Join Date: Sep 2008
Location: Victoria B.C. Canada
Thanked 111 Times in 102 Posts
Rep Power: 10
Re: Caternary & Chain...
In this area (west coast of B.C.) we cannot rely on shallow depths in most cases and rarely have the room for 10-1 scope. Many bays are small, crowded or both. Often there is 15' or 20' of depth close in where there is not much swinging room, move out and the depth is very quickly over 100'.
To quote Steve Dashew regarding anchoring in B.C.'s Desolation Sound
"...surrounded by a lot of 40' to 50' yachts. Water is 55' deep at half tide.We set the big Rocna at 2.5 to 1 scope and then with a firm bite shorten scope to 1.6 to 1 scope. If you calculate the angle off the bottom, combine the chain length with Wind Horse's length, we need about 150' of swinging room. Compare this to a 40' yacht anchored with a normal sized anchor. They will need at least 4-1 and probably 5-1 scope. Take their length and add to it 240' of chain, allow for angles and you have a radius of at least 220' at a minimum. The smaller boat with its undersized (by our standards) anchor takes a lot more room than the bigger boat with its oversized anchor. Is there a lesson here? Not only does it work in crowded anchorages, but it benefits you in secluded spots which might otherwise be too tight with a normal anchor. The anchor, regardless of design, will set faster, being bigger. This means it drags less before it digs in. This reduces the risk of fouling debris."
From another Dashew post: How big should the anchor be?
Yachts in the 30'-40' range - 60lbs
Yachts in the 40'-50' range - 80lbs
A large bay with 10 - 15' depth and lots of swinging room - I wish! I think from this and the PS test anchor weight is everything. Forget the catenary that will quickly disappear in a blow and keep the rode - whether all chain or a combination of chain and rope - light as long as it has adequate strength. This is probably most important for those without a windlass as they (me as well) have to limit the overall weight to something manageable. With a windlass an all chain rode and an oversized anchor is not as much of an issue.
Steve Dashew is very concerned with overall weight and its effect on performance, whether sail or power. His chain has been Grade 70 for many years.
Living aboard in Victoria Harbour
Last edited by mitiempo; 11-10-2013 at 01:17 PM.