I'm working on a simple layout using a sheet of 2" rigid foam. What is the easiest way to "dig out" a creek and pond? Is there a good guide online somewhere?
If you have not bought your foam, I suggest using two sheets of 3/4" foam, That way you can use a box cutter to remove the top layer for ponds and creeks. Otherwise it will be very difficult to hollow out a 1/2"-3/4" divot without going through to the bottom. I don't know of any convenient way to do that.
I've already bought the sheet of 2" foam, but thought about adding a 1/2" or 3/4" sheet on top of it. But I'm unsure about cutting out the top layer.
Adding a 1/2" board on top will work. I held a box cutter at about a 45 degree angle to cut the 1/2" top layer of foam. Use a slight sawing action or the foam will bunch ahead of the blade because it's soft. I used Liquid Nails for Foam (or its equivalent) to glue the two foam layers. You must remove the thin plastic sheet from the foamboard faces before gluing, or you won't get good adhesion.
A hot knife works miracles in cutting through foam. Used like a knife you can angle the cuts for bank slopes. Most craft stores carry them.https://www.amazon.com/dp/B07FKCR47...&pd_rd_r=d7c90b6e-4755-11e9-b867-49bec1c8c3ce I recommend this style of knife that I have been using for years now to carve my foam and I have cut foam out that was glued down. The thin shape allows you to do a lot. Just one caution thought and that is not to force the blade.
I did a review of one that I have about 2 years ago when I finally wore out my old one and bought a new model. The key thing is not to force the knife but rather go slow and let the knife melt its way through. Those blades are very thin and flexible and easily bent or broken. But once you get the knack of using one tis amazing what one can do. Maximum thickness is about 3 to 3 and 1/2 inches of dense foam. They make a thicker bladed one but the thin blade one allows for more intricate cutting.
I have used MEK to "burn" through the pink extruded 2" foam that I used. I was making bar ditches along the side of the roadbed. You have to be careful with the MEK, for sure, cause too many dribbles might go completely through foam. A lot easier than digging out the foam. Carl
We used MEK by the gallons in the aircraft industry, it was banned in California in 1984 and in Oklahoma about 1996. I suggest not using it because of the risk of cancer and because of the fumes not to mention the mess. When I cut foam I use a keyhole saw or hot wire cutter. Joe
I prefer a small linoleum router for streams, using a round bit. Makes a very nice stream bottom, and it’s very easy to meander. $30 at harborfreight.
It’s the baby brother of the big router. Choose a bit that matches the shape of your stream bed. https://m.harborfreight.com/14-in-24-amp-trim-router-62659.html
I wondered about using a router. HF used to have a trim router for $20, but I don't see it on their website.
Do not mess with MEK at all. Used it aircraft maintenance once while in the USN. In training, we were told if it gets on your finger, it soaks in and you will taste it in 5 seconds. They were wrong. It took 9 seconds !!! DON'T mess with it !!!
Yes, I've heard them called "burrs" and "dental burrs" (for the smaller ones). I'm guessing it would create an unholy mess, but I'll be doing it outside.