Posts Tagged With: shear lashing

Pioneering Program Curriculum V: Two-Spar Shear Lashing

This is the fifth post in a series that will eventually comprise an activity-based, unit pioneering program curriculum.

V. With the square lashing under their belts, Scouts can start to actually build pioneering projects. Though the basic and oft-used A-frame can be readily completed using three square lashings, the Two-Spar Shear Lashing is most frequently chosen to start lashing together this common support structure.

OBJECTIVES

  • A. Scouts will demonstrate they can tie a Two-Spar Shear Lashing by:
  •       1) starting off the lashing with a clove hitch around one pole
  •       2) wrapping the lashing rope eight to ten times around both poles
  •       3) taking two frapping turns between the poles around the wraps
  •       4) completing the lashing by applying two half hitches around the opposite pole (clove hitch)
  • B. Scouts will demonstrate they can construct an A-frame by:
  •       1) connecting the tips of two poles with a shear lashing
  •       2) spreading the poles apart to form an inverted ‘V’
  •       3) lashing a pole to the butt ends of the ‘V’ with square lashings

MATERIALS

  • Three Scout Staves for each Scout
  • One 10′ x 1/4″ manila lashing rope for each Scout
  • Two 6′ x 1/4″ manila lashing ropes for each Scout

PROCEDURE A

1) The instructor shares the purpose and application of the shear lashing, explaining how we use it when we want to connect two spars and open them out to form the legs of an A-frame.

2) Scouts gather around the instructor who, using two Scout Staves and a 10′ lashing rope, demonstrates lashing the ends of the staves together with a Two-Spar Shear Lashing, narrating each step as he does.

Two Scout Staves joined at the end with a Two-Stave Shear Lashing

Two Spread Scout Staves Joined at the Top with a Two-Spar Shear Lashing

3) With the assistance of the instructor(s), using two Scout Staves and a 10′ lashing rope, each Scout proceeds to to tie a shear lashing applying the following steps:

  • The two staves are placed parallel to one another either on the ground, resting on a log, or leaning against a wall.
  • A clove hitch is tied to one of the staves at around 6″ from the end. (Depending on the structure being lashed together, the placement of the clove hitch can vary from 6″ to 18″ or more from the end of the spar.)
  • A 4″ to 6″ tail is left in the short running end, which is wrapped around the standing part serving to secure the clove hitch, before proceeding with the wraps.
  • The long running end is wrapped around both staves eight times, evenly and away from the ends. (The directive is 8 to 10 wraps, and sometimes as little as 5. The greater number of wrapping turns, the stiffer the lash will be.)
  • After the wraps, both staves can be held upright and spread a bit to make room for two tight frapping turns taken around the wraps and between the staves.
  • After the fraps, a half hitch is applied to one stave. cinched up close to the fraps and pulled tight. Then another half hitch is applied, cinched up and tightened to form the finishing clove hitch. (Preferably, but not necessarily, the final clove hitch is tied to the opposite pole on the opposite side of the lashing.)
  • The two legs are spread farther apart to form and inverted ‘V’ and the lashing is evaluated to determine if it is well-formed and tight enough to resist sliding.

PROCEDURE B

1) When their shear lashing is adequately completed, each Scout is given a third Scout Stave and two 6′ lashing ropes.

2) With square lashings, each Scout joins one end of the third stave to one leg of the inverted ‘V’ and then the other end of the third stave to the other leg of the inverted ‘V.’ (Both ends should be lashed in the same position on each leg, and the square lashings should be tied tightly so they don’t slip.)

3) When all three lashings are well-formed and tight enough, each Scout should pick up the resulting A-frame and give it a shake, testing that it is indeed sturdy.

Two-Spar Shear Lashing Diagram

Two-Spar Shear Lashing Diagram

INTERPATROL COMPETITIONSimple A-Frame Chariot Race

Related Post with Photographed Lashing Procedure: The Somewhat Ambiguous Shear Lashing

PIONEERING CURRICULUM: MAIN PAGE

Categories: Scout Pioneering | Tags: , , , , , , | Leave a comment

The Somewhat Ambiguous Shear Lashing

Scouts Lash the Tops of Their Sheer Legs with a Two-Spar Shear Lashing to Begin Their Single A-Frame Bridges

Scouts Lash the Tops of Their Shear Legs with a SHEAR LASHING to Begin Their Single A-Frame Bridge

DEFINITION: ambiguous |amˈbigyoōəs|adjective(of language) open to more than one interpretation; having a double meaning; unclear or inexact

Put the two timbers together and tie a clove hitch near the top of one. Bind timbers together by seven or eight turns. Make turns loose, one beside the other. Make two complete frapping turns around lashing turns between the timbers. Fasten securely with clove hitch around one timber. Open out the timbers. Note: Two shear lashings without frappings and with the clove hitch around both timbers are used to lash two timbers into one long one.

From the 1981 Printing of the Pioneering Merit Badge Pamphlet

One Thing is NOT Ambiguous! The Shear Lashing’s USE is quite clear. References to the lashing in John Thurman’s Pioneering books, in John Sweet’s Scout Pioneering, and the Lashing section in the Pioneering Merit Badge Pamphlets by Pioneering Legend Adolph Peschke all describe its fundamental use exactly the same way. Putting it neat like John Sweet: Use a Sheer Lashing “when two spars are to be opened out like scissors to make a pair of sheerlegs,” or right to the point like John Thurman in Pioneering Projects, the Sheer Lashing is “used for lashing together two parallel spars which will be opened out of the parallel to form sheer legs.”

What are sheer legs? Simply put: sheer legs are two upright spars lashed together at the tips with the butt ends splayed apart to support some kind of weight. Most always, in Scout Pioneering we use sheer legs to form an A-Frame.

Ambiguous? Yes. Let’s start with ambiguous spelling! Most modern references to the lashing spell it s-h-e-a-r. Yet, the much respected and revered John Thurman was emphatic that the correct spelling was s-h-e-e-r!

Terminology. In John Sweet’s book, Sheer Lashing has two different forms each with the same name. When two spars are lashed together for strength, or lap-jointed to extend their length a Sheer Lashing is used BUT with the clove hitches tied around both spars and without any frapping turns. He still calls it a Sheer Lashing, but of course this is commonly known as a Round Lashing!  John Thurman refers to a true Round Lashing as the Sheer Lashing Mark II and the lashing used to make sheer legs as the Sheer Lashing Mark I.

Let’s take this opportunity to further clarify two lashing designations that keep popping up. A SHEAR Lashing is used to make shear legs. A ROUND Lashing is used to attach one pole to another in the same direction as in extending the overall length of shorter poles. (It can also be used to bind more than one pole together to make a stronger pole.) SHEAR Lashings incorporate frapping turns. ROUND Lashings do not! Along these lines, the West Country Shear Lashing should be called the West Country Round Lashing, and rightfully so!

Nowhere is this stated more clearly than in Gerald Finley’s book, Rope Works: “West Country Round Lashing is also called West Country Shear Lashing, but this name contributes to the confusion caused by lumping Shear and Round Lashings together. West Country Round Lashing is used to form a rigid joint between two parallel poles; it does not form the flexible joint of a Shear Lashing and it has no frapping turns.”

Two-Spar Shear Lashing. To add to the possible confusion, Adolph Peschke calls what John Thurman refers to as the Sheer Lashing Mark I (which is in actuality THE Shear Lashing) the Two-Spar Shear Lashing. This name can also be related to the tying of a Tripod Lashing With Plain Turns, wherein the procedure is exactly like the Two-Spar Shear Lashing but with three spars. It follows that it’s easy to dub this tried and true form of Tripod Lashing (just like the Two-Spar Shear Lashing) the THREE-Spar Shear Lashing. The Two-Spar Shear Lashing is used to make an A-Frame, and the Three- Spar Shear Lashing is used to make a simple tripod.

Ambiguity in Tying the Lashing. Though the formation is the same: clove hitch around one spar, six to eight wraps, two fraps, finish with clove hitch around one spar, there are varied approaches to actually tying the Shear Lashing. These discrepancies all hinge on… the hinge. (Pun intended.) The spars have to pivot in order to spread out the desired distance. How can this be accomplished so the lashing is tight but not so tight that when spreading the legs into position, the legs and lashing rope resist the strain to the point that something breaks?

  1. One view is to make the wraps and fraps on the loose side, concluding they’ll tighten when the legs are spread.
  2. Another view is to place a small block of wood between the spars to yield adequate room for the frapping turns.
  3. Another view is to make the wraps moderately tight and then before frapping, spread the legs a bit to allow room for the frapping turns, being careful not to close the spars on the lasher’s fingers!
  4. FInally, another view is to complete the wraps, then spread the legs to the desired width, and then take tight frapping turns.

Whatever works well will also depend on the diameter of the spars and how straight they are.

Open out the Timbers. NOTE: Two shear lashings without frappings and with a clove hitch around both timbers are used to lash two timbers into one long one.

The NOTE is a perfect description of what is termed the “Round Lashing!”

Categories: Scout Pioneering | Tags: , , , , , , , , , , , , | 2 Comments

Single A-Frame Bridge

Two A-Frame Bridges in the  Early Morning Fog on Garden Ground Mountain at the Summit Bechtel Reserve

Two Single A-Frame Bridges in the Early Morning Fog on Garden Ground Mountain at the Summit Bechtel Reserve

The simplest of all crossing bridges is the Single A-Frame Bridge. The design was featured at the 2013 National Jamboree which afforded Scouts an opportunity to construct the bridge right on the spot.

Single A-Frame Bridges at the Jamboree

Single A-Frame Bridge Pictorial

Link to: Older Pamphlet InfoThe following text is by Adolph E. Peschke as presented in the 1998 printing of the 1993 edition of the Pioneering Merit Badge Pamphlet:

Building this bridge is quite simple because there are very few lashings needed for the center A-frame. The A-frame is a triangular shape that resists racking and provides strength for the structure.

A-frame. Start this project by determining the depth of the creek or ravine to be spanned. You have to add 8′ to that measurement to get the total height of the legs for the A-frame. For example, to span a creek 4′ deep, the legs of the A-frame should be about 12′ or longer.

This total length allows for the distance from the butt ends of the A-frame legs up to the transom that supports the walkways. The transom should be about 1′ higher than the banks of the creek. It also allows for the height if the A-frame from the walkways up to the tops of the legs to permit free passage for a person along the walkways.

Lay the A-frame subassembly out on the ground to check if the spars are long enough when lashed together for the two requirements mentioned above.

A-frame Legs. When you’ve determined the length of the spars for the legs of the A-frame, lash them together at the top with a shear lashing, not a diagonal lashing. This lashing should be made somewhat loose so that you can spread the spar legs apart to form the A-frame. As you spread the spar legs, the shear lashing will tighten. A little practice will show you how loose to make the shear lashing initially in order for it to be tight when the A-frame is formed.

View of A-frame and Attachment of Walkways

View of A-frame and Attachment of Walkways

Ledger and transom. To complete the A-frame, use a square lashing to lash the bottom ledger across the legs about 1′ from the bottom of the legs. Then lash a transom spar to support the walkways at the proper height in relation to the banks of the creek.

Walkways. The two 10′ walkway sections are made as separate subassemblies. (Refer to “Bridge Walkways.”)

Assembly. After the walkways are made, take them to the assembly site along with the A-frame. Place the A-frame in the center of the creek and heel in the legs about 4″ to 6″ deep. As the legs are being heeled in, level the transom to accept the walkways in a level position.

Single A-Frame Bridge

Single A-Frame Bridge

When the A-frame is upright and the transom is level, lash both underspars on the walkways to the transom with strop lashings at three points. Finally, lash the cross spars at the ends of the walkways to stakes on the banks of the creek with strop lashings.

For safety, it’s best to add a light 1/4″ guy line from the top of the A-frame to both sides of the creek to prevent it from tipping over.

List of Materials for a A-Frame Bridge

  • 2    3″ x 12′ A-frame legs
  • 1    2″ x 6′ bottom ledger
  • 1    3″ x 6′ transom
  • 4    3″ x 10′ walkway lateral spars
  • 12   2″ x 3′ walkway cross spars
  • 4    2″ x 3-1/2′ walkway cross spars
  • 2    2″ x 10′ walkway planks
  • 4    stakes

Single Trestle Bridge

Single Lock Bridge

Categories: Involved Campsite Improvement | Tags: , , , , , , , , , | 11 Comments

Lashing INFORMATION

Link to: Outdoor Skills SurveyThe following text and some of the drawings are by Adolph E. Peschke as presented in the 1998 printing of the 1993 edition of the Pioneering Merit Badge Pamphlet:

We could imagine the first lashing made by man was wrapping a few strips of bark around a stone to hold it to a tree branch to make an ax to hunt and build with. Even today with all our modern ways to hold things together, it is still fascinating to lash sticks or spars together to make a camp gadget or useful structure.

There are still areas in the world where lashing spars (or bamboo poles) is the basic means of building structures. In Scouting, we use the same methods but have replaced strips of bark and vines with natural and synthetic fiber ropes.

The best choice of rope to use for lashing the type of pioneering projects (shown in this pamphlet) is pure manila rope. Therefore, all references to rope used for lashing in this section refer to manila rope.

Yet, sometimes we are faced with a problem—we have to use what is available and economical to get the job done. When making camp gadgets for temporary use, you could use lesser quality, less expensive rope or even binder twine for small projects.

SQUARE LASHINGS ***

The basic type of lashing for most projects is some form of a square lashing. This lashing is used to join two spars together, usually at a right angle, but not always. For example, square lashings are used when building a trestle to join the ledger and header to the legs at right angles. But it is also used to hold the ends of the X bracing to the legs at an angle. (Refer to “Making a Trestle.”)

In this section, three different square lashings are shown: (1) the traditional square lashing, (2) the modified square lashing, and (3) the Japanese Mark II. All three types of square lashings accomplish the same thing by making three wraps and two frapping turns around the spars being held together.

The only difference between these three different square lashings is the type of knot that is used to start and complete the lashing. You may learn that one of these knots is easier to tie, if so, you can stick with the one you are most comfortable with.

In addition to square lashings, you will most likely need to know how to make a diagonal and shear lashings. Some methods of making these types are also shown later in this section.

LASHING TERMS

No matter what kind of lashing you’re making, there are two basic terms you should be familiar with: wraps and fraps. The basic difference between the two terms is that a wrap is made around the spars, while a frap is made around the rope itself.

Wrap. A wrap is a turn made around the two spars to hold the spars tightly together. Usually, three wraps are made to form a square lashing. Some other lashings require more wraps.

Frap. A frap is a turn made between the spars. It goes around the wraps to pull the wraps tighter. Usually two frapping turns are made on a lashing.

Good lashings are not made in a hurry. Each wrap must be made with a strain on the rope. Frapping turns should be pulled up as tightly as possible before the final knot is tied.

ROPE LENGTH

When you set out to make a lashing, the size and length of the rope you need are among the first questions you have to answer. To determine the length of rope needed for a lashing, add the diameters (in inches) of the two spars at the point the lashing is being made. If one spar is 2-1/2 inches in diameter and the other is 3-1/2 inches in diameter, the total equals 6 inches. Multiply by 3 feet to get the length of the rope needed for lashing.

If you use a rope that is too short to make three wraps and two fraps for a lashing, you should add (Splice or join with a square knot) a length of rope to complete the lashing with three full wraps and two fraps. For safety, don’t leave the lashing short.

If you find you have extra rope, make more wraps or fraps to use up the rope to avoid cutting the rope or leaving long loose ends hanging out.

ROPE DIAMETER

In most cases, 1/4″-diameter manila rope should take care of lashing two spars together as long as the combined diameter of both spars is 6″ or less. When the combined diameter is over 6″, use 3/8″-diameter rope.

PIONEERING KIT

If your troop or camp puts together a pioneering kit, it should contain lashing ropes that are cut to standard lengths: 10′, 15′, 20′, 30′, and 50′.

Both ends of these lashing ropes should be properly whipped. It also helps to color-code the ends of all ropes with a bit of paint to denote each length. When storing ropes, make sure they are dry and properly coiled. Never “hank” ropes for storage. That is, don’t wrap them around your hand and elbow to form a coil. Tie each coil with a short piece of cord and store the coiled rope on pegs or in a ventilated storage box.*

TRADITIONAL SQUARE LASHING

Drawing Design from Rope Works by Gerald L. Findley http://www.ropeworks.biz/reader/squarlas.pdf

Drawing Design from Rope Works by Gerald L. Findley http://www.ropeworks.biz/reader/squarlas.pdf

In Scout Pioneering in the United States we most often see the square lashing started with a clove hitch. The clove hitch is tied on the vertical spar, just below where you want to join the crossing horizontal spar (see 1).

Using a clove hitch to start this lashing allows for two things. First, you can rest the crossing spar on the clove hitch to help support it as you begin the lashing while building your structure. Second, the clove hitch helps keep the structure from racking (twisting out of shape), causing the lashing to loosen as it is moved or hoisted into position.

After the clove hitch is tied, wrap the excess short end of the rope around the standing part of the rope (see 2). Hold the crossing spar up to the vertical spar and make three wraps around the spars using the long end (see 3, 4, and 5). Pull each wrap tight to hold the spars together. Make two frapping turns around the wraps (between the spars) to pull the wraps tight (see 6 and 7) and finish with another clove hitch on the horizontal spar (see 8 and 9).

One other point to make about the square lashing is that you shouldn’t be fooled by or limited by its name. Although two spars can be lashed together at 90° using a square lashing, it can also be used to lash two spars together at any angle. For example, a square lashing is used to lash the ends of two light spars to the uprights of a trestle to form the X bracing. A diagonal lashing is used at the center of the X to hold the crossed spars together.

MODIFIED SQUARE LASHING

The modified square lashing was developed because of the difficulty usually experienced when tying a clove hitch to complete the traditional square lashing. The clove hitch that starts the lashing is easy enough to make, but tying a clove hitch at the end of the lashing is a different matter.

As shown in figure 104, the modified square lashing starts with a clove hitch. When tying the clove hitch, let the running end of the clove hitch extend about 12″. Also do not twist the short end around the standing part of the rope as in the traditional square lashing.

After tying the starting clove hitch, proceed as usual using the long end of the rope to make three wraps (see figure 105). Then make two frapping turns (see figure 106).

To complete the lashing, bring up the short end of the rope that extends from the clove hitch and tie a square knot (see figure 107). Bring the short end up in the opposite direction of the frapping turns.

As in the traditional square lashing, there is some disadvantage in having to make the complete lashing using the one end of the rope.

Modified Square Lashing

Modified Square Lashing

JAPANESE MARK II SQUARE LASHING

This lashing is a straightforward approach to the task of lashing two spars together. (CLICK HERE FOR INFORMATION AND PROCEDURE.)

Square Lashing

Japanese Mark II Square Lashing Photographed Procedure

DIAGONAL LASHING ***

When putting crossed braces on a structure to keep it from racking (as used when making a trestle), the most important lashing is the diagonal lashing where the spars cross. (Refer to the “Making a Trestle” section.)

When the cross spars are properly assembled on the trestle, they will be standing apart where they cross. That is, there will be a few inches of space between the spars where they cross at the center of the X. To pull them tightly together, a timber hitch is used to start the lashing (figure 1). As the timber hitch is pulled tight, the spars are sprung together. Next, three wraps are made in each direction across the X (figures 2 thru 5). After the wraps, make two frapping turns between the spars, pulling the wrapping turns tightly together and taking up any slack (figures 6 and 7). Finally, tie a clove hitch on one spar to complete the lashing (figures 8 thru 10). When this lashing is added to the cross braces, it helps keep the trestle from racking. Filipino Diagonal Lashing.

Diagonal Lashing Diagram

Diagonal Lashing Diagram

WEST COUNTRY SHEAR LASHING §

The pattern you make with the rope for this lashing is the same as the one to make the whipping. The only difference is that this lashing is tied around two spars to hold them together.

To make this lashing, tie a series of half-knots (overhand knots) around the two spars (see figure 115). Tie one half-knot in front and the next half-knot in back (see figure 116). Make sure each half knot is pulled up as tight as possible. After tying six to ten half-knots, finish off the lashing with a square knot (see figure 117). By using six to ten half-knots in this lashing, it makes it very strong and effective, but can be a little difficult to untie.

The West Country shear lashing is usually used to tie two spars together to extend the overall length of the spars. When this is done, you should make two sets of lashings, not just one lashing. Make one lashing at each end of the overlapping spars.

§ This lashing is more aptly referred to as the West Country Round Lashing.

West Country Shear Lashing Diagram

West Country Shear Lashing Diagram

TWO-SPAR SHEAR LASHING

There are two applications for the two-spar shear lashing. One is where it is necessary to extend the length of one spar by lashing another spar to it (Sheer Lashing Mark II or round lashing). The second application is when spar legs are to be spread apart to form an A-frame.

In the first application (extending a spar), two lashings are made where the spars overlap. The amount of the overlap of the two spars should be determined by the diameter and length of the spars being used. The lashings should be placed as far apart as possible to maintain the strength needed. **

The two-spar lashing starts with a clove hitch on one spar (see figure 118). After making the clove hitch, wrap the excess part of the short running end around the standing part of the rope (see figure 119).

Two-Spar Shear Lashing Diagram

Two-Spar Shear Lashing Diagram (this drawing has been modified for the purpose of clarity)

Completed Shear Lashing Before the Spars have been Spread

Completed Shear Lashing Before the Spars have been Spread

Shear Lashing After Spreading the Shear Legs

Shear Lashing After Spreading the Shear Legs

Unlike square lashings, the shear lashing requires eight or ten wraps around the spars before making the frapping turns between the spars to pull the wraps tight (see figure 120). This lashing then ends with a clove hitch on the other spar (see figure 121).

If you’re making an A-frame, start the spars side by side and tie a clove hitch on one spar, about 1′ from the top end of the spars depending on the project. Then you can take ten wrapping turns around the spars, making the wraps somewhat loose. The legs can then be spread to the required distance. This should put strain on the wraps.

With the legs apart, you can make the frapping turns around the wraps to pull them tight. Finally, complete the lashing by tying a clove hitch on the opposite spar.

The Somewhat Ambiguous Shear Lashing

STROP LASHING

In some pioneering situations all that’s needed is a few wraps with a rope, a light cord, or binder twine to hold two small spars or sticks together. Wrap the rope or cord around the spars a few times and finish with a square knot. This is called a strop lashing.

A strop lashing can be drawn down tight, or it can be made as a loose wrap so that it allows movement or acts as a hinge.

The strop lashing can have several simple applications at camp. For example, if you don’t want to dig a hole for the staff of your patrol flag, drive a tall stake in the ground. Then use a light cord or binder twine to make two strop lashings about 1′ apart to hold the staff to the stake (see figure 122).

If your patrol just completed a signal tower and you want to show who did it, lash your patrol flag to the top of one of the legs with a strop lashing.

When you’re adding walkways to a bridge, they need to be joined to the trestle to form a single unit. The way to do that is to lash the two walkways to the transom at the center of the bridge with two or three strop lashings (see figure 123).

The ends of the walkways also need to be held to stakes. Use a strop lashing to hold the ends of the walkway to the stakes (see figure 124).

Strop Lashing

Strop Lashing

The Boy-Sized projects provided and designed by Adolph Peschke and featured in the older Pioneering Merit Badge Pamphlet (Single Lock BridgeSingle Trestle Bridge, A-Frame Bridge, Double A-Frame Monkey Bridge14′ Double Ladder Signal Towerdo not require the frequently employed tripod lashing, and hence it’s not included herein.

* An approach that is seen as a practical way to preserve and organize your lashing ropes is to coil ropes of the same length into manageable groupings, i.e. a large coil containing more than a single rope, and then tying up the grouping at one end with a 3′ light cord.

** Round lashings are more frequently used to very effectively extend Scout staves or smaller diameter spars.

*** In a Square Lashing, the wraps and fraps form a square. In a Diagonal Lashing the wrapping turns cross the poles diagonally. Both lashings can be used to join two poles together that cross each other from 45º to 90º.  It’s the Square Lashing that is used most because there is more contact between the rope and the poles, and hence it is stronger. A Diagonal Lashing is used when there is a need to close a gap between two spars or when they spring apart, in other words, when we want to bind poles together where they cross each other but do not touch. This most commonly occurs when the ends of the spars are already lashed in place in a structure, as in forming the X-brace of an H-Trestle. FILIPINO DIAGONAL LASHING

PDF FILE for: Lashing INFORMATION

Categories: Scout Pioneering | Tags: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , | 18 Comments

Blog at WordPress.com. The Adventure Journal Theme.

Follow

Get every new post delivered to your Inbox.

Join 40 other followers