I have been looking at plans for hot wire cutters and it all seems pretty simple and straight forward. However, my question is: is it better to build one with a pivot and tensioning wire or is no pivot and eyeholes with wingnuts enough for tension. I am going to build 2, the largest being about 15" wide for the rocker which will be cut in 2 pieces with the stringer inserted after. The design I liked was built from PVC tube with elbows and had no pivot. It just seemed simple. Any foreseen drawbacks?
check out the posts by Airframe he is the owner of Segway Composites and American Blanks. Ken has some posts with plans for building a hotwire bow. I’m not sure if he ever posted anything for splitting the blank but if you email him he’d probably give you some info.
No, I work in lighting. I do know foam sculptors in the business and have asked them a lot of questions. Also, because I work in lighting, I’ll just borrow a variac for my power source.
Thanks for pointing me in the direction of Airframe. I’ll check out his posts.
Ken had two rectangular frame made out of 2 x 4’s hinged together at one end. The bottom frame was for holding the blank in place and the upper frame had a
hotwire in the middle running the length of the frame. When the blank was in place he would rest the upper frame with the hotwire on the blank, he would flip the switch
on the hotwire cutting a nice clean straight line down the center of the blank. Its kind of elaborate but he was just starting to go into mass production then.
i built mine like the one in the link above... i haven't used mine yet, i'm about 15 minutes away from powering it up... i didn't use plywood though, i bought a length of 1x4, cut it into 3 pieces, and screwed them together at the corners (it was cheaper and less waste than the plywood version)... i bought a variac off of ebay for about $50 shipped and Surfding was kind enough to send me some wire that he recommended.
For the power supply, I’ve used a few and had the best results with the 12V output of a PSU from an old computer! (to start them up you have to short circuit the green wire with a black one, I do that with a paperclip)
You can easily get them for free!
I bought my wires from ebay, search for “nichrome” wire. You’ll find them in differern cross sections and resistances.
For 1lb foam use a power of 35W per meter.
For 2lb foam use 45W per meter
so now you know the needed power, choose the length and you can calculate wich resistance you’ll need to buy for a 12V power supply.
going through some older pics and finding threads for them. here’s a pair of “bows.” the small rail band and outline cutter is a super-cheap hacksaw frame repurposed with a tension spring from the who knows where. the bigger one will do a full width compsand style core if the rails are add-on, or a full blank in halves. it’s laminated from scraps of doorskin ply leftover from a deck replacement on my old fish. i used the west 6/10 epoxy in the caulk tube and zip strapped the lam stack around a 55 gallon drum. again, a salvage spring for extra tension. i use alligator clips at the end of the wire and a battery charger power source. a variac is in my future, along with a wire gauge change to accomodate.