Join Date: Feb 2000
Location: Annapolis, Md
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Originally Posted by deltaten
OK... think I got it!
I can get my head around main sheet angle vis boom position being better purchase and tension w/a traveler.
With the existing locations, there must be/will probably be huge amounts of line consumed in a down-wind run. Scaling the dwgs,there's close to 6 feet between blocks...times four runs of line plus handling end means no less than 30 feet or so. When the boom's out only to 85 degrees, it works out to over 75 feet! That's a lotta line needing to be hauled and possibly laying about the deck until it can be squared away!
Moving to a coach top system reduces that amount considerably. Centered boom position it's more like 17 fee and at the same 85 degrees, it's only 26', even considering having the bitter end running the length of the 'pit!
At somewhere around $2/ft. that's a bit of dollar difference. Not enuff to cover the expense of a traveler; nor moving the purchase; but.....
All that said.....
It's only promulgating an intellectual exercise and trying to shorten the learning curve until I actually get the boat inthe water and move it under sail!
Any input welcome
(I apologize that this is cut and pasted from my own earlier discussion on this same topic.) Beyond the loss of twist control mentioned above, another minor point is, and I know this may sound counterintuitive, unless you run a the mainsheet on a cabin top mounted traveler to a winch, mainsheets on cabin top mounted travelers usually require more line. The reason this is so, is that as you move the traveler forward, you lose the mechanical advantage that the length of the boom provides automatically. As a result if you place the sheets half the way up the boom, you need to double the purchase on the blocks. That alone would mean an equal length of line for an equal mechanical advantage.
But because there is an assumption of equal manual force on the line, and given greater frictional losses due to the extra sheeves, mid-cabin mainsheets are design with greater purchase and therefore require more line. That is why the mid boom mainsheets are often run to winches on smaller boats than would be the case on boats with end boom sheeting.
In addition to all else that was mentioned, there is a good chance that you will also require a new stronger boom and gooseneck since this also means greater forces on both.
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Curmudgeon at Large- and rhinestone in the rough, sailing my Farr 11.6 on the Chesapeake Bay