A method to overcome a common rope problem on different deck levels
Even in our younger days, my wife and I tried to make things as easy as possible on our cruising boats. This is even more important as we grow older. A major modification to make the sails easier to handle on Britannia was to change all five sails to roller furling.
I also wanted to route all the control lines — furling lines, sheets, and outhauls — to the center cockpit, so we wouldn't have to go forward to furl or reef in inclement weather or rough seas. This resulted in 12 lines passing along the deck(s) into the cockpit, in two rows of six Plus five sheets that route to cockpit winches in the normal way.
By any standard that's a lot of lines, but I knew how I would handle them once the lines arrived in the cockpit. I made wooden fairleads to guide them through the front canopy then through two banks of rope clutches with six-line jammers in each. I bought these from Garhauer Marine where they were color-coded. Then I taped names of the lines on the individual clutch levers. The lines pass into the cockpit on either side of the companionway where it's easy to reach and operate the clutches where they feed to two Lewmar 30 self-tailing winches and then coiled around a row of belaying pins to prevent tangles. This is now called "the rope decks."
All this was not difficult to plan and the fairleads, clutches, winches and pin-rails were not difficult to make and install. But one significant problem remained. Britannia has three deck levels: the foredeck, the forward coachroof deck, and the saloon coachroof deck. To reach the cockpit, lines had to be routed up from one level to the next. The jib and forestaysail furling lines and the staysail outhaul were the longest. These had to pass down to the foredeck, then over both coachroof levels into the cockpit. Bringing lines down from aloft and along a deck is easy using blocks anchored to the deck along with line organizers. But routing lines upward and over the edge of a coachroof requires what is commonly called an "over-the-top block."
Over-the-top blocks are available from a few suppliers including Garhauer and West Marine, for about $55 for a single line sheave and $85 for a double. Nobody seems to make more than a double-sheave combination and if you have twelve lines, that works out to be a bit expensive.
In any case all the over-the-top blocks I could find used large sheaves with diameters of 2-inches or more. This results in the lines running about 3-inches clear of the deck and the very serious possibility of someone (i.e.me!) tripping over them. I wanted my lines as close to the deck as possible and my first attempt was to use bulls-eye fairleads with stainless-steel inserts. These are only about $6 each but are intended to lead ropes in more or less straight lines, and often used to route roller-furling lines along stanchion rails. Still, I decided to give them a try and screwed six to my deck, but the nearly 90-degree up-and-over angle resulted in a lot of friction with a good chance of rapid chafe especially for those lines that must rise two deck levels.
Then I discovered that Ronstan made an Acetal (nylon) sheave only 1 3/32-inch in diameter yet wide enough to handle up to a 1/2-inch line for only $3.95 each, (part number RF128). As three of my lines are 1/2-inch and the rest are 3/8-inch this small sheave would work with all my lines.
I decided to try and make my own over-the-top blocks. The photograph of two sheaves shows a finished set of sheaves. The arches prevent the rope from jumping off the sheave when it's slack. The components of the same block are shown disassembled. These are the bottom channel screwed to the deck, rope retaining arches, sheaves, bushings and the through bolt and nut.
TOOLS
I made my over-the-top blocks by hand using hand tools that most do-it-yourself boaters probably have. It's not rocket science but some of the operations do require careful measurement and accurate drilling. It was not difficult to do this and gratifying to see the finished product working so well on Britannia, not to mention the cost savings over commercial over-the-top blocks.
The tools I used were a caliper gauge for accurate measuring, a sharp scribe for marking, a strong vise with aluminum soft jaws, three vise-grips, and a 5/8-inch diameter mandrel to bend the strips round to form the arches. In my 1/2-inch sockets box I found a socket that was exactly 5/8-inch diameter but any 5/8-inch round stock would work. A bench press beats trying to drill holes accurately by hand. The more precise the marking and drilling the better chance there is of making smooth running sheaves. It would therefore be a good idea to invest in a new sharp 1/4"-inch drill bit preferably the type with a pilot point that are easier to center by eye and leave an almost burr-free exit hole. A countersink bit is another important tool for this work and after drilling or sawing all raw edges should be cleaned with a deburring tool or a larger drill and file
I would have preferred to make the blocks of stainless steel, but cutting and accurately bending and drilling even 1/8-inch stainless was beyond the capability of my equipmen, so I choose aluminum. Aluminum can be hand-sawn easily with a hacksaw blade with 24 teeth per inch but I also used a miter saw with a 10-inch diameter 60-tooth carbide-tipped blade that cuts through aluminum like butter with a very straight clean cut. I made the bottom channels from a 12-inch length of 1/8-inch aluminum channel, 2-inches wide with 1-inch sides. I made the rope-retaining arches from a 48-inches length of 1/2-inch x 1/8-inch aluminum strip. This was available from my local aluminum supply shop for $15.
I needed to make one row of six sheaves, a row of three, one of two, and a single, but most sailboats won't need that many and therefore require less material.
MAKING THE BOTTOM CHANNELS
I first cut the channel into 1-inch wide pieces to form the base for a two-sheave block. I needed five of these.
The next drilling operation is critical. It might be possible with a hand-held electric drill but much easier and more accurate with a drill press. Both legs of the channel need to be accurately marked 3/4-inch from the bottom outside of the leg and in the center. I drilled a 1/4-inch hole at these marks from both sides of the legs. This hole position allows the sheaves to rotate clear of the bottom of the channel by 1/16-inch and the lines run out the top of the sheaves at the very lowest point: about 1-inch off the deck. Next I drilled and countersunk two 1/4-inch holes in the bottom of the channel 5/8-inch from inside the channel and the center. This was to locate the attachment screws beneath the sheaves. As a final finish to the channels I rounded the square sharp corners of the legs with a flat-file.
THE ROPE RETAINIG ARCHES.
To form the arches I cut the 1/2-inch aluminum strip into 5-inch lengths so I could more easily bend each around the mandrel. I clamped the socket/mandrel hard in the vise then marked the center of the strips and clamped one to the socket in the center with Vise-Grips. This is to ensure that the aluminum strip will fold evenly around the mandrel in a perfect half-circle, otherwise it will bow upward and not form correctly. I also cut some lengths of the spare strip to clamp between the vice-grips and the material both to prevent them from cutting into the aluminum and to keep the legs of the arches straight.
I then carefully pulled both legs around the mandrel. It was quite easy with vice-grips clamped to the legs to extend the leverage but you can only bend so far before the vice-grips come together. I then squeezed the two sides further with just one vice grip until they were parallel with each other and formed a perfect arch. Then I sawed the legs of the arch off square 1 5/8-inch from the top of the arch. Using a round file and sandpaper, I rounded the top inside edges of the arches a little to prevent the rope from chafing as it passes through. A Dremel with a round sanding drum would also be good for this purpose.
Each arch is now 7/8-inch wide so two will be a perfect snug fit inside the channel that measures 1 3/4-inches inside the legs.
DRILLING THE ROPE RETAINING ARCHES.
With both arches centered in the channel I clamped the assembly in the vice and with an electric drill, carefully and dead level i drilled either side of the arches through the hole in the channel leg. I then reversed the arches and making sure they were centered in exactly the same position, re-clamped them in the vise then drilled through the other side. Do not be tempted to try to drill straight through both arches—it is very unlikely you will be level using a hand drill.
At this point it's possible to push a 2 1/2-inch long 1/4-inch bolt straight through the channel and both arches pinning them together. If your measuring or drilling has not been accurate enough to make it possible to push a bolt straight through, ream the holes level by carefully running a 1/4-inch drill through. I discovered some unevenness when assembling my row of three channels to make the six-sheave block, but I ran a 1/4-inch drill through the whole lot and they work perfectly when bolted together.
SHIEVES AND BUSHINGS
The Ronston sheave has a 5/16-inch center hole and no roller bearings. I bought some small 5/16-inch bronze bushings that fit perfectly inside the sheaves and reduce the hole to 1/4-inch. Unfortunately, they were in lengths of 3/4-inch so I had to carefully saw and file 1/8-inch off one end to make them 5/8-inch long to fit snuggly inside the arches. The sheaves will then rotate on the bushings and the bushings will rotate on the bolt giving an almost friction-free roller-bearing surface for the sheaves.
If the sheaves don't rotate completely freely something is wrong. Perhaps the bushing was distorted in cutting it to length or it needs to be deburred on the inside and maybe also the outside.
ASSEMBLY AND ATTACHMENT.
The photo of the two-sheave assembly shows it with no lines running through. To fix the channels to my fiberglass deck I used 3/4-inch long #12 flathead self-tapping screws that finished flush with the bottom of the channel in the countersunk hole. I screwed these directly into the deck and bedded them with 3M 4000 sealant. It does not seem necessary to bolt these blocks straight through a deck as you would for say, a pad-eye, because when the ropes are under load they press the assembly down to the deck rather than pulling it upward. It is necessary to fix the channel to the deck before assembling the sheaves, then assemble the rest in situ.
Just before this final assembly I used a dab of winch grease on the bolt and bushings but not on the bushing-to-sheave surface. The sheaves and bushings are positioned inside their arches and the arches are pushed into the channel. Then the bolt is passed through the whole lot and secured with a thin washer and nylock nut. I found it best not to tighten the bolt too much allowing some play in the bearing surfaces so everything rolls freely.
The heading photo of six sheaves shows how I joined three two-block assemblies to make a neat row of six. It was just a matter of using a 6-inch bolt through all three assemblies. To make a multi-sheave combination it's best to bolt them all together without the sheaves or arches, position them where you want them on the deck mark the attachment hole centers then drill the holes for the fasteners.
To make the three-sheave block I cut one leg off a channel, then made a corresponding half channel to butt against it. A 3 1/2-inch bolt goes straight through all three sheaves locking them together. Then a fastener beneath each secures them to the deck.
The single sheave leads the jib furling line down to the foredeck so it can be routed up and over the forward coach-roof and then the saloon coach-roof. This block was also made using half a channel, but it has a different shape so I could screw it to the toerail. I secured a small half channel with one of the screws to fix it to the toerail and a 1 1/4-inch bolt fastens the assembly together.
These combinations demonstrate the versatility of this method of making over-the-top blocks. There's no reason why larger combinations could not be bolted together as needed.
Finally, if you want to make these blocks look really professional, polish all the individual pieces on a bench polisher with a large wheel and graphite applicator. The assembled sheave will shine like chrome.
My over-the-top blocks work marvelously and the lines look very neat running close to the deck with hardly any chance of tripping over them.
The total cost in materials was about $120 for 12 sheave blocks or $10 for each control line. This is quite a savings compared to buying commercial units for about $500. This does not count my labor of course, but on boats, that's supposed to be fun.