Behind the mast roller reefing mainsail

[Humblebee]

My old Westerly Fraoch has Facnor behind the mast roller reefing. I'm getting the hang of reefing and unfurling but still jam it occasionally. What puzzles me is, why should the sail be enclosed in an aluminium tube at all? Foresail roller reefing doesn't need the foresail to be wound inside a tube, why should the mainsail?

 

[duncan99210]

So it doesn’t need UV protection. No space constraints for the foresail but the mast gets in the way for the main, hence the need for protection.

 

[WillH]

You should try setting your foresail without the aluminium tube! Though it may not be aligned with the foresail's luff, it nevertheless serves another rather important function in the rigging of the foresail.

Since the mast is not going anywhere irrespective of furling considerations, I think there are benefits to taking advantage of its existing structural features for rigging the mainsail that outweigh the faff of the
potential to jam it. The void inside the mast is a necessary byproduct of making a mast that withstands load without buckling with a minimum weight. We might as well use it for storing a sail. If nothing else, it's tidy. And unless you can settle for the aerodynamics of a loose luff, a furler outside the mast will need to be under some considerable extra tension that can be avoided using the bracing provided by an enclosing mast.

 

[mjcoon]

My old Westerly Fraoch has Facnor behind the mast roller reefing. I'm getting the hang of reefing and unfurling but still jam it occasionally. What puzzles me is, why should the sail be enclosed in an aluminium tube at all? Foresail roller reefing doesn't need the foresail to be wound inside a tube, why should the mainsail?

I think it is because the "tube" takes the sideways tension from the outhaul and wind pressure. The foresail has the same problem but the forestay tension helps and the stay and foil are allowed to bend. The mainsail foil could bend too, but then there would be a gap between it and the mast. And the only tension comes from the halyard.

N.B. I'm not a rigger or yacht architect, just a one-time physicist who has wondered about these questions while sailing too!

Mike.

 

[V1701]

There are systems where the sail is not enclosed inside a tube, just on something like the genoa furling gear sitting just behind the mast. There are two boats with it on my pontoon, I look at them and wonder why they aren't more popular - I'd have thought the reduced potential for jamming/easier unjamming trumps the fact that the sail is protected from UV inside the tube any day of the week...

 

[Stemar]

You should try setting your foresail without the aluminium tube! Though it may not be aligned with the foresail's luff, it nevertheless serves another rather important function in the rigging of the foresail.

Since the mast is not going anywhere irrespective of furling considerations, I think there are benefits to taking advantage of its existing structural features for rigging the mainsail that outweigh the faff of the
potential to jam it. The void inside the mast is a necessary byproduct of making a mast that withstands load without buckling with a minimum weight. We might as well use it for storing a sail. If nothing else, it's tidy. And unless you can settle for the aerodynamics of a loose luff, a furler outside the mast will need to be under some considerable extra tension that can be avoided using the bracing provided by an enclosing mast.

I have neither, but can certainly see how an in-mast system would have advantages over an external one, especially in terms of weight aloft. However, in-mast means a new mast, which must add very significantly to the cost.

 

[Humblebee]

Thanks all, for your comments.
Willh - I take your point about a sail furling inside the mast but this is a separate system attached behind the mast.
Mike, yes, good point, but with conventional slab reefing this doesn't seem to be a problem as long as the halyard tension is set properly.
V1701 - I agree, interested to hear there are systems that do not enclose the sail though.
Cheers all,
Chris

 

[mjcoon]

Mike, yes, good point, but with conventional slab reefing this doesn't seem to be a problem as long as the halyard tension is set properly.

Slab reefing mains typically have the lateral force transferred to the mast at several points either by sliders on a track, in older designs by a bolt rope, and even older by hoops around the whole mast!

Mike.

 

[DownWest]

Few points being missed here.. The foil for a headsail reefing gear is so the sail rolls evenly with the top going round at the same speed as the bottom. Old style furlers like wickham-martin can only fully furl, not reef, as the luff tends to twist.
WilH is talking about using the 'spare space' in the mast. In mast reefers need special sections as you cannot have a simple tube with a slot in the back. It needs, in effect, a mast with an extra section to contain the sail.
Those aft of the mast are retrofit usually.

 

[WillH]

Few points being missed here.. The foil for a headsail reefing gear is so the sail rolls evenly with the top going round at the same speed as the bottom. Old style furlers like wickham-martin can only fully furl, not reef, as the luff tends to twist.
WilH is talking about using the 'spare space' in the mast. In mast reefers need special sections as you cannot have a simple tube with a slot in the back. It needs, in effect, a mast with an extra section to contain the sail.
Those aft of the mast are retrofit usually.

Yeah, my bad. I had no idea these existed, but I was talking across purposes. I imagine that the restraint of the luff to the mast compared to a tensioned cable is the main motivation for adding an enclosing tube in these retrofits.

 

[Humblebee]

Slab reefing mains typically have the lateral force transferred to the mast at several points either by sliders on a track, in older designs by a bolt rope, and even older by hoops around the whole mast!

Mike.

Quite so, Mike, I hadn't thought about that, cheers.