In-mast furler; to buy or not to buy;
Chas, I''m not familiar with the mast cross-section you described tho'' your description was certainly clear; sorry.
I''m surely no more than a student of in-mast furling/reefing systems altho'' I''ve been fortunate enough to see a lot of ocean crossing boats now and talk with some of their crews. And I''ve also tried to regularly do homework on the systems I can at boat shows (last at Southampton last month; next one is London''s blow-out show in January). Thus, my growing sense of the issues and the usage history.
"Rarely do I see blue water boats without RFs. So, if the jury is in, and after all considerations, RFs are used by cruisers in preference to hanks, why is there such a resistance to using RFs on mainsails?
Lots of observations can be made in response to that; I''ll offer four. First, I think you''d be amazed at how often you see a hanked sail on an offshore boat...and yet your observation is quite correct that most crews do have a RF/RR unit for their headsail. Almost always, the offshore boat is going to have a RF/RR headsail system AND an inner stay. Richer crews might have that inner stay permanently installed and with its own RF/RR system...while poorer folks like me might have a release lever, stow the inner stay - tensioned - on the side deck, and then set up stay, sail and sheets before going offshore. But the point I''m making is that the inner stay is what frees folks up to go offshore with a single headsail on their RF/RR foil and usually not experience tons of grief in heavy weather.
Second, we''re talking headsails here - and they''re very different from mainsails, which are usually supported on two of the three sides, or at least on one side plus at the clew. Headsails can do their work efficiently without battens; mainsails can not. And remember that one of the criticisms we use to hear was the weight on the bow plus the windage that a furled headsail put on the boat. One reason you hear less about that now is that boat sizes have grown over the last 2 decades and can better handle the weight; another reason is that a furling system is such a ''given'', as you point out, that it''s now simply viewed as a norm rather than a choice.
A third reason, it seems to me, has to do with the state of technology for mainsail furling systems but not in the way you implied. As folks in earlier times worked their way through the first generations of jib furling systems, old/heavy/awkward/furling but not reefing systems were tossed as the learning curve climbed, the grapevine passed the word, and the wheat was separated from the chaff. While there are, I think, some excellent mainsail furling systems today, we''re still in that weaning process insofar as I can tell, where the minimally capable systems are often seen in greatest abundance (gracious me, look at some of those Beneteau and similar units, just to mention one of many...), we''re still in a place where mainsail furling is viewed and discussed generically (my earlier point), and the sailor is just not yet as educated or discriminating as s/he will become.
And finally, a jib reefing/furling system is a simplier system as it lacks an external spar and makes fewer line control demands, and so there are simply more things that must be right or can go wrong. (And let''s not forget the sail: a poor sail choice will produce a terrible result on a reefed headsail just as it can on a reefed/furled mainsail). Related to this, the greater complexity of the mainsail system also adds additional cost - especially if the system is built cleverly and with quality hardware - and so there''s a cost barrier sailors face with mainsail furling that doesn''t exist to the same degree with jib furling.
You''ll notice that I haven''t offered any reasons that relate to performance. My impression is that, in the real world for most sailors, coastal or offshore, ease of handling and the perceived security and safety of furling over going on deck to douse or reef is more important. Thus, to offer the rationale of lesser performance as a ''reason'' why folks avoid mainsail furling is, again just as I see it, usually not correct...altho'' we hear it frequently.
You''ll also notice I didn''t say anything about the mainsail being the more critical sail in heavy air. On more modern designs with sloop rigs, I''m hearing people say they often douse the main and sail under reefed headsail (or staysail or solent sail) across or down the wind in a serious blow. I rarely hear people talking about heaving to, something that used to be far more common and often requires using the mainsail, but then this often refers these days to boats with far different underbodies. So again, while I may hear non-users saying they don''t want to risk their critical sail (aka: mainsail) to a possible failure in heavy air, in reality I wonder how many owners of mainsail furling systems actually deploy only a small segment of their reefed/rolled mainsail in serious weather.
I would surely be interested in what others have to offer on this topic.