Chapter 6: Spars

The yawl-rigged Navigator has a total of 7 spars. Two masts, two booms, a gaff, bowsprit and boomkin. I decided to make the two masts hollow using the birdsmouth technique. By enlarging the diameter of the mast by 10% and making the mast hollow, the mast ends up being the same strength as a solid mast, but as much as 40% lighter. It is not difficult to do but it requires a table saw and lots of epoxy. The technique is described in several articles at duckwork.com, for example here.

Ripping the strips, scarfing them to length, and cutting the birdsmouth notches was all straightforward.

Featherboards are a must. The tricky bit was the taper. Both masts are larger in diameter at the base than at the top. The mainmast is a constant diameter for roughly the bottom half with the top half tapered. That means that each one of the staves has to be tapered. In other words, the area shown in yellow below has to be removed.

How do you cut a taper that's nearly 10 feet long by a fraction of an inch deep? Thoughts of sophisticated jigs came to mind, but were not appealing. Planing them by hand might work, but seemed difficult to do with any accuracy. Simply drawing a straight line of that length seemed difficult. I pondered this for quite some time then it finally hit me. If I had a long straight edge that I could clamp to the stave, I could trim off the yellow area with a router equipped with a flush trim bit. And what better straight edge than a nice new sheet of plywood?

So I clamped the stave to the edge of a sheet of plywood. At one end (the start of the taper, near the middle of the mast, lower right corner in the photo below) the stave was flush with the plywood straight edge. At the end (end of the taper, top of the mast, upper left in the photo below) the stave protruded above the plywood straight edge by the desired amount to remove. At the midpoint of the taper, it protruded half way up. I securely clamped it in place using many clamps. Like so:

Then I proceeded to trim off the excess with the router. I had to remove and replace the clamps one by one as I went along, but it worked great, and it was quick and easy. And since I was using a sheet of plywood that I bought but hadn't used yet, it cost nothing.

After the staves were cut and tapered, the next step is to glue them up.  This step consumed a lot more epoxy than I thought it would, and required a lot more clamps than I thought. I thought I could just use wire ties, but they do not have sufficient clamping force. The best thing seemed to be hose clamps, but I only had a dozen or so of them. I ended up throwing every assorted clamp I could find at it. This photo was taken after I had removed all the clamps except the wire ties.

At the top, bottom, deck level, and anywhere that a fastener goes through the mast, the mast must have a solid core to prevent the mast from crushing. Prior to gluing up the mast, I inserted octagonal plugs at these locations.

After the epoxy cures, the next step is to round the mast, which involves simply knocking off the corners with a hand plane.

After getting the mast as close to round as possible with the hand plane, the next step is to sand it round. This can be done numerous ways: by hand, with a belt sander belt & drill, various sanding jigs and so on.
I tried several of those methods and found them all to be too time consuming and laborious.

Again, time to ponder. If only I could spin the mast, like on a lathe, then I could easily sand it. But how?
Enter: The redneck Shopsmith lathe!

Disclaimer: While this worked for me, it is dangerous. But not this dangerous. Just because I'm stupid enough to do this doesn't mean you should be.  If you attempt this you are risking serious injury. If your mast flies out and kills you, don't come crying to me, cause I warned you.

To attach the base of the mast to the Shopsmith, I did this:

The base of the mast was cut square, which I inserted into a square hole, attached to a wood disk, attached to a lathe faceplate, attached to the shopsmith.

At the other end, I inserted a lag bolt into the top of the mast, which went through a hole in a piece of oak, which was securely clamped into a bench vise.

Then, making sure the speed was set to the slowest possible speed on the Shopsmith, I turned it on. As the RPM's increased, the mast started to wobble in the middle, but I found that if I loosely held it there with my hand, it would spin with little or no wobble. So with one hand holding the middle, and the other hand holding some sandpaper, I proceeded to sand the entire mast. The sandpaper would heat up quickly so I had to make frequent pauses, but I was able to sand the entire mast completely round in about 10 to 15 minutes.

Chapter 5: Hatches

The area between bulkheads 1 and 2 is a dry locker, accessible through two removable hatches located in bulkhead 2 right above the front seat. This dry locker also doubles as an air chamber for flotation, so the hatches need to be as watertight as possible. My goal was to make the hatch covers as large as possible and to develop a latch that would secure the hatch covers tightly but still enable them to be removed easily. This is what I came up with:

The hatch openings each measure 420 x 265, which is big enough to stick your head and an arm through.
The hatch covers were made from the pieces cut out to make the access hole, with a 40mm frame piece glued on. The forward face of this frame will have a rubber seal made of weatherstripping applied.

The latch handles were made from scraps of mahogany with a bolt imbedded. The latch is made of pieces of oak with the center tapped for the bolt. Screwing the handles clockwise latches and tightens down the hatch cover for a watertight seal. Screwing them counterclockwise until they completely loosen allows removal of the hatch cover. Stop blocks attached to the bulkhead control when the latches stop. The latches remain attached to the hatch cover and they can be easily replaced when worn out.

Chapter 4: The Transom

Not much to say about the transom. I sorted through my sheets of mahogany plywood and selected the one that had the most interesting grain pattern.

I decided to add an outboard motor mount to my transom. I purchased a removable mount from duckworks.
I reinforced the transom by filling in the area above the starboard seat with 20mm mahogany.

Chapter 3: The rudder

Next I made the rudder. Making the rudder is very similar to making the centerboard.
First, I sorted through my stack of recycled mahogany and selected the lightest and darkest pieces. I ripped them into strips and alternated colors and grain direction to make the blank.

Then I ran the blank through the Wagner Safe-T-Planer to flatten it.
Next I drew the profile from the plans directly onto the blank. I decided to leave the trailing edge straight because the striped mahagony seemed to look better that way. Then I airfoiled the blank with the safe-t-planer like I did the centerboard, except for the fiddly bits around the uphaul and the flat area at the top. For those, I switched from the safe-t-planer to a router bit in the drill press.

Finally I bandsawed out the profile and applied a coat of varnish. I still need to finish adding more coats of varnish.

Chapter 2: The Centerboard

Next, I decided to tackle the centerboard. I found an excellent guide on building centerboards and rudders on the web here:



I tried my best to follow it closely. First I ripped strips of clear Alaskan yellow cedar.

Laminated them making sure to alternate the grain direction to prevent warping.

Because Alaskan yellow cedar is fairly soft, I used mahogany on the leading and trailing edges of the board for extra strength.

I don't have a thickness planer, but I use a device called a Wagner Safe-T-Planer that works very well. It fits into a drill press and it's kinda like a 2 3/4" wide router bit. Here is a youtube video showing how it works:

I mounted the planer in the Shopsmith and wheeled the Shopsmith over my workbench. I mounted the centerboard blank on wheels and rolled it around under the planer until it was flat. Then flipped it over to do the other side. After checking it with a micrometer I was amazed at how flat it turned out.

To do the airfoil portion, I made a paper template of the airfoil shape and glued it to the bottom end of the blank.

Then I mounted the blank back on the wheels, but this time I tilted the blank so that the cutter was cutting the material outside of the template. I had to hand-carve the blend between the airfoil and the top flat section. I used a forstner bit to hollow out a section to hold the lead, filled it with lead scraps, then topped it off with epoxy & wood flour mix.  Here is the completed centerboard.

Chapter 1, Templates

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The first step in building a Navigator, according to John's plans, is to scarf together two sheets of 9mm plywood to make the bottom panel. Unfortunately I was working in a 1-car garage at the time, with plans to enlarge it later, so space was at a premium. I wanted to work on some of the smaller pieces first, saving the larger bits for later when I had the space to deal with them. So I jumped ahead to step 3, bulkheads. I guess you could say that things already weren't going according to plan!

John's dimensioned plans are drawn at 1/5 scale. I needed a way to get them drawn full sized on the plywood, and I also needed a way to arrange the pieces on the plywood to minimize waste. I decided to draw the bulkhead pieces in a CAD program. This, I thought, would allow me to print out full sized templates and also play around with arranging the parts efficiently.

To make a long story short, this turned out to be more effort than it was worth. When I printed the templates, they didn't print exactly right. There was some distortion in scale that took me a while to sort out. Also, arranging the parts on the plywood on the computer was time consuming and cumbersome.

I eventually got the templates to work.

As for the parts arrangement, I found a far more simple solution: I simply traced the parts from John's plans, onto some tracing paper, cut out the parts with scissors, and arranged them paper-doll style on top of a piece of construction paper sized to 1/5 the size of a real 4x8 sheet of plywood.

Worked great!

I traced the templates, then the bandsaw quickly made a nice stack of bulkhead parts.