Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam?

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shareahack

Active Member
RPF PREMIUM MEMBER
Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam

Happy Jurassic June!


Sorry for the delay in posting...it took a few weeks (off and on) but I'm happy to say the fiberglassing is finally DONE!


I waited out the winter and moved the project outside into a car shelter to avoid any possible VOC problems from the epoxy and dust particles from the fiberglass.


I decided not to mess with any polyester resin (yet) due to the risk of melting the foam. I used almost 3 gallons of epoxy to cover the entire surface area of the skull.


I ran out of the original 2 gallons of counter top resin I had so I decided to buy smaller batches as I needed it to finish the fiberglassing.


The second type of epoxy I tried was West System (way more expensive but clearly superior than the counter top stuff...cures extremely hard and more sandable).


When I ran out of West System, I tried some cheaper "Envirotex" brand that I found at Michael's (the 50% off coupons didn't hurt!). To compare, 1L of West System was around $80 (with hardener) and the Michael's stuff was around $30 for the same volume. The cheaper brand cures slightly more "rubbery"/flexible but it was perfectly adequate for finishing off this stage of the project.

shareahack_diy-trex-skull-cnc-epoxy-resin-comparison.jpg


I used a combination of fiberglass mat and woven cloth. Lost track of how many sheets I bought but it was quite a few (maybe around 10 sheets of 8 sq feet - so around 80 sq feet was needed to coat the whole skull.

shareahack_diy-trex-skull-cnc-foam_3dmodel_27-mixing-epoxy-resin.jpg


I started with the hardest part (the teeth) and laid down the glass strips in a combination of ways (lengthwise, spiraled around the tooth, etc).

shareahack_diy-trex-skull-cnc-foam_3dmodel_28-fiberglassing-teeth.jpg


I removed the wooden supports from the lower jaw and drilled/tapped a couple of metal corner brackets to act as a linkage to connect the left and right lower jaw pieces with a single screw.

shareahack_diy-trex-skull-cnc-foam_3dmodel_29-lower-jaw-linkage.jpg


Before fiberglassing the rest of the skull I started with reinforcing all the metal mounting points and linkages.

shareahack_diy-trex-skull-cnc-foam_3dmodel_30-reinforcing-mounting-points.jpg


The mat was more epoxy-hungry than the cloth and it took a lot to saturate it but it was perfect for molding around awkward shapes and crevasses. The woven cloth helped to bridge the mat and add good structural reinforcement.

shareahack_diy-trex-skull-cnc-foam_3dmodel_31-fiberglass-awkward-shapes.jpg


Sometimes the fiberglass wouldn't 'stay down' very well especially when it was hotter outside. My solution was to lay down the glass in position as best I could, wait a couple hours for a bit of curing to take place and then push down the parts that were springing up into the foam - this worked out well because after a few hours the resin has more of a putty consistency.


A cool little tip I found out: After laying down a strip of glass, the little left-over strands/resin on your gloves - you can work them into a little ball and use it like a putty/filler to cover up an exposed area or hard to reach place.

shareahack_diy-trex-skull-cnc-foam_3dmodel_32-fiberglass-putty.jpg


Finally everything is coated and extremely durable...I'm hoping it will last forever! Next I need to clean up all the sharp fiberglass spillovers and knife-like edges.

shareahack_diy-trex-skull-cnc-foam_3dmodel_33-fiberglassed.jpg


A full timelapse of the fiberglassing (condensed to 1 minute) can be watched here:


https://www.instagram.com/p/BkcQ5EwhpR4/?taken-by=shareahack


Thanks for reading!
 

tarnyloo73

Well-Known Member
Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam

Great project and looking good. Must make one for myself one day.
 

Lunajammer

Active Member
Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam

I admire your knowledge and mastery of the materials. Your commitment to the project is also admirable and the results are fantastic. Really looking forward to seeing where this ends up. Nice work and thanks for sharing your techniques.
 

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shareahack

Active Member
RPF PREMIUM MEMBER
Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam

Decided to spend some time reinforcing the teeth... I figure the teeth will be the first thing my nephews want to run up and grab. The fiberglass has made them pretty strong as-is but I want to make sure they can withstand the full force of a group of 5 year olds :)

I found a bunch of scrap threaded rods, screws and metal dowels:

shareahack_diy-trex-skull-cnc-foam_3dmodel_34-teeth-reinforcement.jpg


I measured/cut the rods to length and sharpened them all to a point:

shareahack_diy-trex-skull-cnc-foam_3dmodel_35-teeth-reinforcement.jpg


For the threaded rods, I made little slots to be able to use a screwdriver to drill the rods down below the teeth tips:

shareahack_diy-trex-skull-cnc-foam_3dmodel_36-teeth-reinforcement.jpg


Now time for the root canals...I drilled holes in all of the teeth to get the metal rods seated:

shareahack_diy-trex-skull-cnc-foam_3dmodel_37-teeth-reinforcement.jpg


Drilled the rods deep into the skull, passed the "root" of the teeth into the skull. For the small teeth I just used regular long construction screws:

shareahack_diy-trex-skull-cnc-foam_3dmodel_38-teeth-reinforcement.jpg


Quick video of the process here: https://www.instagram.com/p/Bkx5UhihTPr/?taken-by=shareahack

Next I'll be shaping the tips of the teeth with bondo and probably covering them in more resin/fiberglass.

Time to stop procrastinating and start cleaning up / sanding the fiberglass (I've been dreading this part!).

Cheers
 

animator

Well-Known Member
Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam

This is just the best project ever!

I showed this thread to my son who loves dinos and he said, "Daddy, you couldn't do that." ...reality is harsh
 

shareahack

Active Member
RPF PREMIUM MEMBER
Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam

Thanks animator! Honestly this is the first project I've ever done like this (my first time using resin/fiberglass too). Somehow got the idea and just had to pursue it as I'm sure everyone here can relate :) Jury's still out on what the final product will look like lol :)
 
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tarnyloo73

Well-Known Member
Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam

Good call making the teeth nephew proof. Kids are masters of incidental demolition :)
 

animator

Well-Known Member
Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam

Any updates? I can't wait to see more!
 

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shareahack

Active Member
RPF PREMIUM MEMBER
Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam

Any updates? I can't wait to see more!

Sorry for the delay between postings! I'm definitely caught in a 'perfectionist' rut trying to make all the details as close as possible to the "STAN" skull casting. Using bondo to try and match up all the imperfections (it'll never be perfect so I need to accept that and move on at some point :lol).

I decided to only use hearty materials (fiberlgass/bondo) instead of various foam coats or plasters because I really want this thing to last.

Quick photo of where I'm at right now:

shareahack_diy-trex-skull-foam-bondo_final-touches.jpg


I'm considering 'sealing' the bondo in resin (dyed black/dark drown) to make it scuff-proof in areas prone to wear and tear. So if the paint gets scuffed off, black resin will appear underneath and it won't need as many touch ups in the future (in theory).

Here's a quick video I posted a couple weeks ago of fixing the teeth tips with Bondo: https://www.instagram.com/p/BmMiwTsnYn-/?taken-by=shareahack
 

animator

Well-Known Member
Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam

WOW! That really does look like a museum display! Stunning work!
 

13doctorwho

Sr Member
RPF PREMIUM MEMBER
Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam

I every time I see an update on this I feel like I've wasted my life. Such an incredible project. It's going to be EPIC when it's on display!!!!!!!!!!!!!!!!!!!
 

tarnyloo73

Well-Known Member
Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam

Sorry for the delay between postings! I'm definitely caught in a 'perfectionist' rut trying to make all the details as close as possible to the "STAN" skull casting. Using bondo to try and match up all the imperfections (it'll never be perfect so I need to accept that and move on at some point :lol).

As someone who dabbles with recreating dinosaur skulls myself, I totally get this obsession.
I will say this though, some museum reproductions are pretty rough and badly defined. There's a rex cast in a museum near where I live and yours is already looking crisper. On your last photo the sutures look convincingly deep and well defined giving a good impression of an object made from separate bones.
 

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shareahack

Active Member
RPF PREMIUM MEMBER
Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam

As someone who dabbles with recreating dinosaur skulls myself, I totally get this obsession.
I will say this though, some museum reproductions are pretty rough and badly defined. There's a rex cast in a museum near where I live and yours is already looking crisper. On your last photo the sutures look convincingly deep and well defined giving a good impression of an object made from separate bones.

Thanks @tarnyloo, that means a lot coming from you! Very much appreciate the feedback, back to the mines I go... :)
 

animator

Well-Known Member
Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam

I hate to be a pest... but eagerly awaiting an update or even just more pictures!
 

shareahack

Active Member
RPF PREMIUM MEMBER
Re: Full Sized T-Rex Dinosaur Skull - advice on coating/finishing/painting rigid foam

I hate to be a pest... but eagerly awaiting an update or even just more pictures!

No worries thanks for the nudge! My bad for not being more active on this project..sort of hit a few snags...I brought the skull to Maker Faire in its unfinished state because had I put the final polyester resin coat on, it would have flooded the place with toxic fumes. So I decided to delay the finishing until after the show. I ended up mounting it on a temporary rig with an actuator so the kids could remotely open/close its mouth (the final display will be static and the jaw more connected):

shareahack_trex-dinosaur-skull-makerfaire_001.jpg


This CNC'd lever toggles the open/close switches, there's a quick video here on IG with the skull shown at the end:
https://www.instagram.com/p/BophVy6Blxz/?taken-by=shareahack

shareahack_trex-dinosaur-skull-makerfaire_002.jpg


Since then it's gotten a bit colder and there's already snow on the ground here in Canada so it's a bit harder to work outside right now. I'm hoping for another good 1-2 mild weeks here to finish it before winter really hits so fingers crossed!
 

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