The bottom of our Core Sound 17 Mk3 has now been glassed, the keel has been added, the mast staves have been scarfed and the birdsmouths cut. It's been a busy couple of weeks!

 

With the boat now upside down, the first order of business was to user the router to cut the slot for the centreboard. The router rested on an angled jig so that the flush trim bit was cutting parallel to the sides of the centreboard case. Once the slot was cut, I removed the spacers that had been taped inside the case to keep it at the correct width while being glued in place.

I rounded the edges slightly using the router, and then finished with sandpaper.

I checked to make sure that the centreboard fits. Yes, it does 😀

The chine edges were chamfered, using a plane, and then the filled holes were sanded flat. The chine edges were then rounded using an 80 grit sandpaper. The dust and grit was vaccumed out of the holes, getting them ready to be filled.

The transom was also chamfered and then sanded round.

The holes were coated with unthickened epoxy first, and then filled with thickened epoxy.

The next morning was spent sanding the filled holes, with the random orbital sander, and with sheets of sandpaper.

The centreline was marked to 10mm from each side, and planed and sanded to accept the keel batten that will be glued and screwed in place once the fibreglass cloth covers the hull.

You can get a pretty good idea of how well you're progressing by looking at the glue lines you are planing down through.

Once the base for the keel batten had been planed, I cleaned it up with the orbital sander, and then by hand.

The fibreglass cloth was draped over one side of the boat, covering the sheer strake join up to the centreline.

Initially the cloth was held in place with masking tape, but once we started pouring epoxy this was no longer necessary.

Jim, another Wooden Boat Association member, mixed epoxy, and poured it along the cloth, while I spread it with a spatula.

We started in the middle of the boat and worked toward the stern, covering the bottom chine first.

When I started on the side, Jim poured epoxy along the edged of the bottom chine, and I scraped it over the edge with the spatula.

By starting in the middle of the boat I was able to stretch out the cloth and work out any wrinkles as it was glued to the hull.

The cloth was cut to the corner of the chine and transom join, folded over, and epoxy was applied to the edges using a brush.

I like using a spatula to spread epoxy over fibreglass cloth, as it lets you fill the weave but doesn't let you leave too much epoxy anywhere.

The cloth was epoxied to the sheer strake, finishing it with a brush.

Even being as careful as possible, there was quite a lot of epoxy dripping onto the floor, so the plastic sheeting was essential.

I used one of the pieces of cloth cut off the end to cover the section of the transom where the ladder will be fitted, to strenghten it.

The excess cloth was trimmed with a Stanley knife, and the edges were pushed back down with a brush.

Before applying the second epoxy coat to the hull, I cut the fibreglass cloth off the inlet and outlet holes for the water ballast tank.

Epoxy was poured onto the hull and scraped over the fibreglass with a spatula to fill the weave.

I poured epoxy over the top edge of the side chine and then quickly wiped it with the spatula to spread it across the surface. as it ran down.

After spreading the epoxy with the spatula, I brushed the chines to prevent any runs.

Before the next coat I checked for any lumps, and sanded them down.

Each coat used less epoxy than the one before it, as the surface became smoother.

The epoxy also seemed to run more quickly, so I had to work faster as well. Brushing to prevent runs had to be done after each coat.

I paid particular attention to the centreboard slot, making sure that the edges were well coated with epoxy.

The epoxy is definitely spreading further by the time I get to four coats.

The excess epoxy was either spread further along the hull, or scraped into the pot and poured onto the hull further along. The spatula could also be used as a shovel, to remove the excess epoxy.

The aim was to cover the surface with epoxy, without leaving enough excess to cause runs.

The more vertical surfaces were certainly challenging, and spills were inevitable, making plastic drop sheets an absolute necessity.

The sheer strake was coated using a roller, as this was much less messy when working the negative angle!

Some of the Hoop Pine offcuts from the masts were trimmed down for the laminations I will use for the keel strip. I taped the strips of Hoop Pine together for the keel strip, and then planed a 20 cm taper into the stern end. The forward end of the keel strip needed a longer taper, so I marked it on the side of the lamination and cut off as much of each laminate as possible before planing the rest to a smooth taper. After checking that everything looked right on the boat, I laid the first strip of 3mm 316 Stainless Steel on top of the lamination, and then cut another piece to complete the length.

I bent the short strip at the stern to match the taper in the lamination.

I marked where I wanted screw holes along the length of the steel strip, and then used my portable drill press to cut them. I used some small blocks to make a jig to hold the steel in the right position for drilling. The holes were finished with a countersink bit, so that the screw heads will be flush. The steel strip was taped to the laminations and then placed on the hull, centering it at the bow and stern. The steel strip stopped the wood from flexing. I drilled and screwed the stern and bow ends first, made sure that it saw straight, and then drilled and screwed the rest of the keel strip. Once the dry fitting was complete I removed the screws and took the keel strip off the hull.

Before gluing the keep strip to the hull, I sanded along the centreline to make sure there would be a good mechanical bond.

The laminations for the keel strip were laid side by side and coated with unthickened epoxy. The lower three strips were turned over and also coated. The top wooden strip wasn't coated on the upper surface, as the stainless steel strip will be removed once the epoxy has cured. Thickened epoxy was spread on the upper side of the three lower strips, and then the strips were pressed together. I had marked the side of each strip, showing where the screw holes were. This helped to align the strips properly. The stainless steel strips were covered with tape so that the epoxy wouldn't stick to them when they were screwed to the top of the assembled keel strip. The stainless steel strip ensured that the keel strip would remain straight, and I could also apply pressure to the top to prevent any gaps in the laminations.

Thickened epoxy was squeezed along the centreline, piping it out of a sandwich bag with a corner cut off. The laminated keel strip was carefully lifted into place, and then screwed down fore and aft. The screws fit perfectly into their predrilled holes Once the keel strip was locked in place fore and aft I screwed the strip in all along the centreline. The excess epoxy, the "squeeze out", was scraped off with a spatula. The keel strip was then weighted down with bricks, to make sure there was good contact between each lamination, and also with the hull.

I cut the scarf joints on the first of the masts. The best timber I could get was only 4200mm, and the masts are 5715mm, so they have to be scarfed. A jig held the stave tightly in place, and the handheld circular saw made the required 8:1 cut, sliding diagonally on the top of the jig. A clamp was used to stop the stave from moving while it was being cut. Scarf joints should be staggered around the mast, so the diagonal join in each stave starts where the join in the previous stave finished. Once the first stave was cut to length, there was no need to measure the length of the other staves. It was just a matter of starting the cut at the bottom of the scarf joint in the previous stave, and then matching the overall length of the other staves.

The scarf joints for the second mast were cut today. It was the same process as yesterday, perhaps just a little bit faster.

After cutting the scarf joints for the mast, I removed the temporary screws in the keel strip. Because the screws went through several layers of epoxy as it cured, I had to heat the screws for much longer in order to remove them. The tape on the stainless steel worked perfectly, and the steel rubbing strip lifted off without any trouble. I sanded and rasped the epoxy off the top of the keel strip. In the coming days I will apply a fillet to both sides of the keel strip, and fill the screw holes with epoxy. The keel strip and adjacent plywood was sanded and vacuumed prior to applying a fillet along the length of the keel. The screw holes in the keel strip were covered with unthickened epoxy. This will slump into the holes, coating the sides, but not filling them. These screw holes will be reused, to fit the stainless steel strip. The keel and adjacent ply was coated with unthickened epoxy, prior to adding the fillet. The first part of the fillet was piped along the keel, and then shaped with a curved spatula. The epoxy pushed off to the sides was scraped off and reused further along.

The first set of mast staves were scarfed today. I set up a jig the let me glue up all 8 staves at the same time. Both edges of the scarf joint were first coated in unthickened epoxy, to prevent starvation. Then one edge was coated with thickened epoxy and pushed against the other part of the stave in the jig that aligned each piece properly. The jig has gaps the width of the staves, so the two pieces can butt up against each other, but can't go any further, giving a smooth match. The spacers are coated with tape, to stop the staves from adhering to them if any epoxy seeps into the gap between the stave and the spacers. Squeezed out epoxy is scraped off the top of the staves, and then spacers covered in tape are placed on top of each stave. Strips of timber rest on these spacers, and weights are added, forcing the two parts of each stave to align with each other.

A second, thicker, fillet is applied along the keel. The first fillet has cured enough to let me add the second fillet with no slumping. The thicker fillet will support the keel stip, which is not covered with fibreglass cloth as it is intended to be sacrificial.

The keel and fillets have to be covered with three coats of unthickened epoxy, so I sanded the fillets smooth first. Rolled up sandpaper works well for inside corners, but for most of the keel I wrapped the sandpaper around a piece of PVC tubing.

I used up some of my dwindling supply of fast hardener in the epoxy so that I could easily add two coats to the keel today.

While the first coat of epoxy was curing on the keel I took the first set of mast strakes out of my jig. The jig worked suprisingly well! None of the strakes were glued to the spacers, and the joins all look good. The strakes for the second mast were fitted into the jig. The 2 pieces for each strake were pushed against the spacers, and the spacers were screwed into place. The edges were coated in unthickened epoxy, and then one of each pair was fitted into the jig. Thickened epoxy was spread along the joint of the second half of each stave, and it was then placed in the jig and pushed against the first half of the stave. Squeezed out epoxy was scraped off the top of the join and reused for the other staves. Spacers were placed over the top of each scarf joint, and weights were added to make sure that each join stayed true as the glue dried.

The keel was coated with a second layer of epoxy with fast hardened. Screw holes along the keel had another drop of epoxy added, to make sure that they are well coated.

A third coat of epoxy was brushed over the keel strip and fillets, with final drops added to the screw holes along the keel.

The staves for the second mast were released from the jig. The masking tape and gaffer tape along the spacers separating each of the staves worked well, stopping the staves from gluing to them. The surface epoxy was sanded off each of the mast staves. I then used a belt sander to remove the surface epoxy from the glued-up internal mast sleeves, before they were cut to 122cm.

I made a jig that held the mast staves, so that when it passed through the saw blade it would cut the correct taper from the top down to 183cm from the bottom of the mast. Measurements for the taper was marked onto 3mm ply and a line drawn to connect all of the points. A fence was then screwed onto the plywood, following the taper. When the jig was finished, staves were taped to the fence. When the jig was passed through the saw bench it cut the top of the stave to 18mm and gradually tapered down to removing nothing at 183cm from the bottom of the stave. Unfortunately, I didn't record the jig in use. It did work extremely well, producing consistent tapers on each stave.

When I checked the clearance of the centreboard in the case I found it was a little loose, so I've added a layer of fibreglass cloth to increase the thickness at the top of the board.

Before cutting the birdsmouths in the mast staves I ran a test piece through the sawbench, and noted the height of the blade and the offset of the fence. The fence was then reversed and the second cut was made to complete the birdsmouth, again noting the blade height and fence offset. Once I was happy with the dimensions of the birdsmouth it was time to cut it into the staves. To keep it simple, I made the first cut into all 16 staves. The timber finger, bolted to a spring clamp, has enough force to keep the stave down onto the saw blade When all 16 staves had been passed through the saw bench, I reversed the fence and made the second cut, to complete the birdsmouth.

The birdsmouths were cleaned up, if needed, with a plane and a fine chisel. The staves were then dry fitted to form the masts as a test. I won't be glueing them up this week, as the Melbourne Boat Show will be occupying my time.

The centreboard was still a bit loose in the case, so I added a layer of fibreglass cloth on the other side of the centreboard as well.

After a bit of trimming the internal sleeves for the lower sections of the masts fit well. When the masts are glued up the internal sleeves will be slid up into the bottom of the masts.

I cut some plywood into the panels that will support the masts when they are being glued. I marked the centrelines on each panel first. I then marked the centre of the support lines for both masts. When these panels are mounted on the work benches and horses I will use stringlines to get everything straight and level. I measured distances along the masts and the diameters at those distances, and marked these details on the support panels. Using my old secondary school technical drawing compass, I scribed the lines that will support the masts at that point along the length. For the intervening distances along the mast I used calipers to determine the width of the mast at that point. Taking the measurements from the calipers, I used the compass to scribe the half circles to cut in the plywood to support the masts when gluing them up. Before heading up to the Melbourne Boat Show, I cut out the slots for the masts to rest in while gluing them up.

I cut templates that I can use to check for shape and size of the mast profile at different distances along the mast. Where I didn't have a hole cutting blade the right size I scribed the correct diameter with my compass and then cut as close as possible to it, finishing to the correct size with jigsaw and rasp. I will be able to slide these over the mast to the appropriate distance from the top, to see how much more material has to be removed, and how close I am to round.

I decided to turn the slots in the mast supports into rectangles so that the masts would properly sit in them before the edges had been planed and sanded. The slots are still the same height and width. It's just the corners that have been removed. I'm using two slots in each panel so that both masts can be worked on. I will probably only plane and sand one at a time, but they will both be glued up at the same time. I've made six support panels so that the masts don't flex between each station when being glued.