Miscellaneous |

I am owner of an Island Gypsy 44 ( 38,000 lbs ). I am looking for

recommendation in terms of anchor. Could anyone tell me what the best

could be for such a boat?

Thank you.

Patrick Lorrain

M/V Ursule

Antibes, France

Patrick, I am still wrestling with the same question for my yet to be delivered Krogen 39.

It is 35,000 pounds and has a frontal area of about 160 square feet so it is probably a

little smaller then yours but in the same ballpark. I will give you my opinion but your are

not going to like it.

Use the biggest anchor and rode that will comfortably fit on your bow. Either use nylon

rope rode or make and use a couple of good snubbers to ameliorate the shock loads of

an all chain rode. (See Snubbers.)

That's the bottom line. If you want to start at the top, it goes like this. The force on the

anchor line is given by Skene as f(# / sq ft) = 0.0053 V^2 where V is the wind velocity in

knots. So, for 160 sq ft, the force due to a 30 knot wind is F = 0.005 x 30 x 30 x 160 =

720 #. But this number does not account for the shock loads due to waves or wind

gusts nor does it include a safety factor nor does it consider the forces, be they plus or

minus, due to the boat sailing on its anchor. However, the American Boat and Yacht

Council says that the wind load on the average 40 ft boat will be 1200# in 30 kn winds,

and that this number does not include a safety factor, and anchor systems must be

designed for a force larger then that quoted. Why the deference between the numbers,

I don't know, maybe to account for waves. So lets use the ABYC number and throw in a

50% safety factor. (You don't like 50%? OK pick a number, but remember, you want to

be able to close your eyes and go to sleep at night.) Don't get too discouraged yet, for

there are still more inconsistencies and semi arbitrary decisions to be made.

So, what wind strength do you wand to design for? 30 kn is common for weekenders

but not world cruisers. How about 40? Why not 60? Or more? You have to draw the

line somewhere. Consider 42 kn for an every-day working anchor. The ABYC number

for this wind is 2400#, or 3600# with a 50% safety factor. The comparable high tensile

chain is 5/16" with a working load of 3900# and a breaking strength of 11600# and its

comparable rope is 5/8" with a breaking strength of 12200#. On the other hand, you

could go up one size to 3/8" hi test chain (5400# / 16200# with ¾" rope (16700#) and

that would buy you a few more knots (60kn winds give 7200# anchor loads, with a 50%

safety factor included.)

Now all you have to do is decide on an anchor. I don't want to get into the details about

various bottom conditions or the pros and cons of various anchors or the scaling of test

data from one anchor size to another. Suffice it to say that most anchors do not do well

in all bottoms, some anchors don't do well in any kind of bottom, there are lots of

opinions and little hard comparative test data, and the data does not support many of

the opinions and advertised performance. Also note that most manufacturers base

their anchor recommendations on 30 kn winds. There have been numerous excellent

letters to the list that you could refer to for guidance. There is also the Puget Sound

anchor tests reported in the Practical Sailor.

If you were to decide on a CQR, as most world cruisers do, so I am told, all I can tell you

is that a 45# CQR will not do for 42 Knots. The best it did in the Puget Sound tests was

1463# in mud and 1450# in sand, a bit short of the desired 3600#. In fact it wont even

do for 30 knots of wind either, which requires 1800# of holding power for a 40 footer.

Maybe the 60 pounder will work but will it fit on your bow?

So what type of bottom do you want to set your anchor in?

Good luck

Nick

p.s. 8-15-06:

I ended up with two approximately 45# concave anchors on my bow. One is a Super

Max that is super in sand and softer bottoms, and the other is a Spade that is super in

sand, grass and harder bottoms. I am very pleased with this combination. The chain is

300 feet of 3/8 inch Hi Test. The snubbers are 25 feet of 1/2, 5/8, and 3/4 inch

stranded nylon.

recommendation in terms of anchor. Could anyone tell me what the best

could be for such a boat?

Thank you.

Patrick Lorrain

M/V Ursule

Antibes, France

Patrick, I am still wrestling with the same question for my yet to be delivered Krogen 39.

It is 35,000 pounds and has a frontal area of about 160 square feet so it is probably a

little smaller then yours but in the same ballpark. I will give you my opinion but your are

not going to like it.

Use the biggest anchor and rode that will comfortably fit on your bow. Either use nylon

rope rode or make and use a couple of good snubbers to ameliorate the shock loads of

an all chain rode. (See Snubbers.)

That's the bottom line. If you want to start at the top, it goes like this. The force on the

anchor line is given by Skene as f(# / sq ft) = 0.0053 V^2 where V is the wind velocity in

knots. So, for 160 sq ft, the force due to a 30 knot wind is F = 0.005 x 30 x 30 x 160 =

720 #. But this number does not account for the shock loads due to waves or wind

gusts nor does it include a safety factor nor does it consider the forces, be they plus or

minus, due to the boat sailing on its anchor. However, the American Boat and Yacht

Council says that the wind load on the average 40 ft boat will be 1200# in 30 kn winds,

and that this number does not include a safety factor, and anchor systems must be

designed for a force larger then that quoted. Why the deference between the numbers,

I don't know, maybe to account for waves. So lets use the ABYC number and throw in a

50% safety factor. (You don't like 50%? OK pick a number, but remember, you want to

be able to close your eyes and go to sleep at night.) Don't get too discouraged yet, for

there are still more inconsistencies and semi arbitrary decisions to be made.

So, what wind strength do you wand to design for? 30 kn is common for weekenders

but not world cruisers. How about 40? Why not 60? Or more? You have to draw the

line somewhere. Consider 42 kn for an every-day working anchor. The ABYC number

for this wind is 2400#, or 3600# with a 50% safety factor. The comparable high tensile

chain is 5/16" with a working load of 3900# and a breaking strength of 11600# and its

comparable rope is 5/8" with a breaking strength of 12200#. On the other hand, you

could go up one size to 3/8" hi test chain (5400# / 16200# with ¾" rope (16700#) and

that would buy you a few more knots (60kn winds give 7200# anchor loads, with a 50%

safety factor included.)

Now all you have to do is decide on an anchor. I don't want to get into the details about

various bottom conditions or the pros and cons of various anchors or the scaling of test

data from one anchor size to another. Suffice it to say that most anchors do not do well

in all bottoms, some anchors don't do well in any kind of bottom, there are lots of

opinions and little hard comparative test data, and the data does not support many of

the opinions and advertised performance. Also note that most manufacturers base

their anchor recommendations on 30 kn winds. There have been numerous excellent

letters to the list that you could refer to for guidance. There is also the Puget Sound

anchor tests reported in the Practical Sailor.

If you were to decide on a CQR, as most world cruisers do, so I am told, all I can tell you

is that a 45# CQR will not do for 42 Knots. The best it did in the Puget Sound tests was

1463# in mud and 1450# in sand, a bit short of the desired 3600#. In fact it wont even

do for 30 knots of wind either, which requires 1800# of holding power for a 40 footer.

Maybe the 60 pounder will work but will it fit on your bow?

So what type of bottom do you want to set your anchor in?

Good luck

Nick

p.s. 8-15-06:

I ended up with two approximately 45# concave anchors on my bow. One is a Super

Max that is super in sand and softer bottoms, and the other is a Spade that is super in

sand, grass and harder bottoms. I am very pleased with this combination. The chain is

300 feet of 3/8 inch Hi Test. The snubbers are 25 feet of 1/2, 5/8, and 3/4 inch

stranded nylon.