Thank you for these replies. I'd never heard of Garhauer, but their products look well designed. They have European distributors, so within reach here. 

Peter, those Ronstan 2-stage sheaves are wonders of Praezisionsfeinmechanik, but way beyond my reach economically. Very interesting, all the same. I wonder if a junk sail would be heavy enough to transfer the load from the ball race to the fixed spindle. If not, this would render the technology superfluous.

Overlapping slightly with the thread dealing with cockpit rope bags, I'm thinking of replacing my halyard blocks with ball bearing ones in the hope that a 3:1 tackle would then be sufficiently powerful, replacing my present 5-part one.  I usually use a 2-speed winch to finish hoisting my mainsail anyway, and I'd love to spend less time bagging the halyard tail after making sail. Additionally, there's so much friction in my 5:1 halyard that the mainsail will not self stow, needing a hand on deck to pull it down while coming to anchor.

Using ball bearing blocks on both halyard and sheet makes it a lot easier to raise the sail.  We used to find that Badger's sheet blocks started to fail after about 10,000 miles - 10 years sailing for weekend sailors, due to the constant movement of the sheets.  Manufacturers don't generally recommend them for halyards due to the tremendous loads placed on them and the fact that the block doesn't turn for hours - maybe even days - at a time.  We junkies can ignore this recommendation.

I also use Garhauer blocks and apart from the fact that they can give you a very nasty black eye, would unreservedly recommend them, too.  They have a ten-year guarantee, which they honour, so there should be no worries about their longevity.

David Tyler wrote:

I used Garhauer ball bearing blocks on Tystie's heavily loaded halyard with complete success - about 8000 miles with no problems. Recommended.

Thanks for that David. What were the balls made of - I see Garhauer blocks offer Delrin or  "Torlon", which I assume resists crushing more readily?

I used Garhauer ball bearing blocks on Tystie's heavily loaded halyard with complete success - about 8000 miles with no problems. Recommended.

Arne recommends ball bearing halyard blocks, but would these be any use on a long passage offshore? They are not meant to be used for a static load, as will be imposed by a halyard in a Bermudan rig, where tight luffs are needed. I wonder if this limitation applies to junks, where the load is no greater than that exerted by the weight of the sail? 

Does anyone have experience of using ballrace halyard blocks in a junk? Which ones can be relied on to last well?