Two Hulls are Better than One

At last I feel like I am actually building a catamaran. The second hull is set up beside the first. The disadvantage of building a catamaran, however, is that I now have to complete all those same steps I took to get the port hull up to the stage it is now. It really is almost like building two boats, but at least the steps are straightforward and the experience of the first hull will help me build the second one faster. In addition, I already have patterns for all such parts as the floors, bunks, and deckbeams so there won't be any time wasted figuring those things out.

Space is tight in the shed, which is just over 14 feet wide inside, and divided by a support post in the middle. I used the long workbench one last time to wire the hull panels together.

After wiring it together, I slid the hull off the bench into temporary rope slings to get it out of my way while I dismanteled the workbench and cleaned out a building space in this half of the shed. Suspending the hull from the rafters is a really useful technique I learned from Thomas Nielsen's Tiki 26 build. It comes in handy at many stages of the construction and makes it easy to manipulate these long, awkward-shaped deep-V hulls while working on them. In the first stages, however, the boat has to be stabilized in cradles on the ground to get and keep everything in line.

After the bench was out of the way, I put the bulkheads in while the hull was still hanging, then lowered it into V-shaped cradles and leveled it, using a string line pulled from stem to sternpost to make sure everything was in line. The hullsides were then pulled in tight using a series of Spanish windlasses, and epoxy was poured along the keel. Before I left it yesterday, I had made most of the keel fillets and tabbed in the bulkheads with small, partial fillets to hold them in position.

First Hull Aligned and Leveled

Today I installed all the bulkheads in the port hull after first working on the keel wires to straighten a twist in the keel strip. It took some effort to get all the bulkheads seated properly and lined up on their position marks, then I pulled the upper sides of the hullsides together with a Spanish windlass near each bulkhead position, as shown below. This simple method worked well, and holds the tension well since the line I used was some old Dacron Sta-Set that has low stretch.


The hullsides at the stern are under more tension than any other part of the hull when bent into place against the sternpost. Rather than fighting wires in this difficult area, I used screws through the sides and directly into the sternpost after first making sure it was vertical.



Final alignment was achieved through the use of various levels and taut lines, one from near the top of the stem and sternpost and one from the bunk bearers from bulkheads 1 to 5. The hull was nearly self-aligning, thanks to the accurate design of the parts by the Wharram team, but some minor tweaking was easily done after the V-supports were blocked up under the keel and the tension was released on the ropes I had suspended it from yesterday.

When I was satisfied that everything was level and straight, I did an intial epoxy pour with a slightly thickened mix that filled the narrow gaps between the keel strip and hullsides. This will hold things in place while I'm away for a few days working. It will likely be sometime this weekend before I can continue work on the hull, but it feels great to see it taking shape and at last it feels like this really is going to be a boat.

Port Hull Assembly

I had a productive day beginning early this morning with finishing the epoxy coating on the other hull panel. This was cured by noon and this afternoon I began assembly of the port hull, first by drilling the wire stitch holes in the stem and sternpost and then in the bottom edges of the hullsides. Putting in the wire stitches took some time, but went smoothly. Below is the finished wiring job, with the hull panels flat on the workbench.


Since I used screws to hold the top edges of the hullsides together at the stringers, as Thomas Nielsen suggested in his blog about building his Tiki 26, the whole affair was quite stable to move once the wire stitches were in place. I needed to get it off the bench, which is located on one side of my work shed, and move it out into the yard where I could then back it into the other half of the shed where I have the space to build it. (Moving it out into the yard to do this was necessary because of the center support posts that are in the way in the shed.) Moving the assembly was easy with the use of one of my hull dollies I built for my Tiki 21, Element.

After rolling the hull back into the shed on the other side of the posts, I then made two slings from some old jib sheets and hoisted the hull from the rafters, lifting it clear of the dolly and high enough off the ground so the skeg would not touch. I couldn't wait to see how the hull was going to look so I got some bulkheads and tried to open the hullsides. As it turned out, the wire stitches were a bit too tight, so I had to first loosen all of them before I could fit any bulkheads. With the stitches loose, I was able to spread the sides apart with no problem. This is much easier to do with the hull suspended in slings, rather than resting in cradles. (Another great idea from Thomas.) I still had some prep work to do on the bulkheads, such as sanding the cured epoxy near the edges where the bulkhead to hull panel fillets will be, and making some temporary stiffeners to screw onto the top edges above the sheer line. Since I'm making a slight modification in this area, my bulkheads are cut off a few inches above the sheer and I won't be adding permanent deck beams or the cabin parts of the bulkheads until the hulls are built to this level. Getting to this point is inspiring, and I decided to take another day off from my paying work so that I can finish the bulkhead installation tomorrow and try to get things aligned and leveled so that I can begin joining these parts together permanently with epoxy.

Assembling the Hullsides

Yesterday I assembled both hullsides for the port hull. This involved joining the three panels that make up each hullside with buttblocks, and glueing on the stringer that goes on the inside of the top edge of the lower hullsides. Since I only have room for one of these at a time on my workbench, I had to wait on the epoxy to cure before assembling the second one. Shown above is the first side, which I moved out in the yard onto some pallets for applying the second and final coat of epoxy to the whole inside surface. The other side is now assembled on the bench. The epoxy glueing the butt blocks and stringer on it was not cured last night, but at first light this morning I'm going out to remove the screws and clamps so I can get a coat of epoxy on it. Hopefully today if the epoxy cures fast enough I'll begin the wire stitching process and will get the two hullsides wired together along with the keel strip, stem and sternpost.

Scarfing Keel and Hull Stringers

Today I moved my table saw and other tools from the garage shop to the newly-roofed building shed, along with the finished stem, skeg, and bulkheads for the first hull I plan to assemble, which will be the port hull. I only had a couple of hours to work today, but in this time I was able to rip some 18' by 3/4" Doug Fir stock into strips for the keel and the hull stringers that go on the top edge of the lower hullsides. Since these parts needed to be longer than 18', it was necessary to use scarf joints to extend them. Shown below are the four stringer parts that I used to make up the two long stringers, which are approximately 23' long. The fastest and easiest method I've found for cutting scarfs is to stack them with each one staggered back the amount of the scarf ratio, then cut the excess material down with a handheld power planer until a smooth "ramp" is created. This is further smoothed with a belt sander. Turn half of these around so the cut surfaces are end to end, and glue them together with epoxy.



Here are the staggered pieces, in the first stages of cutting down with a power planer. Since I wanted a 10:1 scarf ratio on these joints, the amount of offset is 7.5" (for a .75" plank thickness).

The finished ends after smoothing with a belt sander. (These are shown slightly out of alignment for clarity.) This is much easier and faster than it looks, and only takes minutes for the whole operation once you've done it couple of times.

The finished scarf joints clamped for glueing. Keel stinger on the left, two hull stringers on the right. These joints will be cured in the morning. I also sanded the epoxy coated inside surfaces of all the port hull panels, in preparation for a quick second coat. Then I will be ready to join the panels with the butt blocks and glue on these hull stringers.