Chapter 50
Stropped Blocks

sail boat plan

Good Looking And Really Efficient, These Blocks Are Not Difficult To Make If You Go About It Properly

Rope-stropped blocks may be old fashioned, but they do give a cruising boat a salty air. And in addition they have several advantages over the modern type. First, they are quiet; they won't clatter noisily on deck or against the mast. Neither will they mar your paint or varnish, for the rope strops act as built-in fenders. Then, being streamlined and without outside metal parts, they are not likely to foul anything. And all important for many of us, they are not expensive, nor are they difficult to make if these instructions are followed.

Bronze roller-bushed sheaves, either those removed from your old blocks or new ones bought without shells for the purpose, should be used. Their size, as necessitated by the diameter of the sheets or halyards used with them, will then determine the size of the shells to be made.

The first thing to do is to make an accurate layout of the block based on the size of the sheave. In Fig. 1, the common 1/2-in. size is shown. A layout for a 5/8-in. sheave would merely have a larger mortise and 5/8 in. of wood all around it. With a 3/8-in. sheave, the thickness of the wood about the mortise could safely be reduced to 3/8 in. To lay out a double block, merely leave a wall of wood between the two mortises. In any case, finally make a pattern or template of Masonite or stiff cardboard for the mortise side.

While lignum vitae may be the ideal wood to use for block making, it is almost impossible to secure. Black locust and osage orange are good substitutes and teak and ash are also satisfactory. All are much easier worked than lignum vitae is, but they are inclined to check if proper safeguards are not taken. First, the wood used must be thoroughly seasoned and clear ol knots and defects; then the finished shells should be soaked in boiled linseed oil before fitting their sheaves and strops. Aside from preventing checking, such treatment will harden the wood and give a waterproof finish. Put each shell as it is finished in a container large enough to hold all of the shells and still be only about two thirds full. Place this in another shallow container of water, put it on a stove, and heat the oil to just short of the boiling point for an hour or so. Allow to cool, remove the shells, and wipe off the excess oil. This oil finish can be left or, if you wish, the blocks can be varnished or painted after the oil hss set on the surface.

sail boat plan

Three sizes of stropped-block shells in varying of construction. Employ seasoned wood.
 
Several completed blocks, a partially completed grommet, and sheaves and pin for another block.
 
Your layout will give the size of the stock necessary. It is a good idea to have it dressed a trifle oversize. Then cut to length (Fig. 2) and, using the pattern, mark the shape. The next thing to do is to cut or scribe the lines shown in Part 3 of Fig. 2, using a marking gauge or a bench saw set to cut xr, in. deep. Note that the lines for the sheave mortises are cut on both top and bottom faces and that those for the strop groove are cut on both sides. The cuts beyond the ends of the mortise will later be removed when rounding the block. While this rounding will also remove most of the groove cuts, they will in the meantime help locate the hole for the pin accurately and can later be extended completely around the shell.

Bore for the pin hole next and then bore a series of holes to help in cutting out the mortise. If a drill press is available, by all means use it, otherwise bore by hand, working from both sides for accuracy and preferably using a bit a size smaller than the slot requires.

With the mortise finished, saw just outside the pattern lines, then use a small plane, a coarse file, and sandpaper to get this part of the rounding right before doing the final shaping. The latter must be done largely by eye. A rough holder, as shown in Fig. 3, will be a big help. The strop groove, which is completed last, should be cut large enough to hold the strop, but not so deep as to weaken the shell.

After the linseed-oil treatment mentioned above, fit the sheave, seeing that it turns freely and having the pin just long enough so its ends are flush in the groove. The strop is a grommet made up, as a book on knots wil.1 show, by unlaying a length of hemp boltrope such as any sail maker can supply. This length should be about four times the diameter of the loop required to encircle the block plus enough for the brass sail thimble to be seized in. One strand is used, relaying it about itself until a loop is formed exactly like the original line. The two ends are held by an overhand knot and a couple of tucks. These can be concealed by the racking or throat seizing when finally fitting the strop in place. If a becket is required, another sail thimble must, of course, be allowed for when making the grommet. Using a knot book as a guide, it is not difficult to make a grommet, but it is not easy to come out with the length just right; so make your first one a trial one and then make the others a trifle longer or shorter as required. Paint the strops with Stockholm tar, obtainable at any marine supply house. The jet-black finish not only looks well against the finish of the wood but helps preserve the rope.—Jim Emmett

sail boat plan

sail boat plan

When lines have been stowed away for any length of time, look them over carefully. Discoloration is bad.

Frequently inspect all fastenings in the hull. If this loose bolt had not been found, rudder might have fallen off.

Are You Ready To Move Onto The Next Lesson? Click Here...

COPYRIGHT (C) 2006 WWW.SAILBOATPLAN.NET