: Is there any viable way to heat this kind of shed?

The local hardware store has several electric space heaters. You might look for a "barn heater" which is designed for use in sheltered conditions, and has a shut-of switch which turns the thing off should it tip over. Get a heavy-duty extension cord as the heaters usually draw a lot of current.

On a sunny day you'll trap some solar assistance which can kick the temperature up 40 degrees or more abovew the outsuide temps -- while the sun is shining. Once the sun sets that heat leaves quickly as there is not any insulation to speak of.

Since the top is plastic, and does not "breathe" I'd stay away from kerosene space heaters. They put out a lot of BTUs, but you have little fresh air, so whatever Carbon monoxide the heater produces is going to stay inside with you. not a healthy situation.

If you have free lightbulbs (some electric companies still give them away) and some wire, you can string together 10 to 15 sockets and suspend them. With 100 watt bulbs this will give 1000 to 1500 watts of radiant heat -- about the same as the commercial heaters -- and also illuminate your work area. You can focus the heat and aim it at your work by mounting the bulbs in a piece of aluminum rain gutter, or heat duct. the heat duct material is sold in the form of an open letter "C", in 4 foot long sections. it is meant to be closed into a tube, but you can leave it open, mount a row of lightbulbs in it, and shine it at your work.

If you jsut want to buy "of the shelf" radiant heat sources, a few 300 or 500 watt halogen flood lights will do the same, and these will let you aim the heat and light at your boat. wtih careful adjustment, the work surface temperature will be good, even if the air temperature a few feet away is chilly.

Farmers use the same principle in their "brood" heaters, which keep an area in a chicken house warm for newly hatched chicks. Instead of light bulbs these things use heating elements which have a base like a light bulb, ans screw into relectors that have porcelain sockets that can take the current and the heat. Rural hardware stores should have such things. The expensive ones have thermostats.

Hope this helps

PGJ

Pictured below is one of the more expensive Infra red brood heaters it is 800 watts and costs about $300. You would get almost the same amount of heat from eight 100 watt lightbulbs mounted in a piece of aluminum raingutter (as a reflector), should you care to try to duplicate the effect on your own.

The specs on this (from http://www.buyfarmstuff.com/products/ranch/kec/poultry.htm )
say that it raises the temperature 49 degrees at a distance of 5 feet, over an area of 5 by 7 feet. If it is aimed to cover a space of 7 by 14.5 feet, and is at a distance of 6 feet away, ther temperature rise is 17 degrees. Bring it a foot closer, so it is 5 feet above your work area, and it willheat an area 6.5 by 12 feet and raise the temperature by 27 degrees.