Harken Loading Formulas  Tech Info  
Harken Loading Formulas 

Block Loading vs. Angle of Deflection: Load on a block is a combination of the load on the line passing through the block, plus a blockloading factor, which is determined by the angle by which the block turns a sheet. For example, a footblock that turns a sheet 180degrees will see a load equal to twice the load on the sheet. A deck organizer, which turns a halyard only 30 degrees, will see just 52 percent of the load on the halyard. Boat Type: Most load formulas assume a medium displacement monohull, but you can easily correct for other boat types. Multihulls have great form stability and speed and will often carry sails very high in the apparent wind speed, so calculations must be done with this wind speed in mind. ULDB's are typically tender and often change sails or reef quite early, so loading may be done at relatively low wind speeds. For example, a modern trimaran may carry its blade jib in 25 knots of wind at speeds over 15 knots for an apparent wind of nearly 40 knots, whereas a ULDB will probably remove its #1 genoa at about 15 knots of apparent wind. 



Genoa Loading System 

Because wind speed is squared, it is the most important variable and can greatly influence loading. Wind speed ( the apparent wind) should be calculated for the specific sail being analyzed. For example, the # 1 genoa on a 25 ft ( 7 m) boat might only be carried in 15 knots of wind while the # 3 blade on a Maxiboat could well be carried in 40 knots. To calculate loading on a genoa lead car, multiply sheet load by the load factor of the sheet. Most #1 genoas will deflect about 45degrees, while a #3 genoa may deflect 75degrees or more. Lead car adjuster tackle load is dependent on the angle of deflection of the sheet in the lead car, but is generally assumed to be .3 of lead car load when deflection is 45degrees and .5 of lead car load when deflection is 60degrees. 



Mainsheet Loading System 

The formula for mainsheet loading is not as widely accepted as that for genoa sheet loads and should only be used as a rough guide for offshore boats from 30 ft to 60 ft (9 to 18 m). Traveler car adjuster load is generally considered to be .2 times car load. 



Rig Dimensions 

The following abbreviations are often used to describe various measurements on a sailboat. Precise technical definitions exist for each abbreviation, but the following is a list of simple descriptions. 



Top 

