NG1 Masthead Assembly

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Isomat NG1 Masthead

The NG1 Masthead for Masthead Rigs is commonly used on Isomat Masts using the NG-28 through NG-51 Mast Sections, See: NG Mast Sections. Larger NG Mast Sections (and sometimes the NG-51) use the NG2 Masthead, See: NG2 Masthead. For Fractional Rigs, See: NG1 Fractional Masthead. The NG1 Masthead for Masthead Rigs is a single casting welded into the Mast Section, easily distinguished from its larger counterpart by having only 2 Sheaves (or provisions for only 2 sheaves) side by side, on the forward side. Masthead allows for 2 Main halyards, 2 Jib halyards, and 2 internal Spinnaker* halyards (using rollers and sheaves above the Jib sheaves) for a total of up to 6 halyards. Sheave Axles are the same in all NG1 Mastheads, but fit in various Axle slots using combinations of up to 3 different size Sheaves and Rollers (listed below) depending upon application. Masthead includes provisions for attachment of Headstay, Backstay, and (2) Upper shrouds using Stemball rigging fittings. Parts for the NG1 Masthead are listed below. Optional Masthead Spinnaker Crane, NG1-2, for running External Spinnaker Halyards, is recommended for long-distance racing or cruising, See: Isomat Masthead Spinnaker Cranes.*



NG1 Masthead Parts

NG1 Masthead Cover Plate: NG1-1: Cast aluminum Masthead Cover Plate for NG1 Masthead Rig Masthead. Masthead Cover Plate keeps Sheaves and Axle in place and serves as Sheave separator, provides level surface for mounting Anchor light, and has slots for exiting other electrical wires. Unit is 10" (255mm) long (maximum) x 2 3/4" (70mm) wide, and is fastened with two (2) 5mm screws, NG1-1S, that thread into tapped holes in Masthead.

NG1 Masthead Sheave, 50mm: NG1-3: Factory standard Acetyl Sheave is 50mm (2") OD x 14mm (9/16") wide x 10mm (3/8") ID.
	NG1 Masthead Sheave, 50mm Aluminum: NG1-3A: Anodized Aluminum Sheave is 50mm (2") OD x 14mm (9/16") wide x 10mm (3/8") ID, and is much sturdier than the plastic version.
NG1 Masthead Sheave, 60mm: 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, 60mm Aluminum: NG1-4A: Anodized Aluminum Sheave is 60mm (2 5/16") OD x 14mm (9/16") wide x 10mm (3/8") ID, and is much sturdier than the plastic version.
NG1 Masthead Spinnaker Roller: NG1-5R: Delrin Roller sheave is 18mm (11/16") OD x 14mm (9/16") wide x 10mm (3/8") ID. For use with Internal spinnaker halyards.
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.