Birdsmouth mast glued up

I have had the parts for the mast cut out and ready to go for about six months (see <this post>), and this weekend seemed like the right time to assemble them.

I decided to construct a jig to facilitate holding the staves in position while getting them clamped up.  I gathered a couple sawhorses and several other stands and spaced them out along the length of the mast.  I then measured the mast rough diameter at each station and cut out matching profiles from some 1/4" plywood.

I then attached some short pieces of 3/4 plywood recycled from the building jig to each support so that I would have something to attach the profiles to.  Setting up a laser level made it fairly easy to align the supports.  On each one I had drawn a horizontal line and a vertical line, and layed out and cut my semicircles from the intersection of the two.  Having the lines left over on the supports was key to easy alignment.

Here's a shot showing the vertical alignment.

And here you can see the horizontal alignment.  I held the profiles in place with clamps until satisfied with the alignment, then drove a couple screws through to fix them in position.

This setup ensured the jig was straight in both directions, and aligning the center points automatically took into account the taper in the mast, which is not constant along the length.  Here's an overall view with the mast dry-fit in place.

With the jig set up, I next ensured I had the plugs for the ends of the mast ready to go.  The top end is plugged by a simple octagonal stick about 3/4" thick.  The plug at the base of the mast is also octagonal, but protrudes from the end with a square section that will fit into the mast step.  

I cut away the top of the plug so there would not be an abrupt transition from solid to hollow. An abrupt transition can cause failure at that point if the mast is under bending stress.  That won't be the case here, as this is a short plug about 1 foot long, and the mast is supported well above that height at the cabin roof, but I had seen it done elsewhere and thought I may as well do it.

With all the pieces ready, I lined up all the mast staves and clamped them together.  I thought it would be easier to apply the epoxy this way rather than handling each stave individually, and it worked out well.

I first wet them out with unthickened epoxy using a short 1" section of roller.  I did the V side and the back side, then the V side again.  The idea is to let the wood absorb what it can, so that it doesn't suck the epoxy out of the joint during glue-up, leaving a weak spot.

Once the staves and plugs were wet out, I mixed and spread thickened epoxy on the V side. I made a little custom spreading stick by sanding it to a point and filing notcches in the edge.

The notches leave some epoxy behind, so that there is an appropriate amount distributed along the joint.

Holding the stick at an angle allows it to fit the sides of the V.

No photos of the epoxy spreading, as things were just slightly frantic at this stage - I wanted to be sure the epoxy didn't start to cure before I could get it all clamped up.  I was glad to have my wife's help mixing up epoxy.

Once all the staves were spread with epoxy it was back into the jig with them, which made the alignment and fitting together of the joints a snap.

I used hose clamps to pull the staves together, and then applied zip ties to hold them in place, then moved the clamp down and repeated.  I had a number of hose clamps, so a left them in place periodically, rather than unscrewing them all the way to move them past the next support cradle.

The next day I removed the clamps and saw that things were looking pretty good.

I got out my block plane and planed down the projecting corners to make the mast 8-sided.

And then planed the corners to make it 16-sided

And then then 32-sided.  The mast is now a bit smaller than the support jig cutouts and tends to slide.  I moved the end support and raised it up to provide an end-stop.

And then planed the ridges again to be about 64-sided.  It's a bit hard to be sure where you have planed and where you have not at this point.

Lots of neat curls resulted.  Too bad I can't think of a use for these.

Next I'll switch to sandpaper to remove the remaining ridges, then round off the top and apply some finish.  Not sure yet whether I want to put a couple coats epoxy and then varnish, or maybe go with white paint instead.

Seat back tops laminated and installed

Before doing any more painting I next wanted to create and install the tops on the seat backs. This is the last structural part of the boat to be built, so getting this done is a great milestone.

I've been thinking over time how I wanted to handle this part.  Some builders don't have any trim installed in this area, and some builders have fairly wide tops installed, the better to sit on. Because I don't yet know whether I'll want to perch up there much, and don't know where the favored location will be if I do, I decided to just install a medium wide top, as I can always modify that later if I want to.

I decided on a top that is about 3/4" thick and 2" wide.  I laminated this up from four 1/2" strips of pine, which take the bend fairly easily.

I put clear packing tape on the tops of the seats, so that I could laminate the tops in place. It was another glue-up that took most of my clamps.  I used C-clamps to clamp sticks to the seatback on the inner part of the curve, then pulled in the ends with the handscrew clamps.  I used lightweight bar clamps down to the bottom of the seat back to pull the top down to the curve, some small bar clamps with sticks to align the top of the lamination, and some small bar clamps and c-clamps to hold the laminations together.  Quite a conglomeration.

After the epoxy cured I had two tops that were curved just right to fit the seat backs.

I knocked off most of the squeeze out with a scraper, and then a quick trip through the planer had them looking nice.

The next step was to determine the edge profile.  I cut off a bit of the extra length and layed out three different radii on the edges.  My largest roundover bit is 1/2" radius, so I used that on the inner top.  I didn't want the outer edge to be completely rounded over, so used a smaller bit on the bottom edge of that.

The only tricky part to fit was the return at the front of the cockpit.  This has a compound bevel where it meets the cabin side, and it's easy to get too short as you sneak up on the right fit. 

But I got this side just about perfect.  As for the one on the other side, well, that's what thickened epoxy is for...

I primed the bare wood with unthickened epoxy, and then used silica-thickened epoxy to glue down the parts. After the epoxy cured and the clamps were cleared away I was pleased with the way things were looking.

And a little sanding dresses it up even further.

When I clamped these for gluing, I tried to let them hang over to the inside just a bit, so that I could bring them back flush with spokeshave, sandpaper and scraper.  This shot is from before I did that.

After bringing the insides flush and cleaning up a bit of squeeze out on the underside I sanded them all over and then finished up with a fillet of epoxy.  Here at the cabin junction:

And all along underneath the edge.

I climbed in the boat and tried them out and found this bit of wood provides a really nice arm rest with no sharp edges, and sitting up on top for a bit to stretch my legs if wanted should be very doable, too.  All in all a nice looking and functional addition to the seat backs that finishes things off nicely.

Transom cap installed

With the seat backs in place, I could now move on to install the transom cap.  

This was a bit of a problem to deal with.  It's fairly stiff and needs to be beveled on the ends to fit against the deck.  As I was fitting this I discovered that I had beveled the top of the transom in the wrong direction (lower in back), so I fixed that first.

After a bit of trial and error I got the bevel right on the cap right, and with a set of helping hands secured the ends with a block and screw.

To fill the void under the cap and above the deck, I shaped an insert that I could glue in place.  You can see here I cut it a little short, but a little thickened epoxy will take care of that more easily than remaking the part.

After gluing in the spacer blocks I glued down the transom cap and held the ends in place with three screws each.  

I also glued the doubler under the cap at the same time.

After the epoxy cured I unclamped and sanded a roundover on both edges.  Looks good and really stiffens up the transom. 

Cabin roof installed

With the cabin sides installed and the cleats attached and beveled, the next step was to install the cabin roof.  I had been a bit apprehensive about this because of the difficulty of clamping.  

I put a couple boards across the roof and used two web straps to pull the roof to the curve of the supports.  The front strap is attached to the building jig under the hull, and the rear strap goes through the portholes and hooks into the hatch cutouts in the front face of bulkhead 4.

The straps pulled the top into the general position, but it was clear I'd have to do better to keep the top from bowing up, and to get the edges down tight to the cleat.  I decided to use screws for clamps, since it appeared to be the only option.  

To hold down the center I prepared a couple sticks and predrilled the screw holes.  For the edge of the roof I prepared a bunch of blocks to spread the pressure out.   I planed both the sticks and the blocks to the correct thickness to ensure the screws penetrated an appropriate depth. 

I applied thickened epoxy to the supports and screwed down the center of the roof, then bent the roof down with the web straps and screwed the blocks along the edge.

The blocks pulled down the edge real nice, and only one screw stripped out its hole.

 While the epoxy was curing I took the opportunity to spread the first coat of epoxy over the deck and cabin sides.

After the epoxy cured, I removed the straps and the blocks and was happy to find that nothing went 'sproing'.

I planed the edges flush with the cleats and filled the screw holes with fillet mixture. 

At the same time I filleted all the joints underneath between the roof, bulkheads, cabin beams, and sides.  Working through the bulkhead 3 hatch openings I could reach all the joints in that area also.

After the epoxy cured I scraped the nail holes flush and sanded the roof in preparation for fiberglass.  But before that is applied I will attach doublers to the front and rear edges of the roof and round over the front and back edges of the cleats.

I'm glad to have this part installed.  This boat is really starting to look like a SCAMP now.

Gunwales in progress

Next up to install are the gunwales that stiffen the upper edge of the hull and provide a place to glue the deck to.  I looked around through my lumber stacks and found a couple 10 foot 1 x 8 pine boards that were relatively clear and I started ripping stock for the gunwales.  I had to work around a few knots, so I cut them out and rejoined the pieces with epoxy-glued scarf joints.  I cut them with the bandsaw and then finished them on the disk sander, which gave a nice surface with square faces, and all pieces the same.

I was concerned about the scarf joint's ability to stand up to the heat of steaming.  I read somewhere epoxy is good to about 180 degrees, and of course the steam is about 212 degrees.  I scarfed a test strip and steamed it and was able to bend it to the curve of the hull without failure, so I went ahead with the real stock. Here I'm again using lay-flat plastic tubing as my steam box, which lets me clamp the piece in place while the steam is still flowing.

CRAAACK!  Yep, scarf joint gave way.  <sigh>  The epoxy in the area of the scarf looks kind of grainy or crystalized - must be from the heat.  I broke the joint the rest of the way, and reglued it, then steamed the wood on either side of the joint separately and clamped it in place.  After the wood cooled, I removed the plastic and reclamped the gunwale and left it for a few days while I worked on other things.

Then I removed the gunwale and applied thickened epoxy and clamped it on.  I used a few 23-gauge pins through the gunwale and into the edges of the bulkheads to keep things from sliding around too much while I used most of my clamps to hold in in place.  I didn't need to clamp very hard, but needed a lot of them to pull the hull and the gunwale together all along the length.  I cleaned up the squeeze-out and left it to cure.

After removing the clamps, it looks pretty good.  There's a slight flatness in the area of the scarf joint, but it's not very noticable and I can probably improve on that after the deck is installed and I fair the edge of that.

The gunwale on the other side has two scarf joints, though, so we'll see how that goes.  

After the gunwales, I'll need to cut and install the carlins (which are the same size as the gunwales and run parallel to them about 4 inches inboard, to support the inner edge of the deck). I may rip the stock for the mast/boom/yard from my stock of sitka spruce and see if I have enough of that leftover to use for the carlins. If so, that is long enough to not need any scarf joints. 

Cockpit sole installed!

With the little hatch locating triangles installed on the bottom of the cockpit sole, it was time to give that surface a final coat of epoxy in preparation for installation.

I had trial fit the sole multiple times to ensure the process would go smoothly when all the cleats were covered with thickened epoxy.  This also allowed me to see where there were any gaps that would need clamping.

I mixed up a couple batches of thickened epoxy and applied it to the cleats, then with two helpers dropped the sole into place.  I then used some sticks and clamps to push down in a few places, and spent some time scraping off excess epoxy from the hold.  The floor hatches gave good access for this, and allowed me to confirm I had good contact.

This was a big step to get done, one that I had been dreading for some time.

Cockpit sole laminated

Well, here's a job I had been putting off for a while.  The cockpit sole (floor) is made up of two layers of 9mm plwood that need to be laminated together. Getting these property aligned and sufficiently clamped was something I had been worried about.

The builder's manual suggests doing this in the boat, first gluing down the bottom layer, then screwing the top layer to the bottom layer and venting the epoxy out through a whole array of 1/4" holes drilled for the purpose.  My objections to that method are 1) it's hard to work inside the boat, 2) it would be a pain to fill all those screw and vent holes, 3) it would be more difficult to fillet around the edges.

I decided to laminate the two layers on the bench.  And since I have a number of hatches in the floor, I felt I could get good clamps in the center areas of the floor.  I made sure I had a good coating of epoxy in the areas around the hatch openings and in the areas where I have drainage channels from the hatches to the gutters along the edge of the floor.

Next I took two 2x4s and jointed one edge straight.  I then ran them through the planer to straighten the opposite side and ensure they were the same thickness.  I set these up on a table and shimmed them until they were parallel.  This allowed me to elevate the parts above the table and have room for clamps.

Then I spread thickened epoxy with a grooved trowel.

And proceeded to use almost every clamp I own in the glue-up!  

After the epoxy cured I ran a fillet along the edge of the gutter. 

I even remembered to keep my drainage channels clear of epoxy both in the glue up and the filleting!

I'm glad to have that job done.