Originally Posted by StuM
It seems to me as though both splices are essentially the same.
They both have a full fid bury of the cover. And I believe you are wrong in your earlier comment about the core bury. Both have a full fid length of core buried beyond the eye. (Look at where the Premium cover bury starts in the core - two fid lengths plus the eye circumference)
Thanks for looking at this and responding Stu
. I find it interesting and challenging working out the logistics. It greatly helps my understanding. I find this stuff fascinating.
Could we take this step by step? I can then work out why we are seeing this differently.
Both techniques mark the cover the length of one fid plus the loop from the end and pull the core out here. Premium call this point B and Samson call it X.
Both the core and cover are only affected for a bit over a fid length beyond for the Premium method. That is the length of the bury of the cover plus a bit extra to allow for the slight rearrangement of the relationship between the core and cover when the core is pulled out. Samson allow for this with their pull and milking at the start and this shifts the core out a little - it is only few cm, nothing dramatic. So Samson have allowed for the rearrangement.
Nothing happens beyond there for either region. We only need to consider this area.
Am I right to start with? This is the basis for some of my thinking.
There are 3 big differences I then see between the 2 methods:
1. A full fid length of cover in the Premium video is only fed into 0.75 of fid length of core (C' to D'). It needs more than one fid length of core to bury a fid length of cover in it, not less, so the full fid length cannot possibly be buried. Sampson use 1.3 fid lengths to ensure full bury (Mark II to Mark III) of a bit less than a fid length (T to the tail end) into the core.
So the cover is definitely not buried in the core the same amount to start with. Premium is significantly less.
2. At the crossover point Premium start the bury of the cover in the core a full fid length away from where the core was pulled out of the cover ie the start of the loop of the eye. Samson insert the cover only a third of a fid length away.
3. At the crossover point Premium start the bury of the core in the cover where the tail emerges from the core and this seems to end up about a third of a fid length from the start of the loop of the eye.
In the Samson method this occurs at the marked point T which is 8 strands from the start of the loop of the eye.
Given we are looking at only a fid length of core and cover involved beyond the eye of the loop, these are big differences, not minor.
I predict for the Premium method when load is applied without the stitches
the core is going to slide down closer to where it originally started and even less of the cover will end up buried in the core. This will not be at all visible or felt. The cover will still remain buried in the cover for a full fid length (unless the splice fails).
The length of bury of the tail will simultaneously shorten (again, not visible at first). If it shortens so much that it does not stay buried beyond the loop then you will actually feel the core is not in the loop and the splice weakens dramatically as it is just relying on the strength of the cover.
Originally Posted by StuM
The only difference lies in:
1. Samson cut off about 2/3 of a fid of core, Premium about a fid.
From the ropes used in the videos, I'd guess that the difference is a result in the different core/cover tightness/proportions requiring the difference - which I'm sure they both determined by experience, not by an empirical measurement.
Yes, this may be part of why the difference occurs. But if it is, I would not use the Premium technique for any other brand of similar double braid polyester. I think it is bound to have significantly less strength. Way too much core is cut off.
Maybe there is something unusual about the initial relationship between the core and cover for Premium lines. Maybe it is the final stitching that saves it. I tend to think it is probably the latter.
Also, I think looking at the video it is actually a bit more than a fid length that is cut off for the Premium method. Have a close look. My gut feeling is that when heavy/prolonged load is applied the core and cover will tend to want to realign as they were initially. If this is the case, if this much core it cut off when only a fid length of cover in buried in the cover, the tail of the core will definitely slide into the loop. That last bit is just simple geometry.
I am super uncomfortable about this. I don't like it at all
Originally Posted by StuM
Samson taper a greater length of cover and core
Samson bury the core tail first, Premiuim bury it last.
2. Tapering Method. I'm really in two minds about this.
Premium's will give more compression
and I'd expect it to be less likely to slip than the Samson method.
Samson's will give a smoother tapered finish and slightly less "choke effect" at the end of the buries, so would be marginally less subject to stress at the bury end.
I don't know what occurs for double braid. My opinion regarding this is only related to what occurs when single
braid is buried. Unless the taper is very gradual, significant strength is lost
(I will see if I can find the exact figures for single
braid, but I vaguely remember there is about a 20% loss with no taper).
Samson must have a good reason for taking such care with a gradual taper. I doubt they would waste so much time and effort if it was unimportant.