Splice strength

[osprey877]

Anybody know what the strength is of a Samson class 1 double braid backsplice? The splice results in a small eye of just the cover ie no core , with 1 fid length of cover buried in the core. I would like to put a shackle in the small eye and use it for a hal yard. Is the splice strong enough for this?

[Paul L]

The splice does not end up with an eye with just the cover. The double braid splice ends up with the core and cover running the full lengths of the eye in different directions. Getting the tension equal on the cover and core makes it a strong splice. Done correctly it is fine for a halyard.

[UNCIVILIZED]

A splice in double braid, using just the cover to make a small loop is referred to as a Reeving Splice. Which are very handy for re-leading halyards, but aren't structural in nature.

[StuM]

Originally Posted by UNCIVILIZED

A splice in double braid, using just the cover to make a small loop is referred to as a Reeving Splice. Which are very handy for re-leading halyards, but aren't structural in nature.

AKA Flemish Eye. And yes, they are only intended to take the load of leading a halyard, not for taking any real load.

[UNCIVILIZED]

Here's a link that shows & describes how to install such splices. They take like 5min. each, & are priceless to have. http://www.cruisersforum.com/forums/...ml#post2234681

[svHyLyte]

Originally Posted by osprey877

Anybody know what the strength is of a Samson class 1 double braid backsplice? The splice results in a small eye of just the cover ie no core , with 1 fid length of cover buried in the core. I would like to put a shackle in the small eye and use it for a hal yard. Is the splice strong enough for this?

You might want to read through a thread on another forum concerning the matter before committing to eye splices for your halyard(s). See (click on) Mind Your Hi-Tech Splices!!! - SailNet Community

[Pyxis156]

Thanks for posting that link HyLyte, most interesting to me was the testing they did on the segment of 10-year old sun exposed dyneema halyard that broke at 4,000 lbs over the rated breaking strength! You don't find too many data points for how dyneema actually holds up under extensive UV exposure, and it was very encouraging to me for our new dyneema halyard.

[StuM]

Originally Posted by svHyLyte

You might want to read through a thread on another forum concerning the matter before committing to eye splices for your halyard(s). See (click on) Mind Your Hi-Tech Splices!!! - SailNet Community

That post doesn't say what size the shackle was, but it exposes a major consideration: Bend radius is a critical consideration with HMPE lines.

Too small a radius can have two effects, both of which can lead to line failure at lower than expected loads:

1. Lack of stretch means that individual fibres will progressively fail from the outside inwards as they in turn the strain and fail individually over time.

2. Friction where heavily loaded HMPE constantly moves slightly over a pin can cause heat build up and plastic deformation on the inside of the turn.

To quote Evans Starzinger (from his 2013 paper "Dyneema®/ Spectra® Lifelines" ):
"High modulus lines are weakened if they are taken around tight turns. The entire load comes on the few fibers on the stretched outer edge of the turn and they break and then the line zippers inward. This is why knots dramatically weaken these lines (as discussed below) because the line takes sharp turns inside the knot.
With HMPE line, an 8:1 bend radius (the radius of the bend compared to the diameter of the line) is considered gentle enough that no strength is lost, while a 5:1 radius results in a loss of about 15-20 percent of the line
strength and is the minimum bend radius recommended. This means that the splices need to go around something (sailmaker thimble, ferrule, low friction ring, pulpit tube, etc) that is (at least) five times the diameter
of the line..."

[Paul L]

Originally Posted by svHyLyte

You might want to read through a thread on another forum concerning the matter before committing to eye splices for your halyard(s). See (click on) Mind Your Hi-Tech Splices!!! - SailNet Community

The OP was not referring to Hi-tech line, he specifically said 1 double braid splice.

[thinwater]

Originally Posted by UNCIVILIZED

A splice in double braid, using just the cover to make a small loop is referred to as a Reeving Splice. Which are very handy for re-leading halyards, but aren't structural in nature.

I've tested cover only splices at about 70-85% line strength, depending on the details (the top performers were lock stitched). The thing is, there are still 2 legs going over the ring, and the strength loss around the bend is very low because the cover flattens.

Much stronger than you think, stronger than most knots. The vulnerability, more than strength, is chafe on the eye.

[Jim Cate]

Much stronger than you think, stronger than most knots. The vulnerability, more than strength, is chafe on the eye.

Another factor is that with no buried core, protected from the sun, the cover is subject to UV damage with no "back up". I had a cover only end to end splice fail from this issue... granted it was kinda old line with considerable sun exposure.

Jim

[osprey877]

Originally Posted by thinwater

I've tested cover only splices at about 70-85% line strength, depending on the details (the top performers were lock stitched). The thing is, there are still 2 legs going over the ring, and the strength loss around the bend is very low because the cover flattens.

Much stronger than you think, stronger than most knots. The vulnerability, more than strength, is chafe on the eye.

That's also what my intuition says. I think I'lll add the lockstitches and keep my fingers crossed!

Thanks all

[roverhi]

Throw away the shackle and just tie the halyard to the sail. Makes it ieasy to change the wear points on the line and plenty strong. Have sailed more than 10,000 miles with none of those pesky shackles that love to conk you on the head if they get loose.