All heating jokes aside...

The best way I've found to heat a boat interior evenly is to use a small space heater with a fan. They don't cost too much, have good temperature control and heat relatively evenly. A straight lightbulb, as many have pointed out, heat very unevenly and can cause hot spots. They also don't shut off when it gets warm enough.

If you want to go with a light bulb, fix a socket on a piece of wood and cover it with a tin coffee can. Punch holes in the sides of the can and cut squares out of the base. This allows the heat from the bulb to dissipate through the coffee can while letting cool air in through the bottom. It takes a short while to rig this up but is safer than a bare lightbulb.

: Hi all,

: I make preparations for closing some seams with thickened epoxy. Because I
: need good temperature, I think of warming up the kayak from the inside:
: ..I need a enery-saving, cheap, reliable method with good distribution of
: the warmth to minimize tension.
: What I have in mind is just a principle: ..a small unit (1 lightbulb)
: combined with a small fan ("PC fan") to distibute the warmth
: evenly. The deck openings could be covered with plastic to keep the heat
: inside. It should be easy to build such a tool.
: What do you think?
: -Joachim-