How difficult or easy is it to rip 1/4", 3/8", and 1/2" thick sheets from a 3" block of minicell foam with a table saw? I can buy a 12" x 12" x 3" foam block from NRS for $15 and get all the foam I need. The other option is getting three sheets, one of each thickness, for $60 from Amazon.
I had no problem cutting and sanding the edges smooth of 1/2" thick foam sheet for hip pads, but sanding the face of a pad cut from a 3" block seems like it will be difficult, especially if the sheet is 1/4" thick.
I’ve used a radial arm saw with a carbide blade to cut blocks out of packing foam (similar to water noodle foam, but more rigid feeling). I’ve also used a hand-held oscillating saw to to cut denser foam (not official minicell, but similar in density). Both worked fine. I expect that you could rip minicell, assuming you’re talking about ripping through the 3-inch section, not making thin 12x12 sheets.
If you try it, please let us know how it works. Thanks!
Forget the table saw, it will just make a mess and trying to control Minicell foam when cutting with one is challenging at best, dangerous at worst.
A band saw is the best tool for cutting foam and that’s actually what they use in manufacturing foam sheets and products. However, the blade is essentially a long knife (no teeth) and the saw is called a “slitter”. I haven’t seen these blades for typical band saws, but they may exist.
Cutting 1/4" sheets is going to be difficult and I don’t think I’d attempt it. The material is simply not rigid enough for that. You may be able to do the thicker sizes, but you won’t know until you try it. If you decide to give it a shot, cut the thinnest slices first, while the block is still thick and reasonably rigid.
I’ve made a lot of Minicel parts using a band saw, but haven’t tried “resawing” to make sheets.
I am cutting 1/4", 3/8", and 1/2", 12" x 12" sheets out of a 12" x 12" x 3" block. Allowing for blade thickness, this should yield enough sheets of varying thickness to fit the kayak. Am thinking a random orbit disc sander will work to smooth the 12" x 12" face.
You can reduce the surface roughness by sanding, but the best you’ll likely achieve is a suede-like surface. If you want it really smooth, coat the finished parts with Plasti-Dip or something similar. It’s also possible to smooth and harden the surface by passing a flame over it (it’s polyethylene), but you can also melt it in a heartbeat.
I have always cut Minicel with a band saw or a knife, and shaped it with a Surform tool or sandpaper (sometimes a sanding drum), but I haven’t tried an ROS on it. You have to keep in mind that the surface is soft, flexible and grippy. It’s not like working with wood. Just when you think you’ve got it nailed, it will grab a saw blade and drag the piece into it, ruining your work. Take extra precautions to protect your hands and keep them away from the saw blade.
You’d need at least a 6 inch depth of cut to cut 12" x 12" sheets. I don’t have any experience that would help there. I do think that the sander will create a fuzzy surface as it will tear the foam. Fortunately, none of the foam cuts I’ve made were on a surface that was exposed in use so the appearance wasn’t critical.
Buying the thicknesses you need sounds like a smart move to me. I’ve never bought anything thinner than 1/2" and frankly, very few of the parts I’ve made for kayaks are flat.
There’s another way to get a smooth surface. Make your pads undersize by the thickness of the thinnest material you have, then laminate a layer on the outside. I recall seeing thin sheets of closed cell foam at Hobby Lobby, 12" square or possibly larger and I think they even have it with an adhesive back. I can’t vouch for how well it will work, but it’s pretty cheap so it may be worth a try.
You can sand Minicel to an acceptable surface, the key it to not use much pressure, so it doesn’t grab and tear. Start with 80 grit, then move up to 120-150 grit if you want to refine the surface more. That’s what I typically do.
You might be able to use a crosscut sled with a table saw.
The zero tolerance will have to not have any blemishes and you could screw a block of wood forward of the material and over the top to keep it from squirming.
I always used a Japanese pull knife to cut it and clamped a fence in place.