Installation advice

We aim to list here the various tasks required to fully install and implement Dinghy Derrick with a realistic assessment of the skill base required.

Fitting the electrical system

Installation of Dinghy Derrick (D.D) can be a 'do-it-yourself' level project for people with good practical skills, but DIY electrical installations are rarely as elegant and neat as professional jobs, so we would urge a little more attention to detail.

The yacht may have an unused circuit breaker or unused slot for an extra breaker, so in this case continuity with the existing switchgear is important and you should obtain a breaker of the correct rating and type (see our Installation Manual) to replace or insert in the existing panel. Alternatively obtain a Carling breaker from ourselves to install.

This breaker will be connected to the main leisure battery bus bar where the other breakers draw their current from. The other two components, the changeover contactor and the radio receiver can be mounted on a small board, maybe 200 x 200mm, together with the two fuses required by the radio receiver. Cables are then run from this board to the circuit breaker and also to the windlass (min. 16 and to the location of the auxiliary deck switch (4

Typically, the board would be mounted behind the existing control panel in a void easily accessible with the cable runs supported on small adhesive cable mounting pads.

The cable entry to the windlass is via the base and a waterproof cable gland with some added sealant wherever the cable emerges from a hole in the deck or other structure. This work requires a degree of tidiness and preparation but is otherwise quite straightforward and the installation guide is well illustrated so it is within the capacity of any competent DIY person.

Fitting the transom bracket

The issues concerning mounting onto the transom are dealt with on a separate page TRANSOM MOUNTING ISSUES. The work for fitter involves taking the Transom Plate, aligning it at the correct point and using a fine pencil through the four square holes to mark the drilling positions on the hull.  There is a degree of tolerance built into the system.

Then some sealant is smeared inside each hole and bolts are passed through the holes and tightened. A spirit level is used to check that the two brackets lie parallel to each other.  If not, they are rotated slightly until true, and then tightened down.

Thereafter, the assembly of the frame onto the brackets is a straightforward job which can be accomplished in less than an hour by anyone able to use spanners.

The primary issue is where this work gets done. It is entirely feasible to do this on a yacht when afloat but to ease this the yacht should be moored stern-on and very close to the pontoon. This will allow the fitter to sit on the pontoon whilst drilling holes and to lay out the framework components on the pontoon before drawing them forward to the bracket and inserting the hinge pins. The work can be done from a floating dinghy if the above is not feasible but it will be more difficult and require two people.

Alternatively the boat may be taken out of the water, chocked up on the quayside, and the work done there.

Again the quality of workmanship required is not onerous and provided that four holes can be neatly drilled in the right place, the remaining work is straightforward.

Fixing the rigging

This will require the use of either a bosun's chair, or mast steps, or the hire of a cherry picker platform. The requirement is to access the masthead and/or the upper reaches of the backstay. Here we fit the ARK tang plates supporting a pulley block, and each halyard has to be tied off and the return loop threaded through a pulley block. The amount of work required depends on whether the yacht in question has unused sheaves in the masthead, or unused holes on the masthead plate or requires local work.  The layout is 2:1 normally but for heavyweight loads (say 95-130kgs) using a 3:1 gives a smoother action.

The remainder of the rigging work is done at deck level and at dinghy level and requires no special access.  Once the halyards are rigged up top, the ARK open cheek pulleys are slotted on with a three point array of short lines to the Davit Arms and Transverse Link. There is a formula provided on how long these lines are to be and the geometry of the lift and launch cycle is closely connected to getting these lengths correct. There will inevitably be a degree of trial and error, because every yacht and every dinghy is different. You should allow half a day for experimentation, albeit guided by the instructions, to optimise the dinghy rigging to achieve the most elegant lift and launch geometry.

Again, this is a DIY job, but inevitably any professional installer who has done a number of such projects will be able to reach the best conclusion more quickly.

Fitting the windlass

The most difficult part of the operation is the decision as to where to mount the windlass and to plan a clean and square-on feed of the halyard onto the windlass drum.  There are clear instructions as to how to achieve this, but it will require thought and planning.  The preferred positions are bolted down on the forward deck alongside the mast base, or in a stern locker.  

The base of the windlass can be fixed with 4 x 8 mm screws provided . The area of the deck or locker which DD is fixed to needs to be assessed for strength. The issues are the same as mentioned in the transom fixing issues, namely that the type of load taken by the windlass is very simple,  i.e. in a straight line along the direction of the halyard as it leaves the drum.  This could be vertically upwards in which case the deck structure is pulled upwards, or could be parallel to the base of the windlass in which case the loading on the deck is a side sheer force.

The halyards from each side are joined into one on the down line to the windlass drum.  Alternatively the drum maybe drilled to terminate a 2nd line at the other end and both halyards fed onto the drum after matching their tensions.

As in any case where anything is fixed to a yacht, reinforcement of the yacht structure may be required, but this can normally be achieved without great difficulty.  If one considers that the maximum service load is 130 kg (286 Lbs)  plus the frame itself of 44 kg (97 Lbs), carried through a 2:1 reduction, then the masthead or backstay carry half of that load. The half load borne by the windlass is the same as the weight of a single person standing on their 2 shoes, albeit acting up not down. There are few places on a yacht which are unable to bear the weight of single person, otherwise they would fail in service duty anyway.

Fixing the pushpit coupling blocks

The block is made from an engineering plastic, ultraviolet resistant and also acts as a galvanic isolator so Dinghy Derrick is outside of the yacht's earthing system. The block comes with a drop nose pin so as the track arm approaches the pushpit top rail the pin is inserted. The blocks are attached to each side of the pushpit using a special clamp we provide.

This is the only installation operation requiring a hole to be drilled in stainless steel, when an 8.5 mm hole is to be drilled through the track arm to exactly match the same level as the pushpit top rail. Drilling in 316 stainless steel requires a slow drill speed and a high-quality cobalt or similar drillbit. One hole is drilled in each track arm.

With the track arms in their carriage position either vertical, or more usually canted slightly forwards, the pushpit carries the horizontal accelerations caused by the yacht motion plus part of the rotational moment of the track arms downwards under the gravity load of the dinghy, the balance being borne by the halyards.

Overall the load is quite modest and with the pushpit structure having usually three or four deck bolts supporting a 90° structure, this will have a negligible effect on the loading.  Again, it should be compared with the design function of the pushpit which is to halt a human body thrown with impact, typically 75 kg at 1 meter/second.

If the fitter is concerned that the structure is old and the mountings historically poor, then it is again a straightforward matter to reinforce such a pushpit. This may be done with an extra tube at an angle to the deck in a manner of a flying buttress or adding a tensioning wire to a deck bracket to pre-stress the structure. Again there are illustrations of how to do this in the instructions.

The operation again is within competent DIY standards except for pushpit reinforcement where a rigging company would be better employed.