Cunningham configuations

[Dalliance]

This spring I will be adding a couple sail controls the boat has been lacking; a rigid vang and a cunningham. The lines for these, as well as the outhaul, will be run back to cabin top rope clutches at the cockpit. Halyards and mainsheet already are. All the hardware will be Garhauer. My question has to do with the cunningham set-up.

My original intent was to set it up using a fiddle block and a fiddle block with a becket deck mounted at the mast base. With a line from an eye strap on the mast though the cunningham kringle to the upper block and a line through the blocks and back to the cockpit, I would have an 8:1 purchase. Seems pretty conventional and it's exactly the configuration diagramed in the Harkin catalog.

Maybe I am over thinking it, but it occured to me this morning that I can simplify this by running a single line from the eye strap on the mast, through the c-kringle, down to a stand-up block on the deck, and back to the rope clutch and adjacent cabin top winch where I would have a 16:1 purchase. The cost saving is negligable and not the point. It would just look a little cleaner at the mast base and I wouldn't have fiddle blocks potentially clanking against the mast. My mainsheet and jib halyard are also located at that winch, so there might be some on and off with lines, but that seems minor.

Why not do it this way? Could 16:1 be too much purchase? Does anyone see any pit-falls to this? How do most boats have the cunningham set up?

 

[Joe]

First of all, 16:1 is overkill... racing catamarans can bend their masts with just 12:1 so your masthead rig certainly doesn't need more than that.

8:1 purchase is plenty of power to make adjustments without a winch. Even 5 or 6:1 will do the job. With that it mind I would consider using a Spinlock PXR type cleat rather than a clutch because you can close and release it from a distance. I would consider the same path with your vang. You'll rarely, if ever, use the winch for adjusting these controls. You should also consider using a smaller diameter, higher tech control line.. firstly, you can then use smaller, less expensive blocks and cleats and, secondly, it will run smoother through the system.

On my Catalina 27 the cunningham is a 5/16 sta set line run through conventional multiple blocks for a 5:1 purchase. The block system is connected to a coated wire pendant with a "cunningham hook" that attached directly to the C-cringle. This gives me the option of disengaging the hook and extending it to the reef cringle.. so I can use if for my forward reefing control.

I wouldn't worry about the assembly banging on the mast... even under no tension it will not swing freely.

 

[sinnettc]

I like the idea of the cringle hook. I've been scratching my head over using the forward reef point and that seems like way too easy a solution.

FWIW, my cunningham is lead to a track mounted swivel jam similar to http://garhauermarine.com/catalog_process.cfm?cid=63. It's on the cabin-top jib track. Mine is 1:1 though, just one turning block at the base of the mast. I have the same thing on the other track for the vang (which is not 1:1).

 

[rardiH36]

For what its worth, I've found that the 6:1 cunningham purchase at the mast that is then led back to the cockpit on my 1980 Hunter 36 is sufficient to pull the luff quite taught (i.e. scallops are gone) on the lower 1/3 of the sail when the wind gets heavy. I have to pull the line with pressure, but its not a real strain. Give thought to how often you will be adjusting the cunningham on a typical outing. Generally its not very frequent and the length of the pull is not very much.

As to to your query about too much purchase: The cunningham cringles on my two mainsails are not reinforced nearly as robustly as the tack or the reefing cringles/tacks. Too much pressure on the cunningham cringles from a winch might cause a tear? That would be a drawback of tensioning the line with the winch.

 

[Dalliance]

Thanks everyone. This is all good advice. I had a feeling the 16:1 purchase could be overkill and you've confirmed it. I will stick with my original plan for 8:1 purchase. You've also given me some other things to consider like the cunningham hook and the possible alternatives to rope clutches.

Thanks again,

JB

 

[Stu Jackson]

Consider this: Save some $ on the hook, just run a line through your c cringle to a cleat on the other side of your mast (if you have one). If not consider putting one on. The hooks, I've found, come out, especially the cunningham hooks, and years ago I replaced one on our C25 with an S hook, which stayed in place. When we installed a cunningham on our C34, I wanted to avoid the metal at the sail, so simply ran a line from the blocks through the cringle. I have a single with a becket down to a fiddle, line runs to a block at the base of the mast, deck organizer back to cockpit to a swivel cam cleat. Gives plenty of purchase, no winch required for use.