Your strongest knot

[Micromeister]

The bowline is not the best choice since it can come untied if it gets slack in the rope. If it stays taught it is a good choice.

Andrew

incorrect Andrew:
A bowline if properly tied will not loosen taught or slack. it's one of the most secure knots.

There are many knots that work well for those who know how to tie them. Personally I use three half hitches for securing most shockcords to nosecones or transitions with a butterfly tied about 1/3 of the way between body and nosecone for attachment of Chute or streamer with either a larks head or Snap swivel. Bowline anchor knot around the motor mount. Sometimes a simple overhand loop to join Kevlar to elastic.

Many would say 2 or in this case 3-half hitches could come loose when not under load. In larger lines 1/4" diameter and Up that would be true, in braided or twisted 50 to 300lb kevlar and most small round cords it's not even an after- thought anymore. The only time these hitch knots loosen or are removed is by cutting them off.
Don't believe everything you hear or read on-line from Climbers...What we're doing and laying your life on a knot are two very different things.

 

[Pat_B]

I like the figure-8 because the end of the rope goes back out from where it came from, leaving the loop clear of any excess rope. The bowline terminates with the end of the rope coming back into the loop and is not as clean as the figure-8.

Also, the bowline is great under tension but can start to loosen when not under tension, and actually much worse with intermittent tension which tends to loosen the knot. The ability to be easily untied when not under tension actually makes it nice for climbing when you want to quickly untie it, yet have the safety of a tight knot while climbing. I used that knot thousands of times during my climbing days and every smart climber always backed the knot up with a few hitches on the loose end of the rope so that the loose end wasn't able to be pulled through the knot when not under tension. The bowline is known for having this flexibility or being self-adjusting by tightening up under tension and loosening when not under tension. I'd prefer you not listen to Micro as us climbers have a ton of experience with this knot.

Many of the knots that were designed for fishing were obviously designed with small diameter fishing line and tend to have an excessive number of overlaps. Those knots tend to get a little large when used with larger rope.

I'd stick with climbing knots rather than fishing knots for larger diameter cord.

 

[MarkII]

You make excellent points, Pat_B. I have read about the same issues with the bowline knot. After seeing all of the testimonials to it here, I felt that some caveats should have been made, but I lacked sufficient expertise and experience to make them myself. I'm glad to see those issues discussed in your post.

I have only worked with small diameter rope in rocketry, so I interpret questions like the one that started this thread from that perspective. Obviously, knots created for fishing line may not be especially effective for half-inch rope, and I would have had no idea what to use in the latter case. My impression, though, is that with larger rockets, flat strap, tubular nylon or tubular Kevlar are the norms for recovery harnesses, and in these cases the harnesses are terminated with sewn loops and the connections are made with quick links rather than knots. Loops avoid the material fatigue that is generated by knots, I understand, and in the case of, say, a 30 lb. rocket, you don't want to take any chances. I am not very experienced with the high power end of the spectrum yet, though, and perhaps climbing knots are used for connections in high power applications more often than I realize.

One thing that I haven't seen any mention of yet are eye splices. I have never made one myself, but I think that splicing is something that ought to be given more consideration when using round rope in these applications. A splice is far more secure than a knot and it does not weaken the rope. It is, however, permanent, unlike the case with a knot. But nearly all of the rope connections that I make in rocketry are never intended to be undone anyway.

 

[MarkII]

Another thing that I want to mention is that aramid fiber rope (i.e., Kevlar) is non-absorbent and slippery and therefore does not hold knots particularly well. My own experience with Kevlar twine confirms this; many knots easily loosen and come undone with it despite being well-tied. I have had somewhat better success with microbraid Kevlar cord, probably because the braiding introduces more friction. Another thing to mention is the fact that although Kevlar has tremendous linear strength and is very hard, aramid fibers are surprisingly susceptible to fraying and breaking when they are bent at sharp angles, which knots tend to introduce. Kevlar string and twine is substantially weakened when it is tied into a knot; in many cases it becomes much less strong than equivalent natural fiber cord (sisal). I have had several first-hand experiences of this with the lightweight Kevlar thread (28 lb.) that I have used in micro rockets. While it can develop quickly and very visibly in lightweight Kevlar thread, the same process surely occurs in heavier weight cord as well, but perhaps at a slower pace. I haven't seen it yet with braided Kevlar (including TK), so perhaps that type of rope construction helps to spread the load out and create fewer localized hot spots. I have no doubt that even braided Kevlar will rapidly weaken when knotted, though. Splices or sewn loops rather than knotting would clearly seem to be the better choices for connecting this material then.

 

[darisd]

What an amazing thread!

Unfortunately, I seem to have taught myself a slipknot that is not on the list at Animated Knots. It is close to the Duncan Knot... something I must have taught myself over the years tying fishing tackle (by trying to imitate something I saw obviously). I use alot of Kevlar, and as Mark states above, it is slippery and prone to fraying at sharp bends. I like this particular knot because I can easily see how much cord the knot is taking and not have to cut/melt/tape the free end again when done: this is a very good aspect to consider with parachute rigging. They do tend to "weld" themselves in with Kevlar (cold flow is probably more accurate) but my paracord knots are quite easy to loosen if needed. But amazingly strong: just two weekends ago I had an early deployment at >100 Mph that tore webbing stitches straight off four of the 12 chute lines, but the cords are still firmly attached to the webbing.

I should take a picture of my knot later...