Using the 14′ Double Ladder Signal Tower as a point of reference, here are the plans for a very tall campsite gateway that stands out (and up) and serves as an impressive feat of Scout engineering. One of the perks included in this project is it provides an opportunity for new Scouts to experience hoisting a “boy-sized” structure replete with their own special colors e.g. their patrol flags.
Since this 14-foot structure isn’t climbed on, the spars can be considerably thinner in diameter. Bamboo is ideal. Lashing on those flags attached to each corner creates a spectacular effect and hence the name “4 Flag Tower!”
14′ Tower Gateway Schematic / Gateway to a Scout Expo Photo
Note: This design is not self-standing. Therefore, using it as a gateway at a camporee or Scout Expo with the necessary guylines requires an area wide and deep enough to accommodate a 16 x 16-foot space.
Scouts lash together a 4′ Side.
Materials Needed:
four 2-1/2 to 3-inch x 14-foot leg spars
six 2-inch x 8-foot X-brace spars
four 2-inch x 6-foot X-brace spars
four 2-inch x 6-foot support spars
six 2-inch x 4-foot leg spreader
forty-five 15-foot x 1/4-inch lashing ropes
four 25-foot guylines
eight 24-inch pioneering stakes
Assemble the 4-foot sides. Begin by laying out two pairs of 14-foot spars for the tower legs, side by side, 3 and 1/2 feet apart. Be sure the butt ends are even at the bottom so the tower will stand up straight.
NOTE:All lashings need to be very tight.
Diagram 1
Lash the legs together starting with a 4-foot bottom leg spreader about 6 inches up from the butt ends. Lash on a 4-foot middle leg spreader in the middle of the 14-foot legs (7 feet up), and a 4-foot top spreader about 3 inches from the top of the 14-foot legs.
When the legs are joined with the three 4-foot spreaders, lash on two 6-foot X-brace spars using square lashings to lash the ends to the legs, and a diagonal lashing where they cross, forming a trestle in the bottom half of the legs (see diagram 1). Three of the ends are lashed to the outside of the legs, and one on the inside, so that a slight gap is created where they cross. As the diagonal lashing begins, this gap will be cinched together with the timber hitch. Repeat the whole process with the other two 14-foot legs.
Diagram 2
Join the 4-foot sides. Turn both sides up horizontally, parallel to one another about 5 and 1/2 feet apart. Make sure the bottoms are even.
Lash on one of the 6-foot support spars directly above the 4-foot middle spreader (see diagram 2).
Lash another one of the 6-foot support spars directly under the 4-foot side spreader at the very top.
Lashing the X Braces with a Diagonal Lashing.
Now, lash on two of the 8-foot X brace spars diagonally between the two 6-foot supports using square lashings to lash the ends to the legs, and a diagonal lashing where they cross forming a trestle in the top part of the wide (6-foot) side (see diagram 2). Three of the ends are lashed to the outside of the legs, and one on the inside, so that a slight gap is created where they cross. As the diagonal lashing begins, this gap will be sprung together with the timber hitch.
Lash the other side. To make the lashings on the other side, you have to get the whole crew together to carefully lift and roll the tower over 180° so that it’s laying on the X-brace, and the other sides of the 4-foot sides are easier to get to.
Repeat the same procedure as before.
Scouts carefully lift the structure and rotatie it 180° to lash the other side.
Lash on the middle X-brace. This X-brace is what will keep the four sides from racking. Lash the two remaining 8-foot X brace spars diagonally across the legs just under the 4-foot middle leg spreader (see Tower Gateway Schematic on the top of this page). Use square lashings to lash them to the legs and a diagonal lashing where they cross. To accomplish this, some crew members will have to hold up the top of the tower so that there is better access to all four ends of the 8′ X brace spars.
Lash on the flags. If you want a flag or flags to fly from the top of the tower, lash the flagpole(s) to the top of each tower legs using a couple of tight round lashings.
Tower Gateway Layout
Anchors and guylines. When all the lashings are done, move the tower to where it will be hoisted. Before actually hoisting the tower, lay out the position of the four legs on the ground. Then determine where the four anchors for the guylines will be placed to steady the legs of the tower.
Using the pioneering stakes, build four 1-1 anchors. Each should extend 16 feet, 45° out from the leg.
NOTE: Make sure the flags are unfurled before hoisting the tower.
Hoisting the tower. You’ll need a whole crew to do the hoisting. Get ready to hoist the tower by delegating the following:
One signal caller who tells the crew members when and how fast to pull on the ropes.
One safety officer who observes for all safety considerations and signs of trouble during the hoisting.
Four Scouts to serve as “Lifters” to lift the top 6′ support spar that’s on the ground. Their job is to first left and then push the tower up.
Two Scouts, one on each of the 2 guylines attached to the legs, to make sure the tower isn’t over pulled and topples over
Four “Pullers” who will use the two guylines as hoisting ropes to pull the tower until it is standing
We did it!
When everyone is in position, the signal caller should direct the Scouts on the hoisting ropes (the pullers) to hoist the tower into position, while the lifters start lifting. Care should be exercised not to over pull the tower.
As soon as the tower is standing, four Scouts should temporarily tie the guylines to the anchors using a roundturn with two half hitches.
Heeling the tower. If the tower is uneven, you can heel the the butt ends of the legs 4 to 6 inches deep as needed to make it more level.
Tighten the guylines. As soon as the tower is in position, go to each of the anchors and untie the Roundturn with Two Half Hitches and replace it with a rope tackle. Use the rope tackles to hold the tower steady, by gradually applying strain to each of the four guylines at the same time. Do this by tying a butterfly knot in each guyline about 6 to 8 feet from the anchor. Then wrap the running end of the guyline around the forward stake of the anchor and back through the loop in the butterfly knot. When rope tackles are tied to all four anchors, gradually tighten the lines. Apply enough strain to each of the guylines to hold the tower firm and in a vertical position. Then tie off the rope tackles and secure the running ends with half hitches.
Hoisting a Larger Version: 17′ high x 8′ wide x 6′ deep
It’s a pretty safe to say most Scouts love to climb things. So, it makes sense that if a monkey bridge is combined with something to climb on, it will be even more fun. The challenge in constructing a project like this is to assure the structure can safely support not only the weight of those climbing on the platforms, but also the continual stress created by repeatedly crossing the rope bridge. Building this version of a double platform monkey bridge entails quite a few subassemblies and a procedure with many steps. Basically, with the materials listed, the ropes span a distance of 25 feet between two identical square platforms 4 feet wide and 8 feet high. At the front of each platform is an X-brace just under 5 feet high, providing a V for the foot rope. The hand ropes run through the junction where the X-braces intersect the top of the front legs, and then extend down joining the foot rope at a log-stake anchor 10 feet behind the back of each platform.
Bridge in operation during a Scout Expo
Here are the materials needed to construct the project:
eight 8-foot x 4-inch spars for platform legs
four 8-foot x 3-1/2-inch spars for X-braces
four 6-foot x 2-1/2-inch diagonal side braces
eight 4-foot x 3-inch spars for side base spreaders (4) and platform supports (4)
sixteen 4-foot x 2-inch spars for ladder rungs (10), handrails (4) and X-brace leg spreaders (2)
twenty-four 4-foot x 2-inch floor spars
two 4-foot x 4-inch log and stake anchor logs
sixteen 30-inch pioneering stakes for 2 log-stake anchors
sixteen large wooden stakes for the 8 guyline 1-1 anchors
sixteen small tourniquet stakes
two rope grommets with large O-rings
one 70-foot x 1/2 or 3/4-inch manila foot rope
two 70-foot x 1/2-inch manila hand ropes
eight 8-foot x 1/4-inch manila spanner ropes
thirty-six 15-foot x 1/4-inch manila lashing ropes
twenty-six 20-foot x 1/4-inch manila lashing ropes (for X-braces, base spreaders and platform supports)
eight 25-foot x 3/8-inch manila guylines
four 35-foot x 1/4-inch manila lashing ropes for floor spars
six burlap or canvas saddles (for the foot rope and hand ropes)
two large mallots
Binder twine
Tape Measure
Anchors are being built as sides are being connected.
Tips:
• Participants should be well-acquainted and experienced in the skills required for building this project.
• Select a project leader who will divide the participants into work groups, assign tasks, and oversee operations.
• Before proceeding, position the materials in proximity to the location where the project will be placed. It’s good to organize the materials by the tasks for which they’re needed.
• Depending upon how many Scouts are participating (will there be a small group of 6 Scouts, or a large group of 24), many of the subassembly steps needed to finish the project can be completed simultaneously. This division of labor can enormously streamline the project’s completion.
• If the opportunity presents itself, it can very helpful to initially lay out the hand and foot ropes, in conjunction with completing Task E, before proceeding with Tasks A & B.
• The following tasks can be completed at the same time:
Tasks A 1 & 2 / B 1 & 2 / Tasks D 1 & 2 and E
Task C 1 / Task C 2
Task F 1 & 2 / Task H 1 & 2
Tasks I & J / Tasks K, L & M
• If one task is taking longer to complete, workers from other groups can lend a hand and help finish it up so the next step can commence.
• Placing a 4-foot spar underneath the spars lying on the ground, in a strategic position, will raise the project sides up and make lashing much easier.
• There are 64 square lashings in this project and, for stability and safety, they must be tight! For speed and efficiency, the Japanese Mark II Square Lashing is highly recommended.
Schematic of Ladder Sides
TASK A – 1 & 2: Building the ladder sides of the platforms. 1) Lay out two 8-foot legs side by side. Space the spars apart so that the distance from the middle of each spar, at both the top and bottom ends, is 40 inches. Use a tape measure. Also, make sure the butt ends are at the bottom and absolutely even. Starting 6 inches up from the butt end, connect the legs by lashing on a 4-foot ladder rung directly above the 6 inch mark, with tight square lashings.
Using a tape measure, measure 5 feet up from the butt end of each leg, lash on another ladder rung, directly below, just touching, the 5-foot mark, ON THE OTHER SIDE (what will become the inside) of the legs. See the diagram on the right.
Right in the middle of these two ladder rungs, lash on another ladder rung, and then, between the middle ladder rung and the top and bottom ladder rungs, lash on two more. Use tight square lashings.
2) Repeat the whole process on two other 8-foot legs for the other platform.
Assembling an X-Brace Side
TASK B – 1 & 2: Building the X-brace sides of the platforms.
The premise for these sides is the X-braces have to cross each other just under 5 feet for the foot rope, and they have to intersect the tops of the legs equally on each side for the hand ropes. Because of the size of the spars involved, and the necessity for very secure connections that do not shift, use 20-foot lashing ropes and two Scouts for each X-brace square lashing.
1) Lay out two 8-foot legs side by side. Space the spars apart so that the distance from the middle of each spar, at both the top and bottom ends, is 40 inches. Use a tape measure. Also, make sure the butt ends are at the bottom and absolutely even. Starting 6 inches up from the butt end, connect the legs by lashing on a 4-foot ladder rung as a leg spreader, directly above the 6-inch mark, with tight square lashings.
Schematic of X-Brace Sides
With a tape measure, mark 56 inches up from the butt end of each leg.
Temporarily stretch a piece of binder twine over each 56-inch mark and tie it to each leg to help define where this intersecting line lies. It’s at the middle of this line where the X-braces need to cross so that the foot rope will extend just underneath the floor spars of the platform.
Lay out an 8-foot X-brace spar diagonally in such a way that the top end lays over one leg about 4 inches from the top of the leg, and extends out approximately 6 inches from the side. Angle the spar so that it will cross the middle of the intersecting line (56 inches up from the butt ends of the platform legs). Line up the bottom end of this X-brace so that it is positioned under the bottom of the opposite leg. Lash the spar in place with tight Square Lashings.
Lay out a second 8-foot X-brace spar on top of both legs so that it creates an X. Angle this spar so that it will cross the middle of the intersecting line (56 inches up from the butt ends of the platform legs). Make sure this spar also extends out approximately 6 inches from the side and that it intersects the leg at the same distance from the top as the X-brace on the other side. Lash this spar in place over both legs with a square lashing. It’s between the top of the front legs and the extension of the X-braces that the hand ropes will be supported.
Now, with a diagonal lashing, lash the middle of both 8-foot X-braces springing them together where they cross, using a 20-foot lashing rope.
2) Repeat the whole process with the two remaining 8-foot legs.
Schematic of Connecting Sides
TASK C – 1 & 2: Connecting the Ladder and X-brace sides. (If Task E has already been completed, before joining the ladder and X-brace sides, carry the two completed sides for each platform to the approximate location where they will eventually be positioned.)
1) Turn both a ladder side and an X-brace side up horizontally, parallel to one another. On the X-brace side, make sure the leg spreader and the X-brace spars are facing out. Space the legs apart so that the distance from the middle of each leg, at both the top and bottom ends, is 40 inches. Use a tape measure. Also, make sure the butt ends are absolutely even. With tight Square Lashings, join both sides by lashing a 4-foot side base spreader to the legs just below the bottom leg spreaders with a 20-foot lashing rope.
On the inside of the platform, using a 20-foot lashing rope, lash a 4-foot platform support to both legs so that the top edge comes up to 58 inches on both sides (directly under and as close as possible to the top ladder rung on the ladder side.). We will be laying the floor spars on top of this support.
Lash a 4-foot hand rail (same as ladder rung) to the top of both legs.
Lay a 6-foot diagonal side brace diagonally over both legs, between the base spreader and platform spreader, and lash in place using square lashings.
To join the other side, carefully lift and roll the platform over 180°, supporting the spars as much as possible, and repeat the above steps.
2) Repeat the whole process to join the ladder side and X-brace side of the other platform.
TASK D: Stand the platforms upright. With three Scouts lifting at the ground-level handrail, and two to three pulling on the other handrail, raise the platform to an upright position. If TASK E has been completed, we can proceed to Task G.
TASK E: Site preparation. Begin by stretching a length of binder twine along the center line of where the ropes will span. Drive a tent stake into the ground marking the center.
Working from the center, measure 12-1/2 feet toward each end and drive another tent stake to mark where the X-braces of each platform are to be placed. They should be 25 feet apart. Then with two other tent stakes, mark out another 14′ to where the anchors are to be built.
TASK F – 1 & 2: Build the anchors. The foot and hand ropes will be attached to anchors at both ends.
1 & 2) Build a log-and-stake anchor (also known as a log and picket holdfast), 14 feet from where the X-braces of each platform are to be placed. To make the log-and-stake anchors, place one of the 4-foot x 4-inch logs perpendicular to the pull of the line, 14 feet from where the X-brace side will be. Drive in a row of four pioneering stakes spaced evenly in front of the log, leaning them back at a 45° angle. Slip a rope grommet through an O-ring and then slip the ends of the grommet around the log (see diagram). Drive a second row of pioneering stakes 24 inches behind the front stakes. Then anchor the front pioneering stakes to the rear pioneering stakes with a tourniquet made of binder twine or rope using four tent stakes. After twisting the tourniquet tight, hammer the tent stake into the ground to keep it from loosening.
TASK G – 1 & 2: Position the platforms. All hands on deck! Move both upright platforms into position no more than 25 feet apart. Place them on the binder twine that marks the center line of the bridge, making sure the X-braces of each are facing each other 10 feet from the center mark.
Bridge in Operation at a Council-wide Scout Expo
TASK H – 1 & 2: Lash on the floor. Lay 4-inch floor spars on top of the platform supports so that the ends extend out evenly on each side. Using the Double Floor Lashing and the 35-foot lashing ropes, lash the floor securely in place.
TASK I – 1-8: Add anchors for platform guylines. For added stability, we’ll be adding four guylines to each platform. To start, measure 10 feet, 45° out from each leg and drive in a 1-1 anchor.
TASK J – 1-8: Secure the platforms. Attach one of the 25-foot x 3/8-inch guylines to each leg, directly above the floor spars, with a roundturn with two half hitches.
Extend the guyline down to the corresponding 1-1 anchor and attach it to the anchor with a rope tackle. Repeat this process at each leg.
TASK K: Foot rope. First place a piece of heavy canvas (called a “saddle”) in the top V formed by the X-braces. This will protect the foot rope and allow it to slide a little as needed.
If the foot and hand ropes are not already laid out during Task E, two Scouts will be needed to stretch the foot rope out, aligning the center of the rope with the center stake along the binder twine.
Next, lay the ends of the rope over the saddle in the V formed by the X-braces on each platform. Then, maintaining the rope’s center alignment between the platforms, extend the rope under the platforms, through the ladder sides and pulling it somewhat taut, thread the ends through the O-rings attached to the log-and-stake anchors. Tie these off temporarily with a roundturn with two half hitches.
TASK L: Hand ropes. Two Scouts will be needed to stretch the hand ropes out on either side of the foot rope, aligning the center of each with the center stake along the binder twine.
Climb the platforms and place saddles in the crotch between the X-brace extensions and the front legs. Maintaining the center alignment between the platforms, place one hand rope over its corresponding saddles. Then extend the rope down, crossing it over the outside of the top ladder rung, pull it taut, and thread the ends through the O-rings attached to the log-stake-anchors. Tie these off with a roundturn with two half hitches. Repeat the process for the other hand rope.
Good Show!
TASK M: Stringer ropes. Now add the stringer ropes that will go from the foot rope to the hand ropes. Start by tying the center of an 8-foot long stringer rope at the center of the foot rope, using a clove hitch. The stringer rope is tied around the foot rope so that both ends are 4 feet long. Add two more stringer ropes on both sides of the center stringer rope (so there are five stringer ropes in all), tying them about 4 feet apart.
Tie one end of each stringer rope to one of the hand ropes, again using a clove hitch. Then do the same with the other ends of the stringer ropes, attaching them to the other hand rope.
TASK N: Tighten the foot rope and hand ropes. Now you can put a strain on the foot rope. Undo the Roundturn with Two Half Hitches, and make a rope tackle on each end of the foot rope. Two Scouts will need to adjust the tension at each rope tackle so that the middle of the rope stays midway between the platforms.
As needed, adjust the tension of the hand ropes by tightening them at the anchors and retying the roundturn with two half hitches.
Final testing. With caution, one crew member can get on the bridge as all lashings, anchors, and knots are observed by the safety officer and all other crew members. Make adjustments as required.
Safe operation calls for only one Scout to be on the foot rope of the monkey bridge and up to two on either platform at a time.
The following text is by Adolph E. Peschke as presented in the 1998 printing of the 1993 edition of the Pioneering Merit Badge Pamphlet:
PIONEERING PROJECTS
The craft of building with ropes and spars continues in remote areas throughout the world today. Scouts can apply the skills of knot tying and lashing to build pioneering structures that are needed to make living in camp a little more comfortable. Whether you build a simple gadget, or a bridge to provide a shortcut to the swimming pool, pioneering can be rewarding and fun.
The pioneering projects shown here, along with the suggested sizes and lengths of spars, are intended for building “boy-size” structures; that is, projects that can be built by boys of Boy Scout age.
You don’t have to build a huge tower to learn the skills and enjoy the fun of pioneering. These projects are designed so that you can build them in a few hours with a minimum of equipment and supplies. Yet, you will still learn how the basic pioneering skills of knot tying and lashing must work together with the design of a structure to produce a sound, safe pioneering project.
Building these projects will be much easier if you put together a pioneering kit first. The success of any project is directly related to the planning and preparation you put into the project from the beginning.
Here are some things to take into consideration before you build a pioneering project:
Decide on the type of project you want to build. Take into consideration the equipment, the number of people needed, and the time required to build it.
Check the site where the project is going to be built. Collect all the information that you will need when building the project. For example, are there any natural anchors for guylines? How wide and deep is the creek where a bridge is to be built?
Make a rough sketch of the project or work from an approved plan drawing. Along with the sketch, have a list of equipment that includes all the equipment you’ll need. You don’t want to start a project and later learn you need something you don’t have.
Select the necessary spars you’ll need for the project, making sure that you have enough spars with the proper butt diameter and length to build a safe project.
Determine the size and lengths of all the ropes needed for lashings, guylines, etc.
Before you start building, determine if the project can be divided into subassemblies for ease of lashing and erecting. Assign crew members and a crew leader to each of the sub assemblies, based on skill level and experience.
Go over the plans with all the crew members. Assign only one person to give signals when raising all or part of the structure.
As you’re building the project, frequently check the progress to make sure it is being done with safety in mind.
A word about the appearance of the project: Part of the skill in building with ropes and spars is to select the spars that are best suited to the structure. In some situations, the supply of spars might be limited.
It is not necessary for your project to be picture perfect, but rather that it is structurally sound. If one or two spars are a bit longer than required, that’s fine as long as the lashings are in the proper location for strength and the diameter of the spars will carry the load applied.
Try to avoid cutting off the ends of spars and ropes just to fit a certain project, especially if you’re working with spars from a pioneering kit. The next crew might want to build a different project and could use the spars and ropes at the original lengths.
The spars used for a pioneering project should have the bark removed for two reasons. Bark beetles and other boring insects can seriously decrease a spar’s strength, and inspection is easier with the bark removed. Also, if the project racks, the bark under the lashing can be loosened, which in turn makes the lashing loose and adds to the possibility of making the whole project wobbly and unsafe. (And, bark under a lashing can be rubbed off in the process of setting up a project.)
Note: Any pioneering structure that is to be a permanent camp improvement should not be left with only lashings. It needs to be bolted together for safety and maintenance.
This wash station is the ideal First Class Camp Gadget! It’s sturdy, portable, and very useful when camping away from washroom facilities. Inherent in its design is a sound approach to a variety of pioneering concepts and skills. When this project’s built with all the lashings tight and all the legs, cross bar, and support pieces properly positioned, it’s a fine example of a well-engineered, highly functional camp gadget. Each of the three legs making up the tripod gets a lashed on support piece, and the wash station’s stability stems from the fact the design contains three triangles.
Getting it done!
To start, you’ll need six good, straight sticks as follows:
two 2-foot x 3/4 to 1-inch for the leg braces
two 4-foot x 3/4 to 1-inch for the back leg and crossbar
two 5-foot x 3/4 to 1-inch for the front legs
For the lashings, you’ll need:
one 10-foot x 1/4-inch manila rope for the tripod lashing
six 6-foot x 1/4-inch manila ropes for the square lashings
NOTE: This and several types of camp gadgets can be happily lashed together simply using binder twine!
You’ll also need
bar of soap in a sock with a 3-foot cord
small to medium-sized towel with a 3-foot cord
No. 10 can with a bail or 4-quart cooking pot with a bail.
Here’s the assembly procedure:
Position of the sticks.
Make the tripod. Using the 10-foot rope, lash the two 5-foot sticks and one 4-foot stick together with a tight tripod lashing. The 4-foot stick should be in the middle. Make sure the “butt” ends of all three these sticks are even. Separate the legs and set the tripod up. The success of this project relies on a well-tied, tight tripod lashing.
Lash on the braces. Using four tight square lashings, with the 6-foot ropes lash one end of the 2-foot sticks to the 5-foot legs and the other end of the 2-foot sticks to the four-foot leg.
Lash on the crossbar. Using two more square lashings, tightly lash the other 4-foot stick to the top extended sections of the two 5-foot sticks to make a cross bar for the towel and soap-in-a-sock.
Add the soap, water, and towel. Tie the end of one 3-foot cord to the soap-in-a-sock and the end of the other 3-foot cord to the towel, and hang them on either side of the 4-foot crossbar.
Washing his hands before breakfast on a cold, winter camping trip.
Hang the can filled with water to the end of the 4-foot stick extending from the front of the tripod.
During the camping trip, change the water as necessary. See that the soap-in-a-sock is not left in the can after use as it will melt.
One of the beauties of using metal containers is that in cold weather, the can of water can be heated in the fire.
Adjusting knots and lashings after the first test crossing.
The well-known, time-tested, traditional Monkey Bridge is perhaps the most familiar of all Scout pioneering projects. It’s frequently featured at Scout Expos, Camporees, Scout Camps, and is often a central attraction at public gatherings where Scouting is represented.
The following instructions and guidelines are provided by Adolph Peschke, taken from the 1993 edition of the Pioneering Merit Badge Pamphlet:
Using a double A-frame to build a monkey bridge is a departure from the usual X-frame that supports the foot rope and hand ropes. This new method has two distinct advantages over the X- frame version. First, the double A-frame provides a wider base making it less likely to tip over. The second advantage is that the positions of the A-frames can be adjusted so the span between the hand ropes can be narrowed for better balance as you make the crossing.
Building the A-frames. The first step in building the monkey bridge is to build four A-frames using the 8-foot spars for the two legs, and 6-foot spars for the ledger. Lay out the first set of three spars (two legs and one ledger) on the ground in position for lashing. Before lashing, drive three stakes, as follows, to help you make all four A-frames the same size: Drive a stake at the top to mark where the leg spars cross. Then drive stakes to mark the positions of where the bottom ledger crosses the legs. This will also indicate how far the legs are spread apart. Now you can lash the four A-frames together, laying them out one at a time using the stakes. Remember that all three lashings on the A-frames are square lashings, even though the spars cross at less than 90˚ angle.
Schematic of A-frame alignment
Double A-frame. When you have four A-frames, you can lash two of them together to form a double A-frame. (see figure 140). Lay one A-frame on the ground and then put another on top of it so that the bottom ledgers overlap one-half their length (approximately 3 feet). The first step in lashing the A-frames together is to go up where the two legs cross (the X formed by one leg from each A-frame). Then with a good tight square lashing, lash the two legs together.
Note: The point where these two legs are lashed together is where the foot rope will rest. You can adjust the overlap of the two A-frames to adjust how high the foot rope will be off the ground. Also note where the tops of the A-frames are, because this is where the hand ropes will be. To complete the double A-frame, stand it up so the butt ends of all four legs rest solidly on level ground. Lash the two bottom ledgers together where they overlap with three strop lashings. Now repeat the entire process to build the second double A-frame.
Laying out the distance between A-frames and anchors
Site preparation. Before you can erect the double A-frames, you need to prepare the site. Begin by stretching a length of binder twine along the center line of where the monkey bridge is to be built. Working from the center, measure 10 feet toward each end to mark where the A-frames are to be placed. They should be 20 feet apart. Then mark out another 10′ from each A-frame to where the anchors are to be built.
Note: These dimensions are for building a bridge with a 20-foot span. This is the maximum span for a bridge using a 50-foot rope. The extra 30 feet of rope is needed to have 15 feet of rope at each end for the proper distance from the A-frames to the anchors (10 feet) and for the knots at the anchors (5 feet).
Build the anchors. The foot rope will be attached to anchors at both ends. Before erecting the double A-frames, build a 3-2-1 anchor, or a log and stake anchor, 10 feet from where the A-frames will be erected (see figure 141).
Rope grommet. After the anchors are built, attach a rope grommet with a ring or shackle in it. (You can make the rope grommet with a 10-foot length of 1/2-inch diameter polypropylene rope. Tie the ends together using a carrick bend, and permanently secure the ends with some strong twine).
Position the A-frames. Prepare to erect the monkey bridge by moving the A-frames into position no more than 20 feet apart. Lay them down on the binder twine that marks the center line of the bridge.
Hand and foot ropes. Now you can prepare the foot and hand ropes for the monkey bridge. Lay the foot rope in a straight line off to the side of where the A-frames are laying. Then lay the two hand ropes on the ground next to each other so they’re parallel to the foot rope and 42 inches away.
Stringer ropes. Now you can add the stringer ropes that will go from the foot rope to the hand ropes. Start by tying the center of an 8-foot long stringer rope (use 1/4-inch manila rope) at the center of the foot rope, using a clove hitch. The stringer rope is tied around the foot rope so that both ends are 4 feet long. Add two more stringer ropes on both sides of the center stringer rope (so there are five stringer ropes in all), tying them about 4 feet apart. Tie one end of each stringer rope to one of the hand ropes, again using a clove hitch. Then do the same with the other ends of the stringer ropes, attaching them to the other hand rope.
Assemble the bridge. You’re just about ready to assemble the bridge. First place a piece of heavy canvas (called a “saddle”) in the V formed by both double A-frames. This will protect the foot rope and allow it to slide a little in the V without interfering with the lashing rope.
Schematic of foot, hand ropes and anchors
Now get the crew together to erect the bridge. You will need a safety officer to watch for any problems that might occur, and a signal caller to tell the crew members what to do. You will need two Scouts to lift and hold each double A-frame in place, two more Scouts to lift the foot rope into the V of the double A-frames, and two more Scouts to lift the two hand ropes into place at the tops of the A-frames. Lift everything into place. Then, holding the A-frames steady, temporarily tie the hand and foot ropes into the rings of the grommets using a roundturn and two half hitches (see figure 142).
Tighten the foot rope. Now you can put a strain on the foot rope. It’s not necessary to use block and tackle since this will put too much strain on the lashings, anchors, and the foot rope itself when there is a load on the bridge.* Whatever strain three or four Scouts can put on the foot rope by pulling it by hand will be enough. As soon as the bridge is used a few times, there will be a sag in the rope. This is fine because it means that you are working with reduced strain on the foot rope as a safety measure.
Tighten the hand ropes. Next, tie the hand ropes to the top ends of the A-frames. First, loosen one end at a time from the anchors. Then, use a clove hitch to tie the hand rope to the top end of the leg of the double A-frame. As you’re tying these clove hitches, adjust the strain on the sections of the hand ropes between the double A-frames to match the sag of the foot rope. Also, adjust the length of the stringer ropes so there is even strain between the foot rope and both hand ropes. After the hand ropes are tied to the tops of the A-frames, move down and retie the ends of the hand ropes to the rings in the grommets using a roundturn and two half hitches.
Final testing. With caution, one crew member can get on the bridge as all lashings, anchors, and knots are observed by the safety officer and all other crew members. Make adjustments as required. Then secure the running ends of the hand ropes and foot rope with a piece of cord. Safe operation calls for only one Scout to be on the foot rope of the monkey bridge at a time.
LIST OF MATERIALS FOR DOUBLE A-FRAME MONKEY BRIDGE
eight 4-inch x 8-foot A-frame legs
four 3-inch x 6-foot ledgers
fourteen 1/4-inch x 15-foot lashing ropes for Square Lashings
one 1/2-inch or 3/4-inch x 50-foot rope
two 1/2-inch x 50-foot hand ropes
five 1/4-inch x 8-foot stringer ropes
six 1/4-inch x 10-foot lashing ropes for Strop Lashings
six pioneering stakes for each 3-2-1 anchor
eight pioneering stakes for each log-and-stake anchor
one 5-inch x 4-foot spar for log-and-stake anchor
two 1/2-inch x 10-foot polypropylene ropes for rope grommets
two pieces of scrap canvas for foot rope saddle
binder twine for anchor tieback straps
* It has been found that a rope tackle in the foot rope at each end (not a block and tackle) tightened by one Scout is an excellent procedure to maintain the optimum foot rope tension, and an easy-to-use remedy for too much sagging due to repeated, heavy use and over stretching. There are other configurations used to initially tighten and keep the hand and foot ropes at the optimum tension during use, depending on the weight the bridge must withstand and the amount of traffic it will bear.
SCOUT PIONEERING 