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  #1  
Old 10-03-2007, 04:38 PM
pkrogh pkrogh is offline
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Join Date: Oct 2007
Location: Nordland, WA
Posts: 4
Default Amsteel standing rig?

Hello, I'm a new board user and I strongly suspect that my questions can be answered by the very experienced folks here. Any and all opinions and information you care to offer will be very welcome!

The boat in question is a Clipper CM/4c built in 1973 and designed by William Crealock as a "cruising" version of his CM Quarter Tonner.

The specs for the boat:

LOA 23-7, LWL 18-6, Beam 7-11, Disp. 2,000 lbs., Ballast (swing keel) 540 lbs., Mainsail area 78 sq.ft., Jib 105 sq.ft., Genoa 181 sq.ft.. IJPE of 25.00' / 10.17' / 20.92' / 7.58'. Wire size is 1/8" and pin size is 1/4". Forestay, backstay, two lower shrouds per side and one upper (with spreader) per side. Chainplates are quite stout made of SSTL and mounted with three big bolts (and backing plate) each.

It's a lot of fun to sail but the standing rig is in sad shape. The boat has owned me for only a few months and I would like to clean up a few things like Nicopress eyes on the shrouds, bent turnbuckle screws, shrouds 6" short from cutting out bad ends, etc. Just small stuff you see.

In talking with friends about the various options, it was pointed out to me that Amsteel is now being used for standing rig on quite a few small boats. Brion also talks about this in his Riggers Apprentice. The 'new' Port Townsend 15 boats now being sailed here have, I'm told, Amsteel rigs with aluminum deadeyes instead of rigging screws.

So I offer a question for the consideration of this board:

On page 137 of the Apprentice there is a Formula for determining shroud loads. When I put in the numbers for this boat and turn the crank the following numbers fall out:

Lower shrouds 1,125 lbs. and Upper shrouds 1,687 lbs.

Whoa, Nelly! This sounds way too high to me. Now I admit I'm no math whiz but this is pretty simple for a formula. I've checked my math and my measurements. And checked the Clipper literature measurements against my measurements. All match.

Can the loads really be this high? Have I turned the crank the wrong way?

Once I get a handle on the real shroud loads, I'll be back with more questions on rigging this boat with the new-fangled spider silk.

Deadeyes. I wonder if I still have some of that Lignum stashed away?

Thanks,
Pete
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  #2  
Old 10-09-2007, 06:10 PM
pkrogh pkrogh is offline
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Join Date: Oct 2007
Location: Nordland, WA
Posts: 4
Default Rig loading calculation question .....

Let's try again, shorter this time.

On page 137 of the Apprentice there is a Formula for determining shroud loads. When I put in the numbers for my boat and turn the crank the following numbers fall out:

Lower shrouds 1,125 lbs. and Upper shrouds 1,687 lbs.

My boat: Clipper CM/4c

LOA 23-7, LWL 18-6, Beam 7-11, Disp. 2,000 lbs., Ballast (swing keel) 540 lbs., Mainsail area 78 sq.ft., Jib 105 sq.ft., Genoa 181 sq.ft.. IJPE of 25.00' / 10.17' / 20.92' / 7.58'. Wire size is 1/8" and pin size is 1/4". Forestay, backstay, two lower shrouds per side and one upper (with spreader) per side. Chainplates are quite stout made of SSTL and mounted with three big bolts (and backing plate) each.

Can the loads really be this high? Have I messed up the calculation somewhere?

Thanks,
Pete
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