NG1 Masthead Assembly

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Isomat NG1 Masthead

The NG1 Masthead for Masthead Rigs is commonly used on Isomat NG-28 through NG-51 Mast Sections, and on some Sparcraft Masts. See: NG Mast Sections, and Sparcraft Mast Sections. For NG1 Fractional Rig Mastheads, See: NG1 Fractional Masthead. Larger Mast Sections (and sometimes the NG-51) use the NG2 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. Headstay attachment requires use of an NG1 Stemball / Eye Adapter, also commonly used on Backstays for fitting Insulators; Upper shrouds use Swage or Norseman Stemball 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, and is listed below.

NG1 Masthead Parts

NG1 Masthead Assembly - Complete: NG1-1AC-__:
The NG1 Masthead Assembly (for Masthead Rigs) is a single casting, NG1-1B, welded into the Mast Section which 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. Sheaves (up to 6) fit on 'Drop-in' Sheave Axles, NG1-6, in various Axle slots using combinations of up to 3 different size Sheaves (and Rollers) depending upon application. Masthead Cover Plate, NG1-1, keeps Sheaves and Axle in place. Masthead includes provisions for attachment of Headstay, Backstay, and (2) Upper shrouds using Stemball Swage or Norseman rigging fittings. All Furling Headstay attachments require use of an NG1 Stemball / Eye Adapter. Commonly used on NG-28 through NG-51 Mast Sections, the NG1 Masthead (Body) is (maximum) 5 1/16" (130mm) wide x 13 1/2" (340mm) long (on top). To order, please specify size and quantity of sheaves, or Mast size and requirements. *Optional Masthead Spinnaker Crane, NG1-2, for running External Spinnaker Halyards, is recommended for long-distance racing or cruising, and is listed below.

NG1 Masthead Body: NG1-1B:
The NG1-1B Masthead Body is a single casting welded into the Mast Section. The main frame for the NG1-1AC Masthead Assembly, the NG1 Masthead Body is (maximum) 5 1/16" (130mm) wide x 13 1/2" (340mm) long (on top).

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 Spinnaker Crane: NG1-2:
Heavy SS Masthead Spinnaker Crane is designed to attach to standard Isomat NG1 Masthead Rig Masthead. Crane allows for off-center attachment of one or two standard swivel blocks for external spinnaker halyards, See Spinnaker Halyard Blocks. This method of running spinnaker halyards has less friction and eliminates the chafe on halyards that is inherent in the standard internal halyard design – it is the only choice for long-distance racing or cruising. Halyards can be led internally; running from the swivel block to an entrance 5-8 feet down from the masthead, but this method does add a potential chafe spot. SS Plate is (maximum) 3 7/8" long x 4 3/8" wide x 3/16" thick, and projects 2" forward of the masthead. Mounts on top of Masthead and Cover Plate with (2) 4mm (5/32") screws that replace the Cover Plate screws, and (2) 1/4" bolts and locknuts. Mounting requires drilling (2) 1/4" holes in the masthead. Unit comes complete with fasteners. Masthead Spinnaker Crane will not fit Fractional Mastheads.


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 & Rollers in all NG1 Mastheads.
	Masthead Spinnaker Roller & Axle Kit: NG1-6K: Kit consists of (2) Rollers, NG1-5, and (1) Masthead Sheave Axle, NG1-6, required for use with Internal spinnaker halyards. Axle fits in forward slot in NG1 Masthead.

NG1 Stemball Cup Washer - 26x11mm: NG1-CW11: Standard NG1 Stemball Cup Washer is used with swage and mechanical Stemballs in NG1 Mastheads, Spreader Bases, some Stemball Backing Shells, and in other applications. Type 316 SS Cup Washer is 26mm (>1") OD x 11mm (7/16") ID x 11.5mm (7/16") high. For use with 5/32", 3/16", 7/32", 4mm, and 5mm Standard Swage Stemballs, and 5/16", 3/8", and 7/16" threaded Stemballs.
NG1 Stemball Cup Washer - 26x13mm: NG1-CW13: Standard NG1 Stemball Cup Washer is used with swage and mechanical Stemballs in NG1 Mastheads, Spreader Bases, some Stemball Backing Shells, and in other applications. Type 316 SS Cup Washer is 26mm (>1") OD x 13mm (>1/2") ID x 11.5mm (7/16") high. For use with 7/32", and 5mm Standard Swage Stemballs, and 7/16" threaded Stemballs.
NG1 Stemball Cup Washer - 26x16mm: NG1-CW16: Standard NG1 Stemball Cup Washer is used with swage and mechanical Stemballs in NG1 Mastheads, Spreader Bases, some Stemball Backing Shells, and in other applications. Type 316 SS Cup Washer is 26mm (>1") OD x 16mm (5/8") ID x 11.5mm (7/16") high. For use with 1/4", 9/32", 6mm, and 7mm Standard Swage Stemballs, and 1/2", threaded Stemballs.
Swage Stemballs for Imperial Wire
Swage Stemball for 5/32" Wire: RS-SB-5M4: Swage Stemball for 3/16" Wire: RS-SB-6: Swage Stemball for 7/32" Wire: RS-SB-7: Swage Stemball for 1/4" Wire: RS-SB-8: Swage Stemball for 9/32" Wire: RS-SB-9M7: Standard NG1 Stemball Swage is used with Imperial (US Standard) 1x19 wire and appropriate Stemball Cups in NG1 Mastheads, Spreader Bases, some Stemball Backing Shells, and in other applications.
Swage Stemballs for Metric Wire
Swage Stemball for 4mm Wire: RS-SB-5M4: Swage Stemball for 5mm Wire: RS-SB-M5: Swage Stemball for 6mm Wire: RS-SB-M6: Swage Stemball for 7mm Wire: RS-SB-9M7: Standard NG1 Stemball Swage is used with Metric 1x19 wire and appropriate Stemball Cups in NG1 Mastheads, Spreader Bases, some Stemball Backing Shells, and in other applications.
*NG1 Stemball / Eye Adapter for 3/8" (or 10mm) Pin: NG1-SBE-6:* *NG1 Stemball / Eye Adapter for 7/16" (or 11mm) Pin: NG1-SBE-7:* *NG1 Stemball / Eye Adapter for 1/2" (or 12mm) Pin: NG1-SBE-8:* SS NG1 Stemball / Eye Adapters have a 26mm (>1") head diameter. Length from base of Stemball to Pin center is 4" (100mm), or 4 1/4" (108mm) on 1/2" size. A variety of other NG1 Stemball / Eye Adapters are available with or without a Toggle, See: NG1 Stemball / Eye Adapters.

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