Chapter 4: Keel Assembly

Now it is time to start assembling the hull. From now on, it is recommended to print out assembly drawings to check the combination of each part and to check and measure the positional dimensions, so that you can refer to or measure the dimensions according to the description.

The first structural assembly is the keel. Although the keel is called a keel for convenience in accordance with a normal kit, the keel structure of an actual ship is a complex structure consisting of several members joined together before and after, above and below the straight member at the bottom of the hull., which is called the original keel. Refer to the Keel-Deck drawing to see the overall structure.

*As a rule, parts to be used after this will require removal of burnt marks on the cut surface except for designated areas, and at the same time, the cut surface must be finished at right angles. Each part has a pre-defined grinding allowance for shaping according to the thickness of the parts, so that the original dimensions of the part can be obtained by shaping.

The grinding allowance is the minimum required, and the amount is being specified on the drawings in the OffsetData folder. Check by referring them or measuring the cutout dimensions of the part. First, use a right-angle shaping jig or similar tool to get the gist of the grinding process, but be careful not to cut too much. The use of a micro belt sander, which is not affected by the size of the curvature, is also effective for parts with many concave surfaces, such as frame parts.

(1) Main body of keel

The keel body is flat assembled in two dimensions, so we do not use the hull assembly jig yet but assemble it on the assembly diagram (Keel-Deck diagram) pasted on a flat plate.

* Referring to the parts list or layout drawing, locate and detach the next parts.

* Referring to the parts drawing, the keel is fabricated with a notch at the front-most part of K1, and the false keel is cut at the length of each part and then 45-degree shaping of the joint is performed. It is recommended to use the jig shown in [Fig. 2-02].

*Then, grind each part to the degree of right-angle shaping of the end face (to the extent that some burnt marks remain).

*Adhere keel, upper false keel, and lower false keel to each other. The keel and upper false keel should be aligned at the front edge, and the lower false keel should be 1 mm in front of that front edge. When combining several of these parts, it is better to first glue and assemble them individually in a rough-finished state, and then perform finish sanding of the entire assembly to absorb any errors in the combination.

*As you can see, the structure is exceedingly long and narrow, so when gluing and drying, prepare a holding aid to prevent bending or warping [Fig. 4-01]. When the finished keel is aligned with the drawing, the rear end is longer than the drawing. This will be shaped to match the sternpost after it is assembled later, so leave it as it is for the time being. 

*Here, rabbeting is performed on both sides of the keel. The secondary processing from now on will be done with general-purpose tools, assuming that we do not yet have such an environment, although there would be easier to do so if we had electric tools or other tools. Furthermore, as explained in the "Beginner's Course Textbook," the rabbet is formed the entire length of the keel, including the stem section, and its cross-section changes depending on its position [Fig. 4-02], so these would be rather difficult to handle without manual processing. As shown in [Fig. 4-03], a guideline for processing at a specified width is to draw a line on the edge of the part while holding the needle to the edge of the part with a compass with a slightly extended shaft needle, so that a line can be drawn at a constant width regardless of the straight or curved edge. The rabbet width should be 1.0 to 1.2 mm.

(2) Stem-related

Separate the next parts and remove the burnt mark from the required portion. In shaping, care should be taken to ensure a constant degree of mutual adhesion, as curved surfaces are often joined. The combination of each component is shown in [Fig. 4-04].

* Glue STM-H and STM-L. STM-H is flipped over and then joined to STM-L. This allows the scarf area to be left as a tar trace without grinding. Other sanding surfaces are adjusted to the drawing or temporarily assembled on the apron or deadwood. After the gluing is dry, refer to the section on the keel body for the rabbeting process.

* Glue Ap of aprons together. One side is already inverted, so it must be flipped over again and then glued in place, as with the stem. When joining two faces in this manner, the joining surfaces should be sanded with about 400-grit sandpaper in advance to remove surface debris and roughness. When the gluing is dry, taper it so that the top edge is 7.5 mm wide, and the bottom edge is 5 mm wide. Note that the taper should be divided from the center.

* The three deadwood parts should not be glued to each other yet.

* After shaping of each part is completed, the keel body, stem, and deadwood (DWF1) are aligned on the drawing and glued together. Pay particular attention to the position of the red arrow part in [Fig. 4-05]. To prevent the adhesive from sticking to the drawing, work with a clear folder of stationery between the two.

* Glue the apron to the inside surface of the stem by inserting it into the top edge of the deadwood. Be sure to secure the center position and ensure that the taper is equal on both sides.

* DWF2 and DWF3 are assembled after secondary processing as described in section (5).

(3) Sternpost-related

Separate the next parts and remove the burnt mark from the required portion. The combination of each component is shown in [Fig. 4-06].

One of the peculiarities here is that in GRANADO, the center of the transom is sandwiched between the sternpost and inner sternpost. The transom is joined at both ends and the center, but if the center of the transom is glued here, the two ends may not properly contact the cant frame due to the assembly error. Therefore, keep the sternpost and inner sternpost only as their respective sub-assemblies, and assemble them to the keel body a little later in the process. However, check that the mutual positional relationship is accurate on the assembly drawing.

*Glue SP2 and SP3 in sequence on both sides of SP1 of the sternpost.

*Glue ISP2 to both sides of the ISP on the inner sternpost.

*The three deadwood parts should not be glued together yet.

* Only the deadwood DWA1 is glued in place on the keel body. Deadwood is thinner than keel, so when gluing on a flat surface, the center position can be maintained by applying a 1 mm thick wood piece to the back surface.

This state is shown in [Fig. 4-07]. The hog is also seen in the figure, but its assembly will be explained later.

(4) Hog

Above the keel body, between the deadwood at each end is a member called a hog (or rising wood) that holds the lower end of the square frames. This time, instead of the flat shape shown in the assembly drawing, it is cut in the notched shape shown in option 2 of the hog drawing. This allows for almost non-adjustable positioning of individual frames.

* Glue the hog parts Hog1 through Hog3 to the keel body in sequence. The hogs on both sides of the center hog2 are cut inverted, so the front and rear orientations are swapped again to assemble them. The entire piece will fit correctly between the front and rear deadwood, so refer carefully to the assembly drawings and assemble so that the notches are positioned as shown in the drawings throughout the entire piece.

* Make holes to secure the keel to the jig. The state of the keel up to this point is shown in [Fig. 4-08], and the holes are also shown in the fabricated state. Their positions are 125 mm and 297 mm from the front-most edge of the keel, respectively, as shown in the figure (clearly marked on the jig), and they are the center of the double frame that comes to that position. Since the nut is to be embedded here so that it cannot be seen from the outside, the hog is first cut 5.5 mm in length from this position by dividing it into front and rear sections.

* Next, drill a 3.2 mm vertical hole in the center of the keel at this location. When using a manual tool, such as a pin vise, be careful to ensure verticality.

* Embed a hex nut in the area where the hog was cut. 5.5 mm is just the dimension that the flat side will fit into, but the top of the nut will protrude from the width of the keel if it is left as, it is, so file the top of the nut until it is 5 mm wide. When embedded in the notch in this condition, the nut will be pinched around it and will not move, but if there is any rattling, it is recommended to fix it with two-component epoxy adhesive just to be safe [Fig. 4-09].

* From now on, there will be many processes to cut parts and plates into smaller pieces as secondary processing. Conventional small saws have large blade thickness and pitch, which can catch and damage materials. The "Super Fine Cut Saw" introduced here has a blade thickness of 0.1 mm and a blade pitch of 0.3 mm, the smallest level in the industry, and is ideal for precision processing of structural models, etc. [Fig. 4-10]. We highly recommend its use.

The keel is now ready to be set in the jig. To check the fit, the sternpost and inner sternpost are temporarily assembled (dotted with tight bond) and aligned to the jig. Check that the top of both ends of the keel and the keel fixing holes are well in place, and if there is any misalignment, etc., correct the situation accordingly. If the process has been faithfully executed so far, it will fit the jig without the need for modification. Laser cutting is that accurate. Two sets of M3x16mm pan head screws with washers are used to secure the jig.

* Tight bond adhesion can be easily removed by heating the bonded area with a hair dryer or the like, rather than soaking it in water as with ordinary bond. The remaining adhesive can be easily removed with a knife or similar tool while the parts are still warm, so there is no risk of damaging the original shape of the parts.

(5) Secondary processing and assembly of deadwood

The deadwood step, which has not yet been assembled in the process so far, has some interference with the cant frame that will be assembled at an angle to it. This is the part that rises vertically between the steps. It is necessary to make a diagonal cut here at the same angle as the cant frame angle at that location. The processing procedure is the same for both the front and rear sections, so I will use the rear deadwood as an example.

* Mark the even-numbered cant frame angle with an angle gauge or similar tool as shown in [Fig. 4-11]. If a gauge is not available, a template with a protractor or other tool to draw a predetermined angle is applied and processed.

* Roughly cut with a cutter, then finished with sandpaper. Note that the steps on the port and starboard sides are different angle direction from each other.

* Once angled, glue each deadwood step to the designated position on the keel deadwood DWA1 (DWF1 for the front). The positions are clearly indicated on the drawings and must be assembled correctly.

* After gluing, the excess protrusion is done in the shaping process after the cant frame is assembled.

The keel assembly is now complete except for the sternpost. Refer to [Fig. 4-12] for the installation status on the jig. The frames pictured together will be explained in the next.