Building Allie Kat
A Somes Sound 12 1/2
The Building Jig
Putting together the building jig was straightforward. The plans provide all of the details. There are a lot of parts (especially the transom support: 15 pieces!) which means a lot of careful measuring and cutting. It took a lot longer than I thought.
I invested in a laser line level and I think it helped enormously. I was able to get the jig up on its legs and level without any fuss or shimming. With the jig frame on the floor and the laser in the middle, I clamped a yardstick to the side beams at each leg position. Then I was able to get the right length for each leg (legs near the garage door are about an inch longer than the ones at the other end). Then with the jig frame up on horses I screwed the legs on. When I put the whole assembly back down on the floor it was perfectly level.
At the start, before putting any part of the building jig together I placed marks on the two side beams and the center beam to indicate locations for each frame station. After the jig was up on legs and square I installed the center beam. I used the vertical line of the laser to line up the marks on the three beams which will insure that each of the molds will be perfectly square when they get installed.
Now I'm finally ready to actually start building a boat!
Molds and Frames – there are rules.
Taking time before assembling the building jig to clamp the side rails and the center rail together and mark the station locations paid dividends. And I was careful to make sure that it all went together square. So setting up the station molds and web frames should have been a snap, but it wasn't.
Positioning - I admit to some serious confusion at the start.
Brooks talks about positioning Molds in his book. He defines the smooth face of the mold – the side that does not have gussets holding it together – as the "working face." This is the face that will be lined up on the station lines. I think it is simpler to call it the "station face." The rule is simple: molds forward of the widest part of the boat go on the aft side of the station line (the station face is on the station line and the gusset side of the mold is facing aft). Molds in the aft part of the boat go on the forward side of the station line. Easy, right?
I thought it should be easy until I noticed on the drawings that the web frames in the bow of the boat were drawn forward of the station lines, not aft as stated in the rule. It turns out that frames have a different rule and it is opposite of the mold rule. Brooks does not mention this in his book. But Greg Rossel covers it in an excellent article for Wooden Boat Magazine on setting up molds and frames. There's a link on my Tools and References page.
Once I figured out where exactly to position the frames and molds, things went quickly. I needed to cut a notch in the Sta 14 mold for the center beam, and the frame extensions for Sta 2 is 3-1/2 inches wide – dimensions for the other extensions aren't specified. I used the laser line to keep everything centered and a bubble-level to make sure everything was plumb. I double checked square-ness at the mast frame by taking diagonal measurements from the center point on the forward crossbeam on the jig.
Positioning the Transom
The transom is held on the jig by a transom holder. The scaled plans give details for construction. I built it to the best of my ability and had high confidence that I had it right. The plans give dimensions from the transom shear forward to station 14 - that was spot-on. But the bottom of the transom was much too close to the 14 mold. There wasn't room to get the keelson over the 14 mold and onto the transom knee. Not even close. I spent a couple of days checking everything and could find nothing wrong. To check the positioning and angle of the transom I made a plywood template of the Stern Post, Deadwood, Keel, and Keelson from the full sized plans. When I laid it on top of the molds it showed that the transom was at the wrong angle. The scaled plans call for a transom angle of 43 degrees. I tipped it steeper to 47 degrees and everything fit. The shear moved a quarter inch aft but remained at the proper distance from the jig line. Problem solved! Before and after pictures below:
Shaping and Installing the Keelson
My planks were roughly 11 inches wide and well over 12 feet long. The rough plank was resawn and smoothed to half-inch thickness. Like almost every other piece of wood on the boat, this is not something I wanted to mess up and have to do over - besides being expensive, there's a long lead time in ordering these large boards. Being the way I am, I laid out the 7 - 3/4 inch wide shape of the keelson with one edge aligned on the edge of the plank so that there might be some usable wood left after sawing. Then I cut to within an eighth inch of my lines. The board was full of tension and when I was done i found all of my straight lines were impossibly bent. Fortunately I was able to use this "ruined" plank for the keel which is a bit smaller in all dimensions than the keelson. Strangely (or luckily) the next two boards I pulled from the pile were perfectly stable - I gradually trimmed them to size but didn't need to because they never warped at all. To keep the sides perfectly square with the face of the plank when I planed, I did it with the plane riding on its side on a table (a picture is worth a thousand words). The aft end of the two layers of the keelson need to be notched and beveled to fit tightly against the transom. I made templates (or you could say practice runs) with a scrap piece of half inch wood. There's a photo below showing the notched shape on the aft end of the inboard half of the keelson.
After I had the two halves (inboard and outboard or upper and lower) of the keelson shaped, I clamped them in position bent over the molds and web frames for a couple of days. I did this in August and it was plenty hot and steamy in my garage workshop. I was hoping to get them used to the bend so that maybe it would make the final install easier - I think it helped a little.
The first glue joint was the inboard keelson at the aft end. I braced the forward end up high so that the board did not have any bend as it lay on the transom knee. I used plenty of thickened epoxy to fill the gaps and screwed it down onto the knee with drywall screws. I removed the screws after the epoxy hardened.
I got my friends Dave and Deb to help with the rest of the job. We used paint rollers to spread unthickened epoxy on the joining surfaces, then we added plenty of thickened epoxy. With Dave on one end and me on the other we lined up the outboard half with the inboard at the transom (see short video below), and then clamped them together just at the aft end. Working forward, one station at a time, we clamped and screwed the two pieces together and down on the molds. I'm smiling in the photo below because the lineup and fit at the bow stem was perfect. It's good to be lucky.
Photos below show the two halves clamped in position getting used to the bend. Dave working hard with a stir stick (he actually did some other work, but Deb didn't get any pictures to prove it). Me smiling at my luck. A lot of clamps. The finished keelson. And the short video of Dave and me joining the outboard half to the inboard while trying not to smear the thickened epoxy out of the joint.
Laminating the Floors (they're not for walking on):
Floors are installed in the bilge and extend part way up the sides. They're like shortened frames. They strengthen the bottom of the boat and in this boat they provide a place for the sole beams to land. The sole goes on top of the sole beams and that is what the sailor walks on.
Floors at stations 7, 8, 9, 10 and 11 are made of laminated strips of Douglas Fir. The floor at station 12 is solid mahogany. The plans call for constructing the floors before the planking is installed. The floors follow the curve of the hull, where the planking would be, so temporary floor battens are installed over the molds and web frames to clamp the laminations to, giving the floors the right shape. I added cleats to the floor battens to help me keep the floors straight and parallel to the construction molds.
I used the plastic wrap method that Brooks describes in his book to help keep the epoxy contained and to make sure the floors don't stick to the battens. I recommend folding over the end of the plastic wrap and clamping it shut to prevent squeeze out from dripping on the shop floor and shoes.
The floors came out of the wrap basically encapsulated in epoxy. I used a bench plane to smooth the side that had been resting against the mold (or the cleat) – this is the "station face", or the side of the floor that will be lined up on the station line. I used a spoke shave to clean up the inboard side of the floor (the side facing down when clamped to the battens). The outboard side which was the up side when clamped in place, came out relatively clean.
Once cleaned up and labeled, the floors got stored away. They will be installed after the planking and the centerboard trunk are installed and the hull is flipped to right-side up.
I spent some time thinking about the shape of the floors (it turns out over-thinking). I wanted to make sure that the floors all lie flat against the hull planking and also run straight athwartship so that the floors are parallel to each other.
I sent a note to John Brooks asking if I will need to bevel the floors after the glue-up to make them lie flat against the hull. He said "No" all that's needed is to joint the sides.
Because of the fore to aft curve of the hull, and the requirement for the floor to lie parallel to the station lines, the veneers will slip sideways in the stack. The resulting rhombus shape fits against the hull perfectly. This drawing exaggerates what it looks like. The cleats I added to the floor battens helped line up the stack of veneers at the between-molds stations. Clamping the stack tight to the floor battens and hard against the station molds or the cleats caused the veneers to twist and slip into the rhombus shape.
The station 12 floor was easy. I got the shape for the station face from the full size drawings. Then beveled the bottom edge to fit against the keelson. I screwed it to the station 12 mold and did a rough bevel for the planking using a batten to check the angles as I removed wood. I'll finish the job during planking. After the garboard and the second plank go on, I'll remove and store this floor for final installation later, along with the rest.