Isomat NB55 Boom

Isomat NB-55 Boom Section 810H Measurements (OD): 7" x 5 1/8" (180mm x 130mm) Wall Thickness: .114" (2.9mm) Weight/ft.: 3.72 lbs. Weight/M: 5.55 kg Moments of inertia: Ixx = 20.42", Iyy = 6.97" Moments of inertia: Ixx = 850cm4, Iyy = 290cm4 Circumference: 20 7/8" (530mm) Sail slides: 1/2" round slugs (A018, A118) or 1/2" boltrope Lower Track: 31mm x 4.5mm (1 7/32" x 5/32") Alloy: 6061-T6 Standard Lengths: 14'9" (4.5M), 15'9" (4.8M) Common Boom usage: Bavaria 390, 410, 430; Belliure 39, 50MS; Beneteau First 38S, 435S, 456, 456S; Carat 44, 45;
Catalina 380, 42; Colvic 50; Condor 40; CS 40; CSY 50; Elvstrom 42; Feltz 14M; Formosa 53; Freedom 35, 36; Glacer 12.5M, 15M, 424, 495; Grand Soleil 46; Hunter 37.5, 43, 45; Idylle 15.5; Island Packet 44; Jeanneau OD35;* Kirie Feeling 13.50R; Mason 43K, 53K; Nauticat 52; Northwind 47; OY 46C; Pearson 39; Reinke 15M; Seatramp 39; Sirena 44; Skorpion 2, 4, 1200; Stic 11.95, 45.3; Swan 431; Tania 46; Tayana 42, 52, 55; Trewes 53; Vagabond 52K (main); Vanguard 14.5M; Whitby 42K (main);** Zenith 50, 51;

Isomat NB-55 Boom Section Isomat NB-55 Boom Section is stocked in a variety of lengths fully anodized. Sections can be ordered bare (unmachined), or cut to shorter lengths with or without milling for other components. Painted finishes and other lengths are available on special order. If you require a complete Boom Assembly, you can select from components below and contact us with specifications. If you require components not listed below please contact us with details. All NB-55 Boom Ends have provisions for 4 internal lines.

NB-55 Boom Components Although no other components have changed, the NB-55 Boom has been produced with 2 Different Gooseneck Arrangements. New-Style Goosenecks are listed below; Old-Style Goosenecks are listed separately. Old-Style NB-55 Gooseneck Assemblies and Parts. Note that some Booms have been produced with the Isomat AutoReef (single line) Reefing System, using specially modified Boom End castings. For details, See: Isomat AutoReef System.

NG2 Gooseneck Bracket: NG2-11: Cast aluminum Gooseneck Mast Bracket for use with NB-32, NB-40, and NB-55 new-style Gooseneck Assemblies. Bracket for NG-51 through NG-86 Mast Sections is 4 3/4" (120mm) high x 3 1/2" (90mm) wide, and is fastened with eight (8) 1/4" (6mm) rivets. Bracket has 22mm (7/8") hole at top and 8mm (5/16") hole on bottom side, for use with any of the NB2-1 Vertical Gooseneck Toggle Pins. Though actually a Mast Component, this item is also listed here for your convenience.
NB-55 Gooseneck Assembly Complete: NB55-1AC: Cast aluminum Gooseneck Assembly incorporates provisions for internal outhaul and 3 internal reef lines. Internal lines run over delrin sheaves, and down past lever action cams. Cams can be removed to allow lines to go straight down to the deck. Includes Vertical Gooseneck Toggle Pin with reef hooks, and tack shackle. For use with Isomat Gooseneck Mast Bracket (NG2-11), which has 7/8" hole at top and 5/16" hole on bottom side. Parts for NB-55 Gooseneck Assembly.
NB-55 Gooseneck Ass'y: NB55-1A: As *NB55-1AC, above, but with sheaves, cams, and axles only. Does not* include Vertical Gooseneck Toggle Pin with reef hooks, and tack shackle. Parts for NB-55 Gooseneck Assembly.
	NB-55 Gooseneck Casting: NB55-1: Replacement Casting only, for any of the NB-55 Gooseneck Assemblies listed above.
	NB2 Boom Sheave: NB2-10: Acetyl Sheave is 60mm (2 5/16") OD x 14mm (9/16") wide x 10mm (3/8") ID, and fits in upper (aft) slot in Gooseneck Casting.
	NB2 Boom Sheave - Aluminum: NB2-10A: 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.

*Spar Cleat – 6 3/8": NGC-6:* Cast Aluminum Cleat is 160mm (6 3/8") long. Other Cleats have also been used on this boom section, and are listed separately. Other Isomat Cleats.
Exit Plate – Large Snap-in: NG2-7: Large Black plastic Snap-in Exit Plate eliminates line chafe, and accommodates a maximum of 5/8" line. Exit Plate measures 4 1/2" x 1 5/16" (115mm x 34mm), and installs in cut-out 1" x 4 1/4" (26mm x 112mm). Other Exit Plates have also been used on this boom section, and are listed separately. Other Isomat Exit Plates.
AutoReef Internal Shuttle Block: NB2-20: Cast aluminum Shuttle Block incorporates (2) 35mm (1 3/8") Delrin Roller sheaves, NB2-20R. Used with Isomat AutoReef (single line) Reefing System.

NB2 Boom Bail Ass'y: NB2-15A: SS Articulating Boom Bail fits in integral slot in underside of NB-32, NB-40, NB-55, and other boom sections with an underside boom bail slot that is 31mm wide x 4.5mm deep. Bail is made from 10mm rod. Formed plate is 3.2mm thick and measures 4 3/4" (120mm) long x 1 3/16" (30mm) wide. Fastens with (2) 1/4" (6mm) rivets.
	NB2 Boom Bail: NB2-15R: SS formed rod bail only, as used in NB2 Boom Bail Assembly NB2-15A, above. Bail is made from 10mm (3/8") rod, and is 2 3/4" (70mm) long x (maximum) 1 15/16" (50mm) high.
	NB2 Boom Bail Plate: NB2-15BP: SS formed plate only, as used in NB2 Boom Bail Assembly NB2-15A, above. Plate is 3.2mm thick and measures 4 3/4" (120mm) long x 1 3/16" (30mm) wide. Fastens with (2) 1/4" (6mm) rivets.
NB2 Boom Bail Ass'y - Heavy-duty: NB2-15AW: As NB2-15A (above), but Bail is reinforced with a welded crossbar. This heavy-duty option prevents the bail from compressing in extreme circumstances and is used primarily on larger boats.
	NB2 Heavy-duty Boom Bail: NB2-15RW: SS formed rod Bail only, reinforced with a welded crossbar, as used in NB2 Heavy-duty Boom Bail Assembly NB2-15AW, above. Bail is made from 10mm (3/8") rod, and is 2 3/4" (70mm) long x (maximum) 1 15/16" (50mm) high.

*NB2 Boom Vang Attachment Lug - 14mm (9/16"): NB2-16-14:* SS Boom Vang Attachment Lug fits in integral slot in underside of NB2 and FB2 Boom sections and has 14mm (9/16") hole for attachment of Sparcraft Pneuvang. Slide plate (3mm) is 6 1/2" long, and is welded to 5mm (3/16") thick Triangle. Unit slides into track and fastens with (4) 1/4" (6mm) rivets. Also used with NG1 Isovang. *
*NB2 Boom Vang Attachment Lug - 16mm (5/8"): NB2-16-16:* SS Boom Vang Attachment Lug fits in integral slot in underside of NB2 and FB2 Boom sections and has 16mm (5/8") hole for attachment of Vang. Slide plate (3mm) is 6 1/2" long, and is welded to 5mm (3/16") thick Triangle. Unit slides into track and fastens with (4) 1/4" (6mm) rivets.
*NB2 Boom Vang Attachment Lug - 22mm (7/8"): NB2-16-22:* SS Boom Vang Attachment Lug fits in integral slot in underside of NB2 and FB2 Boom sections and has 22mm (7/8") hole for attachment of NG2 Isovang. Slide plate (3.2mm) is 8" long, and is welded to 6mm (1/4") thick Triangle. Unit slides into track and fastens with (4) 1/4" (6mm) rivets.
*FB3 Boom Vang Attachment Lug - 22mm (7/8"): FB3-16C-22:* Heavy-duty Cast SS Boom Vang Attachment Lug fits in integral slot in underside of NB2 and FB2 Boom sections and has 22mm (7/8") hole for attachment of NG2 Isovang. Investment Cast SS Vang Attachment Lug is 255mm (10") long x 29mm (maximum) wide, hole center is 65mm (2 1/2") from Boom bottom. Unit slides into track and fastens with (6) 1/4" (6mm) rivets.

Isomat Isovang Isomat's Isovang is a tubular Hard (solid) Vang with integral sheaves and line that is Spring cushioned for Boom support. Commonly supplied with new boats, it is also a favorite addition to older boats with Isomat Spars. See: Isomat Isovangs. For Isomat Mast-mounted Brackets and Toggles to fit any Vang, See: Isomat Vang Brackets & Toggles.

NB-55 Outhaul Cars The Isomat NB-55 Boom Section is unique, in that it has been produced with 2 different sail Grooves. Some NB-55 Booms have a narrow sail groove tunnel that is 20mm (13/16") high x only 20mm (13/16") wide. Outhaul Cars that fit that unique Groove configuration are listed below. For Standard Outhaul Cars & Slides, that fit the more common (wider) sail groove tunnel used on Isomat & Sparcraft Booms (26mm (1") wide), See: Outhaul Cars for Isomat, Francespar & Sparcraft Booms.

*NB-55 Narrow Outhaul Car - Special: NB2-18AS:* Special SS Outhaul Car is as NB2-18A, but designed to fit in older Isomat NB-55 Booms with a sail tunnel that is only 20mm (13/16") wide. Assembly is 92mm (3 5/8") long. Car rides on 4 Special Narrow wheels, below, and features a 12mm (7/16") clew attachment pin and a 10mm (3/8") pin for attachment of the outhaul pennant.
	NB-55 Narrow Outhaul Car Wheel - Delrin: NB2-18WDS: Delrin Wheel for Special Narrow NB-55 Outhaul Car is 19mm (3/4") OD x 7mm (1/4") wide x 10mm (3/8") ID.
	NB-55 Narrow Outhaul Car Wheel - Stainless: NB2-18WSS: SS Wheel for Special Narrow NB-55 Outhaul Car is 19mm (3/4") OD x 7mm (1/4") wide x 10mm (3/8") ID. *
	NB-55 Narrow Outhaul Car Axle: NB2-18XS: SS Axle for Special Narrow NB-55 Outhaul Car is 10mm (3/8") OD x 19mm (3/4") long.

NB-55 Outhaul Ass'y Complete: NB55-2A: Cast aluminum Outhaul Assembly incorporates provisions for internal outhaul and 3 internal reef lines. Sheaves and sheave axle slide in from the aft side simultaneously, and are held in place by the outhaul and/or reef lines. Rib on aft upper side allows for topping lift attachment.
	NB-55 Outhaul Casting: NB55-2: Replacement Casting only, for the NB-55 Outhaul Assembly.
	NB2 Boom Sheave: NB2-10: Acetyl Sheave is 60mm (2 5/16") OD x 14mm (9/16") wide x 10mm (3/8") ID.
	NB2 Boom Sheave - Aluminum: NB2-10A: 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.
	Sheave Axle for NB-55 Outhaul: NB2-13: SS 'Drop-in' Sheave Axle pin is 10mm (3/8") diameter x 79mm (3 1/8") long.
NB-55 Outhaul End Plug: NB55-2EP: Black Plastic End Plug covers opening in back end of NB55-2 Outhaul Casting. New 'Bird Nest Buster' snaps into place, blocking the hole, but is easily removable for access to lines. If you've ever had a nesting problem, here's the solution.

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