synthetic rigging termination

[markxengineerin]

Colligo uses a teardrop shape for some of their parts, but I'm planning to make something more simple, just keeping them round. To the left of the red dashes there will be no material


Is this a problem for the splice or dyneema strength? Some of their other products are round or close to round, so, I'm guessing not, but wanted to check. Teardrop does look cooler, but it's cheaper and easier to make round.

[Dave_S]

I'm guessing it's not a problem. Most images you see of them installed the eye in the termination is larger than the tear drop shape and the line isn't in contact with the section you intend to delete anyway.

I suppose there is an increased risk the round could roll out of the eye ? Unlikely when under load.

[Breaking Waves]

Originally Posted by markxengineerin

Is this a problem for the splice or dyneema strength? ]

Yes, if the Dyneema is spliced tightly to a ring (non-teardrop shape) it causes a high throat angle which increases hoop loads (effectively decreases the Dyneema strength).

Whether it is a 'problem' depends on how over-speced your Dyneema is. For most 'yachting' applications the Dyneema is so over-speced it makes little difference, but there are occasional applications (often up in the rig on racing boats) that have quite tight margins and then it can become a problem.

[Dave_S]

Originally Posted by Breaking Waves

Yes, if the Dyneema is spliced tightly to a ring (non-teardrop shape) it causes a high throat angle which increases hoop loads (effectively decreases the Dyneema strength).

Whether it is a 'problem' depends on how over-speced your Dyneema is. For most 'yachting' applications the Dyneema is so over-speced it makes little difference, but there are occasional applications (often up in the rig on racing boats) that have quite tight margins and then it can become a problem.

Agreed, so it needs to be spliced as it would if it were a year drop shape.

[Breaking Waves]

Originally Posted by Dave_S

Agreed, so it needs to be spliced as it would if it were a year drop shape.

yes. The general practice is the ratio of splice length to width should be a minimum 3:1 and preferably 5:1.

This tends to mean that it is not snug/tight enough to be 'captive' on a ring shape. Depending on the specific application it can work off the ring. It can be made tight/snug on a ring by using a tapered whipping up the throat (essentially you use a tapered whipping to replace the teardrop part of the thimble) - need a minimum of skill to do this neatly.

[markxengineerin]

This tends to mean that it is not snug/tight enough to be 'captive' on a ring shape.

Thanks everyone- my application is captive by the turnbuckle prongs/mast tangs, so there won't be any slipping off either way.

if the Dyneema is spliced tightly to a ring (non-teardrop shape) it causes a high throat angle which increases hoop loads

Makes sense


Does anyone know of a comprehensive approach to sizing the length of each line? My plan is to set up a few short test pieces and learn how much a splice "stretches" / how much pre-load/ how many pre-loads are necessary to become stable, but it would be nice to avoid this work or copy someone else's technique. Colligo has this info but likely specific to their own fittings. I will be using turnbuckles which have 3.4" of adjustment, so I need to be close, especially accounting for small creep each year and thermal changes. The chain plates I made are slightly different than the originals, leading to another source of error when planning. Is it practical to re-do a splice if I guess wrong?

[Seaslug Caravan]

Originally Posted by markxengineerin

Colligo uses a teardrop shape for some of their parts, but I'm planning to make something more simple, just keeping them round. To the left of the red dashes there will be no material


Is this a problem for the splice or dyneema strength? Some of their other products are round or close to round, so, I'm guessing not, but wanted to check. Teardrop does look cooler, but it's cheaper and easier to make round.

Why so chunky.

This huge turn radius garbage has been well and truely put to bed.

Blue wave and others have some nice dyneema end fittings, if you want ideas.

Discussed Ad Nauseam over the years. Start here …… https://forums.sailinganarchy.com/in...meter-dyneema/

Google will turn up more.

[markxengineerin]

I was not aware of the debate about the 5:1 ratio, just assumed it was standard, and hadn't found the right words to search on google. Based on the new reading, I might go down towards 1:1 depending on how things look visually with the chain plates. The only downside of larger diameter seems to be that it might be ugly.

[Breaking Waves]

Originally Posted by markxengineerin

T
Does anyone know of a comprehensive approach to sizing the length of each line? Is it practical to re-do a splice if I guess wrong?

yea, the systematic approach is to make test pieces, stretch them with a come-along (or other tension device) and measure the splice growth and the rope constructional stretch and apply those two factors to your full length. If done carefully that can get you very close.

If you make one of the spliced loops quite long and leave the tail on the splice sticking out from the bury, and then stretch it all, you can then adjust the length by pulling the tail in or out (and then ofc properly taper and bury it). That is a bit sloppier approach but will also get you in the right place.

Originally Posted by markxengineerin

I was not aware of the debate about the 5:1 ratio, just assumed it was standard, and hadn't found the right words to search on google. Based on the new reading, I might go down towards 1:1 depending on how things look visually with the chain plates. The only downside of larger diameter seems to be that it might be ugly.

In testing, you only need about 1.2 : 1 (or greater) to maintain full strength inside a loop at the bend radius under static loads. The 5:1 is only necessary outside a loop when both ends are working, like a halyard over a sheave.

These is some small evidence that bigger than 1.2 :1 bend is useful in the 'real world dynamic loads' to prevent wear at the contact point (as you increase the contact patch). I have not seen any evidence that there is much gain in this aspect beyond 2:1.

And to be clear there are two factors at play which sometimes get confused because the ratios are similar - one is the bend radius and the other is the throat angle of the splices loop. The throat angle needs to be greater than 3:1 and preferably 5:1. They are somewhat related because the bigger (better) the bend radius the smaller (worse) the throat angle (holding loop size constant - making loop bigger then improves throat angle).

[seandepagnier]

I have read the difference from circular to teardrop is not as much as expected especially if you have a 5:1 ratio. Regardless you could simply splice the loop not as tight and have no loss of strengh correct?

The issue then is if the shroud goes slack the thimble can fall off. So I was thinking to simply lash it or tape it, or even screw 2 3d printed plastic pieces into the teardrop space.

[Breaking Waves]

Originally Posted by seandepagnier

I have read the difference from circular to teardrop is not as much as expected

yes, this is correct. In actual testing, it is rather less than the 'worst-case trigonometry' suggested it would be.

especially if you have a 5:1 ratio.

That does not really matter/affect the strength loss from the throat angle. Bend radius over 1.2:1 are all > '100% line strength' so the failure point will not be in the bend (except note the comment in my post above about dynamic wear).

Regardless you could simply splice the loop not as tight and have no loss of strengh correct?

Essentially correct. If you make the loop big enough to have a 5:1 length to width ratio then the strength loss from extra hoop loading is minimal.

The issue then is if the shroud goes slack the thimble can fall off. So I was thinking to simply lash it or tape it, or even screw 2 3d printed plastic pieces into the teardrop space.

Yes, correct. In the commercial world the answer is to have a 'tubular thimble', so the rope runs thru a tube around the bend and is thus captive. You can make a lashing to create a 'textile tube' to make it captive. You can also make a big loop snug to a round fitting with a tapered whipping up the throat. So, various ways to address the issue.

.........

[markxengineerin]

Got the easy parts done, the ones that pin to the chain plates and therefore are just plain round pieces. I don't have a CNC lathe, so I milled them using the cutter shown- not the most efficient way to do it but it worked. The next parts are the trickier ones, which bolt to the mast and have the radiused groove at a 15 degree angle to "square". I'll post some more picture when done.

[markxengineerin]

Here's one of the angled ones that will through bolt to the mast, 2 on each side for the lowers and one on each side for the uppers. I think the angle is 11.5 degrees (don't quote me) calculated from the boat's geometry.

Next step: anodizing

[Benz]

Looking good. What alloy did you use?

[markxengineerin]

Regular old 6061 T6
I am slightly concerned with the long term situation between the anodized aluminum bore and the stainless pin. I will coat the interface with TefGel and hope for the best, but did notice that some (not all) of Colligo's have what looks like a fiberglass bushing in this location.

I probably should have just made the pieces from titanium and been done with it forever, but aluminum parts got done probably 10-20x quicker so it's worth a try like this.