SV Pilgrim - 1979 Morgan 382 - Homeport: Beaufort, NC

Sunday, September 6, 2015

Replacing the Leaking Quarterberth Port, the Exterior Story – Part 1

Our previous post, Replacing the Leaking Quarterberth Port, the Interior Story, explains why, and how we removed the original port.  The post also shares our reasoning for replacing the port with fixed pane window.

As many boat projects are apt to do, the exterior story begins with… creating a template. 

Creating a 1/4" plywood template of the window pane.
Yes, that is an electrical tape canister we are using for the corner radius. 

The template will allow us to “test” the aesthetics of the panel prior to cutting into our limited supply of acrylic material.  The template will also serve as a guide for the router bit used to trim the acrylic.  ½” plywood was my preferred template material.  Unable to find an appropriate piece of scrap we used ¼” plywood.

Pleased with the look and fit of the template, we then transferred the shape to the masked acrylic.

Template dimensions transferred to the masked acrylic sheet.

Ok, time for a disclaimer… our experience working with acrylic, Lexan, Plexiglass, and similar materials is very limited.  We welcome any comments or suggestion on working with these types of materials. 

The material we are using is ½” thick Chemcast Cell Cast Acrylic Sheet.  We reclaimed the scrap material from a project on another vessel.  Since the material was previously installed it lacked the protective coating found on virgin material.  When possible we kept the pane masked with painters tape during the install process.

Prior to cutting the actual pane, I experimented with various cutting tools and techniques.  The jigsaw with Plexiglas specific blades generated too much heat.  The heat melted the acrylic and created a rough, scored edge.  Perhaps the jigsaw blades would work better on thinner material?  Using the hand held circular saw with a multi-purpose blades (24 to 40 teeth) yielded similar results to the jigsaw.   The best solution I found was to use a fine crosscut blade (90 teeth) in the circular saw to rough cut the acrylic. Then use a router with a flush trim bit for the final shaping.

With the template as a guide, I used a router with a flush trim bit to clean up the edges of the acrylic window pane.

I clamped the rough cut pane atop the plywood template.  The template then served as a guide for the flush trim router bit.  Since the guide wheel on the router bit transfers any irregularities from the template to the finish material it is important to sand down the rough edges of the template.  Yeah, I learned this the hard way.

Unfortunately the painters tape masking did not play nice with the router.  My solution…

Masking the base of the router proved more effective than masking the acrylic face.

Remove the masking from the acrylic and place a couple strips of masking on the base of the router.  Masking the base of the router worked for both the flush trim bit and the round over bit used to radius the outside edge of the pane. 

Next the edges of the acrylic were sanded beginning with 220 grit and progressing up to 600 grit sandpaper.  Sanding the edges up to 600 grit brought them back to a dull, smooth surface.  I certain by a polished edge could be achieved if so desired.

To Be Continued…


  1. You can flame polish those edges by passing them across a buffing wheel - like this:


    1. Bob, thanks for the link.

      Two questions for you...
      1) Can you give me additional details about your buffing wheel? Mounted on bench grinder or chucked in drill?
      2) Is Plexiglas a proprietary name for acrylic or is it a different material?

    2. Bench mounted. Don't think you can get enough RPM from a drill. But an a repurposed angle grinder would work.

      And yes, Plexiglas is a brand name for polymethylmethacrylate, AKA "acrylic"

      And good on you for choosing acrylic over Lexan/polycarbonate - it will last far, far longer in the UV

    3. Bob,

      Thanks for the information.

      I've been temped to purchase a buffing wheel for the bench grinder. Think I'll head over to Amazon and see what is available.

    4. Get two - one for tripoli and one for rouge. They're cheap at Harbor Freight...

  2. Let the acrylic sit in the sun for several hours before installation. It flexes much better when warm.

  3. Here is some good info on windows similar to what you are working on:


    1. Thanks for the link. Looks like I'll be following another refit project.