Below are initial set-up instructions for the Nighthawk kitset IOM. You can then adjust as needed later to suit your local conditions and preferred mode of sailing.
There are two versions. Those in italics are for the original Nighthawk with the winch on the deck, the others are for the Mk II with the winch under the foredeck. The hull shapes are the same.
Adjusting the hull trim
Fitting a new fin
As in the assembly instructions, draw a transverse line on the fin 320mm below where it exits the hull (on some tape) and mark on it the point 642mm (633mm) from the bow point.
Balance the bulb on a round pencil and mark the balance point. You need to fit the fin so this point is at the 642 point (4mm behind the 633 point).
The hull draft should be 55mm, so the maximum distance allowed from the hull to the bottom of the bulb is 365. Adjust the fin length so this distance is 5 mm less than this.
Finally the bulb should ideally also slope upward about 2 degrees, and of course it has to be aligned with the fore-aft axis of the fin. When you have all that about right glue it in or use another fin bolt at the bottom.
A useful trick for gluing the bulb on is to undercut the bulb slot slightly, and also drill a couple of holes through the end of the fin (where it sits in the slot). Epoxy will flow into the spaces and hold the bulb firm, and you can get it out again by softening with boiling water.
For a fin with bulb already attached
You need to get both the CoE and the CoG in the right place. If you follow the kitset instructions the CoE should end up correct, though you may need to trim the top of your fin.
For the CoG, balance the whole thing upright on a round pencil or similar, ensure the CoE line is vertical and mark the balance point of the CoG at the bottom. This should be on the CoE line (4mm behind the CoE line). If not you should be able to adjust the position of the ballast weights instead – moving 200gm of weight by 100mm is equivalent to moving the fin position by 8mm, so you can work out how far you will need to move the weights.
The finished boat should need about 200gm of extra lead weights to make 4kg, and these can be placed to trim the hull correctly. When you float the finished boat the bow point should be about 8mm out of the water, and at the stern the water should lie just at the lowest chine. If not move your ballast weights to adjust.
The suggested set-up for the winch is as shown in this photo ( this photo). You need a single and a double block with at least 320mm clear between them. The winch holes fit a Smartwinch, and Mk II has pre-drilled holes for the blocks as well.
(If you find the mainsheet getting caught in the winch drum when gybing, and you’re already using the winch to wind in, you’ll need to add a drum cover. Make a hat-shaped strip of plastic (along, up, across, down, along) and hold it in place over the drum with double-sided tape).
The simplest way to hold the rudder servo in place is to use cable ties.
The custom mast step supplied fits the mast slots. The forward mast slot is about right, but try the aft one (with more rake than below) if you want the boat to follow wind shifts more.
Measure the distance from the top of your bottom mast band to the cockpit floor and use this graph to get the distance from the bottom of the jib band to the top of the (ply) bow.