Butterflies at Christmas

December 30, 2015  Hours spent building to date:  1,916

I wanted to do something special for the Tardis over the holidays, and decided to tackle the forecabin hatch.

I have always admired “butterfly” hatches on classic boats.  They open up from the sides as pictured below, and since they were invented in the days before Lexan, they always have bronze rods to protect the glass, another beautiful touch.

“Real” butterfly hatch in action (this one’s on Ebay for $750)

But butterfly hatches have three major problems:

•  The joinery is very complicated, so they often leak.
•  Since they open from the sides, when a boat is at anchor the wings don’t let in much air from the direction of the wind.
• The hinges and geared devices used to open the wings are hand made from precious metals by an ancient craftsman named Percival in an obscure village on the south coast of England.  One set is priced to feed Percival’s family for an entire year.

But as always, Mark Smaalders to the rescue!  In the plans there is a sketch for a “faux” butterfly hatch.  It looks like a butterfly hatch, but is all one piece.  It opens fore-and-aft on a conventional frame with plenty of area for modern sealing and a gutter all around it to take away any errant drips.

There are a lot of pieces involved in the construction, but no curves, so the joinery was pretty simple.  I used a product called “Miller Dowels” for the wood-to-wood fastening.  They are installed special stepped drill bit that provides a hugely strong gluing area, and I think the dowels look great against the dark mahogany.

Setting and glazing the Lexan was not so simple:

Lexan reacts to ammonia, so epoxy and polyurethane products can’t be used as sealant.  The only product that will work for sure is Sika 295, a modified silicone.  The instructions and every site I read pretty much imply that this is a total, sticky mess to work with.  So I masked off every piece of the frame — top, bottom and sides.  But I neglected to mask the glass itself, and when I pushed it down into the Sika, it curled up and over onto the glass, without one molecule landing in the taped area.  I think this was due to gravity,  static electricity in the Lexan and the fact that it is so slick.  I tried to clean it up with a putty knife and mineral spirits, but only managed to smear Sika all over the glass, my tools, my clothes and three pairs of rubber gloves.

So that piece of Lexan went into the trash and I started over.  Better this time, but since the frame already had Sika on it, I couldn’t tape the bottom of the glass.  But gravity pulled most of the excess down toward the bench, and I could clean up what stuck to the glass.

For try number three, I taped absolutely everything but the area where I wanted Sika, tooled it out with a tongue depresser, threw away about 100 yards of Sika-infested tape, declared victory and went home exhausted.

I felt much better when I brushed on a sealer coat of varnish today and watched the magic happen.  Sort of the Tardis Project version of lighting up the Rockefeller Center tree.

Basic frame pieces ready for assembly

Gluing up the window frame

Routing out a rabbet for the glass.

Glass set in Sika 295 and tooled — third try

Glass in the frames ready for attachment

Trimmed out, sanded and ready for bronze rod assembly

Frames are attached with Miller Dowels

Hatch with sealer coat of varnish