A typical davit employs a single line unrolled from a drum whereas all dinghies have 2 lift points towards the stern. So a ∧ strop is used offering no resistance to the dinghy rolling except by the proximity of the arm or another stabiliser strop.
Dinghy Derrick by comparison permits up to 9 connection points along the length of the Davit Arm (shown here), so it is easy for users to choose 2 possibly 3 ideal locations. The strops do not withdraw in the manner of a davit, instead they are very short fixed length with shackles at each end, as in the 2nd photo.
Choice of suspension/lifting points
Ideally the Arm will be positioned along the length of the Transverse Link and with connections holes chosen for the eyebolts to sit directly above the dinghy lifting points using the shortest strops possible.
The exceptions to this ideal:
- Some dinghies have a single forward lift point set so far forward as to lie partly under the joint of the 2 side inflated cushions. Here the Davit Arm should be moved inboard so the strop lies at an angle to clear the cushion to avoid chaffing.
- The primary issue lies with the outboard motor and it’s design of transom bracket. An ideal design as in these photos permits the motor in transit to be rotated side on and sit almost entirely aft of the transom plate with only the clamps inboard. So strops which lay vertically from lift points on the inside of the dinghy transom to the Davit Arm do not cause the Arm to touch the motor. On some outboard designs this is a matter of degree and close proximity of the two is not desirable.
To allow for differing outboard mountings
There are at least 4 ways to ensure that there is no impact on the outboard motor if it's bracket does not recede aft far enough:
- ARK supply an optional Dinghy Transom Bracket with an extension arm (see Gallery). This projects the lift point up to 200mm inboard of the transom so as to clear an obstructive outboard engine. It fits to the transom using the existing transom hole where the lift eye would be bolted. The arms hangs down when not in use so as not to intrude into the passenger space.
- The Davit Arm can be positioned further inboard along the Transverse Link so the strops rise at an angle away from the transom lift points.
- On most RIBs, GRP or aluminium, extra floor lift points can be fitted to use instead of the transom lift points.
- Auxiliary lift lines can be installed inside the dinghy which run from the forward lift points to the transom lift eye and then strops are attached to points along this line far enough inboard of the engine.
Positioning of the Track arms
These are the 2 arms which hinge on the yacht transom surround (as in adjacent photo).
On most modern designs of yacht the separation of these (centre to centre) would be typically in this range:
2615mm (Hanse 345), 2670mm (Bavaria 37), 3040mm (Oceanis 35.1) and upwards.
With dinghy lift points on a typical 2.8 metre rib being at 1.8- 1.9 metres apart, the track arms should lay outside of the motor.
The yacht transom brackets have hole sets where the fitter inserts a drop nose pin to set the lower limit of the Track Arm’s rotation when the dinghy is afloat (see last photo lower pin). In the event of the track arms needing to be positioned closer than is ideal to suit limitations of the yacht transom (i.e. existing backstay plates or tapered stern) then the Track Arms will be set up to rest at a higher level and in the extreme case, a slightly longer strop maybe required on the innermost of the 2 at the stern.
The dinghy may also be adjusted to hang in a lateral position with the transom further inboard and opposite track arm laying above the bows, so there is no risk of conflict between the upper housing of the motor and the track arm during launch.
So in most set ups, conflict with the motor in the launch phase will not be a problem. The issue does not apply during normal carriage or the elevated position because the Track Arms then point near vertically upwards.