My Take on a Hot Wire Cutter for Foamy Radio Controlled Planes.




I need to build a hot wire foam cutter to build my next RC Aircraft, and I documented it for a friend over at Hope you like it's unique features, like portability, size and ease to build.

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: Assemble the Supplies.

I come from Australia so a lot of this is based around Aussie shops/products.

I went to Bunnings for 1 metre of 15mm PVC pipe, two 15 mm elbows, and two 15mm end caps, 1 metre of dual core speaker wire (the guy gave me 2 metres for the price of one, so very happy with that.) some single strand picture hanging wire, and electricians tape, things I gathered from around the house were; an eye bolt, the spring from inside a pen, two Phillips head bolts with four washers and four nuts, and a male Deans connector.

Step 2: Cut the PVC

I cut the PVC into three pieces, two were 30cm long and one 40 cm long (the biggest foam I will be cutting is 34 cm long).

Step 3: Assemble the Frame.

Connect the 40 cm length of PVC to the two elbows, one 30 cm piece into each elbow and an end cap on each end.

Step 4: Drilling

I used calipers to determine that the speaker wire is 6mm thick, and drilled a 6mm hole in one of the elbows.

Step 5: Speaker Wire

I split the cable into two, to 80 cm from one end, and fed the ends down different "arms" of the cutter frame.

Step 6: End Caps

I measured the bolts and drilled a hole in each end cap, and stripped the wire, formed a loop that fits over the bolt and assembled both end caps, I took the Phillips head bolt and placed one washer on it, the the wire loop, then another washer then fed that through the end cap, and fastened it on the outside with a nut.

Step 7: The Cutting Wire

I took the picture hanger wire and took out a length, about 45 cm or so, and looped it around one of the bolts and secured it with another nut. At the other end I made a loop at about 36 cm from the secured end, and fed it into a spring from inside a pen, I then drilled a hole on the arm without the hanger wire attached to it and threaded in the eye bolt. I attached the free end of the spring to the eye bolt and wrapped the remaining hanger wire to the Phillips head bolt sticking out of the end cap and secured another nut over this.

Step 8: Powering This Thing.

I stripped the remaining ends of the speaker wire and soldered them to a Deans connector.

I can now do two things;
- power it from a three cell LiPo
- take it absolutely anywhere (not tied to mains power)

Cuts like a hot knife through foam... ;-)

First Time Author Contest 2016

Participated in the
First Time Author Contest 2016

Be the First to Share


    • CNC Contest

      CNC Contest
    • Make it Move

      Make it Move
    • Teacher Contest

      Teacher Contest

    7 Discussions


    3 years ago

    Nice! Would you consider adding a stand for it to rest on? I think it would be way easier to use it that way

    2 replies

    Reply 3 years ago

    Do you mean a stand for while it's in use?
    I made it to be portable so that it can be used to "freehand" cut foam in three axis using templates for various parts that are up to about 35cm long. I hang it on the wall on two hooks when its not cutting.


    Reply 3 years ago

    I think you should edit that into the Instructable-- Not everyone checks the comment section before they make one :)


    Reply 3 years ago

    I can't find an option to edit the original on my phone which is why I added it as a comment.


    Reply 3 years ago

    ignore that found the option and have now edited it, thanks for the feedback.