Anticipating shrinkage when making a short Amsteel grommet with overlapping buries.

Discussion in 'The Splice Rack' started by Ryan21, Dec 6, 2017.

  1. Ryan21

    Ryan21 New Member

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    Does anyone know if there is a formula for calculating how much extra circumference you need to give yourself in lieu of the shrinkage caused by the diameter of the Amsteel increasing with overlapping buries in a short grommet?

    I am making a block strop for a wooden double block that I use for an all purpose handy billy for boat rigging fabrication; I am used to rigging with 3 strand in either natural or synthetic, I have done a bit of steel work, and some double braid eyes. I have ventured into Amsteel once before to make some shrouds for a sailing dingy of mine but this is the first time I have tried a grommet. The first I made in accordance with samson ropes video of end for end splicing, that shows one fid length for the tapered end plus one fid un-tapered bury on both sides, I measured the circumference of the block and thimble and added some extra by eye for the seizing but due to the large difference in original diameter and the diameter after the overlapping buries it ended up being too short. I tried a second and added 6 cm but there was little noticeable difference. Before I go for the third try I'd like some advice from someone who's done this before.

    thanks

    Ryan
     
  2. Brocky

    Brocky Well-Known Member

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    The general rule is to add a 1/3 to the distance of the bury. This should work if you only overlap the tapered parts of the tails and get a consistent diameter. If the untapered parts of the tails are also overlapping, resulting in two diameters of rope in the cover, then you will need to increase the length.
     
  3. theatertech87

    theatertech87 Member

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    I think it's the Samson directions for a hollow braid loop splice that give you shrink measurements. Should be able to go from there
     
  4. Ryan21

    Ryan21 New Member

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    Thanks for the responses!

    By 1/3 to the distance of the bury do you mean 1/3 more to the total length you've measured for the final circumference you want? Eg. When measuring I measure off the samson recommended 1 fid for the taper, 1 fid full diameter bury, and between my full diameter bury marks my desired measure for my grommet plus 1/3?

    So essentially there is a limit for how short these grommets can be and it's not good to have the full diameter burys overlapped?
     
  5. Ryan21

    Ryan21 New Member

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    So this is what i've done so far.. The extra I gave to my measurement was nowhere near 1/3 more the circumference, so evidently it finished too short, there is no room to clap the seizing on. The old Hemp selvagee made strop is on the right for reference. IMG_0111.JPG
     
  6. Brocky

    Brocky Well-Known Member

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    At this point, since you have some thing for reference, your first attempt, figure how much longer you need the loop, multiply by two, and add it to the length of the first one. This should work as long as the other bury lengths stay the same.
    If the two buries overlap at full diameters, it will be fatter and require more length is the only worry.

    I don't know if it matters but I would place where the buries start either on the top or bottom so that the splice is loaded uniformly.
     
  7. Brocky

    Brocky Well-Known Member

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    Something that just occurred to me, and I checked Samson's printed directions, your bury lengths are for class I rope, and you're using dyneema, which is class II. That requires 2 fid lengths of full diameter and one of tapered.
     
  8. Ryan21

    Ryan21 New Member

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    Yes, you are right, I just found it on there website.. I don't know if that is going to be possible for this application with this short length without overlapping a large portion of the full diameter buries... I will try the second one like that and see if it works, the whole grommet will also be served over with twine.. Ill keep the first one as is, and stick a copy of my first one on the winch at work when I get back to France in January and see if I can make it slip, I can go up to 3.5 metric ton. Of course this setup will never be subjected to loads like that in its service life but its nice to know how strong it is, I don't like to do imperfect work..

    Thanks a lot for all the help, you guys have a wealth of knowledge on this forum!
     
  9. Brocky

    Brocky Well-Known Member

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    Another way to do it since you are both serving and seizing it, would be to to insert one end of the rope into the other end. Take the bury to the insertion end, cut it off even with the end and bury the cut end, and place the union of the two ends in the area where you seize. This way the loop would be two full diameters the entire length.
     
  10. jmcscrap

    jmcscrap Active Member

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    [​IMG]
     
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  11. Ryan21

    Ryan21 New Member

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    Finished the first essay, this one turned out a little bit long but its not worth cutting it and wasting this material, it will do its job just fine. Ill make the second one a little shorter and perhaps try the suggestion that Brocky gave in the last post. Definitely a little trickier than measuring for a 3 strand strop, but I like pushing the envelope with materials and traditional techniques. I have also never seized with Dyneema before and frankly don't have 100 percent confidence that it has enough friction to hold the traditional flat knot at the end of the seizing, but ill put it through its paces, this tackle has always been a testing ground for me to try different types of strops.

    Cheers

    Ryan
     

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  12. Brocky

    Brocky Well-Known Member

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    Very nice looking work! I don't think the knot will see much load, but might come undone if something were to repeatedly rub against it. I've never got dyneema to melt and glob, so I use super or krazy glue to hold knots or seal class II rope ends.
     
  13. JD3000

    JD3000 Well-Known Member

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    You beat me to it. Well done, Happy Festivus.
     
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