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How do you cut foamboard?


Knower of useless information
So, here's some tools I use for my builds:

Box cutter/folding knife for long straight cuts - https://www.dewalt.com/products/hand-tools/knives-and-blades/folding-fixed-blade-knife/dwht10916

It's a Dewalt folding box cutter, and I love this thing. One of the reasons I like it is because it's not the standard grey, but that bright "construction yellow" color, which makes it really easy to see on my build table and self-healing cutting mat - I tend to "misplace" items on my build table easily, and having them be a bright, obvious color makes it easier to spot. Also, this particular knife has a quick release for changing the blades, which is kind of nice - it means I don't have to use a screwdriver to disassemble the cutter and turn or swap the blade like I would with many other box cutters. Is it necessary? No, but it is nice to not need another tool cluttering up my build table. :)

Blades for folding knife - https://www.homedepot.com/p/Husky-Heavy-Duty-Utility-Blades-Dispenser-100-Pack-HKHT19057/205037418

I bought the 100 pack of these blades at my local Home Depot. I had originally bought a set of 50 blades at the local Harbor Freight, a box of no-name brand blades, because they were like, $3 for 50 of them, I think? Turns out the blades were junk. I could get only a few passes with them before they were dulling and I was having to go through the hassle of sharpening them, flipping them around, or swapping them after a couple of long cuts. Spending a little more for the "heavy duty" blades, they last a lot longer and are well worth it, in my opinion, especially if your box cutter requires you to disassemble and reassemble it with a screwdriver.

Cutting Mat - https://www.amazon.com/dp/B0006SDOFO/?tag=lstir-20

I use a cutting mat like the one above to make all of my cuts. There's a couple of reasons for that - it doesn't dull the blade as quickly as cutting into something harder, and since I'm usually doing this in the living room on a coffee table, it saves my coffee table from getting all of the nicks of the blade (and prevents my hide from being tanned by the wife if it were to leave a mark in the table!)

Cork backed metal ruler - https://www.amazon.com/dp/B00094A48A/?tag=lstir-20

I use a cork backed metal ruler for cutting for a couple of reasons - I can lay it down on my pattern and give myself a nice, straight edge; the cork prevents it from sliding too much when I'm cutting, and I end up getting a nice, straight edge. I only have a 12 inch ruler, as shown above, but they come in 18" lengths for not much more. Also, the metal ruler is nice when I do something like glue poster board down for shaping - the metal prevents my fingers from getting burned and transfers heat more evenly if I press it against the poster board and the foam. See the MiG-3 build video for an example - it really does help save yourself from glue burns and it allows for a smoother edge.

Exacto knife with #11 blades - https://www.amazon.com/dp/B0000DD1N4/?tag=lstir-20

I use something like this to cut my curves and smaller cuts with, such as the rectangular inner holes that a wing spar might fit into. Many times, the box cutter/folding knife blade is too big to get in and cut effectively; the Exacto knife is much more precise and easier to wield. Also, you can buy a box of 40 blades for around $10 for this knife and they'll last you through many builds.

I should mention that I've seen some people say that they use T-squares for their long cuts; I tried to do that and failed miserably, because the straight line cuts never seem to be at right angles to the foamboard - it's always at various angles, and so I could never really get the t-square to sit properly on the foamboard. That's where the cork backed ruler worked much better, at least for me.

Hopefully this info helps with your builds!
On straight cuts a small hobby table saw comes in handy. I use one to cut bevels in control surfaces. If you are using a foam board without paper covering, such as Depron or MPF, then a hotwire comes in handy. It gives a clean cut. Hobby saw post on my blog HERE. Hot wire post HERE. Tips for foam board R/C modelers on my blog HERE.


Nothing too radical for me. I use the adjustable, disposable blades for my main straight cuts, roughing out pieces, and even gentle curves.


A fine tipped X-Acto for the tight curves and fine work. Just go along very lightly on the passes until you're through.


Fiskars 24"x36" cutting mat.


A pair of 12" and 24" steel rulers.


I really like the Logan Foam Works tool for making the partial cuts and bevel cuts. Not a fan of the proprietary blade design, but the blades don't get much use beyond those two cuts, so they last quite a while. I'm sure there are some decent 3D printed version of this concept that would work pretty well also.