The Arctic Tern Project

Volume 6                           Issue No. 2                       February 2009

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Hatches

Ok, this month there was no avoiding it any longer.  It was time to tackle the sliding hatch in the cabin top and the lifting hatch in the foredeck.  But first there was a little bit of deckhouse trim to finish off.

Finishing the Deckhouse Trim

Last month I’d just started on the deckhouse trim that goes in the junction between the deckhouse and deck.  First task this month was to finish that off.  I start by doing 45’s where the side and front pieces meet the corners.  I almost blew it by cutting the 45 in the wrong direction on the corner piece.

 

 

Ok, so all the pieces get mounted with no major catastrophes.

 

 

Then it’s time to round the outside edge of the corner pieces.

 

 

Then I round-over the edges with the ½” radius router bit.  Things get ugly when I start going across the grain on the corner piece and nearly ruin it.  I end up doing the final shaping on the corner piece with a rasp.

 

Ok, the next thing to tackle is the trim around the top of the deckhouse.  I start off by making various sample pieces with subtle differences in proportions and round-over radii.  I finally decided on the foremost one in the picture below.  The dimensions are 7/8” wide by 5/8” thick with a 3/8” radius round-over on the top and bottom.  The edge meeting the cabin side is angled to match the cabin side so the top edge ends up being level with the earth (this looked best to me).

 

I planned on having this trim extend around the corners and along the front and back of the deckhouse so I started on making the corner pieces.

 

 

 

It took me the better part of half a day to do this one corner and it still wasn’t exactly right.  In a flash of inspiration I modified my vision and decided I’d only have the trim going along the cabin sides and forget about the front and back (and therefore had no need for the corners).  Giddy as a schoolboy at the prospect of having saved a week of fiddly work (I still hadn’t worked out how I was going to bend the trim to the front and back camber) I cheerfully went about fitting and shaping the side trim.

 

 

 

Stellar!  I liked it a lot and I wasn’t convinced that extending the trim around the corners and along the front and back would look any better (although it could still be done later if the mood strikes me).  On to my next problem!

Cabin-Top Sliding Hatch

Having exhausted the trim prospects it was time to move on to the hatches.  First step was to cut out the openings.  I’d actually been looking forward to this for some time.  First one on the block was the sliding hatch opening in the main cabin.  I brought out the trusty veneer saw and went at it.

 

 

First pass is pretty good and then I go over it with the hand-plane, rasp, and sandpaper.

 

 

Then I laminated up the log rails (the pieces that the hatch slides in/on).  Dimensions are 1-1/4” (matching in the interior cabin top beams) by approximately 2-1/2”.  I used two laminations of 5/8” for each one to help ensure straightness.

 

Next I needed to fix up the opening a bit where the drop boards go.  Initially I was going to cover this area with a mahogany piece but that wouldn’t really work with the rest of the hatch design.  Everything seems to be inter-related with sliding hatch design.  The width of the log rails determine the width of the vertical trim pieces along side the drop boards, etc., etc.  Anyway, I needed to fix up this edge because I’d done kind of a butcher job with the jigsaw way back when.  So I covered some plywood pieces with packing tape and used them to mould a smooth edge on the opening.

 

  

 

Once this gets cleaned up it looks pretty good.

Foredeck Hatch

While things for the main hatch are curing I move on to the forward hatch.  First step, of course, is to cut out the opening.  I start out gingerly and carefully with the jigsaw leaving lots of overhang to trim by hand later.

 

Then I hit it with the veneer saw, plane, rasp, sandpaper, etc.

 

 

Now I wanted to figure out the proportions of the coaming that will make up the hatch sides.  I had initially thought that the top of the hatch would be level with the waterline.  I made a quick mock-up and discovered this doesn’t look right.  Too forward-slopey; it clashed with the slope of the cabin top.

 

 

Through a bit of trial and error I discovered that things looked best if a batten placed on the bow touched both the forward and back edges of the hatch.  Cool, eh?

 

Back on the Main Hatch

Ok, the log rails had cured and it was time to start shaping them.

 

The design of the hatch I was working on at this point is show below on the left.  Slider on the inside; internal frame; nice low profile hatch cover; simple shape for the log rails.  The only problem with this design is that the forward dam needs to be low for the internal frame to clear and the internal slide track would provide a ready path for water intrusion.  Hmm…the other design I was working with is show below on the right.  Slider on the outside; no internal frame; slightly higher profile for the hatch cover; more complex shape for the log rails.

 

 

I flip-flopped between these two designs several times and each one had several renditions with differing proportions but at least I could start shaping the log rails.  At first I thought I’d forgo the slope on the log rails (most are made with an additional slope forward) as being an unnecessary complication but eventually relented.  I made up this ripping board to put a ½” slope in 4-1/2’ when I ripped the bottom angle in the log rails.

 

Ok, the came out alright and I definitely liked the forward slope.

 

 

Next I fitted the vertical pieces.

 

And trimmed the back of the log rails to match.

 

And fit everything with clamps.  Spacers are made out of scrap plywood to keep the rails parallel and straight.

 

Next was to drill the mounting holes for the log rails.  I had a box of 3” #12s kicking around so decided to use them.  Also, for some silly reason, I thought 6” centers would be good (excessive! 12” centers would be fine).  Also, and this is where brain-fade really kicked in, I decided to drill the holes dead center in the log-rail even though design “B” above, which I had decided to go with, would require a routed channel that would pass very close to the center.  I thought I could get away with it; and for some damn reason just wanted that hole in the center.  Anyway, I drilled the holes and mounted the rails.

 

Next step was to fit the forward dam.

 

I made this device to trace the camber of the cabin top on the dam.

 

 

Final Shaping of the Log Rails

Ok, this is where things got a little ugly for a while but ultimately worked out for the better.  I had gotten some UHMD or something like that (is it really Teflon?) to use as slide material and tested out shaping it with the router, jointer, and saw.  Turns out this works fine.  The material is very slightly thicker than ½” so when making the grooves I needed to do a couple passes slightly offset from each other.

 

 

Ok, on to the log rails.  As I mentioned, I had finally decided on the design “B”.

 

This required a routed channel in the log rail.  Using the core-box bit on the router to remove all of the material doesn’t really work that well as the material tends to want to ride-up on the bit so I started off using a ½” square bit.  This is where things went bad.  The first rail went smoothly but part way through the second rail the router got increasingly “chattery” and finally jammed.  What the heck?  I turned off the router and turned over the piece to have a look and, to my dismay, discovered the depth clamp on the router hand loosened and the router and been progressively burying itself deeper in the log rail.  Crap!

 

I also discovered that my ten #12 mounting holes would have to be moved because when the router dug down to the ½” mark (the final depth of the groove) it exposed the mounting hole.  So ultimately it was a good thing that the router took on a mind of its own otherwise I wouldn’t have found out about the mounting hole problem until much later and it would have been harder to fix.  I think the boatbuilding gods were watching over me and decided to put a stop to this folly before it went too far (at least they didn’t take the end of my thumb off like the last time they intervened).

 

Ok, so I smoothly switched into disaster recovery mode.  First thing was to plug all the stupid #12 mounting holes both in the cabin top and the log rails.  I’d eventually go with #10s spaced on 12” centers and offset to within ½” of the outside of the rails (rather than 5/8” which is the center).

 

And then fill the unauthorized channel in the rail.

 

Next day, I was moving forward again.  I took this opportunity to run the rails through the jointer because I noticed the top edge wasn’t square and I need this edge as a reference for the rest of my cuts.  I also noticed that the bottom angle cut wasn’t the same on both rails so I fixed this up too (thank you boatbuilding gods!).  Then I re-cut the channels in the rails using the ½” square bit; taking a couple passes to make it wide enough for the Teflon.

 

Next I took a couple passes with the core-box bit.

 

I used a bit of sandpaper stuck to the Teflon (is that possible?) to smooth out the channels and make sure they had enough clearance to accept epoxy and paint without binding.

 

Next thing I did was drill the new #10 mounting holes.

 

Despite my best efforts, the forward-most hole in both rails ended up non-vertical so I plugged them up with day-old epoxy (still soft because of cold temperatures) to be re-drilled later.

 

The rails were looking a bit like Swiss cheese, but what the heck, they were going to be painted anyway.  In keeping with the cheese theme, the “cheese-grater” rasp can smooth this soft day-old epoxy immediately but you end up ruining the blade.

 

Ok, another pass with the router for some more shaping of the channel.

 

Then through the RAS for the final cut of the top edge camber.

 

And back on the boat.  Oh yeah!  Looking good.

 

 

Then, one tired Saturday, I cut the tops of the verticals, forgetting that the cut needed to be angled forward and not 90 degrees (oh well, I can fix that up later).

 

Next Time

More hatch work.