January 2019

It is time to announce the winner of our most recent Rigging Puzzle. But first I’ll mention that if you’d like to see previous puzzles, along with a whole bunch of essays and reports from the field, be sure to visit our Blog. And you might also want to take a look at our Front Page, where, in addition to information on rigging services, you can find details on upcoming events, including our 3-day rigging classes, the Seattle Boat Show, a link to our catalog, and news about an upcoming trip to Tasmania. Okay, on to the Puzzle!

 

Last week’s challenge drew a near-record number of entries, from people in a wide variety of rigging interests. You folks are  obviously enthusiastic about loading up hardware. To see the Puzzle, click HERE.

Because the  Puzzle stipulated manufacturer’s recommendations, we will start with Harken, the maker of the diamond-shaped fixed padeye we used. In their catalog Harken says, “For maximum strength, always align fixed padeye bails to the load.” They then give working strengths and breaking strengths for loads applied at various angles, with the highest strength (1) being a vertical load, and the lowest (3) a horizontal load. This is true for all padeyes and eyebolts, because the fasteners are stronger in tension than in shear, and because no leverage is applied when the load is straight up. The trouble is that the only pertinent illustration for this in the regular Harken catalog is this one:

Too many people, including quite a few Puzzle entrants, seem to think that pulling at point 1 produces the greatest strength, regardless of the plane of the pull. The warning in the catalog text, it seems, is easily overlooked. Harken does have a confusion-eliminating illustration for this issue, but for some reason they only show it in their industrial catalog. Here it is:

In the real world, slightly off-angle loads can be difficult to avoid, but they must be minimized, and the puzzle’s arrangement #1 is definitely bad for fixed padeyes.

Harken also makes a folding padeye, similar to the Wichard model we used for the puzzle, and Harken  takes pains to note that, “Folding padeyes differ from conventional padeyes in that the load should be perpendicular to the hinge and bail instead of in line with it. The strongest positions are with the D-ring vertical or leaning toward the fold-down position, which focuses the load on the side anchored with two screws.”

Harken doesn’t have a comparable illustration for their folding padeyes, but Wichard includes this one with every padeye:

Note that the smiley faces apply whether the bail is angled in either direction; I take this to mean that the difference in strength might not be all that significant, despite Harken’s advice.

The lower right frowny face tells us it is a bad idea to pull in line with the bail on a folding padeye, and this agrees with Harken’s recommendation. The idea here is that you would be applying a point load on one side of the fitting, instead of a long bearing along the length of the hinge. This is the pull shown for the folding padeye in arrangement #2, so that one is out.

Note also that the upper right frowny face calls our attention to the fact that there is a limit on how far the bail can articulate towards the two-fastener side. Go too far, and the bail crunches against the base of the padeye, producing some very unfavorable leverage, torque, and point loading. Therefore, when you are installing folding padeyes, see if there is an articulation limit on one side or the other, and then install it so the side with the greatest range of motion is facing the most likely range of load angles. If you have an application where you might need full articulation in both directions, you need a different padeye. In the first iteration of the Puzzle, I had the bail right down at the base of the padeye in arrangement #3, and sharp-eyed readers Ken Ferrari and Robert Salnick saw this. The second version of the pictures showed the folding padeye on the fully-articulating side, and no one was disqualified because of this detail.

The upshot of all this is that arrangement #1 is good for the folding model, but bad for the diamond, and the opposite is true for arrangement #2. The correct answer, then, is arrangement #3.

Congratulations to all of you who chose #3. And congratulations likewise to everyone who gave it a shot. Our winner, randomly selected from the pool of correct entries, is … Tom Dixon! Congratulations, Tom. Let me know which version of Falling you would like to receive — print, audio, or ebook — and what circumference and rope diameter soft shackle you would prefer. For everyone else, thanks for all of your thoughtful responses.

If you didn’t win the drawing, but want a copy of that book, it is available from Amazon as well as iBooks. If you would like an autographed print copy, be in touch with Sue at our shop, by writing to catalog@briontoss.com.

 

 

There’s lots going on at briontoss.com. Scroll to the bottom of this page for details.

The Rigging Puzzle this time is about padeyes, and how to load them. In the pictures below, one padeye is a classic diamond pattern from Harken, and the other is one of Wichard’s nifty folding models.  We loaded them three different ways, all with the leads rising slightly up from the horizontal, and only one of those ways complies with the manufacturers’ recommendations for maximum strength, for both padeyes.  So what’ll it be, picture number 1, picture number 2, or picture number 3?

If you think you know the answer, send it to puzzle@briontoss.com, or reply at the bottom of this page. Feel free to kick this around online, but it won’t count unless you submit an answer. We’ll draw the winner randomly from the pool of correct answers.

The prizes this time: one of our high-strength Spectra soft shackles (suitable for securing to your favorite padeye) and a copy of my book Falling, about the perils and rewards of working aloft. The book is available as a paperback, as an ebook, or as an audiobook, the latter narrated by yours truly.

Entries must be here by noon Pacific Time, January 21st. We will announce the winner on January 23rd. Good luck!

Arrangement 1, top view

Arrangement 1, side view

 

 

 

Arrangement 2, top view

Arrangement 2, side view

 

 

Arrangement 3, top view

Arrangement 3, side view

 

In other news, if you are going to be at the Seattle Boat Show, I’ll be giving a series of talks there about various aspects of rigging. And I will soon be sending reports in from, of all places, Tasmania, at their huge, semi-annual Australian Wooden Boat Show. And finally, we will be once again bowing to popular demand and will be giving another 3-Day Rigging Workshop this April, at our loft in Port Townsend. Still some spaces available, but these workshops fill up fast. For information on all of this, and more, visit briontoss.com

 

 

 

In our most recent puzzle, we asked how much additional tension our rigger Julia Briggs could apply to a line by “sweating” it sideways. Here is the  puzzle, with accompanying video:

Sailors and other rope users are familiar with the process of sweating or swigging up a line: pulling sharply sideways on the fall of a purchase, above the belay point to gain a bit of slack, then quickly transitioning to a downward resolution, so that slack can be taken up at the belay point. The combination of leverage and impact-loading allows you to get more tension than you could by simply pulling down on the line. But the question is: how much more?

In the video below our rigger Julia Briggs is sweating a line in our shop. The line has been set to a starting tension of 200lbs.

Julia weighs 140 lbs.

The line is attached to a load cell that has been set up to read the maximum tension achieved.

So here is the puzzle: how many additional pounds of tension did Julia impose?

Congratulations to everyone who ventured an answer; there was some serious head-scratching going on out there. But the people who got closest to the actual answer tended to be the ones who used actual math, so to explain things, here is a simple-enough-for-my-level-of-comprehension explanation:

The maximum reading on that load cell was the result of two factors: how much force Julia could exert; and the angle that the rope formed at the peak of her pull.

Because she pulled very sharply, she exerted a shock load (accelerated load), which could easily be at least as much as her body weight, depending on how fast she was moving, how elastic the materials were, and how far she managed to deflect the line. For details on calculating shock loads here is a good site: sciencing.com/calculate-shock-load

As you can see from the video, Julia did not deflect the line more than a few inches, but this is actually a good thing in terms of getting a high load cell reading, because her leverage increases as the angle decreases, varying with the sine of the angle formed at either end of the line. If this sounds counterintuitive, there are lots of real-world applications for the idea. For instance, if you are a guitarist, you know how easy it is to “bend” a note up, tightening an already tight string by pushing sideways on it as you pluck it. Now try to get the same effect by pulling in line with the string (without using the lever known as a tuning peg), and you will see how powerful your leverage was. If you are a sailor, you know that as shroud angles diminish, tension on the shrouds goes up. And if you are an industrial rigger, you know that loads on sling legs go up as sling angles decrease towards the horizontal. For more on this, see the “Standing Rigging Design and Materials” chapter of  The Rigger’s Apprentice.

In our example, we started with an initial tension of 200 pounds, minimizing the ultimate deflection, and thus maximizing the potential leverage. Then Julia maximized the effect of her weight with the classic sailor’s Two-six-HEAVE, technique, building up her acceleration to an explosive final pull. And she maximized the shock load with good body mechanics, so that she was pulling perpendicular to the line, arms fully-extended and braced, on that final pull. The result was a load of 563 pounds (!), after deducting the initial 200 pounds. That’s right, she exerted almost four times her body weight on that line. In the real world, we are usually working with more elastic materials and bigger deflections, but you can see why sweating a line can be such a valuable force multiplier.

Given all the variables, it is not surprising that the answers were all over the place, and no one got within 10 pounds of the result, but several of you were quite close, so I expanded the tolerances, and am awarding prizes to everyone who got within 150 pounds, high or low. So congratulations to Nels  Backstom (672 pounds), Ian Duff (420 pounds), a reader identified only as “nopain” (480 pounds), CarlyP (670 pounds), Captain Mike (whose entry was closest, at 600 pounds), my dear friend Ben Stockwell (644 pounds), and Seng (715 pounds, which is 2 pounds over, but what the heck). All of you folks, please be in touch to let me know whether you want the audiobook or the ebook version, and whether it should go to you, or to be a gift.

For those of you who were outside the envelope, it is really easy to get a copy of Falling by other means, by going to Apple or Amazon.

In other news, those in the Seattle area can find me at the Seattle  Boat Show later this month, giving a series of talks about a variety of rigging topics. After that, I’ll be heading to Tasmania for some talks at the wonderful Australian Wooden Boat Show.

Fair leads,

Brion Toss