Isomat Welded Mast Base Exit Boxes

Welded Mast Base Exit Boxes

Some Isomat Masts have Welded Exit Boxes for leading internal halyards out of the Mast at Deck level, rather than higher on the mast using standard Exit Plates. Halyards exit the Mast angled aft, toward the cockpit, eliminating the need for any additional hardware at the base of the Mast and the clutter of exposed halyards on the mast. Welded Exit Boxes are especially common on Cruising Yachts.

Two sizes of Welded Mast Base Exit Boxes are commonly found used on Isomat Masts, both sizes come in Single, Double, and Triple Sheave versions. Sheaves in these units are held in place with a 10mm Spring Pin Axle. Spring Pin Axles have a head like a Clevis Pin, and feature a built-in spring clip that locks them in place. Axle Pins are easily removed by prying under the head and pulling directly out.

For replacement Sheaves and Spring Pin Axles, you'll need to know which size Exit Boxes (or Sheaves) you have, and (for Spring Pin Axles) whether they are Single, Double, or Triple Sheave versions.

NG 1 Welded Mast Base Exit Boxes & Components NG1 Welded Mast Base Exit Boxes use 60mm (2 5/16") Sheaves, Boxes are 3 3/16" high.
NG1 Welded Mast Base Exit Box Kit - Single: NG1-41K: NG1 Welded Mast Base Exit Box Kit - Double: NG1-42K: NG1 Welded Mast Base Exit Box Kit - Triple: NG1-43K: Welded Mast Base Exit Boxes are normally factory-installed, but are also available as add-in kits. Exit Boxes can be welded in at a variety of angles, Welded installation must be performed by a professional. Boxes are 3 3/16" high x 7/8", 1 5/8", or 2 3/8" wide. Kits include extruded Exit Box, the appropriate Spring Axle Pin and 60mm Acetyl Sheaves (NG1-4).
	Sheave for NG1 Welded Mast Base Exit Box: NG1-4: Factory standard Acetyl Sheave is 60mm (2 5/16") OD x 14mm (9/16") wide x 10mm (3/8") ID.
	Aluminum Sheave for NG1 Welded Mast Base Exit Box: 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. Especially recommended for use with wire or small diameter line.
	Spring Pin Axle for NG1 Single Welded Mast Base Exit Box: NG1-41: Spring Pin Axle for NG1 Welded Mast Base Exit Box with one (1) sheave is 10mm diameter with a 32.5mm grip length.
	Spring Pin Axle for NG1 Double Welded Mast Base Exit Box: NG1-42:
	Spring Pin Axle for NG1 Welded Mast Base Exit Box with two (2) sheaves is 10mm diameter with a 52mm grip length.
	Spring Pin Axle for NG1 Triple Welded Mast Base Exit Box: NG1-43: Spring Pin Axle for NG1 Welded Mast Base Exit Box with three (3) sheaves is 10mm diameter with a 71mm grip length.

NG 2 Welded Mast Base Exit Boxes & Components NG2 Welded Mast Base Exit Boxes use 85mm (3 3/8") Sheaves, Boxes are 4 7/16" high.
NG2 Welded Mast Base Exit Box Kit - Single: NG2-41K: NG2 Welded Mast Base Exit Box Kit - Double: NG2-42K: NG2 Welded Mast Base Exit Box Kit - Triple: NG2-43K: Welded Mast Base Exit Boxes are normally factory-installed, but are also available as add-in kits. Exit Boxes can be welded in at a variety of angles, Welded installation must be performed by a professional. Boxes are 4 7/16" high x 15/16", 1 13/16", or 2 9/16" wide. Kits include extruded Exit Box, the appropriate Spring Axle Pin and 85mm Acetyl Sheaves (NG2-3B).
	Sheave for NG2 Welded Mast Base Exit Box: NG2-3B: Factory standard Acetyl Sheave is 85mm (3 3/8") x 15mm (5/8") wide x 10mm (3/8") ID.
	Aluminum Sheave for NG2 Welded Mast Base Exit Box: NG2-3AB: Anodized Aluminum Sheave with Delrin bushing is 85mm (3 3/8") x 15mm (5/8") wide x 10mm (3/8") ID, and is much sturdier than the plastic version. Especially recommended for use with wire or small diameter line.
	Spring Pin Axle for NG2 Single Welded Mast Base Exit Box: NG2-41: Spring Pin Axle for NG2 Welded Mast Base Exit Box with one (1) sheave is 10mm diameter with a 35mm grip length.
	Spring Pin Axle for NG2 Double Welded Mast Base Exit Box: NG2-42:
	Spring Pin Axle for NG2 Welded Mast Base Exit Box with two (2) sheaves is 10mm diameter with a 56.5mm grip length.
	Spring Pin Axle for NG2 Triple Welded Mast Base Exit Box: NG2-43: Spring Pin Axle for NG2 Welded Mast Base Exit Box with three (3) sheaves is 10mm diameter with a 80mm grip length.

Spars, Rigging, and Hardware for Sailboats