Ontario Whitehall Rowboat Project Online Builders' Manual

 

SECTION ONE: PREPARATIONS

CHAPTER 2

the STATION MOLDS


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Think of the STATION MOLDS as solid cross sections of the finished craft.

Generally,they will be centered 12” apart; this is a good spacing for woodstrip-epoxy construction.

 

 There are two ways of obtaining your STATION MOLDS:

(1) MAKE YOUR OWN:

 

If you have a copy of CANOECRAFT by Ted Moores, which will be most helpful in this section, refer to pages 93-96. In that section, Ted describes just how to layout the pattern sheets and how to trace and cut out the molds.

 

You can use plywood (not very dependable as the edges may have voids which will be a problem when attaching strips) or, you can use high density particle board (5/8” thick will be fine). MDF products looked promising but the staples going through the strips in a straight line causes the edges to split so staples hold poorly. 

 

 

4 1/2 sheets (standard 4' x 8') of material are required

for all the station molds and supports.

 

Look at your PLANS PACKAGE and focus on sheets 2, 3, 4 and 5.

All the station molds and support pieces will be found on these sheets.

 

If you are cutting the molds yourself, get the best layout possible. IT IS IMPORTANT TO MAKE USE OF THE FACTORY SAWN EDGES. The ‘straight’ 16 inch base of each mold (the part which will sit on the strongback) should be a factory edge.

 

BEFORE CUTTING OUT THE MOLDS, BE SURE TO DRAW ON THE VERTICAL MIDLINES, THE FOUR INCH REFERENCE LINES, THE FLOORS LINES, THE KEELSON NOTCHES AND CLAMPING HOLES.

(these features are indicated on the plans sheets).

 

Once the molds and supports have been traced out, it is time to cut them out. A hand held jigsaw does not cut a very good line. If a jigsaw is the only option, have some new fine cutting blades (10 teeth per inch), and, cut a bit wide of the line so there will be enough material to sand down to the line.

 

If you are using a band saw, start with a new, sharp blade which should not be more than 3/8" wide. If your saw does not have a broad extension table, be sure to get a helper to support the material—those centre stations are big, heavy and awkward. Leave a little material beyond the line for final sanding to the line.

 

A cautionary note: the tabs and slots (visible in the images further in this section) are only on the CNC machine cut sets of molds. THEY ARE NOT SHOWN ON YOUR PLANS SET. It would be a difficult task to cut these accurately by hand. The tabs and slots are found only on the bow and transom assembly parts.

 

Instead, these pieces (those you cut out yourself) will be connected with hardwood butt blocks about one inch square which join adjacent mold elements such that parts can be screwed to these butt blocks thus creating a secure join. The process is explained below.

 

All the images shown are from a set of CNC cut molds as these have proven to be more accurate than those cut by hand and simply easier to produce.

 

or, (2) PURCHASE A SET OF C.N.C. MOLDS:  

 

 

If you click on the  multi-coloured “K” link, it will take you to the KITS SECTION where more information relating to purchase and shipping can be located.

CNC set of WHITEHALL station molds actually being produced.
                  

C(omputerized) N(umerical) C(ontrol)  machines have the ability to make very accurate cuts, over and over, and don’t take holidays or need a coffee break.

As part of the process of designing and drawing this watercraft, Steve Killing provided the correct computer format files which these C.N.C. machines require to have them cut the parts.

The C.N.C. machine-in addition to cutting out the external shape- also does the following:

- inscribes the station number on each mold, inscribes the very important vertical midline, inscribes the 4” waterline used as a reference, inscribes the floors line (these pieces are made later to hold the floor boards), cuts out a keelson clamping hole, cuts out the keelson notch on top of each mold, and, cuts out the tab and slot features in the transom and stem parts.

One of the four sheets with parts cut into the 4 x 8 panel.

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ATTACHING THE MOLDS TO THE STRONGBACK

This is the point at which it may be well worth the time to sit back and carefully review the first sheet of the plans set (in particular, the lower drawing).

That which is coloured in BLUE is the virtual WHITEHALL.

That which is drawn in BLACK is the focus at this point.

All the BLACK lines are part of the strongback and station molds combination and it these lines which are important for this chapter.

 

PROCEEDING in a STEP-BY-STEP FASHION

The 'line' on the strongback was computer generated and is wider than a pen line so as to show on this image.

This same image is repeated further down so scrolling will be easier in this lengthy part.

 

This IS the time to be certain of the physical location of the strongback. Ensure that there is sufficient ‘butt’ room and that putting things away in the garage or taking things out will NOT force you to move this unit. It stays in place until the hull is built and fibreglassed.

If there is some chance that the kids will bump the strongback, the addition of some sandbags or weights or barriers would be a good move.

 

 

Use a freshly sharpened pencil to blacken the V-shaped inscribed lines on the molds (assuming you purchased a set) and draw a line across the top of each mold right on the midline. This line will be in the keelson notch and will be a great help when lining up the molds.

Next, a series of important lines will be drawn on the TOP PLATE of the strongback.

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The midline is the significant line at this point. Start at the transom end. Make a mark 8 inches in from the edge of the top plate. At the bow end, make a similar mark but begin about 25 inches inward from the end, avoiding the tapered area.

 

It is important from now on to keep in mind that everything done with the molds and the actual boat will involve working outward from a centre line.

Forget about the edges of the top plate; they no longer play a role.

 

In order to make a straight centre midline, find 2 small finishing nails and some black FISHING LINE (heavy duty stuff which will be used several times when building).

 

Partly hammer in the nails at the 8" marks. Stretch the fish line along the top of the strongback and secure at the two nails; there should be lots of tension along the fishline. Avoid using a chalk line; these make a shaky, wide line which will not provide the accuracy required for this task.

 

 

This principal central line will be the foundation line from which all other lines will take their reference.

For example, the vertical midline on the station molds will align along this featured line as the molds go into place.

 

In order to get a pen line directly under the fish line, use an index finger to slightly roll the fish line away, then, with your writing hand, make a pen mark.

Release the fish line—if it is not directly over your pen mark, do this again in a different place. It takes a few tries to get this right. Do this in 4 or 5 locations along the fish line. Remove the fish line and use a good steel ruler or straight edge at least 30 inches long to connect the marks making a permanent straight line down the centre of the strongback. (This is when the white painted surface is appreciated).

Reattach the fish line to the nails to confirm that you have a good and accurate line. Remove the line and nails; but, don’t put the line in the fishing tackle box as it will be needed shortly to align the molds. Be sure the line extends from end to end; use a small square to drop this centre line over the ends onto the edge of the top plate.

The 'line' on the strongback was computer generated and is wider than a pen line so as to show on this image.

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Next, layout the location of the CROSS BLOCKS which will hold the station molds in place.

 

The process starts at the transom end which should be double checked to ensure that it is a square cut and exactly perpendicular to the long midline. Otherwise, once building commences, the transom would not be aligned.

 

Use a steel ruler and not a tape measure.

 

Commencing at the transom end, measure and mark (on the midline) a point 13 5/8”. Then, in succession, from that first mark, measure and mark 13 positions exactly 12 inches apart. The final mark will be just before the start of the taper at the bow end.

It will help if you look at page one of the plans and turn the sheet upside down with a focus on the black lines.

 

 Use a good steel square to make lines PERPENDICULAR to the midline at each of the positions just measured out. DO NOT use the edge of the plywood. Rather, set the long edge of the square on the midline, and square off that. You will need to flip the square over to complete the other side. After this step, you will have a series of lines running from side to side and perpendicular to the midline.

 

The lines seen on the image below were computer generated and are much too wide for real use-this was done to show the layout.

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Next, it is time to prepare the cross blocks.

The ideal size for the CROSS BLOCKS would be 2 inches square. Get as close as you can to this. A soft wood, free of knots, perhaps cedar,pine or spruce, would be adequate.

 

The emphasis is on the' SQUARE 'part. You need to be certain that the block is sitting squarely on the strongback; otherwise, the molds will not be perpendicular to the strongback. You need to make 15 pieces at 16” long.

 

To make less work later, it would be advantageous to predrill holes in the cross blocks. These are centered on what will be the top face and 2 inches in from each end. Drill a 5/32" hole (which is slightly oversized) and do a countersink to hide the screw heads.

 

 

Examine the black lines on the lower drawing of the plans sheet #1.

Be comfortable with recognizing the strongback top plate and the cross blocks (little squares with an “x” inside).

This is important. The location of each cross block is integral to getting the molds placed properly. Observe that the cross blocks are placed such that the molds are not always on the same side of a line. Look at the transom end and the last two cross blocks. Here, the cross blocks face each other.

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  Take time to place the cross blocks according to the drawing on sheet #1.

 

A series of C-clamps is used to hold the blocks on the correct side of the cross block lines. The predrilled holes will be on top. Use a 1/8” drill to make a small starter hole in the plywood top plate by going through the holes drilled through the cross block.

Secure with a 2 1/2" #6 drywall screw. Do not glue these down in case you make an error in placement and need to reposition. Or, if you plan to make several boats, the station blocks may become like Swiss cheese and may need to be replaced in the future.

 

This view is from the transom end. The 16" cross blocks are attached at all the lines from Station 15 (near the transom end) to Station 2 near the bow end. Take the final unused cross block and cut out 2 pieces 4” long.

Shortly, these will be used to hold the two half molds which form station 1.

Use a square to draw a line on the TOP of each cross block which is directly over the long midline. Also, drop vertical lines at this mid position on both sides of the cross blocks.

 

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ATTACHING the STATION MOLDS to the CROSS BLOCKS

 

To begin this process, check that you have the three parts which make up the transom end and the four parts which will form the bow end.

Once assembled, the two ends will act as anchors which will help to align all the other station molds.

 

At the stern end, begin with the TRANSOM ASSEMBLY.

The next photo shows what the three pieces look like when connected.

 

These three pieces were CNC cut and have tabs and slots for quick assembly. You can clearly see station mold #15 which George is attaching to the vertical support piece with a series of 2" #6 drywall screws.

Closest to the end of the strongback is the vertical support (it has the 3 clamping holes down near the strongback) shown on the plans as the TRANSOM MOLD; this piece is straddling the midline.

The angled shelf (shown on the plans as the TRANSOM MOLD SHELF is also visible). You will note that this shelf is sloped; this feature assures that the transom will be sloped as well-all part of the design of the Whitehall.

The  two transom support pieces are shown on the plans on sheet # 5. They have interlocking slots.  The small one inch ‘lip’ which juts out near the middle clamping hole is the place where the real transom will rest as you commence construction.

 

This transom end assembly is designed to hold the transom in its correct position while the wood strips are being added to the hull with a permanent attachment to the transom. Thus, the transom acts as a station mold but it remains as part of the finished craft.

 

If you have made your own molds, you will need to cut some small hardwood BUTT BLOCKS which will be one inch square and will be of various lengths from 6 to 12 inches. These butt blocks get screwed and glued to one surface of the transom supports so that another part can be attached by drilling and screwing through. In the end, the use of butt blocks accomplishes the task of assembling the transom parts just as effectively as the tab and slot CNC parts.

 

 

The grey coloured item at the back of the strongback is a template used to cut out actual transoms; it was set in place simply to show how the real transom will fit with the support pieces.

 

There is a vertical midline on station mold #15 (and all the other molds as well) either CNC inscribed or drawn by you. There is a matching midline drawn on the cross block for station 15.

Align these two and clamp temporarily with two small C-clamps as shown below.

In this photo, George is checking that the vertical midline of station mold #15 is indeed vertical.

If necessary, use thin cardboard shims under the edge of mold #15 to get this line correctly vertical. (Three of the four tabs on this CNC set are seen protruding through their respective slots).

When you have all the transom assembled and aligned, drill two 1/8" holes about 1 1/2" from the ends through the base of station #15 and a small way into cross block #15 and drive in two drywall screws (#6 x 2"). Remove the clamps.

 

When you start construction of the hull, you will have to ‘wrestle’ with some of the strips because there will be torquing forces involved as the strips follow the mold shapes. To avoid the chance of the transom assembly being moved out of line by the twisting forces, this next photo shows the two corner blocks and end stop blocks.

 

They are coloured red so they would stand out. The corner triangles MUST have a square corner.

 

Start with a 4” square piece of hardwood or plywood then split on a diagonal to produce the two triangles with 90 degree corners. Check with a square that the parts are indeed square then predrill  holes (1/8”) through the vertical transom support and glue and screw the corner blocks with #6 x 2 inch drywall screws. These corner triangles are offset by several inches. The two end stops are 4" pieces of leftover butt blocks. Drill and screw these to the top plate of the strongback.

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Next, the other anchor section, that being the BOW END, is put together.

 

This unit is composed of the bow stem, station ONE (in two halves) and station TWO. This procedure is much like that of the transom end. You will commence by clamping station mold #2 to the correct side (see plans) of its cross block and using a level to ensure the midline is plumb (vertical).

 

With the tabs and slots on the CNC parts, the stem mold is tapped into place into station 2. Otherwise, use butt blocks to connect these parts.

At this time, make more corner blocks – two will be 4” (same as at transom) and two will be 2” square to start then split on the diagonal.

 

As was done at the stern, position these with glue and screws to ensure that the stem station and stations 1 and 2 are perpendicular to each other.

 

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Station ONE is composed of two half sections.

They have been reduced in overall width (refer to the plans-sheet #2) by a total of 5/8” which is the thickness of the mold station. If you had elected to use a thicker material, an adjustment would have to be made. The CNC cut molds have small tabs and slots (see photo) which have to be tapped into place. Otherwise, use butt blocks to assemble these parts.

 

(NOTE:in the background one can see a bending jig on which a pair of stems is being made for this WHITEHALL. The bending jig is identical in shape to the stem station mold and extends aft to station 3; it is a wider and heavier reusable fixture. This allows for the continuous production of stem sets. If you are making your own steam bent stem set, you will be using the actual stem station-more on this in the next section.)

 

 

 

 The bow end structure is now complete.

And,as was done at the transom end, make four corner triangles (here shown in red) and attach as before. This will keep the bow stem from being pulled when strips are added.

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In order to get all the remaining molds in place and nicely centered, make two alignment blocks -used temporarily-which will have the black fish line stretched between them.

Find two clean pieces of planed hardwood ¾" thick 2" wide and 6" tall. Since the molds are 5/8" thick, the centre would be half of that thickness or 5/16". Take time making the cutout so the piece has a constant thickness.

 

These two alignment blocks are clamped to the bow stem and the vertical transom support; the same black fish line used to make the midline on the strongback is now stretched tightly and clamped to the alignment blocks.

 

THIS STRETCHED FISHLINE IS EXACTLY IN LINE -ONLY UP HIGHER- WITH THE MIDLINE DRAWN BELOW ON THE STRONGBACK.

 

Stand up on something sturdy to sight straight down; if everything has worked out, the fish line should be about 26” above the strongback and directly over the midline drawn on the top plate.

 

Locate station mold number NINE and place it on the bow side of its cross block (refer to the BLACK lines on the lower drawing of plans sheet #1).

Use two small C-clamps to hold it in place; be sure that the vertical midline of the mold is centered on the midline of the cross block. Standing again on a sturdy box, sight down toward the strongback. In a perfect world, the strongback midline and the stretched fish line and the vertical midline of the mold should all be in alignment.

Use your spirit level to ensure that the vertical midline of the mold is indeed plumb. When all is acceptable, drill two holes about 1 1/2" in from the edges, (1/8" bit) through the mold and into the cross block and then drive in two  2" x  #6 drywall screws. Remove the clamps. With a large station such as the one just installed, the top will feel shaky and loose. That problem will be solved once all the molds are in place.

Remove the clamps and this station mold is now in place.

The remaining stations go into their respective places in the same manner. Constantly check your plans sheet #1 to be sure the molds are on the correct side of their cross blocks.

 

The next few photos show the progress of the remaining molds going into place.

In the image below, the black line was computer generated to simulate the black fish line. It should run straight along the midlines drawn on the molds.

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In the very near future, the building process will involve the use of glue. To prevent the strips from being stuck to any mold, use a block of paraffin wax and generously rub the mold edges to create a barrier which will prevent strips from sticking to any mold.

The real fish line IS visible just above the block of wax.

The second last task in this section involves the addition of small 2" x 2" squares of ¾" thick plywood to the sheerline edge of each mold.

 

These small corners are screwed to the molds with 1" x #6 drywall screws) BUT are recessed in toward the midline by a mere ¼". On stations 9 through 15, the corners go on the AFT side of each mold (both sides for sure); for stations 2 through 8 they go on the BOW end side of the molds.

The purpose of these blocks is to be sacrificial.

When building starts, the first strip (the sheerline strip) will be attached to the molds with screws; the reasoning will be explained in the next section. Unfortunately, the screws will split the 5/8" mold material making it almost useless. The small corners can take the pressure of the screws and, if multiple boats were to be built, can be easily changed.

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The final task in the setting up the station molds is to add on four temporary stabilizer strips.

These can be almost any piece of wood measuring about ¼" x ¾" (almost the same as the strips used to make the hull).

In the photos, the strips are full length but a series of pieces 4 or 5 feet long would work. The stabilizer strips serve to hold the station molds in a vertical (i.e. perpendicular to strongback) position until some rows of boat strips have been attached.

Pat is holding a 24" spirit level against the face of the mold ensuring it is vertical; George uses small finishing nails to secure the stabilizer strip to the mold.

Start at either station 2 or 15 and work toward the opposite end.

 

With two stabilizers on each side, the entire mold  structure is ready to be used to build an Ontario Whitehall.


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