# What size tunnel?



## Biblegrove RR (Jan 4, 2008)

I remember reading an article in GR that used black plastic currigated drainage pipe for a tunnel...? It showed that you can tie a rope through it to form corners etc...
*What size pipe do I get?*


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## barnmichael (Jan 2, 2008)

Big enough for the train to go through.  

I would say at least 14 inch to give plenty of clearance, although I have seen 12" used. It was a little tight. You lose some with the roadbed and of course with the curvature. 
Depends on your scale, also. You'll likely need bigger pipe for 1:20.3 than with 1:32. 

Do you remember what issue of GR? I'd like to look at the rope idea.


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## Paul Burch (Jan 2, 2008)

I use 12" for my 1/29 stuff. For a straight tunnel the track can first be attached to a piece of composite decking which is very stable. It is easy then to slide the track into place . I like to use rail clamps on these sections just in case it needs to be removed for maintenance. It also is a good idea to drill several draimage holes in the bottom. Last I saw the 12" was about $7.00 a foot. The ease of building a tunnel this way makes it well worth it. For tunnel portals I made a couple forms and cast them in concrete at the workbench,then fit them into place with a motar mix.


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## Steve Stockham (Jan 2, 2008)

For 1:20.3 (Fn3) 15" _minimum_ was recommended! The overhand on the swing is the deciding factor.


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## Biblegrove RR (Jan 4, 2008)

Michael... I could not find the issue but here is the idea. Run a rope through the pipe, Curve the pipe and tie the outside ends together. The tighter you draw the rope the tighter curve you get. Then place it where you want and cover it up with dirt. The rope only helps maintain the curve until it's buried. 

Composite decking is great idea...What type of base can I use if it's curved? 
Not sure about drainage holes, I am afraid they may become import holes for water....? 
Maybe pockets should be dug below the drainage holes and filled with loose gravel to help with the drainage? 

thanks a bunch guys!


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## Paul Burch (Jan 2, 2008)

I do put some gravel beneath the pipe to allow for drainage. I have never had a problem and I live in the rainy northwest.


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## Biblegrove RR (Jan 4, 2008)

Lowe's wants $130 for 20 ft of the 15" stuff!









Menards should be cheaper, going to check


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## Paul Burch (Jan 2, 2008)

Some of the landscape supply places handle the stuff and will sell by the foot.


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## 3lphill (Feb 22, 2008)

Good Morning All,


Before giving your $$ to a big box store get a price from a supply house. On the west coast I like Ferguson inc. I think they are national company. I find them to be less expensive. And given the current state of affairs they seam happy to sell anything.


Phillip


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