Finn Boom Outboard End Extension

Finn boom outboard end extension sheave box is designed to lessen the angle the outhaul enters the boom when the sail is at the boom outer distance mark. Suit all Finn booms (NeedleSpar, Holts, etc.)

Replacement for any existing boom outboard sheave fitting, either on new booms or old ones where the end of the boom has been perforated like Swiss cheese with many and varying sheave fittings.

Large 40mm sheave for effortless and smooth outhaul movement.

Designed to slide effortlessly into the end of the boom and fit tightly under the sail track. Mounted by four 5mm bolts from the top. View or download the V-Tech_352 Boom Outboard End Extension information sheet.

Part Number V-Tech_352 -- Boom Outboard End Sheave Box  -- NZ$90.00 (ex GST)

Finn Boom Outboard End Extention


Construction Material
Sheave Size
Dimensions Internal Boss
Dimensions Sheave Box
Safety Strop Mounting

- Acetal Plastic Body and Sheave
- 40x8mm on 8mm Pin
- 33mm Wide, 33mm High, 17mm drop from Top of Boom
- 38mm Wide, 50mm High
- 250 grams
- 5mm Through Hole


Finn Boom Outboard End Extension

  1. On old booms use a drop saw to reinstate a clean and square aft edge. Repair any damage and file smooth inside the end of the boom.
  2. If required, remove 10mm from the bottom of the sail track at the end of the boom (to provide clearance for the sheave).
  3. Fit the V-Tech_352 Finn Boom Extension fitting into the end of the boom with the internal boss up against the bottom of the sail track and with the sheave box tight against the end of the boom. Wedge securely.
  4. On the top face, measure 70mm back from the end of the boom and drill two 5mm holes, 6mm in from the side edges. Drill only far enough to just dimple the Finn Boom Extension fitting.
  5. Repeat hole drilling process 25mm from end of boom or utilise existing holes provided these are not in line with the screw in the internal boss (45mm from the end of the boom).
  6. Remove fitting from boom and drill the dimpled holes in the fitting to 4.2mm and tap to M5
  7. Reinsert and securely mount the fitting using 5x40mm bolts.
    Alternative rear mounting position for when the bottom of the mast track is not in parallel with the top of the boom (due to being butchered) drill a 5mm hole through the side of the boom 25mm from the top face and 20mm from the end. Either drill right through the fitting and use a 50mm long bolt and nut to mount the Boom End Extension or 4.2mm drill and M5 tap the fitting to take 5x12mm bolts.
  8. Dress the boom and go sailing.

For supply contact us directly using the details at the top.

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