Mailport December 2017 Issue

Mailport: Shackle Sense

Shackle Sense

You have written thousands of words about shackles. One item that I don’t think you have ever addressed is the use of ‘double’ shackles. Our boat weighs 14,000 pounds dry (probably 17,000 pounds fully loaded for cruising). We use a 45-pound Manson, 200 feet of 5/16-inch G4 chain rode, and a Crosby 3/8-inch shackle (working load limit 2 tons). After hundreds of nights at anchor we have never dragged. We are big fans of a having a single anchor that you trust, and keeping a spare ready—but don’t ever use it unless you lose the one you love. So I have no motivation to change the set up.

shackle chain test
During the past few years, Practical Sailor has been conducting a series of shackle and chain tests at Robertson’s Lifting and Rigging in Sydney, Australia.

But as I walk up and down the docks of the marina where we are presently staying, I see many boats with double shackles, one attached to the anchor and one to the chain and then the two shackles are linked together. In speaking with some of the owners of these boats they claim that double shackles act somewhat like a swivel without the risk. They allow the anchor to articulate, aid in resetting, and make it easier to bring the anchor over the roller and onto the bow without the ‘clunk’ that nearly always occurs. To me this is silly, since the shackle is usually the weakest part of an otherwise good setup. It seems to me that using double shackles merely doubles your risk, but I am curious as to whether this is something you have ever examined or considered.

Eric Vahlbusch

S/V Blessings

New Bern, NC

"D" Shackle
A “D” shackle (top) is integral to a few anchors, making a two-shackle arrangement inevitable.

Ideally, the bow of the shackle should go through the anchor slot, and the pin should connect with the chain rode.

As you point out, we’ve done a great deal of shackle testing in the past few years. We have not, however, ever taken a closer look at the effects of using two shackles instead of one. Based on our experience and past tests, however, we can’t imagine that two shackles would dramatically improve performance. Barring that, why add—as you point out—another weak link? A second shackle is often introduced when the anchor shank is too thick or broad for the shackle that matches the desired chain. This problem is becoming more prevalent as some boaters upgrade to smaller diameter high-strength G80 chain. One of our testers is experimenting with various lifting shackles that might be used to join a small chain to a big anchor and still retain the full strength of the chain. Currently he is using an Omega shackle from Dutch maker Van Beest that has been treated with the Armorgalv process. (See “Anchor Shackles Round II,” PS October 2016.)


Hobie Mirage Drive

Regarding kayaks for cruising (see PS October 2017) We have a 12-year-old Hobie Hank Parker Outback with

Mirage Drive, and unfortunately our experience with the kayak leaves a lot to be desired. Despite its relatively high price and limited use of our boat, the hull has displayed a disturbing tendency to crack in the worst possible places structurally, and in most cases access to repair it effectively has been difficult. Additionally, support from Hobie is well known to be notoriously poor. The seating position on this particular model is also very uncomfortable for someone six feet and taller and the Mirage drive doesn’t adjust much. The pedal drive is severely limited in thin water as well. All of this is fairly well known, and I can only hope that Hobie has seen fit to take responsibility and make improvements in these areas because the concept has such promise. The sail kit, for instance, is fun if somewhat awkward and inefficient.

John Gray

Via email


The Invulnerable Onboard Network

This morning it was announced that the primary (and thought to be most secure) encryption method used with WiFi—WP A2—has a serious flaw that makes it highly vulnerable. I have long felt that the increasing use of WiFi for boating electronics is asinine. The safe choice for boaters, especially bluewater cruisers in less safe places, is to use hardwired Ethernet with CAT -5 cabling. The safe and wise choices for blue water cruisers are:

• Hardwired Ethernet with CAT -5 cabling built into the boat,

• Use an MFD from Raymarine, Garmin, Furuno, Sirnrad, etc. and disable its WiFi,

• Use OpenCPN on a laptop (preferably running Linux) as a backup MFD,

• Use a Raspberry PI NAS (Network Accessed Storage) for storage of naval charts, music (as MP3), video, photography, etc. that is connected to your hardwired Ethernet on-boat networking,

• Avoid accessing websites that only offer HTTP and instead always use HTTPS whenever possible (i.e. secure access),

• Have a single point of egress for Internet from your boat~ a hardwired CAT-5 connection to a Raspberry Pi used as firewall and TOR proxy box (search for the Onion Pi) and connect that hardware proxy box to a single omni-directional WiFi antenna.

If WiFi exits and enters your boat using an up-to-date version of TOR (currently v3) using its web browser and email programs you will be reasonably safe anywhere in the world. The current WP A2 encryption flaw is not the only reason that WiFi use in unsafe ports, marinas, and anchorages is problematic. Even if a crook cannot decrypt your data on WiFi a lot of info is available from just knowing whether WiFi is in use—are you on the boat, are you asleep? Ideally we would have an autonomous means of sending out dummy WiFi messages at time we are off the boat or asleep.

An interesting Linux OS for sailboat cruiser use is Endless OS ( It has the intended use of someone in a poor nation who either does not have Internet access or only very slow access to Internet. It has a good deal of the Internet’ s usefulness stored off-line on your laptop hard disk, and it can access web content that is useful from slow speed Internet access (perhaps at night while you are asleep) and make it available from your harddisk when you want to access it.

People need to be contacting the Endless OS Linux developers and requesting that they create a version of Endless OS that is designed for sailboat cruisers and RVers (both of whom often have only slow WiFi access to Internet at marinas and campgrounds). A sailing/RVing version of Endless OS Linux that had OpenCPN and other programs of use to sailboat cruisers would be invaluable. The Endless OS folks also sell low cost, low power computers with Endless OS Linux pre-installed. It could also be booted up on from a USB thumb-drive with Endless OS Linux (or any other Linux distro-TOR or etc.) on a MacBook or Windows laptop without modifying the hard disk or SSD.

Ed Scott

Taos, NM


3M Foam for Canvas

As a sailmaker and canvas guy, I can say that you almost got there with your report on contact cement for canvas, but you appear to have used the liquid version with a brush (see “Fixing Tears in Sunbrella Boat Canvas,” PS September 2017). In my humble opinion, the only adhesive to use on fabric is an aerosol contact cement. 3M FoamFast 74 is available in many hardware stores. It may be the most expensive, but it is still preferred especially for loaded areas like sails. Mask off an area the size of the patch and lightly coat both sides. Allow to flash off till it no longer transfers. Repeat for structural areas. Carefully align (it’s a one shot deal) and press down thoroughly. Please don’t use duct tape or other gooey glues and adhesives. They will just gum up our sewing machine when you finally bring it in for a real repair and we will have to charge you cleaning time.


Charlie Klein,

Dorsal Sails and Canvas,

Sturgeon Bay, Wisconsin



In the November 2017 issue of Practical Sailor the caption for photo #2 on page 2 in the “How We Tested”

section suggested that the tester had repaired the webbing on a rotted Lifesling II using PL S40 adhesive. The repair was to the Lifesling’s protective cover which is stored on the stern rail. Deteriorated webbing on the Lifesling is a much more significant repair—since this webbing can be load bearing during a rescue.

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