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Old 01-06-2016, 09:59 PM   #72
Nomad Willy
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City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,743
waddenkruiser,
Very good post.
Nylon line re catenary and the resultant lower rode angle of pull on the anchor is vastly inferior to chain. The catenary becoming almost gone with chain only in extreme conditions that would require an excellent bottom and a very high holding power anchor. But the advantage of chain only applies to the lower half of the rode connected to the anchor. Removing the upper half of the chain rode and instead using nylon line would not cause the holding power performance of the rode do suffer.

In posts years ago somebody brought up information (source unknown) that indicated the best place for weight on a rode per the desirable effect on anchor holding was about 15 or 20% up the rode from the anchor. At that point I assumed the optimum place for weight was right at the shank end.

During my 8 years in SE Alaska I found that the fishermen mostly had about 2/3rds of the rode in nylon line. The chain at the anchor shank was very heavy (sometimes studded chain) and one or two descending chain sizes followed that. Some had only two sizes but few had only one like pleasure boats. The reason for this arrangement should be obvious. Concentrate the weight of the rode near the anchor. Here are some pics that illustrate the practice. Many have so little chain you can see the line underneath.

I'm supportive of chain on anchor rodes as is Chapman. But only in limited amounts. Twenty to 30% chain should make an optimum rode. And if more catenary and a more optimum angle of pull is desired just use heavier chain.

waddenkruiser wrote;
"As long as the rode force (the force resulting from the boat pulling backwards) is not high enough to lift the last meters of the rode from the ground there isn't any force acting at the anchor"
I read this as saying that as long as there is chain on the bottom there's no pull on the anchor. I can't come close to agreeing with that but otherwise a good analytical post. Head and shoulders above the typical post on this form ... and others too probably. I look fwd to more analytical contributions.
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North Western Washington State USA
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