The position on the boat where they are to be fitted must be substantially stronger than the davits themselves.Davits
Davits are the structures used to support a dinghy or tender on the stern of a boat. They enable the dinghy to be lifted out or lowered into the water easily, using pulleys or winches.
Choosing suitable davits for a vessel can be a straightforward task, but there are certain points to consider:
The position on the boat where they are to be fitted must be substantially stronger than the davits themselves.
The weight and distribution of the load: if an outboard is to be permanently installed on the tender, then the davit nearest the motor will carry 90 per cent of the total weight of the tender and motor. It is therefore essential to select a pair of davits that each have the strength to support the total weight.
There are generally two mounting positions for davits; on the deck or on the transom. On a steel vessel, the hull and deck may be strong enough to take the weight of the loaded davits, but it is still good practice to strengthen the area as, unless the original hull/deck design allowed for the extra strain, flexing of the metal may eventually lead to failure.
When carrying a heavy tender and outboard motor, the davits must be strong enough to take both the weight and the forces exerted on them in rough weather.
A pair of transom-mounted lightweight davits, each capable of carrying a safe load of 60kg (132lb).
TIP
A common problem when fitting heavy-duty davits is that they encroach on the lower guard rail. This can be overcome in a smart and practical way by cutting the rail and making up end fittings that cap the rail and then bolt onto the davit body, thus retaining the strength of the rail and adding to the rigidness of the davit.
Reinforcement
A simple, mild steel bracket, ground off clean and epoxy coated, will make a very strong, cheap and corrosion-resistant reinforcement for all types of boat. Stainless steel can be used, although it is more expensive. In either case the metal for the bracket should ideally be over-specified with 6mm (¼in) being the minimum thickness. The bracket, which is formed to suit the angle between deck and transom, will ideally be bolted through both the deck and transom to provide a very strong base for the davit.
If you are working on an older boat, the vessel may already have an immensely strong hull due to the hefty lay-up of early GRP vessels, so therefore it may not require additional reinforcement.
Weight
When the davits carry both an outboard motor and a tender, their weights need to be established. If together they weigh 60kg (132lb) for example, then the davits would need to be rated for over 120kg (264lb) as a pair and over 60kg (132lb) individually. You could test each davit with a 100kg (220lb) man swinging from the outer end. The davits may show signs of flexing, but if the transom remains unmoved, the structure is stable. So while it is good practice to follow the reinforcement recommendations, there will always be instances where these can be modified.
Fixing bolts over a moulded knuckle and a spacing pad of ply below the knuckle provide a strong mount. Inside the boat, the only reinforcement needed comprises three stainless steel strips, one behind each pair of mounting bolts.
Mounting pads
Where the deck or transom doesn’t allow the davits to sit squarely with each other, it is a simple job to mould mounting pads to attach them to, although it is essential to use a polyester fibreglass filler to provide enough strength for the load. Ensure you don’t confuse these fillers with ordinary body fillers, which have no strength at all!
A mounting pad on a sloping deck made from polyester fibreglass filler allows the davits to sit squarely with each other.