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West Wight Potter Mailing List maintainer
dfarrell@ridgecrest.ca.us
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> on 2/13/00 8:23 PM, Rich Gort at rich@gorts.com wrote:
> or maybe even more with more blocks, given
> that there must be some resistance in each block
I'm sure a bunch of folks will tell you that the load on the line is less
because more than one length of the line is supporting the keel. You are on
a valid track, however, by mentioning the losses in the system. With a three
part tackle (the stock arrangement), line load for a 390 pound keel is
theoretically 130 pounds. Actually, it's closer to 200 pounds than 130,
because of the high losses resulting from small sheaves, all the extra
turning blocks, and the deforming of the line.
A block and tackle is a marvelous thing, but we often forget about losses
and the fact that, in this example, you have to crank in three times as much
line! TANSTAAFL
Regards,
Bill Combs
-- WWP 19 #439 (Aug 1987) "Ursa Minor" Fort Walton Beach FL ttursine@earthlink.net http://home.earthlink.net/~ttursine -- Never test the depth of the water with both feet
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