05 February, 2010

Making a Portlight Rain Shield

In the previous Blog I exlained how the Fixed Portlights were replaced with Beckson 5"x12" Opening Ports. I soon found out that when it rained the back rake of the cabin collected water in the Portlight coaming. The port could not be left open. The main purpose of the opening Port was to provide ventilation while keeping the nasty Chesapeake flying critters out.

There are several commercial rain shields available. The things that I did not like about them are the cost and that they block some of the ventilation by wrapping down around the Portlight. I had plenty of scrap Plexiglas around the garage. If you understand how to work with this material you can make some nice components for your boat. The hardest part is to cut the material. Straight lines can be cut with a plastic scoring tool available at your local Home Depot. Unlike cutting glass you scratch through the material multiple times until you are about half way through. To snap the piece I use two pieces of wood to support the edge. This is the hardest part of the operation. Practice on scrap material. Curves and inside corners can be cut with a fine toothed jig-saw blade. Again you run the risk of cracking the material. I usually cut outside the line and finish off with a sander or grinder. The edges can also be rounder with the same tools.

Above drawing is a rough template for a 5"x12" Portlight. First you cut out the main rectangle. It is easier to bend the plastic at this point. I found a piece of PVC pipe with the same radius as the Beckson Portlight corners. I marked the rectangle with the location where the radiuses bend start. (dashed lines on diagram) Using a Hot Air Gun I pre-heated between the dashed areas constantly moving back and forth. Be careful not to overheat and burn the plastic. The Plexiglas starts getting shiny and starts to bend. At this point form your curve over the PVC pipe. You do not have too much time. If too stiff continue to heat. Make sure that you have a nice 90 degree bend. Once I have my shape I dip the sheet and pipe in a bucket of cold water to freeze the shape. Test your creation to make sure that it fits snugly over the Portlight coaming.

You will notice that the rain shield points up. To give it a downward pitch you have to cut out two triangle sections across the back. Part of this triangle runs into the curve. First I rough cut the triangle off with a jig-saw. Using a belt sander I removed the final amount and tested the shade until I had a nice tight fit.

The jib sheets tend to get caught on the bottom corners of the shade. To keep this from happening I sanded a nice radius curve. You now should have a basic shade as shown in the pictures.
I wanted the rain shade to be easily removable without any special tools. This was done using four small cotter pins. I placed the shield on the coaming and drilled the holes using the smallest drill bit possible. Make sure that you have enough edge on the coaming. The pins do not snag sheets because they are protected by the shield.

DESIGN PROBLEM: Water tends to leak behind the top joint, puddle and run over the top coaming. The solution was to lay a bead of clear Silicone Caulk across the top. This made the shield less removable. I have towed the boat at highway speeds with the shields installed. No problem if everything is nice and tight.

Another problem: Water sitting inside the lower corner of the Beckson Portlight puddles and can flow over the window gasket with the Portlight open. I carefully drilled three small holes in the coaming to drain this water. (See above picture)

This might not be the best rain shade in the world. But, I do have the satisfaction of building and solving the design.