Load Testing Results

[estarzinger]

And, by the way, this V138 thread seems like a good match to the polyester webbing. The stitches all break, but they also do visible damage to the polyester webbing fabric.

[Jim Cate]

Evans, what size needle do you use with the V138?

Jim

[Seaworthy Lass]

Originally Posted by thinwater

Failure. Too much stress in too small an area. It simply pulled through the webbing at 15% lower load. A good idea that doesn't seem to apply to tubular webbing. 2 trials. I'm a little bummed. I've done this in sailcloth many times, but this different. Idon't think holes matter so much in webbing, or bar tacking would not work. Puzzeling.

It was worth a go.
That's very interesting that it pulled through the webbing. Indicates to me that backstitch has great strength, but a bad pattern of stitches for this purpose. I will have a bit of a play with pattern later (pity I have no capacity to trial strength).

It would be very useful to come up with the best pattern of hand stitches (I know you have put a lot of work into this already), as many cruisers do not have a sewing machine and are hand stitching webbing.

[Seaworthy Lass]

Originally Posted by Jim Cate

Evans, what size needle do you use with the V138?

Jim

Jim, I use a 22 needle successfully. I did a reasonable amount of sewing with V138 before I got hold of Tenara.

[thinwater]

Originally Posted by Seaworthy Lass

It was worth a go.
That's very interesting that it pulled through the webbing. Indicates to me that backstitch has great strength, but a bad pattern of stitches for this purpose. I will have a bit of a play with pattern later (pity I have no capacity to trial strength).

It would be very useful to come up with the best pattern of hand stitches (I know you have put a lot of work into this already), as many cruisers do not have a sewing machine and are hand stitching webbing.

Bear in mind that plain stitching with...

• 1/8- to 3/16-inch spacing
• #4 whipping twine doubled
• 14 full stitiches in a 1-inch length

... reached 93% breaking strength. Since no one actually reaches 100% in webbing, that is about all you're going to get. That is a good pattern. Let me add a few things I'm pretty sure of:

• Heavier thread will pull through.
• Lighter thread will pack less strength in the available length.
• Longer runs in nylon webbing increase the stretch issue; if the join is longer, the throat stitches bear less and less load.
• Longer stitching adds only a little durability; the first row is over stressed and the rest explodes. Spliced nylon webbing will never be as durable in the sun as spliced rope or polyester webbing. A UV coating (Maxijacket?) should help.
• For a straight splice (not eye) the stitching is 2x as long.

Since you can't bar tack by hand, I think this is all you get, which fortunately, is enough.


Polyester webbing? I see no reason why you aren't going to find the same things, although there will be more forgiveness.

• The stitching should still be loaded towards line side.
• Extra stitching will help, since a larger area can bear load. A much more durable construction is practical.
• Stitch spacing should increase to 3/16 inch. There is NO reason to go larger, since in many trials I never saw webbing damage at this increased spacing.

All in all, nylon webbing is not a great material on boats. It's not quite strong enough for jacklines, has too much stretch for most boats, and does not sew terribly well. It's weak in the sun. It is OK for tethers, where some stretch is needed, but dynamic rope is even better at the same weight. If I want loops, I can buy pre-sewn runners for $4-6. It seems I really don't have an application for what I've (we've) learned about nylon tubular webbing! The only thing I actually use it for is chafe gear, where slippery and stretchy is good.

[Seaworthy Lass]

Originally Posted by estarzinger

So, for you "knot experts", are there any other loop knots worth testing in the dyneema? Is there a know that is easier to untie than the figure 8 but may not slip like the bowline? Or a knot that is less bulky than the figure 8 but will not slip like the buntline? Or do we just conclude "figure 8 or splice"?

Hi Evans
Sorry, I coming to this exchange really late. I have just started reading the thread carefully from the beginning. Great work!

I have a keen interest in knots. I think it would be fantastic to find a knot that can be untied that can take a load that is a high % of the breaking strain of dyneema. Or at least finding a knot that gives the best possible results when a knot needs to be untied.

I know the bowline failed miserably with a double double bowline slipping at only 38%. Have you tried a water bowline with a yosemite finish? After a CF member taught me this the year before last I have used the yosemite finish frequently when there is jerking load and I love it. A water bowline would probably give similar hold. Combining the two may give a good result.

This is the water bowline:
Water Bowline Knot | How to tie a Water Bowline Knot | Knots

Look halfway through this page to find the yosemite finish:
Bowline Knot | How to tie a Bowline Knot | Boating Knots

This is how it looks in Dyneema:

[Seaworthy Lass]

I have looked in the past at knots used for fishing that may be useful for dyneema, but I have had no means of testing them. These knots are designed for very thin line, so may not work, but they are worth testing and possibly modifying. I would leave a long loose end as they look as they would all slide a fair bit before gripping. None of these will untie after a load is applied.

The palomar is one of these (already tested).
The 3 others are:
Orvis
Duncan
Trilene

All 3 are quick and easy to tie and unlike the palomar, they can go around a fixed attachment point.

Orvis:

"It is claimed to retain most of the line's original breaking strain."

Orvis Knot | How to tie the Orvis Knot | Fishing Knots

[Seaworthy Lass]

Duncan:

"...recent testing arranged by Mack Martin that showed 82% of line strength"

Duncan (Uni) Knot | How to tie a Duncan (Uni) Knot | Fishing Knots

[Seaworthy Lass]

Trilene:

There are "claims that this knot retains a high proportion of ideal line strength. This is more likely when the thickness of the eye is greater than the line diameter."
This last bit is obvious given the construction of the knot, so would not make it applicable universally.

Trilene Knot | How to tie a Trilene Knot | Fishing Knots

[estarzinger]

^^

The water bowline does not slip, and with the modification of tucking the tail thru is about 50% strength.

I will test the other three.

I do not think any are going to be easy to untie after loading past 1000lbs.

[Seaworthy Lass]

Originally Posted by estarzinger

^^

The water bowline does not slip, and with the modification of tucking the tail thru is about 50% strength.

I think the yosemite modification of tucking the tail through is different to the tuck you tested?

Originally Posted by estarzinger

I do not think any are going to be easy to untie after loading past 1000lbs.

No, they won't be. The water bowline with yosemite finish was the only other knot I could think of that may have a reasonable grip and can be untied. The other 3 would be knots that would have to be cut off, but will probably take a higher load.

[StuM]

Have you tried an alpine butterfly loop?

[Seaworthy Lass]

Originally Posted by StuM

Have you tried an alpine butterfly loop?

Stu, the problem with this is that something needs to be connected to the loop, the loop can't be used to connect the line to something.

[Seaworthy Lass]

Originally Posted by Seaworthy Lass

Duncan:

"...recent testing arranged by Mack Martin that showed 82% of line strength"

Duncan (Uni) Knot | How to tie a Duncan (Uni) Knot | Fishing Knots

Evans, I have been playing with fishing knots and I think the Duncan looks the most promising of the lot without modification. In the photo I took above I did not show it tightened. The turn on the far left needs to be moved to the far right, with the rest of the turns following.

I think it should be tightened carefully by hand and a long loose end left before any significant load is applied (it is hard to know how much it will slip before it grips).

Grog recommends 5 turns. I did 10 in the knot below. I think it would be worth testing the strength of a variety of turns to see what is needed to reach 100% of the line strength. The number of turns may need to vary for different thicknesses of line.

It is very easy to tie (can be done with eyes closed with a bit of practice), but is slower than the EStar. When time is not an issue it may be extremely useful for dyneema if it is as good as it looks. Lots of modifications are possible that may make it simpler without loss of strength, but it is a good start.

This is a Duncan with 10 turns. The central coil looks near symmetrical whichever way it is turned. The loose end is coiled and completely buried in the central coil:

[estarzinger]

Originally Posted by Jim Cate

Evans, what size needle do you use with the V138?

Jim

I am using a 20. Sailrite said 20 - 22.