Anchoring for Hurricane - Shallow Water, Wing Keel
Where I live in NC, we frequently get hurricanes. The water in the river/bay at this point is shallow (10-14 ft.), 1-2 mile fetch in bay, 40 miles in river, storm surges on order of 8-9 ft., and winds now down to 70-80 mph, with significantly higher gusts at this point inland (although there is one storm on record of 105 mph locally). There are four large marinas on our creek and preparation for such storms is roughly 1/3 anchor out, 1/3 get marinas to haul out boats (but land is low lying), 1/3 stay at marinas. In the many past storms (over my 32 years on the creek), there are success and failure stories for each strategy and none seems superior. My previous and current stategy is to stay at the pier as long as I can tie the boat up appropriately....meaning 26 1/2" nylon lines tied to 8 tie points on the boat and to 11 tie points on the pier/pilings. On the open fetch side, because the 3 adjacent private slips are not in use during the storm (trailer boats pulled out), I tie across these slips, adjusting lines to accommodate the surge and the short choppy waves we get over the shallow bottom (6 ft. within the slip area), and adjust lines so loading is well distributed amoung the various lines. My concerns are not pulling the pier down (would be my expense), chafing of lines, line stretch allowing boat to get out of position in slip, and the action of my mast and that of the Pearson 323 in adjacent shoreward slip (the boats seem to have similar rolling/heeling characteristics). This techique has worked in past, but if I can't get to tie across the vacant slips or someone nearby appears to present a special hazard, then I would anchor out in the river/bay (going up a creek is not practical because of draft/depth issues. Anchoring out is dangerous ... lots of boats, soft bottom --- one boat in our marina got $80K of damage when another boat dragged down on it).
I have observed in past storms that some boats get one or more anchor lines wrapped around the keel and wind up presenting a broadside to the waves and wind, usually resulting in dragging ashore. Wing keels such as the one on my Catalina 320 present a special challenge to this issue, as the wings will act as scoops to pick up and hold a slack anchor rode if one is presented to it. In these storms, the wind will come from the east, veer to the north, and wind up coming from the west as the storm moves by. What seems to be the most recommended way to anchor with two (or more) anchors is to set the two anchors 45 degrees either side of the direction from where maximum wind/waves are expected. But, if you plot this out, you will see that as the boat swings, one anchor takes the load and the rode of the other one goes slack. Using nylon rodes in combination with the turbulent wave action over the shallow bottom, the rode is certain to be swept back towards the boat. In the storms, while the wind ultimately moves as above, locally variations in the wind will cause the boat to move about and there is a really good chance that the wing keel will snag the slack anchor rode, loading up the anchors excessively. While going to a chain rode might help this issue, there are reasons to stay with the current anchor, chain, nylon rode combination.
After thinking a lot about this issue, below is what I propose to do. It's a bit different and I would appreciate input/comment from experienced forum members -- if there are problems, then what and why, and what would be your proposal?
The center anchor would be a 43 lb. Danforth/West Marine, 20 ft. chain, 200 ft. 5/8 in. nylon rode laid in direction of maximum fetch/wind (more or less north). Either side at a 7 degree spread would be the other anchors...33 lb. Bruce to the east, 15 ft. chain, 200 ft. 1/2 in. nylon, 22 lb. Danforth to west, 15 ft. chain, 200 ft. 1/2 in. nylon. Thus, initial wind is a side loading situation from the east, with wind increasing to maximum in north region, where anchors are properly oriented with storm for maximum resistence, and finally side loading from the west as the wind, now decreasing as the storm moves past. In principle, this is how the wind should work, but in at least one storm, the maximum wind actually came from the southwest due to cyclonic conditions locally. The lines would be coupled at the boat with a swivel, with backup jumper lines around the swivel in case it failed, and tie points to three different cleats on the boat with chafe protection. The narrow spread assures that, as the boat swings about locally, it never gets enough slack to wrap the keel, and at the height of the storm forces, all three anchors are working together and oriented in best direction relative to maximum wind and maximum waves. One downside, is that this arrangement maximizes the swing area and requires significant separation from other boats. Bottom will be sand or mud. These are the anchors that will be used .... other types are not to be considered at this time.
Sorry for the long post, but the details need to be considered to give a considered opinion. Now, your comments on this proposal please. Thanks.