NG1 Fractional Masthead Assembly

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Isomat NG1 Fractional Masthead

The NG1 Fractional Rig Masthead is commonly used on Isomat Fractional Masts using the NG-28 through NG-51 Mast Sections, See: NG Mast Sections. Larger NG Mast Sections use a welded semi-custom Fractional Masthead. For Masthead Rigs, See: NG1 Masthead. The NG1 Fractional Rig Masthead for Fractional Rigs is a single casting welded to the Mast Section which allows for 2 Main halyards (or 1 Halyard and a topping lift) using a single 'Drop-in' Sheave Axle, NG1-6, and (2) 60mm Sheaves, NG1-4. Masthead Cover Plate keeps Sheaves and Axle in place. Masthead includes provisions for attachment of a Backstay, and (2) Upper shrouds (rarely used) using Stemball rigging fittings. Parts for the NG1 Fractional Masthead are listed below.




NG1 Fractional Masthead Parts

NG1 Fractional Masthead Cover Plate: NG1-1F: Cast aluminum Masthead Cover Plate for NG1 Fractional Rig Masthead. Masthead Cover Plate also serves as Sheave separator, provides level surface for mounting Anchor light, and has slots for exiting other electrical wires. NG1 Fractional Masthead uses a single Sheave Axle (NG1-6) and (2) 60mm Sheaves (*NG1-4*). Cover Plate is fastened with one (1) 6mm screw going through the front of the mast.

NG1 Masthead Sheave: NG1-4:
Factory standard Acetyl Sheave is 60mm (2 5/16") OD x 14mm (9/16") wide x 10mm (3/8") ID.

NG1 Masthead Sheave Axle: NG1-6:
SS 'Drop-in' Sheave Axle pin is 10mm (3/8") diameter x 40.8mm (<1 5/8") long. Used for all Sheaves in all NG1 Mastheads.

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