www.lewmar.com 65Kg 70˚ 100Kg 100Kg 100Kg 100Kg 200Kg 100Kg 100Kg 100Kg 141Kg 100Kg 30˚ 25Kg 40˚ 100Kg Which Size/Load Block? • Each Lewmar block has a specified Working Load Limit (WLL), listed in the product specification table • Match the input from Control Line/Winch to the WLL of the block • Note that the line’s angle of deflection around the sheave affects the load exerted on the block (see table below) Additional Recommendations • Always choose a sheave diameter at least 7x the line diameter. • Ensure that blocks are always fitted so they align with the lines passing through them, particularly on multiple blocks and where lines are periodically slack. • All Lewmar products have been designed, tested, and developed to achieve best possible efficiency; however, no purchase system is 100% efficient.The force achieved at the working end of the purchase will be slightly less than the human load multiplied by the purchase.When calculating the purchase required to achieve a known load, we would recommend allowing a factor of 1.05 per block. Multiply by the number of 180° turns in the rope make in a system to be certain of ‘fingertip’ control. Which Bearing? APPLICATION BEARING RECOMMENDED LEWMAR RANGE Frequently adjusted, free, fast-running systems such as sheets or control lines Ball Bearing Sheave Control Block High-static loadings, adjusted less frequently and mainly cleated, such as halyards Free Spin Bearing Synchro Block Frequently adjusted, high loaded systems, using modern line technology with high load on reduced line diameters. Free spin bearing with ball bearing side thrust. HTX Block A combination of the above Torlon Roller Bearing Racing Block Halyard turning block deflection 90˚ Vang turning block deflection 180˚ Load on block: 50Kg Load on block: 200kg CHANGE OF ANGLE BLOCK LOAD AS % OF LINE LOAD CHANGE OF ANGLE BLOCK LOAD AS % OF LINE LOAD 180° 200% 90° 141% 170° 199% 80° 129% 160° 197% 70° 115% 150° 193% 60° 100% 140° 187% 50° 84% 135° 184% 45° 76% 130° 181% 40° 68% 120° 173% 30° 52% 110° 164% 20° 35% 100° 153% 10° 17% 0° 0% VERTICAL GENOA SHEET ANGLE TOW LOAD AS % OF SHEET LOAD 70º 65% 60º 50% 50º 35% 40º 25% Mainsheet traveller towing load Guide % of mainsheet load 25%
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