Profurl MK0 In-Boom Furling System — Installation Manual

Components

• Luff profiles articulated on the aft face of the mast: one 0.40 m feeder profile (1) carrying the feeder, plus 2 m luff profiles (2); the top one is re-cut to the luff length.
• Connectors/articulations (4) joining the profiles, held by set screws (9) and attached to articulation brackets (5); each bracket takes 2 slide screws (7) in the mast groove, with washer (33) and locknut (8).
• Sheave box (11) at the top of the profiles for the original main halyard, mounted on 2 end brackets (5a).
• Gooseneck (12) on 2 slide screws plus 2 aluminium plates (13), cambered to the mast and pop-riveted (14).
• Boom profile (15) delivered in 3.20 m (10' 6"), with mandrel (16) on bearings and a drum boom end fitting (22); the drum, loaded with the furling line, turns the mandrel.
• 2 adjustable mainsheet bails (25) and a special boomvang (26) on its own mast attachment, with an adjustable boomvang hound (28).

Before You Start

• Not for wooden masts, or aluminium masts with a track added by screws, rivets or glue. Carbon masts: not recommended, special skills required.
• Check the mast for severe corrosion.
• The boom is heavier than a conventional boom: avoid uncontrolled gybes. To gybe, winch in traveller and mainsheet, turn, then release gradually. A tackle as boom preventer is better still.
• A boom brake may be fitted, but release it completely every time you operate the system.
• Warranty: 3 years on parts and materials from date of purchase (original owner).

Tools & Preparation

• Tape, drill and bits, hacksaw (new fine blade), file, plastic hammer, 10 mm and 17 mm wrenches, torque wrench (1daN/m), Allen keys (supplied), 2 clamps with min. 200 mm (7") opening, pop rivet gun for 5 mm rivets, a large sheet of paper with true 90° corners.
• The gooseneck and boomvang plates are 4 mm aluminium: bend them with clamps of min. 150 mm (6") opening.
• Not supplied: a 6 mm furling line and a ball bearing block to lead it to the cockpit.
• Remove the original gooseneck, cleats, winches and anything that stops the forward boom end fitting rotating; do not reuse the original vang attachment (the axes must line up); remove the original feeder.
• Check the slide screws fit your mast track; file or machine their width if needed.

Gooseneck & Luff Profiles

1. Mark line «C» at the lower edge of the original boom. The boomvang must make at least 30° with mast and boom – raise the gooseneck if not. Vang pin-to-pin length: 1100 mm open / 1005 mm closed (imperial values printed as 5' 8 7/8" / 5' 3 3/16", as printed).
2. Mark line «B» 267mm above «C» (imperial printed as 10' 2 33/64", as printed): the top edge of the gooseneck plates.
3. Slide screws into the track: 2 down to the mast foot for the vang attachment, 4 for the upper end brackets, 2 per articulation bracket (tape them above the track entrance), plus 2 for the gooseneck.
4. Fit the gooseneck at 1 daN/m, camber the plates, at least 8 pop rivets per plate.
5. Assemble the profiles flat on the ground starting with the feeder profile, connectors and set screws; leave the last 2 m profile off. Hoist with the topping lift, keeping the column straight, and seat the feeder profile fully in the gooseneck articulation (10). Nylock (31) with a 17 mm wrench, plastic cap (32) on top.
6. Fit the articulation brackets at 1 daN/m. Position the end brackets and sheave box with at least 20 mm clearance to the backstay(s); mark line «A».
7. Measure «A to D», cut the last profile to it and file smooth. Fractional rig or very flexible mast: cut at A/D minus 5 mm (13/64"), keeping the sheave box in place.

Boom & Mandrel

• Case 1: keep the delivered overall length. Case 2: use the extra length to lengthen the boom – it may change helm balance; check the boom end clears the backstay.
• If the full length is used, the rear end fitting is only fitted temporarily for shipping: complete its assembly as if the boom had been cut.
• Remove the rear end fitting (23), pull out the mandrel (keep control of it, do not lose washers 20 & 20a), square the cut with a paper wrap, cut and file.
• Cut the mandrel by exactly the same amount at its rear end only – never cut the drum end. Refit bearing (17) and holder (19), tap M6 (6mm) at 30 mm from the cut end and fit screw (29).
• Mandrel slightly short: loosen (29), push the mandrel forward, pull the holder out until washer (20) touches, retighten.
• Drill Ø 5mm through the rear end fitting holes and fit the pop rivets (37).
• Hoist the boom level, fit horizontal pin (34) and split pin (35). Never drop or raise the boom more than 15° from horizontal – it can damage the gooseneck.

Vang, Mainsheet & Lines

• Ideal vang angle 45°; never less than 30°. Fit the vang attachment on the 2 slide screws left at the mast foot, Ø 5 mm holes, at least 8 pop rivets per plate.
• Set the mainsheet bails with the set screws underneath; with a deck mainsheet ahead of the main hatch, move them as far aft as possible. Tie a stopper knot in the mainsheet so the boom cannot hit the aft shrouds.
• Furling line: ball bearing block (not supplied) at the starboard mast foot, line into the middle of the drum at 90°, small knot hidden inside the drum shaft. Turn the mandrel towards port (seen from above) to load the drum – the line exits to starboard.
• Lead the halyard aft with another ball bearing block and check its mast exit for chafe. Use few blocks, large sheaves, minimal deviation.

Fitting the Sail

1. Check the rear end of the foot track is filed smooth. The sail must follow the design specification and the vang angle must be set (below).
2. Turn the mandrel so the foot track faces up; battens out.
3. Tack slide (38), "hook" forward, into the tack webbing; feed webbing and slide into the port side foot track, then the foot bolt rope; pull the sail forward.
4. Clew slide (39) into the clew webbing, into the mandrel groove; lock the tack slide in the machining at the front of the track and pull the sail back.
5. Clew pin (43), ring up, into the foot track; lash clew webbing to the ring and set foot tension.
6. Battens in, halyard on, starboard knob (32) out about 3 turns, luff tape between the bronze rollers (36), hoist a little by hand.

Feeder & Vang Angle

• Feeder roller gap: knob hand-tight (not over-tight); turn screw (29) with an Allen key until the luff tape is pinched, then back about ¼ turn.
• To re-insert the bolt rope: open the knob a few turns, insert between the rollers into the track, close the knob by hand.
• Vang angle (no wind, head to wind): hoist and tension the halyard hard, free the hound (28) completely, slack the mainsheet, let the boom hang on the sail, retighten the hound.
• Luff tape rolls too far aft → move the hound so the boom angles up a little more. Rolls too far forward → boom angles down a little more.