The Arctic Tern
Project
Volume 6 Issue No. 3 March 2009
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A World Divided
This month I learned that the world is divided into two groups of people: Those who have made a sliding companionway hatch and those who haven’t. I am now in the former group and it feels like I’ve completed some right of passage; a baptism of fire, if you will; that I’m perhaps a little older and wiser; that there’s been some slight loss of innocence. I gaze at the world now with something of a knowing look. Ok, that’s a bit much. But Wow! What a stretch of my abilities.
Companionway Hatch
Last month I’d roughed out the log rails (the things that the companionway hatch slides on) and pretty much decided on a design for the hatch. The first step this month was to laminate the hatch cover since, in this design at least, it pretty much forms the backbone of the hatch. I had a laminating jig kicking around that I’d used to make the mast partner and thought I could maybe use this for the hatch cover as well.
The camber of this jig is more extreme that what the hatch cover will be but that’s ok since there will be a bit of spring-back when the cover is removed from the form and it’ll be easier to take camber out of the cover when attaching it to the half-beams than to put more in.
Ok, so I disassemble the jig and make sure the two camber pieces match up perfectly.
Then I reassemble it into a new jig.
Here’s the thing about this hatch design: the whole thing depends on the laminated top being pretty much perfect with no twist since everything else just hangs off the top. So I’m particularly picky about getting the form square and true with no twist. It’s a difficult, near impossible task, but I give it my best shot.
Next thing I do is dry fit the laminations to see how I’m going the clamp the whole business down. First I try athwartships straps but this leaves the edge a little wavy.
So I then try a couple of very stiff longitudinal pieces and this seems to work better.
I look underneath and all seems as it should be with good contact along the entire jig.
Ok, so I laminate the whole works at give it the heat lamp treatment. It’s pretty cold these days (nothing like putting on ear muffs that have been chilled to a cool -5C).
While this is curing I make up the rest of the pieces; the fore and aft half-beams and the side rails.
The side rails have a bevel on top to match the log rails and the curve of the laminated top. Then I run them through the router to make the lip that hangs over the log rail.
Then I trim down the end where they meet up with the vertical drop-board slide pieces.
Then I shape the fore and aft half-beams and lay it all out to see how it shakes down. Note that for fitting purposes I’ve made the half-beams to be full width (i.e. they go right to the side rails). Once everything has been fit to the laminated top these half-beams need to be cut down so the log rail can pass. Leaving them full width makes it easier to line things up and make sure it’s all good and square and things are properly positioned. It’s kind of like having a full frame for the hatch.
By this time the laminated top has pretty much cured. I check the camber against the half beam and see that, after spring-back, it’s pretty darn close. A little too close perhaps. It would have been good to have a bit more camber in the top.
I lay the top on the log rails and it looks pretty good; it nearly matches the angle on the top of the log rails (but not quite; could have used a bit more camber in the top). It’s ok though. It’s close and eventually I change the angle on the top of the log rails to match the hatch exactly.
Next thing I do is to fit the frame to the laminated top and check for twist with corner-to-corner string lines. Not bad but there is a very slight bit of twist. There’s no way to really remove the twist at this stage so you pretty much just have to live with it. This is why laminating the top is so finicky.
Everything gets screwed down.
I cut recesses for the Teflon runners and then attach them.
And remove the half-beams and try it out on the boat.
It looks pretty good and it actually slides back and forth pretty smoothly. I’m trying like heck to keep things low and svelte and it’s a constant struggle. Everything needs to be made as small as possible.
The next thing I do is round off the corners of the hatch. It turns out a peanut butter jar lid provides a pleasing radius for the corners.
Then I round over the edge with the router. I use a 3/8” radius on the front and back and ½” radius on the sides (because of the camber the router doesn’t cut as deep when rounding over the sides).
Then it’s back on the boat for some more assessment. At this point I also cut a slope in the side pieces to match the log rails.
Still looking good. Next thing I do is make a little top beam for the aft end that works as a grab handle.
I make new Teflon slides and this time attach them with pan head screws that have been sunk in a hole cut with a forstner bit. This works better than the flat head screws in a counter sink hole which tend to deform the Teflon.
I mark where the half-beams need to be cut to clear the log rails and then cut ‘em down.
Then I need to camber the lower edge of the forward half-beam to clear the cabin top.
Since the log rails slope forward this half beam needs to have extra clearance when the hatch is closed (because the hatch cover will move closer to the cabin top as it slides forward). To prevent there being a big gaping crack when the hatch is closed I came up with this innovation:
Hatch closed:
Hatch open:
Ok, so it all appeared to be coming together ok. The next thing I did was to touch up the angle on the top of the side rails and log rails to match the camber that I ended up with in the hatch cover.
Ok, so the hatch is pretty much there. Now I work on the rest of the pieces that frame up the hatch opening. I start with the vertical pieces that the drop boards will slide in. I start off making these pieces 5/8” thick to match the horizontal framing pieces.
Next I cut down the horizontal trim pieces to fit.
Then I realize that things would look much better if the vertical pieces are ¾” thick rather than 5/8” so that they stand out a bit from the horizontal trim pieces. So I rework them out of some new ¾” stock. They then get cut-down so the aft half-beam just clears them. The silver duct-tape thing is a piece of half-inch Teflon to simulate the thickness of the eventual drop boards. I mark the height of the vertical piece on the horizontal trim piece.
Then the trim pieces get cut down to match the height of the vertical piece minus about 1/8” using the same slope as the log rails.
Et voila!
Then the aft half beam gets a pleasing camber cut into it’s lower edge.
Note that there are 1/16” clearances everywhere here. There is no wood sliding on wood, the only thing touching is the Teflon slide in the log rail. I do some final bits of trim/framing and some rounding off to prevent injury.
And then it’s on to the forward hatch.
Foredeck Lifting Hatch
Well, flush from the success of the sliding hatch I moved on to the lifting hatch in the foredeck. I was expecting it to be a bit easier but I knew it wasn’t going to be trivial. Since all the under-deck framing was intended for a hatch that had a top parallel to the waterline (and I had determined last month that this would look goofy) I knew there was going to be some craziness involved.
The first thing I did was to fit the inner trim/framing.
Then the outer framing. Not a single 90 degree cut anywhere here.
Then the framing for the top.
Then I use the router to make the lip.
I round the corners of the lip in the lower frame and fit the upper frame to the lower frame.
Then I round off the outer corners of the upper and lower frames.
And test fit a bit of door skin.
The top is going to be laminated to a final thickness of ¾” but I don’t have enough ¼” ply to do three laminations. Instead, I do two laminations of 3/8” ply. I need to make relief cuts in order to make the laminations bend correctly and not sag in the middle. I learned this trick when I was fitting the deck.
Ok, so the top gets laminated and attached to the upper frame all in one go.
Once it’s cured I trim down the top and clean things up.
Looks ok, but because of the under-deck framing the forward edge of the hatch is canted forward. This looks kind of goofy so I just run it through the RAS and make it 90 degrees to the top.
This looks better.
The next thing is to work out some sort of seal between the top and bottom. I briefly consider weather stripping but this seams a bit hokey. Instead, I route a channel to accept some rubber vacuum-line hose that I had kicking around from my deceased Toyota van.
I think this might work. Next I route out a little recess so you can get your fingers in and open up the hatch.
Then I attach the hinges.
Grab Rails
Next thing to tackle is the cabin top grab rails. Using design described by Fred Bingham in “Boat Joinery and Cabinet Making Simplified” but with proportions modified for my boat, I make up a pattern.
And then test it out on a 2x6 I got from the lumber yard.
Not bad for a first go. I ended up cutting them down a bit too far trying to get the right angle on the bottom so I take another crack at it. I modify the method a little to make things go smoother for when I actually make them out of mahogany.
After attaching the pattern I cut out the excess using a hole saw and a jig saw. You want to leave 1/16” to ¼” here for the router.
Then I have at it with the router using a top-bearing ½” square bit.
Then I remove the patter and cut the piece down the center, separating the two grab rails.
I drill the mounting holes at this stage because I’ve still got a 90 degree on the bottom.
Then I angle the bottoms to near-match the cabin top. I don’t want them completely vertical but I don’t want them to angle out at 90 degrees to the cabin top either.
Then I run them through the RAS to taper each side.
Then I round off all edges with a ½” radius bit in the router. I discover that, because I drilled all the mounting holes already I need to skip over some points with the router otherwise the guide bearing will dive into the hole. I round off these areas by hand after the fact.
All done and looking good.
But a little too high so I cut them down a bit more.
Ahh. That’s better.
Then I do the same thing again but with the African mahogany slab I’ve had kicking around the shop for about 4 years.
I don’t drill the mounting holes all the way through the top at this stage.
The next thing I do is make up strips to go inside the cabin to back-up the mounting fasteners. The fastener holes in these strips need to be drilled at an angle to match the angle on the bottom of the grab rails.
Next I drill the mounting holes through the cabin top; again, at an angle to match the angle on the bottom of the handrails.
And on they go with no fanfare or pictures.
Deadlights and Portlights
Deadlights are non-opening ports; portlights are opening ports. There you go; now you know more than 99% of the people on the planet. I was pretty excited about this phase and had to hold myself back until the hatches and grabrails were done. Incidentally, fitting the grabrails was a bit of a milestone in that all the bits of the boat are now built. Yep, no major construction left to do. Still plenty of work to be done though; a lot of this stuff is just dry fit and will have to be epoxied, etc. But, no matter, it was time to fit the jewellery!
First thing was to make a pattern so I could use the router to cut the deadlight holes.
I thought I’d do the foredeck hatch first as it was relatively expendable should things go bad.
As it was, things turned out ok.
Ok, cabin front is next.
To get the deadlights perfectly centered in the holes I give then a couple wraps of tape so they just fit snugly.
Then I use a bit the same size as the mounting holes to just mark the mounting surface.
Then I mark dead center of each mounting hole.
And then drill the pilot hole.
I mount each one with #8 x ¾” stainless screws for the time being. Not sure how the final mounting will be.
I mark each deadlight with location and orientation because the mounting holes differ slightly in each.
Looks good!
Then I do the aft one. Yeah!
I like it so much I order another deadlight so I can do the starboard side too. Originally, I wanted to keep the asymmetry of having only one but the additional light will be great for reading in the starboard bunk.
Ok, then I start thinking about the portlights that go in the cabin sides. Actually, I’ve been thinking about them for a long time. I bought these portlights very early on in the project because oval ones of the right size seemed really hard to find. Over the years of having them around I’ve grown to like them less. Sure they are heavily constructed bronze but the quality isn’t quite what I’d hoped and, they’re darn heavy! 25 lbs. each means 100 lbs. up high in the boat. Not so good. Also, in keeping with the low, svelte theme these ones seemed a bit too big. Anyway, I started looking around for replacements but couldn’t find any in the oval shape I wanted. I had to do a vision-shift to rectangular. I found a place selling portlights that looked to be of good quality and so made up some mock-ups to determine the size I wanted and the configuration that would look best.
First off, the 3x10s.
Ou la la! Tres svelte! I like. Ok, but let’s try the others.
Next, it’s the 4x10s.
Hmm…a little dumpy. Next, it’s the two-deadlights-one-portlight combo.
Maybe. How about with the 4x15 portlight.
Ok, but I really like to two 3x10s. I think I’ll go with that.
The final thing I do this month is put the finish rings on the inside of the deadlights. I wasn’t sure I was going to do this at first. I thought it might make the interior look a little tarted up but after holding a couple pieces up I thought it looked good and gave it the nod.
Next Time
Interior trim and electrical.