ive seen the hotwire cutters on ebay. will they do the job for surfboards with eps? http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3175372601&category=2563 
Dave, What do you do? Plug it into a wall socket and wait until the wire gets hot? Try not to touch the wire? Sorry, I’m pretty naive about electrical gadgets,but have some styrofoam I might try to shape. Mike
Dave, Dick Van Straalan on the goldie uses a hotwire to cut the blanks that he makes for Rasta’ 4foot stringerless things.
do it the easy way … find a program that does curves (mac surf,auto cad etc)convert it to a pdf file and the polystyrene company will do the rest…they have massive computerised cutters and the cutting is included in the cost of the foam…i just email them the info now, but i used to give them a disc before i got online… regards BERT
simple wood,a pipe rubber (from cycle pipe) battery car or elettricity adaptor (I dont remember voltage)and some nails. simple and easy. for hotwire just ask polystirene factory maybe they can sale to you. I see that about 8 years ago http://www.theglasser.com/ 
The wire size you pick depends on the length and the transformer or other power source you have. Watts/volts= amps, so that if your transformer, say, produces 120 watts at 9 volts, then you have 15 amps to play with. see http://www.wiretron.com/nicrdat.html for data, how many amps it takes to heat wire of a given thickness/diameter to a particular temperature. I’d strongly suggest an appropriate sized rheostat somewhere in that circuit for fine tuning the wire temps. Run too much current, your wire overheats and breaks, too little current and the wire doesn’t cut or drags, giving you a curved surface which you were not expecting. I’d also suggest that you use a transformer or small charger rather than a big ol’ battery charger on ‘high’, as things can get very ugly, very fast. hope that’s of use doc… http://www.wiretron.com/nicrdat.html