Features June 2011 Issue

Smooth Runnings: Bullet Blocks Battle

Rugged gear from Harken and Selden lead the test field.

Photos by Ralph Naranjo and courtesy of Seld?n Mast

Practical Sailor evaluated more than a dozen blocks from eight manufacturers: Barton, Garhauer, Harken, Holt, Karver, Ronstan, Schaefer, and Seldén.

The modern composite marine block remains a distant relative of the first wheel and axle, and traces of its existence as a simple machine date back to about the time when Archimedes began lifting granite slabs.

The application of block-and-tackle use was documented in Sicily as early as 250 B.C. References to a seafaring application of the technology include its use aboard the Asiatic treasure fleet of China’s Zheng He (1405-1433) and by the crew of Christopher Columbus headed toward the Caribbean in 1492. Since then, the quest for lighter, stronger, lower-friction upgrades have unfolded like the history of material science itself. Hardwoods such as lignum vitae not only proved to be the best organic material for making nearly indestructible cheeks (sides) for wooden blocks, but the wood’s ability to act as a bearing surface was also quite impressive. As metallurgical fabrication evolved, bronze bushings and sheaves worked with 316 stainless-steel axles to further lower friction. Roller and ball bearings made modern blocks even slipperier, and by the mid-1980s, the trend was toward making blocks smaller and lighter as well as more efficient. The three decades that have followed have been a composite plastics revolution, and the manufacture of blocks has moved more and more toward esoteric fiber/plastic combinations.

Photos by Ralph Naranjo and courtesy of Seld?n Mast

Seldèn’s 40-millimeter block uses the tried-and-proven stainless ball bearings and race. Metal won’t deform under load or heat.

The last time we tested 40-millimeter blocks was June 2002, and the era of the “hollow block” had already arrived. The name was coined by previous PS testers, and it was given to blocks with larger bearing radiuses. This time around, we found that the makers who had resisted the move toward large, central bearing support bosses had all abandoned their small-diameter axle block design in favor of the larger bearing support surface. Even the ever popular, hollow Schaefer cheek blocks now sport more efficient, larger-radius bearings.

The main difference between this round of testing and the one nine years ago is that we decided to evaluate 40-millimeter bullet blocks at a slightly higher load rating: 200 pounds. This is the 40- to 50-percent stress point for many of the blocks tested, and was within the safe working load (SWL) of all the test products, albeit right on the cusp of the SWL rating for the Holt Nautos 40.

The friction numbers recorded (see the Value Guide table Right) reflect the pull required to keep a closed loop of ultra low-stretch line moving in the two block test system. Those shopping for a bullet-block upgrade should pick a safe working load that takes dynamic force into consideration. If you’re replacing an old block that blew up, determine what its SWL had been and add a larger safety margin. One of the things testers noted this go around was that the ratio of SWL to maximum load or breaking strength varied among manufacturers. In many cases, it’s about a 1:2 ratio, but in others, it’s 1:3, or even close to a 1:4 difference.

The bottom line is that if a block fails during normal use and hasn’t gone through years of cycle loading, it should be replaced by one with a higher-rated SWL. Bigger blocks tend to be stronger, more efficient at the same load, heavier, and more costly. The accompanying tables and photos should help you to pick a product that’s not too large, not too small, and realistically, the best value.

One of the bigger changes we noted this time around was the diversity of attachment methods that have arisen over recent years. Fixed U-shaped metal straps, molded plastic U-shaped cheeks, single-axis pivots, fully universal pivots, and rope strops can answer a wide range of installation requirements. No single system is perfect for all applications, and the right choice should be made on a case-by-case basis. For example, a lazy-jack setup can do just fine with a non-pivoting, fixed strap block while a topping-lift lead may require a block that pivots on two planes in order to align with a fair lead.

What We Tested

This round of testing included a look at products from Barton, Garhauer, Harken, Karver, Holt, Ronstan, Schaefer, and Seldén. All of the units tested were ball- and/or roller-bearing designs, and the trend toward more composite material and less metal was evident.

Karver’s efficiently sculpted alloy, KBO-10 block with its wide bearing race and the pair of Barton 45-millimeter blocks were the only outliers in a very homogeneous grouping. Barton does not produce a 40-millimeter block, so we put its 45-millimeter product in play. Karver refers to the KBO-10 as a 42-millimeter block, measuring the diameter of its sheave groove rather than using the more customary maximum diameter of the sheave side. When measured in the latter fashion, the KBO-10 comes in at a bulked up 52 millimeters. Rather than rating it side by side with other smaller products, we teamed it up with one of our super-slick running Harken 57-millimeter blocks we have been long-term testing. Our thinking was that larger blocks would be more efficient because when subjected to the same load as the 40-millimeter players, the ratio of the load to their SWL would be much lower—an assumption that held up under scrutiny.




The Barton Size 3 is a double-pinned, stainless-steel strapped, modern rendition of a familiar single-block design. It retains the classic guitar-shaped cheek plates, but it also incorporates a large boss supporting the bearing race. A super-smooth spin arises from the combination of Delrin ball bearings and an acetal sheave.

The block comes in a variety of swivel and non-swivel options, and a becket version is also available. Its 45-millimeter sheave diameter puts it in a slightly larger package than our mainstream contenders.

Bottom line: This block is well built, heavier, and larger than most of the others, but it’s cost effective and a good choice for those needing just a little more load-handling capacity.


We received three Garhauer blocks, two 20-13 US series blocks and one 25-13 UAB. Both designs offer a full, 360-degree swiveling shackle. The 20-13 series blocks came in alloy-cheek and stainless-steel versions; both behaved similarly with fairly high friction readings. Rated at a 600-pound safe working load, they are secured by a fairly small Torx screw fastener. Blocks with lower SWL ratings used much larger clevis-pin supports.

However, testers found the Garhauer 25-13 UAB to be an upgrade in design and engineering that solves all of the issues we had with the other two Garhauer blocks. The carefully crafted, large boss alloy-cheek block rolled smoothly under load, ranked high in efficiency, and rides on a clevis pin four times the diameter of the 20-13 blocks.

Bottom line: The 20-13 series’ weight and less-than-robust load support held them back, but we do recommend the efficient 25-13 model.


The master of smooth spin, Harken sent us two versions of its 40C slick bearing blocks. These lightweight composite gems spun like a Vegas roulette wheel, and the diminutive No. 4 Harken bow shackle, found on the swiveling version of the block, fit the center pin stem without any side slop. The sheave ran true even when minor torsion was added to the equation through line lead changes.

Best of all, the engineering was consistent across the board with no areas where excess weight added up or too little material hampered structural integrity. Harken recently introduced a line of soft-attachment blocks that have absolutely no metal components; however, we still feel hard attachments are the best option for cruisers.

Bottom line: The Harken 40C’s bearing races ran smoothly under load, and the connection options provided plenty of installation choices.

The blocks can accommodate lines from 3/8 of an inch to a half-inch. The Karver block (far right) was the largest one tested, with a measured 52-millimeter sheave.


This big boy slipped into the review because, as indicated earlier, its sheave diameter was listed in the manufacturer’s catalog as 42 millimeters, while its actual measurement was 52 millimeters. We kept it in play and teamed it up with a larger Harken Carbo Block just to see if “super sizing” actually lowered friction. Tests results showed that indeed it did, and testers noted that cutting the line-moving load in half was a very noticeable and appreciated benefit.

The Karver KBO-10 in its strop-attached configuration will appeal to most racers, and the Dyneema line is more than strong enough to handle SWL requirements. But like all line-mounted hardware, care needs to be taken to be sure that where the block is attached is free from chafe-accelerating hard or abrasive edges, and the ravages of sunlight must be taken into consideration.

Bottom line: The block is a smooth-running­—and pricey­—load handler that we’ll be sure to include when we look at 55-millimeter blocks.


Holt retails the Nautos block line, which includes the single-sheave, plastic 40-millimeter super-light swiveling block. It features an anodized-aluminum axle on which a composite bearing-supported acetal sheave spins smoothly without any axial deflection. Loaded to its rated 200-pound safe-working spec, the cost-effective gadget shuttled line as efficiently as many of its higher-rated cousins.

Bottom line: The molded, all-in-one cage and cheek assembly may not be as rugged as others, but the unit operates very well at its load limit and is comparably inexpensive.


Lots of design effort went into sculpting the RF45110 and Orbit BB RF45111, two light, non-metal, high-load capable blocks that are available with a conventional pin and rotating shackle or a Dyneema strop attachment. From the carbon-fiber/nylon composite sheave to the fiber-reinforced side plates, the innovative engineering represents a serious commitment to composite structure.

However, during our testing, we noticed a disappointing attribute in both of the Ronstan Orbit blocks: The sheaves had a tendency to rub against the cheek plates. All of the other blocks tested maintained clearance between the sides of the sheave and the inner surface of the cheek plate. The additional friction this caused was likely the reason for the blocks’ somewhat lackluster performance in the efficiency test.

According to Ronstan, “While the sheave rubbing on the cheeks would contribute to the friction, the primary reason for the friction observed is the engagement of the second stage of the bearing system engaging at around the test load. The two-stage bearing system is designed to protect the ball bearings from deforming. At loads typically found on dinghies, only the low-friction ball bearings system is engaged.” In our opinion, that doesn’t make friction at 30 percent of the SWL any more palatable.

Bottom line: The Ronstan blocks’ performance was hampered by sheave-cheek plate friction.


Schaefer knows what it does best, and rather than reinvent shackles and side plates, it dove into refining the efficiency of its blocks’ traditional design. This evolution rather than revolution approach retained the no-nonsense stainless-steel straps and light but stiff alloy side plates. The new twist involves an enlarged central boss that offers greater bearing contact and ultra smooth roll for the Delrin sheave.

Tension loads are well distributed; for attachment, stainless-steel straps tie into stainless-steel toggles, or a pin and universal swivel is used for attachment.

Bottom line: This design is easy to inspect, offering Schaefer-block users a chance to do a bit-by-bit block makeover without changing the appearance of the hardware on board.


These 40-millimeter blocks are a testimony to the company’s commitment to stainless ball-bearing efficiency and long-term reliability. The block frame is a functional glass-fiber/polyamide injection-molded composite that’s more metallic than other product in this round up. But when it comes to roller bearings, Seldén reverts to the tried-and-proven stainless-steel balls and race. Seldén prefers metal because it won’t deform under load or heat, and the alloy they choose is very corrosion resistant.

Options include a block with no shackle; a lashable, molded model; or a pinned-together conventional swivel design. The swivel version also has a neat removable, molded insert that slips over the shackle clevis and locks the shackle in one plane, moving only when it is advantageous to do so.

Bottom line: The Seldén blocks were the smoothest, low-friction 40-millimeter blocks we tested. Both models earn the PS Best Choice pick for this size of bullet block.

Both Ronstan Orbit blocks had enough side play to allow their sheaves to rub on the cheek plates. No other block tested had this problem.


Background testing did show that undersizing a block makes the work harder to accomplish and will shorten the lifespan of the equipment used. When held within the parameters of safe working loads, each of the test blocks delivered acceptable performance, and a few excelled.

Extremely high marks in efficiency were given to Karver for its freewheeling efficiency. But as with a middle-weight wrestler competing in a lightweight class, testers expected such a victory, and to a lesser extent, the same held true for the 45-millimeter Barton product. The latter however, was a much closer match in both size and price and should be a consideration for those looking for a 40-millimeter block makeover.

The main bout was among Garhauer, Harken, Holt, Ronstan, Schaefer, and Seldén, and winners and losers could not be distinguished with a simple flick of the finger, spin of the block, or a look at its construction. It took some in- depth testing and inspection to come to our decision.

The first to fall from the big six was Garhauer’s 20-13 series blocks (aluminum and stainless versions). They succumbed to high friction and a design decision to use a thin Torx screw to connect the swiveling shackle to the block. Garhauer’s newer 25-13 block did not rely on such a connection and carried on into the final round of evaluations.

The next to fall was Ronstan’s 40-millimeter Orbital block, which suffered from sheave-to-cheek plate contact that added friction and caused the block to score poorly on the pull-efficiency test. Its all-composite design and Dyneema strop were appreciated innovations, but the higher friction numbers knocked them out of the running.

Holt’s light, simple Nautos 40-millimeter Organic Block, which proved to be a little powerhouse, unfortunately had a 200-pound safe working load that was half, or even less, of the rating of the remainder of the blocks in contention. In the view of the test team, this was too limiting to keep the block in contention.

The final rating round was among shackle-type, 360-swivel blocks: Garhauer 25-13, Harken 40C, Schaefer Series 3, and Seldén 40-millimeter. Lashing and Dyneema-strop mounting blocks are a valid installation approach among racers, but because of chafe, abrasion, and UV issues, testers felt that conventional hardware was the best bet for cruisers, especially if designers had set up running rigging that way initially.

The final four were a closely bunched fleet. All had scored respectably in every aspect of the evaluation. Each was non-magnetic, corrosion free after the soaking, and close in the under-load pull test. In short, it was hard to pick a winner.

Down to the wire, the Harken and Seldén blocks held the judges’ divided interest. On one hand, Harken has had years to refine composite bearings and has done a great job of it. On the other hand, Seldén is no stranger to making stainless bearings ultra reliable in the marine environment. In the end, the decision went to the block with the slightly more friction-free pull.

When all the salt spray had settled, the Best Choice honor went to both the Seldén tie (404-101-16R) and swivel (404-101-01R) blocks. Harken’s $22 40C (2650) grabbed the Budget Buy pick, and the Garhauer 25-13 UAB and Schaefer Series 3 blocks (300-02 and 300-05) earned our recommendation.

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