Need advice for my cardboard sculpture.

[Antonis13]

Hello all! I started some months ago a cardboard sculpture, through pepakura.
It will be quite big, 2.5 meters tall, 1.5m. long, and 1.4m wide.
The sculpture will be on basically 4 parts. 1 upper and 1 lower body of a man. And 1 upper and 1 lower body of a woman.

When i finish building it, i want to make it stronger. I originally thought to cover the parts with acrylic putty. I tested this in one part and it turned out very heavy and needed LOTS of putty.
The alternative that i thought of, is covering it with resin.

I have never worked with any type of resin before, and i need your help.
First, i can't afford of getting epoxy resin. So i might settle with polyester resin and fiberglass. Will polyester resin with fiberglass do the job? and if so, how strong and light will it be?
Will i need to wrap the sculpture with aluminium tape to protect the cardboard of getting soggy? (To prevent wrapping and anything else).

I probably have a lot more questions, but i can't think of them right now.
What do you believe that is the best route to go?

Thank you!

 

[laellee]

I would paper mache the pieces, and then paint them. You will end up with a very light shell that is also pretty durable.

I did this a long time ago, covers the steps: HOW TO BUILD YOUR OWN GIANT BLUE MARLIN ON THE CHEAP

 

[greenmachines]

Are we talking near completion? Or are you still able to put reinforcement inside?

Also, the weight issue you have raised several times, so I am curious. Are you keeping weight down so it does not collapse or are you keeping it light for a different reason? This will greatly change the answers you get about how to strengthen it.

 

[pengbuzz]

Masking tape. LOTS of masking tape. Preferably 3M office version (stronger adhesive than regular "painters" version).

AND UNDER NO CIRCUMSTANCES SHOULD YOU USE THE BLUE TAPE!

 

[Antonis13]

Are we talking near completion? Or are you still able to put reinforcement inside?

Also, the weight issue you have raised several times, so I am curious. Are you keeping weight down so it does not collapse or are you keeping it light for a different reason? This will greatly change the answers you get about how to strengthen it.

I finished building the man figure. (2 parts, 1 from the waist down to legs, and 1 part from the waist and up arms and head.)
The woman figure, i have made, both legs, arms and her head, and are all separate pieces. So if reinforcements needed, the woman figure will be easier.

Note. that for the project i use microvele cardstock 485gr, basically same cardboard as pizza boxes.
Now, i want it to be as strong and light as me and my budget can so i will be able to move it around different places. Not only inside my home.
Funnily enough, i don't know exactly what i will do with it when i finish it. It will be huge, and i don't have enough space to put it in my house, although i would really love to have it in my home.

 

[Antonis13]

I would paper mache the pieces, and then paint them. You will end up with a very light shell that is also pretty durable.

I did this a long time ago, covers the steps: HOW TO BUILD YOUR OWN GIANT BLUE MARLIN ON THE CHEAP

Very cool work! The Blue Marlin turned pretty good.

I don't really want to paper mache it. I basically want to be able to move the statue around different places. So i want it to be as strong as it can be. And i guess, a way to do that is with polyester resin and fiberglass, to make it more plastic strong.
Although paper mache and resin with fiberglass, is basically the same technique. The only thing it changes is the ingredients.

 

[Antonis13]

Are we talking near completion? Or are you still able to put reinforcement inside?

Also, the weight issue you have raised several times, so I am curious. Are you keeping weight down so it does not collapse or are you keeping it light for a different reason? This will greatly change the answers you get about how to strengthen it.

I am curious of why that.
Does resin adhere better to masking tape than aluminum tape?

 

[greenmachines]

I am curious of why that.
Does resin adhere better to masking tape than aluminum tape?

I asked because internal framing is the best way to make it strong yet lightweight. It always is from an engineering standpoint because it moves the strength around to multiple points instead of at one joint or seam.

The next suggestion is only because I am not sure how strong or how permanent you were wanting and it can get spendy depending on the size of the open cavity.

If it was already completed and had spaces that were very difficult to reach into, you could try a low pressure expanding foam. High pressure will eventually burst a weak case so stay away from that. To do so (and not saying I know enough about your sculpture to make this the decision) you would lightly wrap the outside with cellophane wrap like for food and then get the canned expanding foam and a length of clear flex hose (like fishtank tubing) and that allows you to place the foam all the way at the furthest point as it come out of the can. Pulling the tube out as the foam chases it out. Very messy and tons of prep to get ready. The cellophane wrap gives temp strength to the shell while the foam expands but it might not keep foam from leaking through open points so tape over those with some low adhesive tape before the cellophane.

You can do just foam in the small spaces but in the larger cavities you can fill as you go with chunks of packing foam (formed foam from previous purchase.

All of the above is for intentionally keeping it for quite a long time.

For added strength you can place lengths of plastic rod or wooden dowel while you are foam filling.

But in the end the best way is just internal scaffolding with light dowels or cardboard like the marlin.

 

[laellee]

Very cool work! The Blue Marlin turned pretty good.

I don't really want to paper mache it. I basically want to be able to move the statue around different places. So i want it to be as strong as it can be. And i guess, a way to do that is with polyester resin and fiberglass, to make it more plastic strong.
Although paper mache and resin with fiberglass, is basically the same technique. The only thing it changes is the ingredients.

Paper-mached pieces would be very rigid and light, that 14 foot fish weighed like 10 pounds.

Otherwise use Smoothcast 300 (or 320) epoxy resin and justbrush it on. I've used 320 on pepakura armors, foam, all kinds of stuff, it works well and definitely toughens up pieces. I think the epoxy will be a lot easier for you to work with than polyester resin if you go that route, it also doesn't stink nearly as much.

 

[greenmachines]

Taping had been mentioned earlier. With these resins, if done slowly, no tape is needed. I say this because some tape has a failing bond and it would be that layer that fails even if the resin were over it. But would def ask laellee and pengbuzz on this. I just know that metal tape and many brand of packing tape will dislodge after the gooey portion of the tape crystalizes or powders. Some tapes are meant to be much longer lasting but I couldn't offer a brand on that as I have only had the downside experience of tape crumbling after exposure to heat or dry air for too long.

 

[Antonis13]

Paper-mached pieces would be very rigid and light, that 14 foot fish weighed like 10 pounds.

Otherwise use Smoothcast 300 (or 320) epoxy resin and justbrush it on. I've used 320 on pepakura armors, foam, all kinds of stuff, it works well and definitely toughens up pieces. I think the epoxy will be a lot easier for you to work with than polyester resin if you go that route, it also doesn't stink nearly as much.

The only thing that draws me back from using epoxy resin is the price. I found Smooth-cast 320 0.82kg for 30 euro. While i found polyester resin 1kg for 10 euros. Will polyester resin do the work? I am asking because as i said i have no idea what is going on with resins.

I guess it's a sacrifice i have to do for quality.

​

 

[Moviefreak]

Could you just Mod Podge the surface?

 

[Antonis13]

I asked because internal framing is the best way to make it strong yet lightweight. It always is from an engineering standpoint because it moves the strength around to multiple points instead of at one joint or seam.

The next suggestion is only because I am not sure how strong or how permanent you were wanting and it can get spendy depending on the size of the open cavity.

If it was already completed and had spaces that were very difficult to reach into, you could try a low pressure expanding foam. High pressure will eventually burst a weak case so stay away from that. To do so (and not saying I know enough about your sculpture to make this the decision) you would lightly wrap the outside with cellophane wrap like for food and then get the canned expanding foam and a length of clear flex hose (like fishtank tubing) and that allows you to place the foam all the way at the furthest point as it come out of the can. Pulling the tube out as the foam chases it out. Very messy and tons of prep to get ready. The cellophane wrap gives temp strength to the shell while the foam expands but it might not keep foam from leaking through open points so tape over those with some low adhesive tape before the cellophane.

You can do just foam in the small spaces but in the larger cavities you can fill as you go with chunks of packing foam (formed foam from previous purchase.

All of the above is for intentionally keeping it for quite a long time.

For added strength you can place lengths of plastic rod or wooden dowel while you are foam filling.

But in the end the best way is just internal scaffolding with light dowels or cardboard like the marlin.

Thank you a lot for the lengthy answer! You gave me a new option of doing this!

Do you think that I could probably do this with canned expanding foam?

 

[Antonis13]

Could you just Mod Podge the surface?

I haven't worked with Mod Podge ever, it isn't very common item to find in Greece.
My original plan was to make it plastic type strong with polyester resin.
But greenmachines changed my mind.

 

[greenmachines]

Thank you a lot for the lengthy answer! You gave me a new option of doing this!

Do you think that I could probably do this with canned expanding foam?

The foam fill is a cosplay tailors trick for making a body double of yourself or another so you can measure/drape costumes on the body double dummy. They build a semi-rigid cast of either paper mache, duck tape or both on the person, up to the lower neck (not on). Once the semi rigid cast is removed from the person by cutting along one edge to get them out (very slowly and with safety kids scissors), like opening a mummy wrap, they tape the cut edge back together and use foam fill, the canned pressure type for home air leaks and such.

The trick for reaching those extreme lengths is to add a length of tubing to the nozzle hose on the can. This hose can be draped down into the cavity.

Non of this is my creativity except the hose. That I had to cobble together once for a really tight spot where not even a hand could reach in but it needed to take the foam 2 to 3 feet before letting it expand. The rest is all pulled from other rpf and youtube stuff. I will post any foam fill videos I can find. My only caution is do gravity feed and let it fill upward and slowly. It is crazy messy so gloves gloves gloves and do it outside. Once this stuff touches upholstery or carpet or clothing, that item is forever damaged. Face protection always. Seems like no big deal until suddenly it is an emergency. With a project as large as yours, I would advise having a second person available. Wear clothes you intend to trash or can without tears. Our foam doesn't go very far so I always ended up using more cans than expected. I saw one cosplayer doing a body double cavity and they were putting broken chunks of styrofoam inside as it filled up, to use less expanding foam.

Oh and the hose is trash when done, nothing cleans it out but you can use it on several cans before it dries closed.

Each method has its use case where it works better than the others. The resin coat, the tape cover and others are best case scenario when the object must stay hollow. And both of them are far less destructive to the area you are working in and the clothes you are wearing.