Ratlines and Dynex?

[Joe Henderson]

Dear John,

Still waiting for your reply with solid info re. the above statement.

Please let us know if there is a problem with this material.

We have too many rigs out there relying on Dyneema for us not to follow this up!

Regards,

Joe Henderson.

[Brion Toss]

Hi Joe,
This is a non-issue. It is true, demonstrably so, that compression at a certain level is not a friend to Spectra; that's why knots weaken it so much. But the kind of compression you might get from service and seizings is an order of magnitude or so down the scale. If that kind of compression were a problem, then even putting a braided cover on the stuff would weaken it.
To put it another way, think about the highest compression that the rope is likely to see in a rig: the spreader tips. Here a very short surface area, slightly radiused, doesn't damage the rope. Compare that kind of loading with the teensy deflection caused by someone standing on a ratlines.
Fair leads,
Brion Toss

[Joe Henderson]

Dear Brion,

Many thanks for stepping in.

I agree it is a non issue, we have completed many rigs and sets of running rigging using Spectra/Dyneema from many different manufacturers.

I have absolutely no problem with using the material.

I understand completely about the compression issue re. knots and the way that a Dyneema tension member will interact with the compression members in a structure like a yacht's mast.

I would have no hesitation in applying ratlines to any Dyneema shroud.

My query was directly to John Franta, (who, it must be said, seems to have a vast experience using this material in tension members.) and directly addressed his statement that "Dyneema hates compression" and that large bending raddii should be adopted.

I bow to John's superior knowledge, but, at the same time, I am not convinced that large and fairly unweildy deadeyes are absolutely neccesary in the ends of standing rigging made of Dyneema/Spectra.

Large aluminium plates with plenty of space may be needed if you are trying to cram a few turns of Dynex in as a lanyard, but I doubt that the same exagerated proportions are needed when going to a pin.

Regards,

Joe Henderson.