Selden Electric Furling Mast RD Mk II — Owner's Manual
User guide for the Selden RD Mk II electric furling mast (RD electric furlin gears from 2024, item numbers 540-294-XX and 540-301-XX), synchronized with an electric outhaul winch (SMF) or a hydraulic outhaul (HPS).
System Overview
The drive unit (mast motor, clutch assembly with two clutch plungers, emergency gear) runs on the Selden power supply and SEL-Bus system: the mast motor connects to its own motor control unit (MCU) – furling mast – which talks over SEL-Bus to the outhaul (electric winch MCU for SMF, or the HPS hydraulic outhaul) and to the OUT / IN buttons. Part and serial numbers are on the aft side of the motor facing the sail groove; quote them with the mast ID in any support case.
| Mast motor | IN |
|---|---|
| Peak torque (Nm) | 230 |
| Max power, full torque (W) | 1000 |
| Full load current* 12V / 24V (A) | 100 / 50 |
| Nominal current* 12V / 24V (A) | 40 / 20 |
* Incl. MCU and PSU.
- Clutch plungers switch between ELECTRIC and MANUAL; both in their lower position for electric operation.
- Power off during electrical installation and whenever the system is not in use. Watch the whole furling process and stop immediately on any malfunction; keep clear of the sail groove, winches and moving parts.
Connection & Button Configuration
- Connect the three control cables to the furling-mast MCU in the right sequence: L1 brown, L2 orange, L3 grey. Wrong positions can damage the motor and brake. Full installation and MCU configuration: Selden manual 597-275-E.
- With synchronized hydraulic outhaul cylinder (HPS): press the configuration button on the furling-mast MCU, then push and hold IN until the motor gives its start-up signal.
- With synchronized winch (SMF) – in this order: (A) configuration button on the winch MCU, hold winch button 1 or 2 until the winch signals; (B) configuration button on the winch MCU, hold MAIN OUT until the winch signals; (C) configuration button on the furling-mast MCU, hold IN until the mast motor signals.
- A signal tone at power-up with no button pressed means the push-button cables from the SEL-Bus converter are wired normally closed: switch off and rewire them normally open.
Preparations Before Sailing
- Luff extrusion tension: lift / disconnect the locking tube from the tack assembly, grip the luff extrusion by hand at the upper access hole, disconnect the motor and tension the luff profile with the emergency winch function until you can no longer stop the extrusion turning by hand. Never use the motor for this – risk of injury.
- Always release backstay tension before adjusting the luff extrusion, or its joints can be damaged when the backstay is eased.
- Tune with limited prebend (Selden Hints and Advice 595-540-E).
- Outhaul car stop: start 500 mm from the aft mast wall and adjust; too far aft keeps the foot tighter than the leech and can jam the head of the sail.
- Keep the outhaul routing low-friction and replace worn blocks – the synchronized winch limits force at the winch, so friction reduces clew force and spoils synchronization.
Furling & Unfurling
Before either: sail upwind, ease a very tight backstay to straighten the mast, set the boom angle with the vang / topping lift so the leech is tight and battens parallel to the mast, ease the mainsheet. Don't reef to where battens ride on the sail slot.
Unfurling with synchronized winch (SMF)
- Secure the outhaul on the synchronized electric winch.
- Press MAIN OUT; the winch gives a short warning signal and starts.
- Holding MAIN OUT, press the second button for more speed.
- Full sail: keep the button(s) pressed – it stops automatically. Reduced area: release at the position you want.
- Trim the outhaul with the winch buttons if needed (full winch power).
Unfurling with a non-synchronized electric winch
- Secure the outhaul on the winch, not over-tensioned (the brake may not unlock).
- Press MAIN OUT and wait 3 seconds.
- Holding MAIN OUT, press the winch button; MAIN OUT + MAIN IN together for more speed. If you let go, press MAIN OUT first to resume. Don't let the winch overload the sail.
- Full sail: the mast motor stops itself – release the winch button, then the mast buttons. Reduced area: winch button first, then mast buttons.
Furling
- Free the outhaul but keep it tensioned (about one turn on the winch); press MAIN IN and ease the outhaul as the sail goes in.
- Holding MAIN IN, press MAIN OUT for more speed.
- Release at the area you want or when fully furled.
The motor does NOT stop automatically when furling in: run the last turns slowly and watch the outhaul block so it isn't pushed into the sail groove.
Manual outhaul with electric mast motor
Hold MAIN OUT: the motor pauses unless the outhaul is pulled, and turns as you pull it by hand. Releasing OUT sets the brake. At the end of unfurling the motor makes a short turn to set the brake.
Switching to Manual
- Power off. Insert the emergency handle on the starboard side of the mast; turn it either way while pulling the upper lever (A) aft and up – up to 10 turns may be needed for the clutch to engage. The luff profile is now driven from the handle socket through a worm gear.
- Disconnect the electric drive: pull the lower lever (B) aft and up while turning the handle slightly clockwise to unload it.
- Furl in or out with the handle. The gear ratio is high, so it takes many turns – a power tool with a 1/2" socket is a good option.
Reconnecting the Electric Drive
- Turn the handle either way as you pull the lower lever (B) aft and up (as printed); up to 10 turns may be needed for the clutch to engage.
- Pull the upper lever (A) aft and down while turning the handle slightly clockwise to unload the manual gear.
- With both levers (A and B) in their lower positions the sail is controlled by the electric drive.
Troubleshooting & Maintenance
| Problem | Cause | Action |
|---|---|---|
| Motor stutters, unfurling doesn't work | Control cables wrongly placed in the MCU | Correct the cable positions |
| Constant tone at power-up, or motor runs at power-up and stops when MAIN OUT/IN is pressed | Push-button cables wired normally closed | Rewire normally open |
| Synchronized unfurling not smooth / top of sail jams | Luff tension, rig tune, outhaul car position or routing | See the preparations above |
| Unfurling unusually slow in the cold | Cold motors | Disconnect the motor from the manual gear, take the outhaul off the winch, idle-run the mast motor IN at least 30 sec and the winch on high speed at least 30 sec |
- Annually: remove the screw over lubrication hole A (via the sail opening, or by removing the motor cover on layouts that have one – mast straight and rig tension released), apply WD-40 while turning the mast motor at least one turn, refit the screw.
- Every 5th year: professional service of the mast motor by an authorized Selden dealer.
Need a part that isn't listed? Ask us to source it and quote the part number from the PDF.
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