The formula you are referring to is;
V = 0.85*L*D^2 (where * means multiply & D^2 means D*D)
V = volume in cubic feet of the stowed cable
L = chain cable length in fathoms and
D = chain cable dia in inches
or V = 0.1417*L*D^2
using L in feet.
If you prefer metric use
V = L*D^2/49000
V = volume in cubic metres
L = length in metres
D = dia in millimetres.
But be careful of the basic shape etc. of the chain locker.
- 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.
- 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.
- You should arrange a drainage space at the base of the locker to allow water to run off.
- Arrange the bitter end to have the attachment outside of the chain locker. If you have to release the cable while at sea you don't want to be inside the locker when the cale flies and takes you with it.
The sizes quoted are the minimum and you should increase them if this does not impinge on your design.
I trust I am not teaching granny how to suck eggs
but it might help others who are also wondering.
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
still with me? Good!
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
So there it is!
If anyone needs more info just ask