Dear Rock,
Correctly selected turnbuckles are fine with the new Dyneema types recently developed by companies like Hampidjan, and more recently, Marlow in the UK.
I attach pictures of the Dynex materials fittings we have made in preparation for the re-rig, in Dynex Dux with overbraid, of the 120 foot schooner SOUTHERN CLOUD here in Sydney.
With care, a bit of application and the assistance of a gifted machinist, I arrived at a set of bobbin thimbles that are of a size that fit into the slightly modified mast tangs and turnbuckle jaws.
Everything I have seen and tested and broken over the last 25 years that I have been supplying and using lines and tendons in Spectra/Dyneema leads me to the conclusion that, providing your sizing and end treatment execution are competent and considered, you do not need the huge bending radii that some components on the market exhibit.
The dead-eye and lanyard type thimbles/connectors/what-have-you that are available from Colligo and Precourt, amongst others, are nicely machined and finished but seem to be more suited to do it yourself types of installations or multihull applications, and the like, where the boat often moves more than the rigging, rather than narrow-angled rigs on keelboats.
( Having said that, I used them succesfully in the (not particularly narrow angled ) rigging that Mike Strong supplied to Nacho Postigo's boat as featured on the Colligo website, but that was a while ago and I still think that boat would have been better served if I had insisted on turnbuckles and bobbins. )
For tension members supplied to the aforementioned keelboats and other projects on a commercial basis that I am willing to stand behind ( no pun inteded ) I use either widely available heavy stainless thimbles from Crosby et-al - which I modify - or my own manufacture of bobbin thimbles (in a variety of materials, depending on duty ) fitted into standard turnbuckles and tangs.
At the other end of the spectrum, we are in the middle of supplying two sets of rigging for a new-build International 8 metre that is to be campaigned on the European circuit.
This involved a fair bit of imaginative thought to incorporate the Dyneema into tip cup type spreader fittings and spreader root attachments for the discontinuous athwartships rigging.
This type of rig would not have been possible if we were constrained to using the bend radii and general largeness of Colligo/Precourt type of fittings.
Regards,
Joe Henderson, Henderson Rigging.