Repair sag of papermodel

Discussion in 'How Do I...' started by johanvanacker, May 20, 2019.

  1. johanvanacker

    johanvanacker Member

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    I made the T-rex model some time ago for my youngest daughter. However, now it starts sagging through its legs and it's mouth is now almost touching the ground. Any ideas how to repair this sag and lift the model back up to its original posture? How can I avoid this happening to other models in the future?
    IMG_1155.jpg IMG_1156.jpg Thanks a lot for your help!
  2. bigpetr

    bigpetr Designer/Master Modeler

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    Nice model.

    I dont know how to repair this one, but for future build I would suggest supporting inner structure.
  3. Rhaven Blaack

    Rhaven Blaack ADMINISTRATOR Administrator Moderator

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    You can coat the areas with super glue or use a spray sealant. Both would add rigidity to the areas that are weak.
  4. Revell-Fan

    Revell-Fan Co-Administrator Administrator Moderator

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    Hum... I would say you might have to cut off the lower legs or at least cut them in at the back of the knee to re-adjust it. To prevent further sagging I would put some cotton wool into the legs and / or some wire.
  5. johanvanacker

    johanvanacker Member

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    I thought about using some sort of fill material to prevent the paper around the ankle from buckling inwards. Not sure what is the best fill material for this, since ideally, it should be fluid for better spreading around, but not wet because it's paper.
    What material do you use for making the inner support structure?
  6. daishi

    daishi Member

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    I've used expanding foam for most of my models with success. Especially the non-human ones with multi joined legs.

    My Mass Effect: Grunt model needed it for similar reasons as your T-Rex, I've cut open the sole of the feet, put a little around the knees with the long pipe that the can came with. Stood it in the correct position, and just waited until it hardens. (needed to hold it for a while so I'd recommend a good audiobook or a movie ;) )

    One thing to look out for is not to use much since it will expand a LOT, and It can "pop" the model.
    If the amount is correct there still may be some deformations after it starts to set: i.e. some recesses getting pushed out. It can be pushed back before it hardens completely.
    (Also my models generally have more curved surfaces so I cannot say how it will look on a model consisting of flat polygons).

    Hope it helps!
  7. zathros

    zathros -----SENIOR---- Administrator Moderator

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    You could try a Tea Kettle and steaming a leg at a time slowly, with as little as possible steam directed at the joints that bent. On the other hand, and this I cannot tell from the picture, you could look at where the creases are, I can almost guess from the construction, the part of the ankle up on top of the toes creased inward (see pic below, Red circle), any repair should be done there, even if you cut is as that is where it needs to be beefed up. You could squeeze one or more of those joints, and you will see one move the leg back towards that position( to determine where it failed). The paper has stretched in that area and will no longer support the model the same way, but at least you will find the section that took all the weight, and acted as a fulcrum creating a moment or the torso, bending slowly over time.

    The position that Rex is in now was probably a very common one. You could spray some structural foam in the legs, and make a diorama with some creature, that it's about to eat. :)

    Rex.jpg
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  8. Revell-Fan

    Revell-Fan Co-Administrator Administrator Moderator

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    It really doesn't look too bad this way. Put some little Raptors around him so that it looks like he is roaring at them. Or put him on the edge of a cliff. That might actually look very cool. :)
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  9. johanvanacker

    johanvanacker Member

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    Thank you guys for all the ideas! I think I'll try to strengthen the ankles first with some varnish. If that doesn't work, cutting open the soles of the feet and stuffing with a fill material will be option 2. I'll post some pictures with the result.
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  10. zathros

    zathros -----SENIOR---- Administrator Moderator

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    Skip the Varnish, it won't work. Cutting the bottoms of the feet off is the best way to god, when the model is in the position you way, spray construction from up there, or brace it with Popsicle sticks, or some other kind of wood, with a piece going up to the body, to anchor the strengthened par to the rest, or it will sag somewhere else. I am interested to see you do this. It will make for a great thread!! :)
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  11. Papa Mashy

    Papa Mashy New Member

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    Great model.
    I really like Zathros idea of making a diorama with prey animal.
    So many possibilities.
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  12. johanvanacker

    johanvanacker Member

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    I'm not a diorama type of guy, so I'll stick to strengthening the ankles.
    After fixating the model in the desired position and adding PVA glue to the ankles, the dino is already standing up on by itself.
    I removed it then from the stand to be able to paint the underside as well.
    Side effect of the PVA glue is that the model is now shiny at those parts, so I'll have to do the whole dino now.
    To be continued ...
    IMG_1159.jpg IMG_1160.jpg IMG_1163.jpg IMG_1162.jpg
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  13. Revell-Fan

    Revell-Fan Co-Administrator Administrator Moderator

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    Not bad at all! thumbsup
  14. Cybergrinder

    Cybergrinder Member Extraordinaire

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    To try an prevent the same happening to my Vader model I braced popsicle sticks against the back of the ankle all the way up to the backside :)

    A frame then went around the sticks that extended outside the feet. Seems to have worked, he hasn't drooped yet & the model is nearly 2 years old now.
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  15. johanvanacker

    johanvanacker Member

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    Any particular type of expanding foam you use?
  16. zathros

    zathros -----SENIOR---- Administrator Moderator

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    The all expand, so make sure you have made allowance for the foam to exist somewhere. Biggest difference is closed cell or open cell. You want something that comes in a can, plan on using it, and not being able to use the rest, they have this tendency to clog, and lose pressure, after any kind of storage. Home Depot sells the stuff.
  17. daishi

    daishi Member

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    Zathros said most of the relevant stuff.
    This is what I use http://www.soudal.hu/diy-purhabok/item/352-szerelő-hab, but I don't know if there are many types thou. I do tend to leave a dowel in the pipe so I can yank out the clogged stuff with ease. (after detaching the pipe)
  18. johanvanacker

    johanvanacker Member

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    Meanwhile, I've covered the whole model with PVA glue and the result is remarkable... the dino is standing up again the way it was meant to be. Next time a pass by the shop, I'll buy some expanding foam and try to fill at least the legs with foam to avoid bending of the knees and to give some more weight to the model so that it can stand up on its own. Now it is a bit heavy at the head and it tilts forward when released. The PVA glue also seems to make the model a bit more durable... something I'll try on my next models too.

    IMG_1165.JPG
  19. zathros

    zathros -----SENIOR---- Administrator Moderator

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    It gives the model a nice sheen too!! :)
  20. Revell-Fan

    Revell-Fan Co-Administrator Administrator Moderator

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