Blocks  At Charleston Yachting we carry many styles and sizes of blocks that should provide you with just what you need. The many styles and sizes can be found on our left rail. We carry a full line of Schaefer Marine and Harken blocks. If you know the exact block and its manufacturer’s part type in our search function for a fast find. If for some reason you do not find what you are looking for or have a question regarding an application don’t hesitate to contact us at the link the below. The following are some rudimentary formulas that should help you in making the correct block selection. The loads on blocks are a combination the line pulling through the block and the angle or amount of wrap the line makes around the block’s sheave. The greater the deflection the greater the load a 45-degree turn generates 76% of the load, a 90-degree turn has a load factor of 141% and 180-degree turn generates a load factor of 200%. Other factors that help determine the proper blocks are the length of boat, the boats displacement, and boats righting moment. The largest single factor is windspeed. If you are looking for new jib lead cars consider the differences in the lead angles between your genoas and jibs. A genoa leads angle of deflection should be about 45 degrees, while the lead for a jib or blade might be closer to vertical or 75 degrees thus carrying a much higher load. Here is good formula if you want to see what kind loads you working with for your boat. Sheet Load = SA (sail area) x V2 (wind velocity squared) x .00431 To calculate your sail area multiply your, I (foretriangle height) x J (foretriangle base) divide by 2 and then multiply the result by the LP (distance from luff to clew of your sail). For example: I = 30 J= 10 LP = 155% 30 x 10 = 300/2 = 150 X 155% (1.55) = 232.5 square feet Remember to match the calculated load with the safe working of the block to guarantee a longer lasting and smoother rolling sheave. If this is just too much info, contact us and we will gladly help you choose the appropriate size and model at info@charlestonyachting.com
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