From our previous post, now that we have the Styrofoam cut and snugly fitting into the module frame, we now get ready to permanently glue it into the frame with polyurethane glue. It is manufactured by most glue manufacturers (Elmers, Lepage, etc) and you probably know it best by the catchy brand name of "Gorilla Glue".
Polyurethane glue is an expanding foam glue when it comes in contact with moisture (ie - water). It expands almost like spray foam insulation that you get in the aerosol can. It takes a bit longer than spray foam to set up so we have time to place it into the module frame and work with it. It has the look, consistency and spreadability of corn syrup. It can be spread very thinly while still a liquid. A very, very thin layer of glue will expand to fill the space between the module frame and the Styrofoam. It starts to set up in about an hour and starts to harden an hour later. It will be hardened in about 12 hours and we can work on it in 24.
If we aren't prepared, it can be very, very messy which is why we want a shop rag soaked in varsol before we start gluing. While still a liquid it can be washed off your hands with varsol followed by hot soap and water. Once it sets up, it will take about 10 days to flake off your fingers.
Tools & Materials
Which is why we need the following tools and materials close at hand:
- polyurethane glue
- 1" - 1 1/2" putty knife (for spreading the glue)
- spray bottle of water set to a fine mist (to speed up the reaction of the glue)
- masking tape (to reduce the mess)
- duct tape (to stop the glue from oozing out the top of the seams)
- varsol (turpentine, paint thinner, etc) (for cleaning up before the glue sets)
- shop rags (for cleaning up)
- 2 blocks of wood (to reduce the mess)
- garbage pail (to quickly dump the masking tape and shop rag into)
Clamping the Top Deck
The following materials are for a recommended practice if you have them, but are not necessary to glue the Styrofoam into the module frame. They do, however, make the work a lot easier.
- 2 pcs - 1"x 3"x 48" spruce strapping (or any size to form a 48"x 24" rectangle)
- 2 pcs - 1"x 3"x 20" spruce strapping (or any size to form a 48"x 24" rectangle)
- 6 pcs - 12" wood clamps
- 4 pcs - 1"x 3"x 4" spruce strapping
The polyurethane glue will expand and ooze out of the top and bottom seams between the module frame and the Styrofoam as it sets up. In all cases we'll tape the top of the module with duct tape to limit the amount of oozing coming out the top. Once the glue has set up, we simply trim the excess glue from the top of the module. If we can clamp the spruce strapping to the top of the module, we can almost stop any oozing coming out of the top of the module so that all we have to focus on is the bottom (underside) of the module. It also ensures that the top of the Styrofoam is relatively flush-and-even with the top of the module frame. Here's a photo of my "dry run" for this install to make sure that it all fits together.
And a close-up of how we'll clamp the corners.
Taping One Corner; Blocks On The Floor
For all installs, I place two 18" strips of masking tape in the middle of the end plate and the middle of the side plate. I tuck the 4 corners of the tape into the sticky side to act as a tab when I want to remove the tape. This is where we'll place the 46 1/2" side of the Styrofoam while we apply and spread the glue.
I next place the two blocks of wood on the floor about 18" apart parallel with my feet. This is where we'll place the 22 1/2" side of the Styrofoam while we apply and spread the glue.
Huh! What's this all about??
Think it through. We're going to spread glue on one side. We then rotate the Styrofoam 180 degrees to spread glue on the other side. But we have a problem. The side we want to set down has sticky glue all over it. Where do we set it down!!?? On top of the masking tape for the 46 1/2" side and on top of the wooden blocks for the 22 1/2" side.
I learned this little trick with the blocks and masking tape the hard way when I glued in my first piece of Styrofoam with polyurethane glue. I had glue spread all over one 22 1/2" side and one 46 1/2" side. I went to apply glue to the other sides. Where in the heck do I set this down!!?? Yup, I had one hell of a mess! It took 10 days before I shed all of the glue off my hands and fingers.
Taping The Underside Inside
The following is another one of those options. The polyurethane glue is going to expand and bubble up on the underside of the module on the edge between the Styrofoam and the module frame to form a bead of dried polyurethane glue. We can either leave the bead of dried glue where it is, trim a lot of it off after the bead has dried, or take steps in our prep work so as to minimize the size of the bead.
If we take this latter option, it's a simple matter of taping the inside edges of the module frame and the Styrofoam as shown in the photo below.
As we proceed with the gluing, we'll show you the next steps to take.
In our next blog, we apply the glue and insert the Styrofoam into the module frame.