Lewmar Cobra Steering Systems (PDF)

OWNER'S MANUAL

Specifications, pedestal siting and cockpit reinforcement, rudder stops, Cobra geometry and offset angles, tiller arm, draglink fitting and maintenance for the Whitlock Cobra 6R Deluxe, Cobra 6 Monocolumn, Cobra Premiere XL and King Cobra pedestal steering.

DocumentLewmar Cobra Steering Systems Installation & Maintenance Guide

FormatPDF · 8 pages · 1.1 MB

LanguageEnglish

Download PDF Buy

Specifications Installation Rudder Stops Geometry Maintenance Products

Lewmar Cobra Steering Systems — Installation & Maintenance Guide

Specifications

	Cobra 6R Deluxe / Cobra 6 Monocolumn / Cobra Premiere XL	King Cobra MK6 / Monocolumn / Premiere XL
Max turns lock to lock	1.8	1.5
Standard output lever centres	133 mm	133 mm
Standard tiller lever centres	203 mm	203 mm
Rated output load	10195 N	12234 N
Max rudder torque at midships	210 kgf.m / 2060 Nm / 1520 ft.lbs	252 kgf.m / 3661 Nm / 1824 ft.lbs (as printed)
Max rudder torque at full lock	373 kgf.m / 3661 Nm / 2700 ft.lbs	447 kgf.m / 4393 Nm / 3240 ft.lbs

Five basic components: wheel, pedestal (rack and pinion gearing, friction brake, compass wiring and mounting plate), output lever pre-welded to the downshaft, draglink, tiller arm.
Draglink: AHFT10 stainless with teflon-lined rose joints on the Cobra 6R Deluxe; the larger AHFT12 on the King Cobra. Both have threaded ends for final adjustment.
Tiller arms suit rudder stocks from 1"/25 mmØ to 5"/125 mmØ; special arms for transom-hung or severely raked rudders and linear autopilots.
Wheels from 16" to 48" diameter, Mini Maxi style up to 60". Complies with ISO 8847.

Installation

Sighting: room to control the boat and brace in a seaway, without blocking bilge pumps, sheet winches or locker lids; fit a guard if near the mainsheet. Standard pedestal centres 28"/710 mm (special heights to order); 14"/355 mm and 8"/203 mm offsets to the helm seat are shown in Fig. 1.1.
The draglink should run horizontally ±5°; check the tiller arm can be fitted at the right height on the stock.
Cockpit sole: stiff enough for steering loads and a helmsman thrown onto the wheel. GRP: at least 40 mm total thickness (e.g. 25 mm (1") ply full width between GRP). Ply sole: e.g. 2 × 18 mm ply doublers on 75 × 40 mm (3" × 1½") bearers; solid hardwood no less than 50 mm (2"). Steel: 75 × 60 × 6 mm angle iron, 260 mm min.
Bolt down with Whitlock pedestal bolt sets (countersunk internal socket) or 4 off 75 × 40 × 6 plates as load spreaders.
Fitting: cut a 6"/153 mm hole on the pedestal centre, set the pedestal square to the centre line, drill the 4 off 13 mm holes, bed on non-setting mastic and bolt down with sealant under the bolt heads.

Basic components of Cobra systems

Rudder Stops

The most likely cause of damage is incorrectly set or missing rudder stops. They must stop the rudder before the travel limiter in the pedestal head, beside the tiller arm and rose joint.
They must withstand 150% of the rated load (maximum rated rudder torque) with no significant deflection; bond a resilient facing to them.
Never use the travel limiter in the pedestal head as a steering stop. No warranty where rudder stops are incorrectly fitted.
Rudder travel is conventionally ±36°/72° total; more travel needs different lever lengths, specified when ordering.
Where there is no structure for stops, the Cobra stop ring fits under the pedestal using the mounting bolts (pre-drilled to the offset angle; a spacer ring may be needed). It does not protect the draglink.

Cobra Geometry, Tiller Arm and Draglink

Offset Angle B°

L3 (pedestal centre to rudder stock)	B° (lever offset forward)
Less than 200 mm	Refer to factory (custom)
200-225	25°
226-250	23°
251-300	20°
301-350	17°
351-400	14°
401-500	12°
501-750	10°
751-1000	8°
1000	5°

Notes

Wide angle geometry: the output lever is shorter than the tiller lever (1.52:1), so at midships both levers angle slightly forward by B°.
Table assumes the pedestal is forward of the stock; if aft, use the same angles but offset aft.
Tiller arm: keyway or through bolt; keep the draglink as near horizontal as possible; even gap each side of the cap, bolts tightened gradually to 40 Nm. Stocks raked more than 15° need a special arm.
Draglink: tiller at midships, brake released; at least 16 mm of thread in each rose joint; tighten aeronuts and locknuts; check the 1/8"/3 mm spacer between rose joint and output lever.
Check lock to lock: tiller hits the stops before the pedestal limiter; draglink and rose joints clear; then load the wheel against each stop.

Cobra 6R Deluxe / King Cobra MK6

Once a season remove the 4 countersunk screws holding the top cover; clean and refit with Whitlock anti-seize. Same for the four input assembly socket screws (wheel off; keep the wheel key).
At least twice a season wash the pedestal with fresh water and car wax it; touch up chips with yacht enamel for aluminium.
Periodically check the tiller lever, draglink and output lever nut.
Every two years remove the compass and top cover, inspect the gears, quadrant to downtube fixing and the seal ring; with the wheel against the rudder stop, check for movement between quadrant and downtube.

Reshimming the Gear Mesh

Play of up to 10 mm on the rim of a 1000 mm wheel can develop.
Remove wheel, brake spinner and key, then the 4 input assembly socket screws; refit the wheel without the key and pull out the input socket (a wooden bolster on the hub if needed).
Remove 1 plastic shim between the input socket and the top bowl casting; reassemble with anti-seize.
Strip-down (3.1–3.8): output socket bolts are 3 off M8 with spring washers, refitted with Loctite retainer grade 601; reseal compass and top plate. A new downtube/quadrant needs the output lever repositioned and rewelded with stainless rods (15 degrees forward bias when the pedestal is forward of the stock).

Do not let go of the wheel when going astern: if it runs to the stops at speed, the key, gearing or pedestal can be damaged.

Need a part that isn't listed? Ask us to source it and quote the part number from the PDF.