T&T: Anchor,chain,rope specs and use

[Albin43SDtr]

'Lo All,

Just some observations:

1. At Homestead, FL, after Hurricane Andrew, several ROUND objects, 
including a tall round water tower sitting on a round pipe whose 
diameter was about 1/4 or less of the diameter of the tank, and a 
round plastic playground set at a (?Burger King?) fast food 
restaurant, were standing as if nothing had happened. All of the 
structures around them were extensively damaged, most to the extent 
of having been blown completely away, except the foundations.

2. Few boats will lay quietly to the wind without some "hunting", 
which, of course, exposes a greater cross section than just a bow-on 
aspect. During the last few hurricanes which blew through the Panama 
City, FL area, I watched many boats at anchor, observing their 
behavior. As I recall, only one old shrimp boat actually stayed 
fairly well streamlined to the wind. All of the others hunted to some 
extent, some violently. But even that shrimp boat was occasionally 
almost broadside to the wind, as gusts came from various directions. 
This turned the boat so that is was more broadside to the main force 
of the wind. We like to think that high winds come steadily from one 
direction, but at least in the confines of bayous such as this one, 
they do not. Often the gusts come from up to about 90 degrees or more 
from the main direction of the wind.

3. Even in a hurricane, the wind speed is not constant. As strong 
gusts strike a boat, the boat reacts, according to its mass, as well 
as wind direction and force and wave forces. The effect is to stretch 
the anchor rode, which then contracts. These constant changes are the 
greatest contributor to rode failure in my opinion. That is to say, 
chafe. I have seen well protected lines worn completely through, 
after wearing the chafe protection through (and, often folks neglect 
to properly protect their lines at all).

4. Hurricane holes (places where folks anchor their boats during 
hurricanes) usually have a limited fetch, so that the waves cannot 
build to extreme heights. In our bayou, I have never seen more than 
about 3.5' or so wave heights at the height of hurricane force winds, 
and then only when the storm surge (water pushed into the bayou by 
the storm) is about 4' or so over the spit of land which helps 
protect this bayou. The fetch is then about doubled.

 From this, I conclude that the shape of the object has a great deal 
to do with the overall wind load exerted. Also, a boat is: 1. not 
round, and 2. will not stay streamlined bow-on, so 
calculations/guestimations of wind load must take these factors into 
account. Not being a mathematician nor a statistician, I would not 
presume to be able to calculate what the actual wind loading on a 
boat would be under all of the varying conditions a boat is subjected 
to. Add to that, the wear on the line, especially if it is a used 
line, and the task of deciding what size line is best becomes almost 
impossible from an empirical standpoint. One just has to use 
experience, hopefully gained at others' expense, to determine what 
should probably be best/adequate. Bigger is not always best, as it is 
the stretch in a rode that provides much of the protection to a boat 
in a storm. No stretch, as in an all chain rode, and a boat can be 
violently jerked to destruction. I have not seen that happen, but 
have been told of it by several old-timers, who adamantly feel that 
for a storm, a chain and nylon rode is far better than either alone.

During the last hurricane that came through here, I had about 25' 
more line out on one of my bow anchors than usual because the storm 
surge was predicted to be greater than usual. My little 45# CQR has 
about 15' of chain. The anchor line was almost cut in two about 5' 
from the chain, where the line laid across something on the bottom 
and was cut. Two of the three strands were cut completely in two and 
the last one was partially cut. Old timers have told me to make sure 
that the nylon was not laying on the bottom when the anchor rode was 
taught, as it would cut, especially if laying on oysters. This is 
just a sand bottom, and I didn't think too much of it, but will in 
the future. For what it may be worth, my anchor rodes are 3/4" nylon 
with 15-20' chain on the anchors. For storms, I can put out a 
Fortress 55, a 35# Danforth, a 45# and 60# CQR, plus tie to trees and pilings.


Take care and be safe.

Wayne
M/V Celestial
Albin43 Sundeck