Seamanship

Chapter SIX
Performance Objective 406

The Canadian Forces ships use several types of lifting devices such as hydraulics, portable mounted cranes and forklifts. Before these devices were developed, and even in some instances today, sailors were required to improvise lifting devices. This would have to be done using only the ship’s gear, supplemented sometimes by anything found ashore. Nowadays, ships no longer carry timber spars specifically for improvised lifting rigs.

The type of lifting device Sea Cadets have chosen to rig is the Sheers. Your seamanship skills are now put the test, as everything you have learned to date will be used in rigging Sheers.

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Sheers

Sheers consist of two upright spars called legs, which are lashed with their feet splayed out. This is why this lifting device is often called Sheer Legs. Sheers are suitable for use when the load is not required to move side to side, such as on the edge of a wharf, or on the banks of a river, or in lifting a weight from a boat to the deck of a ship. They can lift a large load because the stress is distributed over two spars.

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Required Equipment

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Parts of the Sheers

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Rigging the Sheers

Head lashing:

1. Lay the two spars for the legs, side by side with the heels together, flush, and the heads supported on a block near the tips; this way the heads are clear of the deck so you can work on them.
2. Cross the legs approximately 1 metre from the heads.
3. Choose a rope, depending on the size of the spars and the weight to be lifted; this is best judged at the time but for our purpose “ manila is sufficient.”
4. Tie a timber hitch around one of the legs either above or below the cross.
5. Make enough round turns around both legs to cover the cross, at least 14 turns.
6. Bring the end of the rope up between the legs, then pass it down between the legs on the opposite side of the cross. Bring the rope up again as before so as to form a frapping turn that binds the whole lashing together. Ensure the frapping turns are applied close to one another and hauled taut. The frapping turns cross the spars as well as the lashing. Apply a minimum of four frapping turns.
7. Complete the lashing by tying a clove hitch - take the line round the leg opposite to the one to which it was originally attached.

Splaying the Legs:

8. Having completed the head lashing, open the heels of the legs out far enough to set up the head lashing taut, so that it binds the legs securely together where they cross.
9. Next, put on the strop for the purchase. The strop must be long enough to enable the block to swing clear between the legs. Attach the strop by slipping it up to the top leg and passing it down over the head of the lowered leg so that it will bind the two together when under load.
10. The upper block of the purchase is hooked to this strop, and the hook is securely moused.
11. Next, secure the topping lift and martingale, or the fore and back guys, to the head of the sheers. If a vertical surface (such as a building, tree or pole) is available for attachment of the topping lift at the level of the head lashing, the topping lift may be of any convenient length. Side guys are not fitted, as sheers need no lateral support.
12. Ensure that the pull of the guys will assist in binding the sheers together, and that the purchase strop is free to take up its natural position as the weight comes on it. Hooks on topping lift and upper purchase block must be moused. Two methods of securing the topping lift and martingale are diagrammed below.

Splay and Heel Tackles:

13. Place the legs roughly in position ready for raising. Point the heels to appropriate shoe. Support the legs laterally by the splay and heel tackles.
14. The distance between the shoes should be one-third of the distance from the foot of the sheers to the crutch (effective length of the sheers).
15. Lead the splay tackle from the heel of one spar to the heel of the other. Secure to the spar with a strop. Ensure the splay tackle is taut and choked before the sheers are raised.
16. The heel tackles guy down the heels laterally and their strops should be kept as low down as possible otherwise the tackles will be heavily stressed as the sheers are raised.
17. Attach the leading block for the fall of the purchase to one leg.
18. Fit thumb-pieces or rope collars to prevent all the strops at the feet of the legs from slipping upwards.
     

    Raising the Sheers:

19. To raise the sheers, place the heels of the spars in the shoes.
20. Heave the splay tackle so it is taut and secured. The heel tackles are like-wise hauled taut to retain the heels of the sheers in position.
21. Have a cadet keep the topping lift taut while the head of the sheers is raised by hand.
22. When the sheers are at an angle of approximately 45 degrees, the strain may be taken by the topping lift and the sheers raised to the working position.
     

    Guys and Footings:

23. Make fast the guys near the tops of the spars with a clove hitch in such a way that the guys will draw the spars together when the stress is applied. To accomplish this, fasten the fore guy to the rear spar and the back guy to the front spar.
24. When using spikes, the grid measurement should be 5.8m x 3.04m with the topping lift spike 7.62m from the centre of the four heel spikes.
25. When using sheers at the edge of a wharf or pier, the fore guy may be dispensed with, but the sheers must always lean distinctly outwards. Never exceed a slope of 3:1. Foot-ropes and footings may be required.
26. Have a tag line attached to the load purchase in order to retrieve the lower block and hook on, without having to enter the danger zone. It is also to be used to control the load while it is being raised. The tag line is to be coiled down after raising the load.
27. Tie a figure-of-eight knot at the running end of all lines.

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Using Heel Strops instead of Heel Tackles

1. If the points of anchorage for the heels of the sheers can be placed symmetrically, it is possible to use strops instead of tackles.
2. This will use the splay tackle alone to set up the necessary tension in the system. This results in a considerable decrease in the number of blocks and tackle needed to rig the system. Such a method may be employed when the sheers are set up outdoors, using symmetrically placed anchor pegs as points of attachment for the heel strops.
3. Such an arrangement is illustrated below. It is important that the distance between the anchor pegs and the length of the heel strops be appropriate.
4. The figures shown in the diagram are suitable for 4.62 metres sheers. For other sizes, the dimensions will have to be worked out through trial and error.
5. The length of the strop must take into consideration the portion that passes around the leg of the sheers.
6. If a vertical surface, such as a building, tree or pole is available for attachment of the topping lift at the level of the head lashing, the topping lift may be of any convenient length. If not, a topping lift anchor pin can be driven into the ground at a 45 degree angle.

Additional Equipment: 4 heel strops - 12mm manila - 1.8 metres long

1. Legs
2. Topping lift anchor
3. Anchor pin 4 Head lashing
4. Heel strops
5. Splay tackle strops
6. Topping lift and purchase strops
7. Splay tackle
8. Topping lift
9. Purchase
10. Leading block
11. Load
12. Twine
13. Shackle

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Zones

1. Mark an area from the centre of the port heel, forward along the port heel tackle to a distance from the length of the sheers, crossing over in an arc equal to the length of the sheers to meet a mark that comes from the starboard heel tackle. THIS IS DANGER ZONE #1.
2. Mark an area from the port heel, along the after port heel tackle to the after port heel tackle standing block then straight across, meeting an identical mark coming from the starboard side. THIS IS DANGER ZONE #2.
3. The two areas remaining on the port and starboard sides of the sheers are the SAFE ZONES.
4. Zones are only in effect once the cadets begin to raise the sheers.

Remember that sheers are particularly suited for use when the load is not required to be slewed, such as on the edge of a wharf or the banks of a river, or in lifting a weight from a boat to the deck of a ship or assisting in the erection of a heavy derrick or sheers. They are stronger than a derrick of equal size and material, because they are made from two spars instead of one, buy they are clumsier and take longer to rig.

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Conclusion

Knowing how to rig sheers is a seamanship skill that will be used at the corps, and even in everyday life. Although the advent of modern machinery on the ships has greatly reduced the need to know about lifting devices, this is a skill that will never be outdated. In addition, it is part of the naval history and tradition that remains an important part of Sea Cadet training.

Other chapters:

Table of Contents | Chapter 1: Serve with a Sea Cadet Corps | Chapter 2: Drill | Chapter 5: Naval Knowledge | Chapter 6 : Seamanship | Chapter 8: Instructional Technique | Chapter 9: Outdoor Adventure Training | Chapter 10: Physical Fitness | Chapter 11: Canadian Citizenship