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  1. ShareAHack.com RPF Premium Member shareahack's Avatar
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    Aug 14, 2017, 2:41 PM - Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam? #1

    Hi all, I'm thinking about sculpting a full-size t-rex skull out of pink rigid insulating foam (mainly because I was able to acquire a a big pile of old used foam!).

    I'll be doing it in manageable sections and then merging everything together at the end.

    I have some ideas about covering/finishing the foam but am wondering if any seasoned sculptors out there had any good tips. The goal is to cover/paint/seal the foam to the point where it looks and feels like a museum resin fossil casting.

    I really like the darker, more matte weathered look (see attachment):



    Ideally the final sculpture will be sturdy enough to stand on and could sit outside and withstand the weather and not easily chip paint (a nice garden centerpiece? ).

    My first instinct was to coat the foam with PVA or something to protect it from any solvent use. Then I would cover the entire thing with fiberglass/resin, maybe do some finishing work with Bondo etc and then paint, weather, and seal it.

    I'm thinking if I use fiberglass it'll introduce a lot of finishing work because of the grid-like fiber texture so I'm wondering if there's a better alternative - maybe something like Line-X (never used it before)?

    Would your local hardware store automotive Bondo resin be good enough or do you think there's a better alternative? (I'll probably need a lot of this stuff)

    Luckily there's a lot of margin for error on the texturing because of the bumpy/broken surfaces of natural fossils.

    If anyone has any better ideas or time-saving tips I would be eternally grateful. Will be posting progress along the way!

    Cheers
    Last edited by shareahack; Sep 26, 2017 at 8:42 PM.
  2. CT1138's Avatar
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    Aug 14, 2017, 3:14 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #2

    That's a cast of "Stan" the T. rex, and one of the best preserved skulls to make reference from. I know a lot of museums use painted foam for their replicas, for example, this Sue head that the Field Museum put out for visitors, which they allowed to be touched. Unfortunately, I'm not sure what kind of foam or paint they used, all I know was that it was extremely sturdy.
  3. ShareAHack.com RPF Premium Member shareahack's Avatar
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    Aug 14, 2017, 3:17 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #3

    CT1138 said: View Post
    That's a cast of "Stan" the T. rex, and one of the best preserved skulls to make reference from. I know a lot of museums use painted foam for their replicas, for example, this Sue head that the Field Museum put out for visitors, which they allowed to be touched. Unfortunately, I'm not sure what kind of foam or paint they used, all I know was that it was extremely sturdy.
    http://i.imgur.com/7FB4WGO.jpg
    Awesome example of what I'd like to have as a finished product. Great-low-profile mounts they're using in that one. Might just stop by the museum this week and see if someone can give me some tips or get some ideas
  4. ShareAHack.com RPF Premium Member shareahack's Avatar
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    Sep 26, 2017, 8:41 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #4

    With winter coming up fast I decided to go full steam on the T-rex skull project since most of the work has to be done outside. Here's a quick update on the progress of the skull

    Here is the scanned 3D model I'm using of what I believe to be the T-rex "Stan" fossil discovered in Buffalo, South Dakota by Stan Sacrison:



    According to the Black Hills Institute, the real-life skull has the dimensions of 58" L x 33" W x 68 1/2" H. (approx. 4.8 feet wide) and I really wanted to make mine match the full scale of the original. Because of this I had to chop the skull model into 8 sections so I could work manageable sections on the CNC router (the router can only work with objects inside of a 2' x 4' work area with a depth of approx 4"):



    To make these 3D files workable on the CNC machine, I "sliced" them up into layers to match the depth of the pieces of foam I had (3" inch rigid pink insulation foam).

    For just the TOP LEFT half of the skull, it took about 5 pieces of foam and a ended up creating a jigsaw puzzle of 25 pieces:



    Need to run right now but more updates tomorrow
  5. clonesix's Avatar
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    Sep 26, 2017, 11:36 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #5

    SmoothOn Epsilon Epoxy coating here: https://www.smooth-on.com/product-line/epsilon/
  6. ShareAHack.com RPF Premium Member shareahack's Avatar
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    Sep 26, 2017, 11:49 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #6

    clonesix said: View Post
    SmoothOn Epsilon Epoxy coating here: https://www.smooth-on.com/product-line/epsilon/
    Thanks @clonesix looks like exactly what I need. I've already got a bunch of this stuff that I'm going to give a try and see how it holds up with fiberglass:

    FXpoxy-Epoxy Resin 2 Gallon Ultra Clear UV resistant (50-60 sq ft) Countertops, Table Tops, Bartops



    Seems like pretty standard epoxy and just going to mix and smear it on the foam with fiberglass. Was even thinking of using old pink 'hair' fiberglass insulation with the epoxy as the 'skin'. Thinking it might be dangerous to inhale if sanded but might be a cool experiment.
  7. RPF Premium Member cavx's Avatar
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    Sep 27, 2017, 5:30 AM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #7

    I am using a very similar product now. If the parts are greater than 5mm thick, this stuff seems to set up nice and the parts can be quite strong, but if they are thin, they may/will remain flexible for some time.

    The stuff I am using has a potlife of almost an hour, demold time after 24 hours and post cure time of 7+ days if not baked. Bake at 70 degrees C for 3 hours to make it hard.

    Yes you can use this with fibreglass matting (woven or chopped) and it will saturate and set like a rock.
  8. ShareAHack.com RPF Premium Member shareahack's Avatar
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    Sep 27, 2017, 7:19 AM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #8

    cavx said: View Post
    Yes you can use this with fibreglass matting (woven or chopped) and it will saturate and set like a rock.
    For sure I've got both of the woven/chopped Bondo stuff meant for auto body work. I feel like if I plaster it on the foam it's going to leave behind a grid-like texture that i'll have to spend more time finishing (with either more resin on top or sanding it down etc).

    What do you think about using that pink cotton-candy type fiberglass insulation?

    Click image for larger version. 

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    I mean it's fiberglass...the strands are nice and small, you can use as little or as much as you want, and you can bend/form the strands to the foam surfaces easier.

    I'm wondering if I combine this stuff with resin it would achieve a nice strong shell over the foam that might be easier to control with less artifacts when cured?
  9. RPF Premium Member cavx's Avatar
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    Sep 27, 2017, 6:33 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #9

    shareahack said: View Post
    What do you think about using that pink cotton-candy type fiberglass insulation?

    Click image for larger version. 

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    I mean it's fiberglass...the strands are nice and small, you can use as little or as much as you want, and you can bend/form the strands to the foam surfaces easier.

    I'm wondering if I combine this stuff with resin it would achieve a nice strong shell over the foam that might be easier to control with less artifacts when cured?
    I have only ever used this stuff in wall/roof cavities. I see no issue with it as long as you get full saturation of the epoxy.

    Just bought 7.5KG of fast(er) set epoxy so hopefully mix, degas, pour and demold all in a day. Last time I used this stuff, parts were still soft for about 24 hours, but then set rock hard. We are also expecting the temp to reach 37 degrees C today, so really happy that will ensure my parts kick properly.
  10. RPF Janitor RPF Premium Member Lear60man's Avatar
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    Sep 27, 2017, 9:42 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #10

    Pink foam would be a nightmare to work with. Go to Home Depot and 'borrow' a hand full, then try to get it to lay down smooth with resin.
  11. ShareAHack.com RPF Premium Member shareahack's Avatar
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    Sep 27, 2017, 10:22 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #11

    Lear60man said: View Post
    Pink foam would be a nightmare to work with. Go to Home Depot and 'borrow' a hand full, then try to get it to lay down smooth with resin.
    I managed to do some cuts already with the old pieces of foam I picked up...it actually wasn't too bad! MESSY, but workable. Will post some pics later tonight.

    I think that because the foam was aged that it was more brittle/flaky and easier to cut.

    This is the old dirty pile foam I grabbed off a guy from Kijiji:

  12. RPF Premium Member 13doctorwho's Avatar
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    Sep 27, 2017, 10:22 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #12

    There's a reason fiber glass mat and fiberglass cloth are thin. It would take a lot of resin to soak that pink insulation. I don't think it's as flexible as you think. Generally people do the bulk layers of fiberglass with the cloth (it's thicker and has random threads). Once the desired thickness is reached you put a couple layers of the mat, that's the tightly woven glass. If you want it really smooth when glass layers are cured go over the whole thing with a layer of just resin. With the fibers cured the last layer won't soak into the fibers so it's like painting on a finish coat.
    Just be careful and wear a mask... fiber glass and resin is nasty stuff.
  13. ShareAHack.com RPF Premium Member shareahack's Avatar
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    Sep 27, 2017, 10:27 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #13

    Lear60man said: View Post
    Pink foam would be a nightmare to work with. Go to Home Depot and 'borrow' a hand full, then try to get it to lay down smooth with resin.
    LOL I just realized you meant the cotton candy stuff. Luckily we're in the middle of roofing renos and I've got an abundance of used insulation that's mostly being thrown away because it's all moldy.

    - - - Updated - - -

    13doctorwho said: View Post
    There's a reason fiber glass mat and fiberglass cloth are thin. It would take a lot of resin to soak that pink insulation. I don't think it's as flexible as you think. Generally people do the bulk layers of fiberglass with the cloth (it's thicker and has random threads). Once the desired thickness is reached you put a couple layers of the mat, that's the tightly woven glass. If you want it really smooth when glass layers are cured go over the whole thing with a layer of just resin. With the fibers cured the last layer won't soak into the fibers so it's like painting on a finish coat.
    Just be careful and wear a mask... fiber glass and resin is nasty stuff.
    Thanks @13doctorwho, good advice. I'll do some tests of all techniques mentioned above. Luckily the texture of the skull is going to be lumpy and imperfect so there's lots of room for error.
  14. RPF Janitor RPF Premium Member Lear60man's Avatar
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    Sep 27, 2017, 11:56 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #14

    Haha. Yea I was talking about the cotton candy stuff. The stuff in post #11 is perfect for sculpting....mold and all!

    Nice kitty BTW.
  15. ShareAHack.com RPF Premium Member shareahack's Avatar
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    Sep 29, 2017, 11:54 AM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #15

    Here's a photo of the CNC being used to cut out the foam T-rex pieces. Pink snow everywhere!



    Each piece of foam is 2' feet x 4' feet. In 3 days of cutting and 5.5 pieces of foam later, I managed to cut out enough pieces to build up just 1/4 of the skull (the top left half):



    Lots of fun punching out the pieces from the foam like a giant hobby model kit:



    And finally we have something that's starting to look like a T-rex! Still lots of gluing, shaping, and excavating the overhangs to do. I'd say I'm about 20% done:

  16. RPF Premium Member kwalsh0000's Avatar
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    Sep 29, 2017, 7:59 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #16

    Love the concept man esp the last pic and how it goes together. Great way to merge techniques. Cant wait to see progress.
  17. ShareAHack.com RPF Premium Member shareahack's Avatar
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    Sep 29, 2017, 10:30 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #17

    kwalsh0000 said: View Post
    Love the concept man esp the last pic and how it goes together. Great way to merge techniques. Cant wait to see progress.
    Thanks @kwalsh0000!
  18. RPF Janitor RPF Premium Member Lear60man's Avatar
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    Sep 29, 2017, 11:58 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #18

    Man....if you took black an white photos, it would look like the 40's
  19. ShareAHack.com RPF Premium Member shareahack's Avatar
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    Oct 9, 2017, 5:57 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #19

    Made a bit more progress on skull. Good news, all the cutting is finished! Just need to manually carve out the overhangs and finishing touching up/sanding (the fun part).

    I used PL construction adhesive to glue the pieces together and then bamboo BBQ skewers to temporarily hold them in place:









    Started roughing out the top internal geometry of the skull by hand:



    A couple bonuses I've learned:

    The teeth overhangs that (stretch across the whole model) are actually useful in protecting the teeth while I work on other parts of the skull. Since they're so skinny they'd be super delicate if they weren't being reinforced by the overhangs. I'll be cutting out the teeth as the last step before fiberglassing.

    The PL construction "300 foam board" glue is actually NOT ideal for foam-on-foam gluing. It doesn't fully cure and leaves the pieces somewhat repositionable...but it does grab well and adequately holds the sculpture in tact...it has the texture/consistency of peanut butter.

    I used the standard PL 3X on the more structural parts of the model and it works great, cures very hard and grabs the foam well.

    The bonus of using the weaker PL 300 for this particular project is it made carving out the internal skull structures way easier when cutting by hand. The PL 3X is very hard to cut through with a knife/saw.

    Happy [Canadian] Thanksgiving!
  20. MooCriket's Avatar
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    Oct 9, 2017, 8:03 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #20

    Looking bad ass!
  21. RPF Premium Member 13doctorwho's Avatar
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    Oct 9, 2017, 9:17 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #21

    That is so freakin' awesome!!
  22. RPF Premium Member Ash's Avatar
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    Oct 9, 2017, 10:13 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #22

    Currently WINNING current ongoing project builds right now in my opinion. This is incredibly awesome and something I've wanted to own since I was a little child. You go ahead and let me know when you work out a kit form.

    -Ash
  23. RPF Premium Member horus's Avatar
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    Oct 10, 2017, 1:06 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #23

    Is this available for sharing the plans?



    I would only ever have space for a head !
  24. ShareAHack.com RPF Premium Member shareahack's Avatar
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    Oct 12, 2017, 7:16 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #24

    MooCriket said: View Post
    Looking bad ass!

    13doctorwho said: View Post
    That is so freakin' awesome!!

    Ash said: View Post
    Currently WINNING current ongoing project builds right now in my opinion. This is incredibly awesome and something I've wanted to own since I was a little child. You go ahead and let me know when you work out a kit form.
    -Ash

    horus said: View Post
    Is this available for sharing the plans?
    I would only ever have space for a head !

    Thanks guys! Appreciate the feedback this is the first time I've done a project like this. Totally with you on the childhood dream @Ash

    Spent so much time this week manually carving out the internal structures...skulls are weird shapes and a lot more work than planned getting the details right.

    @Ash / @horus haven't really thought about a kit or what that would entail but interesting idea. When I find some time I'm going to upload all the models and design files I used (for free) if they can help anyone.

    Will also try to make some videos about my workflow/process. Along the way I realized some areas I could have improved and saved myself a bunch of time. If the weather is good will upload some more pics this weekend!
  25. ShareAHack.com RPF Premium Member shareahack's Avatar
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    Oct 30, 2017, 6:29 PM - Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam #25

    Finally finished carving out the internal geometry of the top part of the skull (took way longer than I thought!). Had to cross section the 3D model and really analyze the internal structure to slowly match it to the foam section by section. Used a combination of serrated knives, box cutters, a die grinder (air) with a rasp bit. In this photo the 4.8ft skull is sitting inside the 8'x10' CNC shed (kind of a snug fit in there right now lol):



    Surprisingly this was by far the most useful tool that I came across by chance. It's a pumpkin scooper that I found at the dollar store. I sharpened the serrated edge using a grinder. Really helped to remove inside material fast in the hard to reach places:



    Had fun shaping the teeth! The final teeth will have the serrations on the back edges (will add after fiberglassing):







    Apparently T-rex's teeth were the size of bananas. Theory confirmed!

    BBQ skewers added for reinforcement:





    Still working on the lower jaw but should be done this week I hope.

    Happy Halloween everyone!

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