Portholes begun

I continue to try to plan and work ahead where possible, and one of the things I have been thinking about are the portholes.  I've seen a variety of ways to build these.  One ingenious one was Mike Monies' idea for the Red Scamp of using clear round hatches.  That's quick, easy, and inexpensive -- all good.  But I wanted better viewing and so was looking for glass.  

I checked into bronze portholes, and could order those for about $700/pair.  Yikes! So, I decided to try something different.  

I went to the local glass shop and had them cut two 5" diameter circles of safety glass.  This is like a car windshield, with a layer of plastic between two panes of glass.  If this breaks, the pieces are held together by the plastic.  (The other two options are plain glass, which would send sharp shards all over if broken, or tempered glass like a car side windows, which breaks into a zillion bits if broken.  I think the safety glass is the right choice.)

After I got the glass (about $30 for the pair), I cut matching holes in the cabin sides, and cut wood backing plates for the inside.  The backing plates cover about 1/4" of the edge of the glass.

Here's what the view will look like from the inside

I centered the rings and glued them on.

And cleaned up the epoxy squeeze out after it cured.

For the outside of the portholes, I'm planning to cast an aluminum ring that will bolt through the inner backing plate.  I hope to seal the glass with a 5" O-ring if I can find that.