inch A-frame legs
- Four 6-foot-by-3-inch ledgers
- 14 15-foot lashing ropes for square lashings (Use 1⁄4-inch manila for all lashing ropes.)
- Six steel rings or locking carabiners to join grommet and rope tackle
- Two 1⁄2-inch-by-10-foot polypropylene ropes for rope grommets
- Binder twine to create loops for tourniquets
- Six 10-foot lashing ropes for round lashings
- Two 1⁄2-inch-by-50-foot hand ropes
- One 1⁄2-inch- or 3⁄4-inch-by-50-foot foot rope
- Five to seven 8-foot lashing ropes for stringers
- 12 24- to 30-inch-by-21⁄2-inch pioneering stakes for two 3-2-1 anchors
- Two pieces of scrap burlap for saddles
1. Begin by building four identical A-frames with the 8-foot and 6-foot spars. Make sure the A-frames are all uniform in size when lashed together. Lash them together with three tight square lashings. You could also use shear lashings at the top of the A-frames.
2. Once you have four identical A-frames, it’s time to make two pairs of double A-frames. Stand up two A-frames so they overlap each other one-half their length (about 3 feet). Join the legs together where they intersect with a tight square lashing. Finally, lash the two 6-foot bottom ledgers together where they overlap with three tight round lashings. Do the same for the other double A-frame.
3. Drive the pioneering stakes into the ground first with three stakes together, then two, and then one. Use loops of binder twine and a small stick in between each set to form a tourniquet. Both 3-2-1 anchors should be installed about 10 feet from where the A-frames will be erected. Place a rope grommet around the front stakes, before applying the tourniquet joining the three front stakes to the middle two.
4. Position the double A-frames no more than 20 feet apart from each other. Lay the foot and hand ropes alongside the A-frames. Attach the stringer ropes to a hand rope with a clove hitch at 3- to 4-foot intervals along the hand rope. Make roundturns around the foot rope and tie the running ends of the stringer ropes to the other hand rope with a clove hitch.
5. Make two saddles by folding pieces of burlap, placing one above the square lashings in the middle of the double A-frames where they intersect. This is where the foot rope will rest.
6. With the double A-frames held in place on each side, place the foot rope over the saddles, and tie the hand ropes to the top of the A-frames with clove hitches on a bight.
7. About halfway between the anchor and the A-frames, tie a butterfly knot in the foot rope to form a fixed loop for a rope tackle (trucker’s hitch). With Scouts still holding the double A-frames in position, use the rope tackles to put strain on the foot rope. Next, pull the hand ropes tight and attach them to the anchors using rope tackle or roundturns with two half-hitches.
8. Once all the ropes are tightened, check the knots and lashings before crossing the bridge. Allow only one person on the bridge at a time.
Bridging the gap
Scouts can celebrate their bridge’s completion by crossing it and reflecting on how the project came together. What went well? What would they do differently next time? What roles did teamwork and leader-ship play in the project?
After it has served its purpose, the bridge can be dismantled: The ropes can be coiled and stored with the poles in a dry place, ready to bring out for the next pioneering project.
Helping Scouts realize they have the power to plan and construct big projects is a practical way to bridge the gap between the promise of Scouting adventure and fulfilling that promise in the field.
Robert Birkby is author of three editions of The Boy Scout Handbook, two editions of the BSA’s Fieldbook and the newest edition of the Conservation Handbook. Find him at robertbirkby.com
Special thanks to Larry Green