Drainage Ditch cutting...

[TundraSpyder]

Looking for suggestions for cutting miles of drainage ditches.
I have 2" foam on my virtually flat layout and used raised cork for the main line and 1/8" cork for sidings. I still need to cut many drainage ditches and I want to lower the contour of the foam in places to vary the height slightly. So I need a power tool method of doing this without creating a giant mess. I have 3 ideas and wonder what works best?

1) Oscillating multi tool seems like an easy way of doing this and can use it to cut plywood out as needed to lower scenery further if needed for creeks
2) Dremel tool with a small sanding drum. Would use the shop vac at the same time to reduce pink spray
3) porter cable restorer. I think you could use the corner to get a v cut (I think. I don't own one)

While I love the idea of the Porter Cable restorer, I think for all but the creek beds on my layout its over kill.
https://www.therailwire.net/forum/index.php?topic=43583.0

Dremel is not going to handle the larger job of tapering down an area well to lower that section of scenery

Oscillating multitool with the tile cutting blade should go through foam like a hot knife I think..

Suggestions, experiences?

[davefoxx]

I just use a 2" snap-blade knife.  To carve the ditch, I cut a "vee" in the foam next to the cork roadbed with two cuts of the knife.  Lightweight spackling smooths this and makes it more of a u-shape.  If I need scenery below track level, I forego the ditch and just cut the foam away with the knife.  This old picture may give you an idea.  The ditch is on the left with the hill above blended into one side of the ditch.  The "fill" is on the right.  You can see ditches on both sides of the cork roadbed under the trestle.



Hope this helps,
DFF

[Ed Kapuscinski]

I just use a 2" snap-blade knife.  To carve the ditch, I cut a "vee" in the foam next to the cork roadbed with two cuts of the knife.  Lightweight spackling smooths this and makes it more of a u-shape.  If I need scenery below track level, I forego the ditch and just cut the foam away with the knife.  This old picture may give you an idea.  The ditch is on the left with the hill above blended into one side of the ditch.  The "fill" is on the right.  You can see ditches on both sides of the cork roadbed under the trestle.

That's my technique too: I use a knife to cut a V that's deeper and bigger than the finished contour should be and then fill and smooth with my terrain covering material.

[Maletrain]

Cutting foam with an Xacto blade is a lot easier when that blade is heated.  I bought a cheap soldering iron with a blade holder attachment at the end.  It gets just hot enough to easily gut foam without any sawing motion or much force, without melting the plastic into blobby surfaces.  https://www.ebay.com/itm/Hot-Knife-30W-HEAVY-DUTY-CUT-CUTTER-PLASTIC-FOAM-NYLON-multipurpose-stencil-cut/313196948348?

There are also some dedicated wire types that can be bent: https://www.ebay.com/itm/Electric-Styrofoam-Cutter-Carved-pen-Hot-Wire-Styro-Foam-Knife-12V-5A-60W/292641088379?hash=item4422c4a37b:g:3~8AAOSw4A5Y2OKF

[Ed Kapuscinski]

Cutting foam with an Xacto blade is a lot easier when that blade is heated.  I bought a cheap soldering iron with a blade holder attachment at the end.  It gets just hot enough to easily gut foam without any sawing motion or much force, without melting the plastic into blobby surfaces.  https://www.ebay.com/itm/Hot-Knife-30W-HEAVY-DUTY-CUT-CUTTER-PLASTIC-FOAM-NYLON-multipurpose-stencil-cut/313196948348?

There are also some dedicated wire types that can be bent: https://www.ebay.com/itm/Electric-Styrofoam-Cutter-Carved-pen-Hot-Wire-Styro-Foam-Knife-12V-5A-60W/292641088379?hash=item4422c4a37b:g:3~8AAOSw4A5Y2OKF

I had a scenario on Windsor St where I needed to "scoop" foam out of a flat sheet to get the contours I wanted. I would've loved those knives! Instead I had to make my "home incineration device" out of a Weller soldering gun and some music wire. It worked but it definitely sketched me out while using it.

[Philip H]

There are also some dedicated wire types that can be bent: https://www.ebay.com/itm/Electric-Styrofoam-Cutter-Carved-pen-Hot-Wire-Styro-Foam-Knife-12V-5A-60W/292641088379?hash=item4422c4a37b:g:3~8AAOSw4A5Y2OKF

Just took delivery of one of these right before the storm for this exact purpose.  May get around to using it this weekend.,

[Maletrain]

I had a scenario on Windsor St where I needed to "scoop" foam out of a flat sheet to get the contours I wanted. I would've loved those knives! Instead I had to make my "home incineration device" out of a Weller soldering gun and some music wire. It worked but it definitely sketched me out while using it.

Amen to the smell of molten foam making you "sketchy".  That is why I liked the cheap soldering iron with the Xacto blade attachment mod.  Mine, at least, gets only to the temperature that makes the foam easy to cut without sawing motion, but leaves a smooth, normally colored surface, not a blackened one.  Of course with something that cheap, I am not going to promise that another copy will result in the same blade temperature.  If it gets too hot, it might be possible to put that adapter on a lower wattage iron.  But, there are apparently two similar but not compatible threads on the replaceable tips to those cheap irons, and I seem to have some of both.  So, the one adapter I have for the Xacto blades only fits some of my collection of cheap irons with different wattages.

[TundraSpyder]

Thanks. I have the Wire cutter similar to the ebay item, but mine only came with a straight want I believe. I used it to cut the foam sheets. Towards the end, and lots of plastic strings everywhere, I discovered that for straight lined the knife was better.

A heated blade may be the best option.

What I really need is like a small heated melon baller with the back cut off  to make a loop... hmmm... I have a grinder.

[Ed Kapuscinski]

Amen to the smell of molten foam making you "sketchy". 

Oh god yea. I remember hanging out with @Black Diamond working on his layout and using his gigantic hot knife. Worked like a charm until the headache kicked in!