Hull insulation

We insulated our westsail above the waterline. Used a 1/2" closed cell rigid foam that could be fiberglassed. Can't remember what kind it was except it was green and little bit crumbly. Cut the foam to fit all the lockers and glued in place. Glassed a layer of mat over it to protect the foam from the contents of the lockers.

The cabin sides and overhead was covered with 3/8" T&G. We furred out the cabin sides and overhead with 1/2 ply stringers and filled the spaces in between with cut to fit styrofoam. We glued it in palce with a water based adesive that didn't eat up the styrofoam. Still seems to be going strong after more than 35 years. We were never on the boat in temps lower than 50 degrees. Boat always felt warm and a couple of kerosene lamps were all we needed to be comfortable in the boat. More importantly for us, the boat was comfortable in the tropics. Can't say it was the insulation, though.

Just got back from spending a week on the boat in 40-45ish weather on my P35. Don't know if insulation is all that necessary. There is some insulation from the air gap between the liner and the cabin. Have had virtually no condensation. A small propane catalytic heater raises the interior temperature about 20-25 degress above ambient on the low setting. Know this isn't freezing weather but most of us don't hang out on the boat when it gets that cold.