Cardboard or Foam?

Jon Majors

Active Member
We're doing Wizard of Oz and I'd like to make a portal by constructing 2 trees on either side of the stage and they meet in the middle at the top. For the cost, I'm thinking of building a 1x4 frame and attached either cardboard or foam to the front. These will be about 10' wide at the base and 22' tall. I don't have experience using either. Can anything plea their case on which is better, as well as suggestions on painting, hiding seams, and fire protecting? Brownie points for photo exxaples. Thank you all!
 
I will admit first thing that I have a bias against using cardboard as a scenic material unless the design calls for it. I would prefer, and have had better experiences with, foam.

I worry about putting the foam directly to the 1x frame. In the past, if I had a flat with foam on it, I would have 1/4" lauan on the frame, then attach the foam to the lauan. This would be for both structure and for adhesion purposes. Especially on something so tall, I wouldn't trust building 1x and foam only with "standard" flat framing practices. If you are going to forgo the lauan and put the foam directly on the frame, I would increase the amount of framing you have behind the foam to accommodate for structure and allow enough surface area to adhere to the 1x. For the adhesive, I would recommend 3M Fastbond NF contact adhesive. You brush or roll it onto each surface, let them dry, and then put them together. Apply some pressure overnight and it holds pretty well. Plus, it's water based, not acetone based, so it won't eat the foam (learned this from experience). I would plan for 2-3 coats of the adhesive because it tends to soak into the foam, and 1-2 for the wood. Carve and paint the foam as needed.
 
I once made a box beam Rafter structure for an old time train station, that spanned 20 feet or more from 3/4 blue foam.. Tacked the initial beam structures with screws then taped with simple masking tape (not the quick release) and painted over for more adhesion. The beams had a small amount of lumber to hold the rafter angle at the peak, but the beams themselves were self supporting. The whole shebang was hauled up and the lumber portions tacked in place, but basically the whole struture was suspended from a single line. The beams were so light that they would have more or less floated down with out hurting anyone had they broken. They hung for about 4 weeks and when the structure was hauled down, we sawed the peak angle away, and stored the beams themselves for future use. Brown base and Black wash graining applied with a wallpaper brush made them quite convincing as the centerpiece for an old train station set. I'm traveling, and will see if I can dig up pics when I get home.
 
Cardboard or Foam? Why, both of course, budget permitting. Foamcore.

But actually I would probably use luaun.
 
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I’ve had good results making tree bark from brown craft paper, or the rolls of brown paper at paint stores. We pull long pieces and twist them into “ropes” then attach to our framing material. The one in the pic is from Alice in Wonderland. I think it was about 10’ tall. Your mileage may vary with the size you need though.
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I don't care for cardboard. I've had it warp. Extruded Polystyrene (XPS) comes in blue or pink and is a go to material for me these days. I've found the 1" stuff skyrocketed in price but the half inch at $14 for a 4x8 to be reasonable. I glue two pieces together to get one inch. XPS cuts nicely with a variety of tools but can also be machine cut with a jig saw, table saw or multitool. For random curves and such, I like to use a blade foam cutter (not a wire cutter) as it melts it here and there, is hard to hold a straight line and therefore gives it a more natural look. You can also sculpt it as long as you keep things sharp.

As for adhesive, 3M 77 claims to be foam safe but it is not safe for XPS.
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I use Liquid Nails "Projects". The OFFWHITE is water cleanup and less than $2 a tube.
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Beware, the WHITE requires mineral spirits. I only found the OFF WHITE at Lowes. ACE and HD only had the stuff requiring mineral spirits. You apply it, spread it with a putty knife, put the two pieces together and clamp for 30-60 mins. You can do mild work with it at that point but overnight is needed for rough work.

Lowes has a fan folded 1/4" XPS foam used to insulate under siding. Each fan fold is 2'x4'.
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It's an upgrade from cardboard. Beware however, it has a coating on it to stiffen the foam and with too much handling, can delaminate. We used it for an exterior on wood frame for a car and a boat. 3M 77 works on it due to the coating and it can also be stapled. Glue + staple is good and joints can be covered with tape and jointers compound if you like an invisible joint.
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The trees are ten feet in diameter? or the whole portal?
If it's proscenium I'd probably go for a flatter design like a standard flat with some returns and EPS foam over the top. OR you could use semi cricular plywood gussets attach Luan strips , use that as an armature then apply cardboard for a base then craft paper for the 'bark' as @Catherder suggested. If you do cardboard that way then get it damp before applying to the tree, it will help it conform to the tree an you could mix some flamex in the water you mist the cardboard with.
If you want to go nuts do What I did and carve a whole 3D tree with a steel armature and tons of VSSD glopped on the outside.
What ever you do be sure to mix in Flamex paint additive, FR1, or coat with Flamex or FlameCheck. Trees are fun!
 
The trees are ten feet in diameter? or the whole portal?
If it's proscenium I'd probably go for a flatter design like a standard flat with some returns and EPS foam over the top. OR you could use semi cricular plywood gussets attach Luan strips , use that as an armature then apply cardboard for a base then craft paper for the 'bark' as @Catherder suggested. If you do cardboard that way then get it damp before applying to the tree, it will help it conform to the tree an you could mix some flamex in the water you mist the cardboard with.
If you want to go nuts do What I did and carve a whole 3D tree with a steel armature and tons of VSSD glopped on the outside.
What ever you do be sure to mix in Flamex paint additive, FR1, or coat with Flamex or FlameCheck. Trees are fun!

Hopefully each tree is 10' diameter, the portal opening would be about 20' with each tree on either side. Can you further explain your 3D tree method?
 
Hopefully each tree is 10' diameter, the portal opening would be about 20' with each tree on either side. Can you further explain your 3D tree method?
Jon, let me try to sketch something for you, easier than describing it because I can be quite verbose...
 
Man, I don't even know if this is legible. I have horrible handwriting. I could do something better in Sketchup or AutoCAD. So it's really simply 'barrel' construction like a roman column. make the semi circles out of plywood. Separate them with 1x4, gusset and cross brace as necessary. on out side luan strips to form the general outline. If you need it apply wire. If you use fewer Luan strips you'll want to bridge the gaps with Chicken wire or construction cloth. Over the top of that apply the cardboard or Heavy paper. Then add crumpled paper, make twisted paper Ropes or use small diameter cotton rope to add texture then paper over top. If you're happy with it paint, If you think you need it for your look, add a layer of VSSD.

Remember all these ingredients are flammable. Use Flammex, or some other additive, all though the process. 10' diameter is a damn big tree ! <there's probably things I left out like "screw the barrel sections together" but I'm trying to not be pedantic>
 

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Man, I don't even know if this is legible. I have horrible handwriting. I could do something better in Sketchup or AutoCAD. So it's really simply 'barrel' construction like a roman column. make the semi circles out of plywood. Separate them with 1x4, gusset and cross brace as necessary. on out side luan strips to form the general outline. If you need it apply wire. If you use fewer Luan strips you'll want to bridge the gaps with Chicken wire or construction cloth. Over the top of that apply the cardboard or Heavy paper. Then add crumpled paper, make twisted paper Ropes or use small diameter cotton rope to add texture then paper over top. If you're happy with it paint, If you think you need it for your look, add a layer of VSSD.

Remember all these ingredients are flammable. Use Flammex, or some other additive, all though the process. 10' diameter is a damn big tree ! <there's probably things I left out like "screw the barrel sections together" but I'm trying to not be pedantic>

I get the general idea, for sure! Thanks for putting so much work into this idea!
 
I'd +1 anything anyone's said about using cardboard ESPECIALLY if you plan on painting it. I've only every had success with it when the design called for the material itself and could "look" like cardboard. Otherwise, in order to make it look like something else, you've got to put more paint/texture on it than it wants to handle and it can warp or, worse, start to crumble or disintegrate.

So, I'll always push for foam. Even 1/2" sheeting you can buy at the big box stores can hold up reasonably well, provided you use good adhesive. jtweigandt's method of screws then masking tape to "dutchman" the seams sounds good to me, though I'd add construction adhesive in there, too.

Just make sure you rig from framing, not from foam!!!

Good luck,
 

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