To Scarf or not to Scarf

THAT IS THE QUESTION

This is a typical scarf joint !

Its a Pain ! , takes lots of time to make and to be done correctly , needs a reasonable level of accuracy . I need to do lots of them as the length of a piece of wood doesn't always ( most times in fact) match the length required for the job . This is the two piece lamination of one of Jigsaw's Gunwales ( side top edge of Hull ) . Currently I make them by rough planing the angular cut using a power planer , then fit into a jig I created and using a router to finish the cut to a more accurate version . Originally I used a bench saw to make the initial cut and then finished with the router , but typically my bench saw has quit ,the blade started to wobble more that it should and under investigation found that a small bronze bush had become worn and havn't been able to find a replacement . My tools are failing already !!!  .

Jigsaw by Name , Jigsaw by Nature

As mentioned , Jigsaw's hulls are made from multiple sections  , each approx 5 meters in length and over 2 meters in width . These are required to be joined before they hit the water and the process of this joining has gotten more difficult since the decision was made to build in wood rather than steel . The connection points should be seamless , structurally sound and connect quickly  , not an easy proposal .

Skin connection is relatively simple , the inner skin of 12mm ply will butt up directly against its opposing section , the outer layer is held back 200 mm from this edge and a 400mm panel is fitted across this gap as the hulls are joined together , another layer or (butt block) is fitted on the inside of the inner skin across the 850mm distance between the transverse frames .

This gives 3 layers of ply with staggered joints across this section of the hulls , and is likely stronger than the rest of the hull .

Connection of the Chines , Stringers ,Keel and Gunwales is more complex as these are constructed of lamination's of solid timber , but again one of the lamination's is butt jointed to its opposing section ( outer piece this time )  , the inner lamination is scarf jointed with a additional section added and a inner reinforcing layer of fiberglass is added for additional strength in a U section covering the top and sides of each of the longitudinal structures.

The fiberglass U section provides a stronger connection than a third layer of wood as it attaches to a far greater surface area.

Technical Spec's

LOA      19.8  meters
Beam       8.4  meters
Draught   0.95 meters
Displacement   38000 kgs
WingDeck Clearance 1.2 meters

Main Power  2  x   150 hp Inboard Diesel

Hull Construction is Ply ( double skin 12 mm marine ply ) over Frame with an outer Layer of Fiberglass , Framing is longitudinal stringers over transverse frames and watertight Bulkheads .

The Beast Reveals Itself

After 8 weeks of Part-Time work ( Evenings and Weekends ) the shape of the beast is finally revealed , well the first 5 meters of it anyway .  Jigsaw's hulls are created in separate sections to be joined at a later stage , you may notice the rather wide stem , this is the base of the conical bow section  to be constructed using a vertical strip plank process . Originally the houseboat was to be made in steel ,  due to cost constraints we changed to plywood but I still wanted the conical bow that looks so good in steel . The first lamination of the Side Chines , Stringers and Gunwale's has been fitted  ,another is still to go and I have still have the bottom stringers to fit .