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[quote=MN3][quote]I don't think changing the way the halyard is rigged will have an effect on mast load. The downhaul is pulling with a given force. Shouldn't matter if it is pulling against the hook or a 10:1 setup, unless you also crank down on the halyard. [/quote]
Bingo - by removing it from the hook you are also cranking down on the halyard (now unlocked)
thus the x amount of force your cunningham/downhaul are pulling is x times 2 (up the halyard and back down)

"Visualize a halyard lock at the top of the mast. With halyard locked it's 1:1 compression on mast to down force on halyard from Main.

Now with a 1:1 halyard, the halyard sheeve is a block and this creates a 2:1 purchase, so you actually have twice the compression force on the stick as halyard tension. "

[url=http://forums.sailinganarchy.com/index.php?/topic/126020-21-halyard-reduces-the-load-on-the-mast/]http://forums.sailinganarchy.com/index.php?/topic/126020-21-halyard-reduces-the-load-on-the-mast/[/url]

furthermore, adding a second block into the mix (say at the top of the mast like my 6.0 has) makes this 2x down to 1.5x

[img]http://www.yachtsandyachting.com/photos/forum/Peaky/2009-03-18_123015_mast_compression.JPG[/img]
Ignoring friction losses... Mast compression is least with a halyard lock (1000N in this example), most with a 1:1 halyard (2000N) and 1500N with a 2:1 halyard.[/quote]

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