At the same time it is apparent to me that there is no single right answer for the bridle itself. While the Mantus construction is absolutely first rate, every situation has a best answer. They have made conservative choices, and I respect that.
For monohulls, a bridle is often used to take the chain load off the windlass, the surge load off the roller, absorb the wave shocks that chain can't, and perhaps keep the boat a little better into the wind. For catamaran bridles are a daily essential, since moored to a single bow they sail at anchor.
- Multihulls must be moored on a bridle or they sail all over the place. With a bridle they sit steady like a rock, the long legs providing the leverage required to keep the nose right into the wind.
- Multihulls with all-chain rodes need the shock absorption. They often anchor in water more shallow than monohulls; a relatively short rode and steeper waves increases the tendency of steep waves to snap the rode tight, creating forces far beyond anything the gear can handle--boats have been lost this way. To prevent this, the legs must be long and sized correctly.
- Some bottoms provide poor holding and anything that can reduce forces will help keep the hook in the bottom.
- The carabiner hook is for moorings.
- The legs must be at least 1 X the beam or they can be difficult to rig in rough conditions. It is good to have the option of working from either bow. This is also a good minimum for keeping the boat straight.
- They must be adjustible if needed. When tying to a mooring ball it can be very handy to shorten them, to hold the ball between and away from the hulls. If the waves are coming at an angle, for example around a point of land, it can be helpful to angle the bow.
- For permanent moorings they only need be strong. Nylon will stretch enough.In fact, often it is desirable to limit stretch to reduce movement in the chocks and chafe. Polyester and even Amsteel can be good choices.
- For anchoring they need be long enough and thin enough to provide stretch. One size lighter than the anchor rope is probably a good starting point, since there are 2 legs carrying the load (though there is some angle). Even smaller can make sense and give a smoother ride, if they are longer (1.5-2 X beam) and replaced more often.
- 3-strand, braid or even climbing rope. Braid and climbing rope have considerably better fatigue life when loaded heavily, particularly in smaller sizes.
- Chafing gear.
- A means of attaching the bridle to the chain that will NOT fall of when the chain is bounced slack on the bottom (back to that shallow draft thing). Ordinary chain hooks can and do come off. A plate is a good method. So is the Mantus chain hook. Or rather I will find out.
- Rolling hitches and cow-hitched slings also work well, for attaching the bridle to the chain and have advantages: easy to release, feed through rollers better, easy on the chain (no wear on the galvanizing) cheap, and totally dependable. I prefer a hook simply because it is a little faster, but that doesn't make me right about this. I use these methods when setting a second anchor (to connect the rodes) and have never had a problem.
What line, how long, and how strong? Like most things, there is not one answer, but I will describe what makes sense for me. Your situation may differ.
For permanent moorings--something I very seldom use--the answer seems relatively simple; plenty strong, at least as heavy as the anchor line but more likely up one size, any rope type, and just sort enough that the ball cannot touch the hulls. Lots of chafe gear. If storing my boat on a mooring I would favor over size line and preferably limited-stretch line to limit movement in the chocks. But like I said, I have no extended real world expereince.
The Mantus bridle package. Heavier line than I use on the Chesapeake, but better for durability and rough use.
For anchoring in open areas. I avoid them, and avoiding them is generally easy on the Chesapeake.
- One size lighter than the anchor line. The load is shared and we can use some stretch. Has to be strong enough to endure full chain working load, but remembering that it is backed-up by the chain and will be replaced every few years.
- At least 1X beam length per leg, preferably more. If there is ANY risk of serious swell in shallow water, 2X beam is prudent. While the chain can absorb gusts and vears, on the bridle is available to absorb a quick rise of the bow caused by waves during gusts that already have the chain straightened out or effectively straight. The chain may not be in a completely straight line, some few feet may even remain on the bottom, but further strain provides no significant lengthening in the few seconds it takes for a wave to pass. If this bow rise is 4-6 feet, then the bridle must stretch perhaps 1/2 of this, or perhaps 3 feet. Thus, at least 25 feet of bridle are needed.
- Two sizes lighter than the anchor line. Where I might use 5/8-inch anchor line, 3/8-inch is perfectally acceptable for a bridle/snubber. I've used old rock climbing lines and been very satisfied, replacing this every 100 uses or so.
- Replace more often. This is not just for wear. The ability of line to stretch fades after a few thousand hard cycles. When the line stiffens noticeably and it is time for replacement. The change in hand is often apparent.
What about strength? the apex is formed by an eye-splice with a thimble and then a Y-splice about 16 inches further down, all proffessionally exicuted and covered with hollow webbing for chare protection. The question is, how does a Y-splice react to broad Y angles? While I'm sure it is 100% strength at shallow angles, when shortened for mooring balls what happens? Given that the Mantus bridle is conservatively constructed this is only an engineer's curiosity.
And what about double braid? The apex will then be formed by either a figure-8 knot (80% strength at low angles, 60% strength at >90 degree angles) or a seizing.
What about 2 legs joined with a shackle? This is quite prone to failure as the angle becomes too wide. I'm sure many of us have destroyed a shackle when it shifted such that the load cam on cross-wise and the threads stripped. Two legs to a plate is tough on the plate but can be designed for. Mine is.
So do your own math. Your anchoring habits may differ.
- Deploying. the bridle can be fed through the roller to the chain and deployed from on-deck, no problem. It will not bounce off going over the roller; I tried this repeatadly and it never shifted. No tendancy to hange-up either.
- Flipping the hook off. While this is possible, it require preactice. It seems clear that it would be nearly impossible to happen inadvertantly, FAR less likely than a conventional hook.
- Flipping of when setting on the bottom. Improbable in the extream.
- Retreaval. While it's possible to flip the hook off, reaching over may be easier. It is not generally practical to bring it up throug hthe roller, at least not on my boat; jams every time. But it comes off very easily if I reach over with one hand.
I'm not yet certain I would use it on a mooring for perminant attachment, for months unattended. I think it would be fine, but I prefer the 100% security of a chain plate with a latch. But for typical cruising, I think it is my new favorite.