Spartan Restoration Tips: Windows and Insulation

While working on our 1955 Spartan, we tackled a couple of projects that taught us some useful lessons—and introduced us to tools we wouldn’t want to be without.

Window Replacement & Gasket Installation

One of the first jobs was replacing a missing window. Along with the glass, we needed new rubber gasket material and the right tool to install it—a Straight Tip Filler Strip Insert Tool. At first, it seemed obvious how it should work, but the process proved a little trickier than expected.

Here’s what we learned:

  • Lubrication is key. Silicone spray is recommended, but soapy water worked well for us.
  • Start at the joint. Begin where the two ends of the gasket meet and feed the lock strip through the tip of the tool.
  • Use a “swimming” motion. Wiggle the tool side to side while pushing it slowly and firmly through the gasket channel.
  • Be patient. If the tool pops out, it’s frustrating to restart. With steady wiggling, you can guide it back into the channel.
  • Leave extra length. Cut the lock strip at least ¼” longer than needed so it stays tight as the rubber naturally shrinks.

Once we got the hang of it, the tool worked beautifully. Honestly, it’s hard to imagine installing this type of lock strip without it.

Insulation Lessons Learned

The other big task was insulation. After considering several options, we chose R-Tech 1-1/2 in. x 4 ft. x 8 ft. R-5.78 Rigid Foam Insulation. It matches the thickness of the trailer’s wall “studs,” so it seemed like the best fit.

Our original plan was to knock out the job in just a few evenings while the weather was rainy. Unfortunately, the moisture inside the trailer—caused by the mix of warm interior air and damp, cool exterior air—wasn’t ideal. We had to pause until conditions improved.

At first, we cut the insulation with a razor knife: measure, slice, snap, and finish the cut. It worked, but it was messy and often left pieces just a little too big. Then a friend suggested a much better method: using a Stanley Sharptooth Smooth Cut Saw (10″ Fine-Finish Mini Utility Saw). It gave us cleaner, straighter cuts with less mess. For curved corners, we simply scored the back of the foam so it could bend along the trailer’s curves.

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