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  • Member since
    December 2005
  • From: west of Portland Oreg.( the city of Roses
  • 583 posts
Posted by TrainsRMe1 on Wednesday, April 21, 2021 1:40 PM

Good day Modelrailroaders

I have a question for you, I'm at the point where I'm going to model a river, since I'm modeling the Cascade Mountains of Oregon, I want my river to be rapid flowing, now, I have a foam subfloor,   and I plan to use the Woodland scenics materials for the project, would it be better to cut out a section of plywood for my river bed, or would the foam be ok ??? Thanks looking forward to hearing from you all!!Cool

  • Member since
    September 2003
  • 20,264 posts
Posted by Overmod on Wednesday, April 21, 2021 2:11 PM

A lot of the 'best' answer is going to involve how you plan to make that river.  For example if you plan to cast it, you need to exert tremendous care not to leave even the slightest leak, or allow one to strain or soak its way open.  This is difficult in different ways with regular plywood or typical foam; some of the 'revealed wisdom' on rivermaking and water over the years here suggests other methods of forming the channel.

  • Member since
    March 2002
  • From: Milwaukee WI (Fox Point)
  • 11,339 posts
Posted by dknelson on Thursday, April 22, 2021 10:13 AM

I used the Unreal Details "Magic Water" two-part epoxy product on my layout, and the river or creek bed was foam, sculpted a little with hot wire and covered with greenish ground foam with strategically placed rocks and logs (and one actual detail that I remembered seeing in that very creek as a teen: a coupler and its drawbar had evidently been pulled out on the grade and had been thrown over the edge of a bridge landing in the water, very visible for years until it was covered with silt and algae). 

That way I could texture the creek bed as I would regular scenery before the "pour."  I prefer to put the colors and textures on the bed rather than add tints to the "water."  

And before the "pour" on my layout I created a small creek or river bed out of a hunk of foam to try out my various ideas - an idea which I recommend by the way.  It is a skill and all skills take practice.

In both the testing sample and the final product on the layout the biggest challenge was exactly what Overmod mentions: tightly sealing every place where the liquid could escape, because it is almost unbelievable how well we think we've sealed something for liquids versus the unpleasant reality.  In both cases I created end "dams" of sheet styrene, very well secured to the foam creek or river bed with flexible adhesive caulk.  The trick was to remove the dam after the water hardened without ripping out some of the foam but a sharp knife and patience did the trick.

The effect of rushing water I added after the base pour had hardened.  And again I practiced that also on my little sample water feature.  As a rule scenery experiments are easy to rip out and do over but for water features I think it pays to create a practice example first rather than experiment on the layout itself.

Dave Nelson

  • Member since
    February 2005
  • From: Vancouver Island, BC
  • 23,272 posts
Posted by selector on Thursday, April 22, 2021 10:44 AM

This is where I would very seriously ask myself why I would not use gel gloss medium.  You needn't worry about the medium 'running' and sagging, or flowing, into places where you had hoped it wouldn't, and you needn't worry about leaks.  Instead, you craft your river bed, gouging and filing, cutting and rubbing, and when you have it looking much like you fancied it, start with a single layer of painted gel gloss medium.  When that cures to clear, add another layer...and so on.  You can add talus and other debris or erosion artefacts as you need to, maybe best right after that first layer and embed it to fix it into place.

A rushing stream won't look as deep and dark like the slower murkier ones will.  So be careful about how you prep the river bed in terms of shading with craft paints.

  • Member since
    January 2017
  • From: Southern Florida Gulf Coast
  • 17,546 posts
Posted by SeeYou190 on Thursday, April 22, 2021 10:52 AM

Would it be better to cut out a section of plywood for my river bed, or would the foam be ok?

Either one will be fine for the base to model the river upon.

When I model a water feature, I cover the base with a layer of drywall joint compound and work the surface perfectly smooth. Then I build up the river on top of that.

Since the base will be covered with joint compound, plywood or foam will both work equally well.


Living the dream and happily modeling my STRATTON AND GILLETTE Railroad in HO scale. The SGRR is a freelanced Class A railroad as it would have appeared on Tuesday, August 3rd, 1954, in my personal fantasy world of plausible nonsense.

  • Member since
    January 2010
  • 2,616 posts
Posted by peahrens on Thursday, April 22, 2021 2:59 PM

Perhaps some of the following my be useful in your approach.  I included a depressed corner on my plywood cookie cutter layout, taking the idea from the 2012 Virginian Project Layout.  I created sloped sides with hot glued cardboard strips plus plaster cloth and then applied Sculptamold.

 IMG_7156 by Paul Ahrens, on Flickr

Next I painted on my latex earth tone and added scenery to the side slopes.

 IMG_7166 by Paul Ahrens, on Flickr

Next was to paint the river bed with blended shades of blue to tan to imply the varying depth. 

 IMG_7165 by Paul Ahrens, on Flickr

I added some small stones in the river bed and along the shoreline.  Then added a first layer of water, using my chosen Mod Podge Gloss medium.  It goes on looking like white glue and within a couple hours turns to clear.  One photo shows it mid way clear and the other when not quite finished.

 IMG_7167 by Paul Ahrens, on Flickr

 IMG_7168 by Paul Ahrens, on Flickr

Next I added some white paint on the upstream side of rocks in the stream, as well as a white streak past the rocks, to simulate some churning at the rocks. (I may have done this earlier).  Then I added another layer of Mod Podge to the level I wanted.  Some rocks are submerged, others just partially.

 IMG_7176 by Paul Ahrens, on Flickr


Modeling HO with a transition era UP bent

  • Member since
    September 2004
  • From: Dearborn Station
  • 23,461 posts
Posted by richhotrain on Thursday, April 22, 2021 3:50 PM

Great sequential series of photos, Paul!  Yes


Alton Junction

  • Member since
    January 2004
  • From: Canada, eh?
  • 13,314 posts
Posted by doctorwayne on Thursday, April 22, 2021 11:38 PM

Very creative treatment of an external corner....

I have to agree, that's a nice looking scene, and one that's not seen often...very imaginative use of your space, Paul.


  • Member since
    February 2008
  • 2,094 posts
Posted by kasskaboose on Friday, April 23, 2021 7:07 AM

Great work on the river along the layout.  It demonstrates a great level of detail and creativity.

To the OP's Q: I would suggest using Plaster of Paris to ensure whatever water product you use doesn't seep through the foam.  

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