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STARSHIP DESCRIPTION

Starship is a 39 foot Pearson center cockpit cruising cutter: Model 390   She was built in 1972 and was sailed from her East Coast factory through the Panama Canal and up to the San Francisco Bay Area.  She has a centerboard for shoal draft cruising.  Her hull is fiberglass, and her spars are aluminum. She is diesel powered, has approximately 160 gallons of fuel, with a high capacity alternator to charge her two battery banks of gelcells.  She is also equipped with a wind generator, as well as multiple solar panels for 12 volt DC service, plus an inverter for 120 volt AC. She has two autopilots - an electrically driven Raymarine unit and a Monitor wind vane . A watermaker supplements her 120 gallon water tankage.

The interior is divided into three cabins - a stern cabin with navigation station which was added, and therefore not shown on the layout above, the main cabin with galley table and settees, and a forward cabin generally used for storage or guests.  Both the stern cabin and main cabin have fully enclosed heads with showers and pressure hot and cold water. In addition, the center cockpit has a full canvas enclosure and a steering station with instrumentation.

STARSHIP is equipped with a 4kw, s radar several VHF radios, many GPS units, a HF single sideband radio, Weatherfax, five laptop computers, and all the usual advanced electronic navigational tools and devices including emergency locator beacons.  Full charts of the world are aboard as is an electronic chart plotter.  An inflatable dingy, powered by a small outboard engine is on board, and a life raft with full survival gear housed in a canister is mounted on the stern cabin.

Her sail inventory follows:  Mainsail with two sets of reefs, a trysail set on its own track for heavy weather, a roller furling genoa, a roller furling storm jib set as a staysail, two spare jibs, a cruising spinnaker and large drifter that can be set on poles - she carries two spinnaker poles.

STARSHIP is fully equipped for sailing long distances, with many spares on board.

Technical data: (ALL THE FOLLOWING INFORMATION WAS TAKEN FROM THE PEARSON WEB SITES)

Designer: Bill  Shaw

Model 390

Number built: 40

Years built: 1972-1973

Length Over All (LOA): 39.0 feet

Length Water Line (LWL): 33.7 feet

Beam: 13.0 feet

Length/Beam ratio: 3 to1

Length (waterline)/Beam ratio: 2.59 to 1

Displacement (design): 20,600 pounds

Draft, centerboard up: 4.3 feet

Draft, centerboard down: 7.6 feet

Ballast: 7,600 pounds

Ballast ratio (BR): 37% 

Main sail area:  353 square feet  

Foretriangle: 364 square feet

Hull Speed  7.77 knots (theoretical)

"I"   47.7 feet

"P" 47.0 feet

"J" 15.6  feet

"E" 15.0 feet

Main/Foretriangle ratio: .97

Sail area/ Displacement ratio (S/D): 15.2 

Displacement/Length ratio  (D/L):  241      

Capsize Screening Factor (CSF): 1.90

Motion Comfort Ratio (MCR): 29.4                     

Boat Dimensions

LOA = Length Overall. length from stem to stern not counting projections of pulpits or spars.
LWL = Waterline Length. Length at Waterline when the boat is at rest.
B = Overall Beam. Widest part of boat
D = Draft. Deepest extent of hull, typically bottom distance from waterline to bottom of keel.
Disp = Displacement. (weight of boat), the weight of the water displaced by the boat.
Ballast. weight of ballast
SA = Sail Area. Area of main and the foretriangle based on I, J, P, E dimensions.
 

Rig Dimensions

For the basic sloop (or cutter) there are four figures to describe the size of the rig: I, J, P and E.
I = Foretriangle Height. This is the distance up from the shear line (gunwale) to the top of the hoist for the highest headsail. From the IOR rule it is the highest of the following: the intersection of the headstay (or an extension of it) and the front edge of the mast (or an extension of it), the center of the eye for the spinnaker or jib halyard block. This is a little confusing (and why shouldn't it be?) and you may have hard time finding a sailmaker who can actually tell you what this dimension represents.
J = Foretriangle Base. This the distance from the front of the mast to the point where the headstay intersects the shear.
P = Mainsail Hoist. This is the distance beween the black bands (not always marked, except for racing) on the mast.
E = Mainsail Foot. This is the distance beween the black bands on the boom (not always marked - pin to pin).
 

Hull Speed:  (1.34 times LWL)

This is the theoretical hull speed for a displacement hull (like most sail boats). It is a function of the length of the wave created by the boat as it moves through the water. Wave speed is a function of wavelength, longer wavelength is faster. Longer boats make longer waves. Since longer waves are faster boats that make longer waves are faster. The hull speed may not be as precise a figure as the formula leads you to believe since LWL is not static. As the boat heels it can increase. Older racing boats with long overhangs used this to get some extra un-measured LWL to beat the rating rules of the day. As the boat goes faster the bow and stern are immersed deeper in the wave made by the boat. This also increases waterline. In the 19th century sailing ship speeds were often expressed with a hull speed factor. A ship might have a speed factor of 1.17, meaning it can make a speed of 1.17 x sqrt(lwl) [Chapelle]. There are conditions where you can exceed the theoretical hull speed. Surfing down a wave for example.. When surfing or planning the hull is not in a displacement mode. So hull speed may be a bit of a moving target.

SA/D = Sail Area Displacement Ratio

SA/D = SA / (Disp / 64)^2/3 [
This ratio is an indicator of how much sail area a boat has relative to it's displacement. A boat with a higher value will accelerate faster and get to hull speed with less wind. All else being equal, the boat with the higher SA/D will be a better light air performer. This is basically a power to weight measure.

D/L = Displacement Length

D/L = (Disp / 2240) / (0.01*LWL)³  The displacement length ratio is a measure of a boat's speed potential. For displacement boats (most sailboats), speed potential is a function of waterline length (unless your planning or surfing down a wave). Longer waterline boats can go faster. Lighter boats accelerate faster and reach hull speed with less wind. All else being equal, the boat with the lower D/L will be a better light air performer. Lower displacement will also make a boat more sensitive to loading. 2000 lbs of gear will have a larger effect on performance for a 10,000 lb boat than for a 20,000 lb boat.

These two ratios together (SA/D & D/L) can give a good comparison of two boats speed potential relative to one another (all other things being equal of course). If boat A has a SA/D of 19 and a DL of 230, and boat B has a SA/D of 16 and a DL of 230, boat A will probably be a better light air boat. As the wind pipes up boat A will probably be shortening sail before boat B and the effective SA/D may then be the same. Boat A's advantage will then disappear. However, speed potential is not all there is to performance.

BR = ballast ratio

BR = Ballast / Displacement  The ballast ratio is a measure of the percentage of a boat's displacement taken up by ballast. It can give some indication of how stiff or tender a boat may be. Note that it takes no account of the location of the ballast or of the hull shape of the boat. Two boats can have the same ballast ratios with very different righting moments. If the hulls are the same, boat A with all it's ballast in a bulb at the bottom of the keel will be stiffer then boat B with a long shoal draft keel even though they may have the same BR. Racing boats tend to have higher BR's then cruising boats.
 

L/B = Length/Beam Ratio

L/B = LOA / Beam
This is simply the length overall divided by the beam.

LWL/B = Waterline Length/Beam Ratio

LWL/B = LWL / Beam
This is the waterline length divided by the overall beam. All other factors being equal (of course they never are) the longer boat will be faster (in displacement mode, not planning/surfing). Waterline beam might be interesting to know but it is not a commonly reported figure.
 

OR = Overhang Ratio = (Overall Length - Waterline Length) / Waterline Length

OR = (LOA-LWL) / LOA This is the overall length minus the waterline length divided by the overall length. A larger value indicates longer overhangs. A value of 0 would mean no overhangs. Boats with longer overhangs have more reserve buoyancy. Also, as a boat moves faster the bow and stern waves move to the ends of the boat. Longer overhangs let the waves get longer. The overhang ratio has been influenced by rating rules. Under rules that penalize LWL more then LOA longer overhangs developed. The IMS rule has lead to shorter overhangs. Moderate overhangs are considered by some to be good for ocean voyaging boats. The reserve buoyancy helps keep the bow from submerging in waves and helps reduce pitching.

CSF = Capsize Screening Formula

CSF = Beam / (Disp/64.2)^1/3 The capsize screening formula is a somewhat controversial figure. It came into being after the 1979 Fastnet race in England where a storm shredded the race fleet. The Cruising Club of America (CCA) put together a technical committee that analyzed race boat data. They came up with this formula to compare boats based on readily available data. A lower value is supposed to indicate a boat is less likely to capsize. a value of 2 is taken as a cut off for acceptable to certain race committees. However this is an arbitrary cutoff based on the performance of boats in the '79 Fastnet. The CSF takes no account of hull shape or ballast location. The CCA characterizes the formula as "rough". They go on to say that "While the capsize screening formula places a limit on excess beam, which is important for good stability range, it does not control for another main determinant, ballasting. With only simple data, this is as far as we can go." Naval Architect Robert Perry calls it,"...far too simplistic to be always accurate, but it is one of the currently popular ways of looking at a boat's offshore suitability." (Sailing Magazine, Nov. 2001, p.44). Any two boats will have the same CSF value if their displacement and beam are the same. One could have a light hull with 50% ballast in a bulb at the bottom of an eight foot fin, the other could have a heavy hull with 20% ballast in a 2 foot deep full length keel. The stability characteristics of the two boats will be drastically different despite the identical CSF value.
 

MCR = Motion Comfort Ratio

MCR = DISP / (.65*BEAM^4/3(.7*LWL+.3*LOA))  This ratio was invented by Ted Brewer who say's he dreamed it up "tongue in cheek" as a measure of the motion comfort of a boat. A boat that has a more corky motion is considered less comfortable then one less affected by wave action. A higher value is better (if you like comfort). Smaller and beamier boats tend to have a lower ratio. This is best used to compare boats of similar size. A 26 footer should probably not be compared to a 40 footer using this ratio. The ratio is a factor of LOA and LWL and it may assume that boats with long overhangs tend to have wineglass shaped cross sections which provide more gradual buoyancy as they are immersed. However, a boat like a Valiant 42 has a long LWL for it's LOA and possesses this more wineglass shaped cross section. The ratio also favors displacement (higher gives larger result) and there is no accounting for distribution of weight. It also takes no account of waterline beam, a value that can be quite informative but is rarely available on stat sheets