Tunnel Portal Redo

P

phils2um

Phil S
11 Sep 2015
347
123
Ann Arbor, Michigan
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.

121007_c54576bbec5c656af775ee6894470853.jpg


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.

121013_06876240c0dda7de61eda2e6f506b06d.jpg


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.

121017_a72a8909cd89cf6f206634285e761f09.jpg


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.

121015_ccd33ff98c1daeee74e71112c75e611a.jpg


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.

121031_4c10471ffcb6a8d1454d933695f2618f.jpg


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.


121035_25971bc45bd94499ad37166bd91c0c01.jpg


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.

121038_f43a8c76f153a143f2a026b7b718b285.jpg


121039_180624fb51132e685e3bfe1c42547d1e.jpg


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.

121041_f4fa82fffe69056b7d30ef257cc09243.jpg


Phil S.
 
Last edited:
JimmyB

JimmyB

Phase 1 complete, roll on Phase 2
23 Feb 2018
1,866
275
65
Weston-super-Mare
Very good, and a nice use of an alternate material.
 
dunnyrail

dunnyrail

DOGS, Garden Railways, Steam Trains, Jive Dancing,
25 Oct 2009
15,025
458
71
St.Neots Cambridgeshire UK
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.

View attachment 250922

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.

View attachment 250925

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.

View attachment 250927

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.

View attachment 250926

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.

View attachment 250934

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.


View attachment 250936

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.

View attachment 250937

View attachment 250938

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.

View attachment 250939

Phil S.
Very nice, just needs a little blending into the ground with perhaps some small vegetation added as well. Depending on the Location ‘Mind your own Business (baby’s tears)’ if shady or ‘Sedum’ if Sunny will add a ‘lived hear ages’ look. You could also consider a bit of Smoke Blacking above the centre and perhaps an odd smudge of a natural green to represent other small growth in the Stonework.
 
PhilP

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
23,632
535
Tamworth, Staffs.
Do the smudge with a candle with a long wick held under the portal, it will soot up quickly and will look very realistic (because it is really soot).

Greg
is that a good idea on foam insulation? - A candle flame is very hot.. Physics and chemistry going on, is pretty awesome as well! :nerd::)
 
PhilP

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
23,632
535
Tamworth, Staffs.
Was just adding a note of caution.. Would not want the reworked portal damaged..
 
dunnyrail

dunnyrail

DOGS, Garden Railways, Steam Trains, Jive Dancing,
25 Oct 2009
15,025
458
71
St.Neots Cambridgeshire UK
Have to say a quick blast with some Acrylic Rattle Can Matt Black would be a safer and quicker fix. Fire and Expanded Polystyreen are never happy partners, no matter how careful you are.
 
P

Paul M

Registered
25 Oct 2016
3,269
265
56
Royston
Have to say a quick blast with some Acrylic Rattle Can Matt Black would be a safer and quicker fix. Fire and Expanded Polystyreen are never happy partners, no matter how careful you are.
Especially after a that hard work:tmi: