STATS***
Length Overall 24′ 4″
Length Waterline 18′ 0″
Beam 8′ 0″
Draft 3′ 8″
Displacement 4050 lbs.
Sail Area 300
Displacement To LWL = 383
Theoretical Hull Speed = 5.69
Sail Area To Displacement = 16.42
LWL To Beam = 2.25
Motion Comfort = 24.1
Capsize Ratio = 1.87
Pounds Per Inch = 515

***Please credit Ted Brewer for these numbers and algorithms and much of the verbage below. His book Ted Brewer Explains Sailboat Design is well worth study.

B/Disp
Ballast / Displacement is an indication of stiffness and expressed as a percentage. Stiffness has to do with how much sail the boat can carry before heeling and so has a relationship to achievable speed. In other words, people cruising are likely to reduce sail if the boat is heeling dramatically and making the voyage less comfortable. A boat that can carry more sail before heeling can be sailed faster more comfortably.

D/LWL
Displacement / Length ratio allows us to compare the displacement of different sized boats as being in a “weight class”. Originally cruising hulls were expected to be 300-400 or higher, but modern design is driving these numbers lower. You still want to see over 200-250 for an offshore cruiser and some of the most respected cruisers are much higher.

SA/D
Sail Area / Displacement area in a nondimensional number that gives an indication of light air performance. It is calculated as Sail Area divided by Displacement in cubic feet to the 2/3 power or in spreadsheet language: SA / ((Displacement /64)^.67)
Note that displacement is divided by 64 to convert pounds of displacement to cubic feet of sea water displacement – sea water weighs 64 pounds per cubic foot.

Comforts
Comfort or sea-kindliness is a Brewer-invented term to account for motion comfort. A motion comfort number of 40 or more is quite acceptable. Note that smaller boats, having a higher beam/length ratio, have lower comfort numbers.
Displacement in pounds/(0.65*(0.7*LWL + 0.3*Length)*(Ballast^(1.33)))
Capsize Ratio (Cap R)
Capsize Ratio should be under 2.0 for cruising boats. Lower is better for offshore use.
Beam /((Displacement/64)^(1/3))

Hull Speed
Hull speed is calculated from water line length: (1.34*(LWL^(0.5)))

Additional Notes:
Ballast (lead) 1800 lbs.
The current prop is a 3 blade, 10:8
Soda blasted hull clean, applied three layers of Interlux Interprotect 2000e epoxy barrier coat (alternating white and gray layers), and painted two coats of black Interlux Ultra antifouling paint in July, 2011.

As an aside, here is a photo of the original cast bronze tiller plate on this Columbia 24. It’s hard to see in the picture, and I’ll upload a better shot soon, it shows the boats pedigree; it was built by Glass Laminates in their Costa Mesa, CA plant in 1963, and that it is hull number 30.

“Also of note is Columbia’s early model numbering scheme. During the mid-sixties Columbia made three 24 ft models concurrently: the C 24, the Contender, and the Challenger. They also made two 29 foot models concurrently: the C 29 and the Defender. To differentiate among the 24s and the 29s, Columbia used the following model numbers:” ~ Columbia Yacht Owners Association’s Hull Information tab – http://www.columbia-yachts.com/

Continue reading →