Nick Nice to hear from you Nick. You have asked an extremely interesting question. >>Don, are you sure of the 5.5 number?<< I got those numbers based on actual tests run independently by Robert Smith and myself. Comparing the actual measured wind loads with ABYC values show the ABYC numbers to be off from about 3.9 to 5.9 depending on the boat and other circumstances. Normally if there is a difference, when comparing measured loads to calculated loads, I would feel that the measured loads are probably correct. In this instance however, since both my tests and Smiths test results agree quite well the error seems to definitely be in the tables and calculations. As I said earlier, ABYC themselves admit to a large safety Factor, and I quote ABYC, "Bob Org, assumed a worst case situation the figures were subjected to a hefty, but now unknown, safety factor" Well it is no known again the safety factor is between 4 and 6. On the other hand, if you take dynamic loads into account, the ABYC tables look progressively better until you face extreme dynamic conditions then my calculations show the ABYC tables under estimate the load by a factor of 2 or so., especially with all chain rode. Not good. >>The boat, a Krogen 39, has about 160 sq. ft of frontal area. So tarting with F = 0.004 AV^2 the anchor force due to 42 kn. winds, no gusts, no breakers, no waves, no safety factor, is 1129 pounds. << The calculations you did above are based on the classic drag equation which is the same equation used by Robert Org and also has considerable safety factor built in. In your case, It is just hidden in the drag coefficient (.004) and the over estimation of the exposed area. I do not know how closely you calculated the exact exposed area, but if you used some sort of rectangle (heightXwidth) it is probably quite a bit over the actual true wind area. Earl Hinz spent considerable effort calculating the area for an example boat in his book and checking his numbers as best as I could I figure his numbers are about 1.5 higher than actual. (Better than most calculations.) >>The ABYC number for a 40 foot power boat is 2400#, for a ratio of 2400/1129 = 2.13. Not too bad considering all those no's, and not very close to 5.5.<< Nick you have to expect that these two numbers would agree they are based on the same equation. The difference is that ABYC doubles their number to account for Dynamic loads. If you did the same, your numbers would only be off of the ABYC number by 6%. Peanuts in the anchoring world. You see what I am saying here Nick is that you can not use the drag equation to check the accuracy of the drag equation. I know this is upsetting information, we have all relied on these tables for ages, but both Robert Smith and I believe it is true. Bob has been trying to convince people since the early 1990's, I had no hard data until 1997. Ok, so if this idea is right, why do anchors fail? Because anchor load is only 1/3 of the question. The other variables are poor anchoring techniques and bottom strength. But don't let me get to far ahead. If you have other questions, keep the cards and letters coming. Don Dodds North Pacific Research