So I want to add an anchoring system to the tug. It never had one before as it was used as a harbor tug that was always tied up to a pier when it was not pushing or pulling. She did not have berths for sleeping either – she was what was known as a “bucket” boat, because you brought your lunch or dinner bucket onboard every day.
So there is a very nice example of a low deck profile vertical anchor windlass on the fireboat, John J. Harvey. The anchor chain comes in through the hawsepipe, through a chain stopper and then 270 degrees around the vertical windlass and then falls into the anchor locker.
And here is a pix of the bow of New York Central No. 13. I got this hawsepipe from Jimmy Gallagher when he sold the Yankee. I have just sandblasted the iron to a dull grey color and the primer coat is on its way!
So how much weight must this windlass pull up to raise all the anchor chain and the anchor?
Lets start with the anchor chain. I think I want to use 3/4″ stud link chain. This is the size used on the tugboat Bertha and she is about the same length and displacement as NYC 13.
Using the dimension charts here:
3/4″ stud link is 5.33 pounds per lineal foot.
Anchor chain is measured in a unit called shots.
1 fathom = 6 feet
1 shot = 15 fathoms = 90 feet
weight of one shot = 480 lbs
The best scope to use when anchoring is about 7 to 1. Scope, which is the ratio of length of chain to the depth measured from the highest point (in our case, the hawsepipe) to the seabed. For example, if the water is 50 ft deep, and the hawsepipe is 10 ft above the water, the scope is the ratio between the amount of chain let out and 60 ft.
Height from hawsepipe to waterline = 10 feet
Max depth to anchor in = 50 feet
=60 feet x scope of 7 = 420 feet of chain needed to anchor safely in 50 feet of water
So how many shots is that?
420 feet / 90 feet per shot = 4.6 shots, so lets round up to 5 shots.
Lets add in an extra shot, in case there were some very deep anchorage.
So 6 shots of chain = 6 x 480 pounds = 2880 pounds
So what about the weight of the anchor? We have to lift that up too.
I have onboard already, two different standard stockless anchors:
One is a small “lunch hook” anchor with the number “5″ on one of the flukes. Judging from its dimensions and comparing to the specs for new anchors, it weights 500lbs.
The other is a bigger one and given its measurements, it weights 1000 lbs.
So the total weight of the ground tackle (bigger anchor plus chain) is 2880 lbs + 1000 lbs = 3880 lbs
Lets add in a 3x safety factor so:
Needed windlass pulling power = 3 times the ground tackle = 3380*3= 10,140 lbs