Chain locker

Volume

V = L * D^2 / 49000 (conform RINA)

• V = chain locker volume in cubic meters
• L = chain cable length in meters
• D = chain cable diameter in millimeters

The calculated volume is the minimum and ample reserve space should be allowed.

Basic shape

• If possible it should be circular in plan view. If it must be rectangular make it as square as possible. If it is rectangular with more than 1.5 to 1 proportion of long to short sides the cable may not lie properly.
• The locker should taper towards the bottom
• There must be no side stiffeners or obstructions to the cable. If this is not possible then angle bar stiffeners should be welded mouth-on i.e. to form a V shape on the bulkhead or use half-round bars. If possible fill up the mouth-on angles with wood and plenty pitch. The same with a pipe-pipe but preferably use a solid half-round.
• If the chain locker is high do not fit a ladder, cut semi-circular holes in the locker bulkhead to form hand and foot holes. Pitch them about about a foot apart horizontally and about 9 or 10 inches max vertically. Remember you'll be very close to the bulkhead and you won't be able to see too well. Grind the edges smooth to prevent injury to your hands.
• The height of the stowed cable (assumed stowing flat or horizontal) should be at least 3 times the diameter of the locker with an allowance of half the diameter to the lip of the chain pipe. If not circular use the diagonal instead of the diameter.
• The chain pipe should be vertical and situated at the middle i.e. at the centre of the circle or at the intesection of the diagonals if not circular. The lower edge of the pipe, the lip, should be flared and very strong and it should be on level with or just below any beams or longitudinals under the deck that is the crown of the chain locker.
• Remember that the cable is only the length stowed in the locker, theoretically you can reduce the actual length by the distance from the anchor shackle to the lip of of the chain pipe. If there are two anchors you'll only stow half the cable. It is obvious but you would not believe how many people have used the entire length on two for one locker.

Further requirements

• You should arrange a drainage space at the base of the locker to allow water to run off.
• The clench plate for securing the end of the cable has to be above the chain storage.

Just in case; Circular Using the minimum height of stowed cable as 3 times the locker diameter then pi/4*dia^2 is the area and 3*dia is the stowed flat cable height

and pi/4*dia^2*3*dia = Vol = 2.356*dia^3 so that dia = 0.75*Vol^(1/3) or 0.75 times the cube root of Vol

Rectangular Say the width of the wide side is W and the width of the narrow side is N. Call the proportion W/N f so f =1 for a square and f = 1.5 for the limit as mentioned above.

The floor area = N*fN = fN^2 The diagonal = (N^2+f^2*N^2)^0.5 = N*(f^2+1)^0.5

Vol = The flat, stowed volume = area*3*diag Vol = fN^2*3*N*(f^2+1)^0.5 = 3*f*N^3*(f^2+1)^0.5

so then N = [Vol/(3*f*(f^2+1)^0.5]^(1/3) simplify this to N = Vol^(1/3)*a coefficient that depends on on f

Prop'n 1.00 to 1; N = 0.6177, W = 0.6177, diag = 0.8736 Prop'n 1.25 to 1; N = 0.5502, W = 0.6878, diag = 0.8808 Prop'n 1.50 to 1; N = 0.4977, W = 0.7466, diag = 0.8972