PLYWOOD BLOCKS
By David N. Goodchild

My first thought in making the blocks for TOAD was to use rope-stropped blocks as pictured in Hervey Garrett Smith's The Marlinspike Sailor. His drawings are reproduced below.

I made a couple of attempts to reproduce this type of block with reasonable success. However, I decided that I much preferred a metal strap in place of a rope strop, and it was clear that these would be much faster to produce than the mortised type. An example is shown below.

I started out by making the classic block, with the cheeks separated by spacers and a hooped strap which would be attached to a tang by a shackle. I purchased a Delrin sheave for the line and made the cheeks from oak flooring scraps which I happened to have available. When I put it all together though, several things troubled me. The flooring scraps were a little narrow when the tongue-and-groove was trimmed off and the sheave therefore projected slightly more than I wished. I also did not like the resulting elongated shape. It was clear that I would need some other material for the cheeks.

I thought about this for a while, and in cogitas I realised that the hardwood cheeks on the $45.00 blocks we see advertised in the yachting press were really an anachronism, albeit a beautiful one. I believe the development was as follows. Originally, all blocks were mortised in very hard woods and rope-stropped, as were Smith's versions shown above. Subsequently metal-strapped blocks appeared, and the wood was mainly relegated to the function of cheeks, and this function is primarly that of fairing. In fact, it would be very possible to make a block with just the straps and the sheave were it not for the possibility of snagging them on lines and fittings. It was apparent to me therefore that the cheeks could be made of almost any material which would serve this function. All of the strain would be taken by the straps. I then thought to use plywood. This has worked out superbly, and I can use the odd-shaped scraps of 3/4" plywood left over from bulkhead and central-girder making. I made a set of sample cheeks from this material, and tried a coat of epoxy and spar varnish on them. They came up beautifully.

I was still unhappy with the sheaves however, because I had to buy them for $3.00 apiece. I planned to make up about 60 blocks for use and for spares, and this would be $180.00 just for sheaves. Not good!

I decided to try plywood!

I had already tried making up sheaves from the oak flooring scraps and this had worked out fairly well, but the use of plywood offered me several further advantages. The oak would have its grain oriented in only one direction and thus would take the strain in the wrong direction at least 50% of the time. The plywood, because of its cross-grain plys, would have its grain oriented in a useful direction for the vast majority of the time. I made up a couple and tested them satisfactorily.

At this point I had a hooped strap with plywood sheaves and cheeks. I was progressing nicely I thought. Then I went shopping for shackles. When I finally found one that was appropriate, it cost six dollars! That would be $360.00 just for shackles if my inventory of 60 was to be maintained. Even less good!

By using plywood for cheeks and sheaves, and a piece of scrap steel from the back of a set of steel shelves for the strap and a couple of brass bolts and nuts, I had got the cost of making the prototype block down to about 20 cents! I wasn't about to spend six bucks for a shackle to fasten a 20 cent block to a fitting or a line. It just didn't make sense.

Cogitas ergo explicatum!

I looked at the shackle and how it joined the block and realized that if I eliminated the hoop and instead terminated each side of the strap in a rounded end with a hole in each, I could join the two with the pin of the shackle, with a clevis pin, or (with thanks to John Marples) with the shank of a bolt with the threaded end shortened.

I could get clevis pins from the marine store for just $2.00 each. By eliminating the $3.00 sheave and the $6.00 shackle I had already saved $9.00, or a total of $540.00. I was rich! Better still, I knew I could get galvanized clevis pins from an auto supply store for even less.

Now I come to the final innovation in this block-making effort. While making up the first prototype of this final design (Block; Toad, Mark V, Mod 1), it occurred to me that I really did not need the spacers, (the filler pieces at the top and bottom of the block). If I held the block apart by the use of steel tubing, I could get the same effect as the spacers and enjoy faster and easier construction. A schematic of the final assembly is shown above.

The two straps lie in dadoes cut into the inside face of each cheek. The sheave axle runs through the cheeks and the straps in traditional fashion. The cheeks and straps are held together by two round head machine screws which run through two pieces of steel tubing. Tightening these two screws fastens the block together tightly and completely. The clevis pin functions both as a pin and a shackle.

One big advantage of this method of construction lies in the convenience of being able to make up the block inventory as parts only, and then put them together as needed. Since all that has to be done to make up a block is to insert the axle through the sheave and the straps, insert and tighten the bolts and fasten in the axle retainers, assembly is simple in the extreme. But an even greater advantage is that by making just three different strap types, and stocking a few bolts of different lengths, I can make up a very large variety of blocks, with and without beckets.

I will say however, that after I had come up with this idea, I was reminded of the old BlocKits from the early 70's. These were similar arrangements of cheeks, straps and sheaves, which the buyer could purchase in individual pieces and thus make up finished blocks from the parts. (They weren't as pretty as mine though!).

To actually make up the blocks all I needed now were materials. I hate buying anything at the marine store for this boat if I can avoid it. I would much rather make it up from something else. Accordingly, I went to my favorite steel scrap yard and bought about 80' of 1" x 1/16" steel bar for the straps. and 12' of 3/8" chrome molybdenum steel rod for the axles. The latter was a real find. The twelve feet of chrome steel rod cost me two bucks! The 80' of 1" steel strap cost me .25 cents per pound., or $4.00!

Now all I needed was the tubing for the fastening bolts. At my local auto supply store for $2.48, I bought 48" of electro-galvanized steel tubing which would just slip snugly over the bolts. Enough for 24 single blocks.What was this? Why it was brake line! It's perfect for this use. Final cost was about 21 cents per block. That's acceptable!

The first thing I did was to rip some scrap plywood to the width of the cheeks, plus a little extra. Following this, I dadoed the 1" valley for the straps into the rectangular pieces. I then traced out the shape of the cheeks and cut them out on the band saw. I located the three holes that would pass through the straps, (the axle and the two fastening bolts), and made up a Master Strap of each type to be used for all subsequent measuring. I then borrowed a "chop saw" with a Carborundum cut-off disc and sliced off all the straps to the three lengths necessary to make up the block parts. I used the Master Strap to mark out the locations of the three holes to go through each strap and drilled these. Then I rounded over the tops and bottoms of the straps to match the contours of the cheeks.

I also used the Master Strap to locate the three holes in the cheeks, drilled these out and then sanded the cheeks to their final shape. By turning the cheeks over so that the face was up, I had the locations for making the counterbores for the nuts and the heads of the fastening bolts and for the axle covers. I used Forstner bits to cut these counterbores.

The only thing that remained to make were the sheaves. I had previously experimented with using the lathe to make these but abandoned this quickly as it proved too clumsy. The method I ended up using was simple, and utilized the drill press. I first cut out the circles with a simple hole saw of a little larger diameter than my finished 2" sheave size. I used a machine screw and two nuts and washers to chuck the sheave blank into the drill press, and set the machine to its highest RPM.

I first used a small round shaping tool from the lathe to rough cut the valley, then made up a smaller but similar tool from an old screwdriver. This enabled me to turn a small, deep valley of the right size for 3/8" line into the sheave. I finished it up with sandpaper while still turning in the drill press. I enlarged the axle hole to take a piece of 7/16" I.D. nylon tubing (it is self-lubricating) to use as a bushing, pressed this in using the drill press and ended up with a very nice sheave made from plywood. I then used the band saw with a metal-cutting blade to cut the axles to length and to cut off the brake line to the right length for the stand-off tubes.

The only thing left were axle covers to go on the outside of the cheeks and retain the axles.

In a fine British publication, (and aren't they all), called Classic Boat, I had previously seen English pre-decimal pennies used for this purpose. Since I had quite a few on hand, I planned to use them.

Test assembly was simple. I laid the straps into the strap-valleys, pushed the axle through the cheeks, straps and sheave, then put the fastening bolts through the cheeks, straps and stand-off tubing and tightened the nuts. I had previously drilled two holes through the sides of each of the pennies, and I fastened the axle covers into the counterbores with #4 round head brass wood screws. Finally I inserted the clevis pin at the top of the straps. The block was assembled!

I finished the blocks while disassembled. I coated the cheeks inside with one coat of Epoxy and two coats of Polyurethane. I did the same with the sheaves. On the outside of the cheeks I used two coats of Epoxy, two of Polyurethane, and two coats of Spar for gloss and UV protection. I put the straps in the pile to go to the galvanizers. Finally, I wire brushed and buffed the pennies until they shone brightly with their natural copper sheen, and then sprayed them with three coats of a good clear lacquer.

My .21 wood-cheeked block was finished!

NOTE: There have been some changes since I wrote this article and I have now decided to go back to rope stropped blocks after all. I came up with some good ways of making these two and I will post that article in a few days. Also, I will have some results of the tests I ran for load-bearing on the steel-strapped blocks described above.