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Old 05-11-2012, 12:05 PM   #8
LittleGoat
Real name is Jarom
 
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Join Date: May 2010
Location: Beautiful NW Oregon
Age: 41
Posts: 632
Re: New "project" boat - RIB

Quote:
Originally Posted by Devildiver View Post
MORE QUESTIONS:

I've read a lot on the subject of anchor setups for different length boats, and the general consensus is from the anchor, at least your boat's length in chain (size varies?) + a 5:1 rope/anchor ratio in calm seas or 7:1 in rough. What I'm having issues with is whether or not this applies to light craft like my RIB? Our seas on the Oregon Coast can be pretty rough, even in the protected bay.

Also, is the mushroom the best anchor shape for a combination of in the rocks and on the sand anchoring?

Thanks again for all of your help, I grew up boating on a lake, but this is my first experience owning a saltwater boat, and I can use all of the help I can get.

Casey
To answer your first part, 7:1 is the minimum from what maritime tradition has held for calm conditions. 10:1 is more likely to hold for rough conditions, especially if you have the anchor tied off lower on the front of your boat. I know that is a lot of rope to have stored aboard a 10' RIB, but it is what is recommended.

As far as rope diameter, the recommendation is 1/8" diameter per 9' of boat. That being said, I wouldn't go below 3/8" diameter because smaller can be hard on the hands. The rule for the chain diameter is half that of the rope. BBB is the standard for chain and galvanized is the least expensive way to go. You are spot on for the length of the anchor chain.

I'm not sure if a mushroom anchor will work on a rocky bottom. The only time I've used one is when I was in a lake on a silty bottom and it did a fine job there. I should also mention that there was little current.

As for the size of the anchor, a lot of manufactures have nice suggestions. I would always go for one rated at 1.5 times the length or weight recommendation of the manufacturer. Personally, I would rather haul up a heavy anchor than not have a boat on the surface where I want it when I come up.

By the way, if you are willing to take me out some time and can't get your buddy's 10hp motor, I have a 15hp short shaft that I'll bring out with us. I'll even provide the gas.
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