Here are some pics documenting the "redo" of my first attempt at creating a tunnel portal using foam insulation board and a "Tippi" hotwire foam cutting tool.
This first pic shows the portal as originally created. There are three things I don't like about this; 1) the scale of the block, 2) vertical courses in the field blocks, and 3) the color.
This first attempt fit the hole pretty well so I decided to just add one more filler layer and a new facade layer. The next pic shows the filler layer glued is place. The layer, consisting of three scrap pieces, was attached to the original portal face with Bordon's Saf-T contact cement. I've found this stuff will tenaciously glue the flat surfaces of foam board without eating into the foam.
This pic is of the Tippi hotwire tool for those who have not see one. The tool has a cutting tip installed. The "scroll-saw" attachment is next to the tool. The tool uses a high resistance NiCr wire to "cut" the foam by melting its way through. I picked this one up at a train show for about $45. It works great on foam insulation board.
The next shot is of the facade layer set in place to check the fit and appearance. The portal opening has already been cut using the Tippi hotwire tool with its scroll-saw fitting. The two beveled edges on the sides of the filler blocks and facade layer were also cut with the scroll-saw fitting. Uniform straight cuts were accomplished by clamping a metal straight edge (metal ruler) on one side and marking a parallel straight line on the opposite side of the block. The straight edge acted a a fixed guide for far side of the hotwire tool as it was visually pulled along the line marked on the near side.
The layer of paint is covering up a first block pattern that I didn't like. What's shown is the pattern I ended up using. The hotwire tool with the cutter shown in the picture was used to make grooves 2-3 mm deep in the facade by following block pattern with the tip of the tool. The grooves for each course of block were done first. This particular cutter was fashioned from a spare wire that came with the tool. It was bent so its tip was the width of the blocks. That made defining each individual block simple with a shallow, straight in plunge between the grooves for the courses.
The next photo shows me carving the blocks.
I used a sharp X-Acto knife to cut the corners and edges off each block. The cuts are deliberately uneven. That's what gives a hewn appearance to the blocks. I found it easiest to first do two edges of each block then flipping the foam around to cut the other two edges. A sharp knife is imperative. Otherwise, instead of being cut, the foam will tear. It was tedious but went fairly quickly because I was not concerned about making nice even cuts.
This shot is of the portal with the facade glued in place and the very dark brown base coat of paint. The grooves were touched up with a fine brush to make sure each groove was completely painted and none of the pink foam showed.
The next two shots show the glued up portal after painting. I used exterior grade latex paint in various shades of brown and beige and also just a touch of red. The color coats were applied by a combination of dabbing the paint on and dry-brushing. Each application of paint was allowed to dry to the touch before the next color was put on.
You'll notice that I was not concerned that the openings lined up perfectly in each layer. I think the end result gives the tunnel walls a rough hewn appearance too.
This last pic is of the finished portal back in place. The color looks pretty good, but I may tweek it a bit sometime in the future if I decide to add wingwalls.
Phil S.
This first pic shows the portal as originally created. There are three things I don't like about this; 1) the scale of the block, 2) vertical courses in the field blocks, and 3) the color.
This first attempt fit the hole pretty well so I decided to just add one more filler layer and a new facade layer. The next pic shows the filler layer glued is place. The layer, consisting of three scrap pieces, was attached to the original portal face with Bordon's Saf-T contact cement. I've found this stuff will tenaciously glue the flat surfaces of foam board without eating into the foam.
This pic is of the Tippi hotwire tool for those who have not see one. The tool has a cutting tip installed. The "scroll-saw" attachment is next to the tool. The tool uses a high resistance NiCr wire to "cut" the foam by melting its way through. I picked this one up at a train show for about $45. It works great on foam insulation board.
The next shot is of the facade layer set in place to check the fit and appearance. The portal opening has already been cut using the Tippi hotwire tool with its scroll-saw fitting. The two beveled edges on the sides of the filler blocks and facade layer were also cut with the scroll-saw fitting. Uniform straight cuts were accomplished by clamping a metal straight edge (metal ruler) on one side and marking a parallel straight line on the opposite side of the block. The straight edge acted a a fixed guide for far side of the hotwire tool as it was visually pulled along the line marked on the near side.
The layer of paint is covering up a first block pattern that I didn't like. What's shown is the pattern I ended up using. The hotwire tool with the cutter shown in the picture was used to make grooves 2-3 mm deep in the facade by following block pattern with the tip of the tool. The grooves for each course of block were done first. This particular cutter was fashioned from a spare wire that came with the tool. It was bent so its tip was the width of the blocks. That made defining each individual block simple with a shallow, straight in plunge between the grooves for the courses.
The next photo shows me carving the blocks.
I used a sharp X-Acto knife to cut the corners and edges off each block. The cuts are deliberately uneven. That's what gives a hewn appearance to the blocks. I found it easiest to first do two edges of each block then flipping the foam around to cut the other two edges. A sharp knife is imperative. Otherwise, instead of being cut, the foam will tear. It was tedious but went fairly quickly because I was not concerned about making nice even cuts.
This shot is of the portal with the facade glued in place and the very dark brown base coat of paint. The grooves were touched up with a fine brush to make sure each groove was completely painted and none of the pink foam showed.
The next two shots show the glued up portal after painting. I used exterior grade latex paint in various shades of brown and beige and also just a touch of red. The color coats were applied by a combination of dabbing the paint on and dry-brushing. Each application of paint was allowed to dry to the touch before the next color was put on.
You'll notice that I was not concerned that the openings lined up perfectly in each layer. I think the end result gives the tunnel walls a rough hewn appearance too.
This last pic is of the finished portal back in place. The color looks pretty good, but I may tweek it a bit sometime in the future if I decide to add wingwalls.
Phil S.
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