IN my last reply I was considering the problem you would have if you applied the fiberglass panels over the teak vernier. Your portlight barrel would not be long enough to reach flush with the collar and your screws would be too short. So I suggested you apply the fiberglass panels directly to the sides of the cabin sides. After some thought, I suggest you remove about 3/16" to 1/4" of the plywood surface and then bond the fiberglass panels to this plywood.
This should not be difficult to do with a good sharp, wide wood chisel. It is plywood and layers can be easily removed this way. You will find you can start and then rip out long strips of a layer until it is all removed to the desired thickness. Fill any deep voids and remove any high spots that could effect the fiberglass panel. Follow with a 40 grit sand. You do not need a smooth surface but you do need an even surface. When you bond the fiberglass panels, the bonding will fill small voids but it will not compensate for “bumps”
We applied our panels with fiberglass resin mish-mash (a putty made up of fiberglass resin and micro balloons. The fiberglass panels are first dry fit to make sure everything fits, then bonded, clamped and braced in place until the resin cured over night.
I suggest the following:
Dry fit the fiberglass panels to fit and cut out the port holes. I suggest you make the join (one piece is not long enough to reach the total distance if you want the grooves vertical) at center of the forward portlight to make it easier to fill and hide.
Cut a bunch of pieces (10 +/-) of wood about 1" to 2" thick the same length as the distance between the inside of the panels from cabin side to cabin side.
Cut about 8 sheets of 3/8" or 1/2" plywood that will be placed against the panels to distribute the pressure when bonded in place. (4 per side) Measure the size of these panels before cutting. Three portlights per side. One plywood panel will go between the portlights (2 total per side) and one at each end (2 total per side)
For bonding you can use mish-mash, 5200 or any good two part bonding putty.
Have six “C” clamp ready to clamp the fiberglass panels and plywood in place.
Apply the bonding material to the fiberglass panels and around the porthole opening on the plywood. Fill any voids in the plywood.
Clamp the panels in place. Start at the forward and aft port hole and clamp the larger pieces of plywood (between portlights) against the fiberglass panels holding everything in register. Do the same to the other side.
Now, using the strips of wood, brace the plywood firmly in place by wedging the pieces evenly over the plywood. Do not remove the “C” clamps because the sides of the cabin are tapered and the braces will want to force the panels to slide. The “C” clamps are to prevent this. If you do have problems, you will have to support the bottom of the fiberglass panels to prevent them from sliding down.
Now apply the plywood pieces at the end in the same manner.
Remove any excess adhesive in the portholes.
After the adhesive is cured remove the braces and plywood pieces. Sand and dry fit the portlights. Before installing the portlights, seal the edge of the plywood. You do not want to take any chance of water entering behind the plywood, the fiberglass panel or the edge grain of the plywood.
When installing the portlights, be certain to bed them with lots of bedding compound.
I am not sure if you intend to remove the hand rail or apply these panels inside.
If you have further problems or questions, you can contact me directly at firstname.lastname@example.org