AON

1:60 HMS Naiad 1797
Part 6 – Stern and Stem Construction
Original post 10/18/10
 
Stern Deadwood
 
After the timbers of the aft deadwood had been fayed and glued together, the next step was to reduce the deadwood above the bearding line to the final width of 14 ½ inches. This width is equal to the full breadth of the deadwood, 18 ½ inches, minus the 4 inches required for the two 2 inch ledges to support the cant frames. These ledges follow a curve on each side of the hull called the bearding line. On Naiad, this was a continuous curve, not stepped.
 
The bearding line needs to be located accurately so that when the hull is faired the feet of the cant frames remain at roughly their 2 inch thickness (.033” at 1:60) and do not get faired down to less or, in the worst case, nothing. The bearding line can be copied from the original draft and put on the CAD version, but I think it is preferable to develop this line directly from the CAD body plan profiles, which are being used for all the other lofting.
 
The bearding line passes through all the points on the hull at which the moulded breadth of the hull is equal to the deadwood thickness - 18 ½ inches. Placing a vertical line on the body plan at half this breadth from the middle line, allows heights to be taken off at each frame line to plot the bearding line in the sheer plane. This was the approach used to plot the forward and aft bearding lines on the Naiad CAD drawings. The bearding line was a bit of a mystery to me until I visualized it in this way.
 
With a pattern for the aft bearding line in hand, the line was then marked out on the stern timber assembly, which was then set up in the milling machine as shown below.
 

 
The next picture shows a closer view of this setup.
 

 
I will not walk through all the steps of this milling process, but only touch on a few points. First, the work, of course, must be horizontal when milling both faces, so the assembly, which when finished will be narrower at the bottom, was not tapered until after this process was complete. Second, the machining was only carried up to within, say 1/16 inch of the bearding line, leaving the final cutting to be done with hand chisels. Finally, with the top deadwood machined to its final width, the centerline of the assembly was then determined from this and marked on all edges of the piece.
 
After this machining, the sternpost and inner post assembly was attached and the whole fastened to the keel. In the following picture this assembly is shown shored up by one of the clamped squares discussed in Part 4.
 

 
Again, at this stage I was taking few pictures. Cutting out and shaping the sternpost assembly was fairly straightforward. Heights and sizes of the mortises for the transoms were taken from the large Centerline Structures drawing.
 
 
The stem, apron and forward deadwood assembly was made and attached to the keel in much the same way as its aft counterpart. Here is an image of the pattern sheet for the forward structure.
 
 

 
There are more complicated components here, but the process is essentially the same. A separate pattern sheet was made for the knee-of- the-head parts. When all these parts were assembled and attached to the keel, the entire assembly was set up as shown below.
 

 
Permanent supports for the beakhead and sternpost were added later to replace the temporary clamped squares shown in this picture holding the ends vertical. The keel was maintained on center with the small wood blocks screwed into the base with another placed just behind the sternpost.
 

 
In the above closer side view, the bearding line still needs a little trimming and the stem rabbet has only been cut at the top, leaving the section down to the keel rabbet still to be done. The “rising wood,” that is, the deadwood in the center section of the hull is also visible in these pictures.
 

 
This picture shows the details of the beakhead assembly with the gammoning knee in place and also the initial fitting up of the bollard timbers. The picture below shows another view of this.
 

 
In the following picture the bollard timbers have been installed, the knightheads shaped and the bowsprit chock installed. Also the first forward cant frames on the port side are being positioned, but I will save the cant frame discussion for later.
 

 
The bollard timbers have a complex shape. The inside faces are curved to match the curvature of the sides of the stem, which expands in breadth as it rises from the keel. The fore surface matches up to the curved rabbet of the stem, then curves aft matching the hull profile. The aft (inside) surfaces are curved to maintain the correct molded breadth at each height. The aft foot is beveled 34.5 degrees vertically with its edge fitting into a relief cut at the same angle in the apron piece above the bearding line. The outside edge, which is thankfully flat, is cut back about 1 inch over most of its length to give an air space when the first hawse timber gets butted up against it. Finally, there is a complicated bit of fancy joinery needed to get the bowsprit retaining chock to fit neatly between the upper parts, called the knightheads, which get their own little bit of shaping. The next picture is a closer view of all this.
 

 
These bollard timbers turned out to be simple forerunners of what was to come with the modeling of their neighbors, the hawse timbers, which will be covered in the next part.
 
Hold Down Bolts
 
At this stage it was necessary to bolt the keel down securely to the building board, and it was a relief to turn to some work I could get my mind around. For the hold down bolts, special threaded studs were machined in brass as shown below.
 

 
Three of these were made and were spaced out on the keel. Eventually they will be the permanent mounting bolts for the model. The idea behind this design is that the smaller diameter threaded part of this (4-40) will come up through the keel. The shoulder of the larger diameter will be stopped at the bottom of the false keel. Three small (4-40) nuts from above and three larger nuts from below will hold the keel down, initially. Eventually a small nut will be embedded just below the keelson. With the shoulder screwed up against the keel bottom, the top of the small section will be cut off flush with the top of the nut. This will prevent the keelson from being popped off by over-tightening this bolt from below later. The larger size nut under the building board or the base of the case will then hold the model down.
 
All this work was completed by the end of February 2010.
 
Ed Tosti
 
 
]2013 Copyright Edward J Tosti

Thanks guys. Here is my story in pictures of how I built up Montagu hawse timbers. If you have any question please ask. To give one some ideal, the were attach to each other and also to the first cant frame and knight head and then as a assembly was taken off of her stem and sanded down to shape, on the outside and inside. Made it a whole lot easier  when it came to sanding the inside, thats for sure. Gary