Best molding and casting materials for a Fett lid

[Artakha]

I was wondering what the best moulding and casting materials are if I want to cast my scratch built Boba lid. I've heard many use Smooth-On products, but specifically which ones? There are quite a few so I'm not sure which would work best for this project. If anyone has done this before and has advice to give, and what products work best in this context, I would be very grateful. My apologies if this topic has been brought up recently.

 

[Darth Voorhees]

I used Smooth-on Rebound 25 to make the mold of my scratch build. Its fairly easy to use and yields excellent casts. You can make the jacket for the mold with Smooth-on's plasti-paste or fiberglass.

For casting, you can use either fiberglass or urethane resin. If you use resin, Smooth-on 65D (rotocast resin) is great to slush cast a helmet. This is what the ASOK helmets are made of.

For fiberglass, you will need a gelcoat as the first layer you put in the mold. You can use a polyester based gellcoat , commonly used for boats. It will need to have wax added, or you will have to add a wax additive to cast with it. You can also use a urethane resin to make a gelcoat, like smooth-on Smooth-cast 320. Then you just lay the glass in with regular polyester fiberglass resin. Bondo makes one that is fairly inexpensive and used by alot of prop guys. It has the yellowish/amber color to it. You CAN get a clear polyester fiberglass resin but they are usually a bit more pricey.

This is what i use, or have used, with good results..."the best" can sometimes be a matter of opinion! Anywho...Hope that helped!

 

[fettfw3]

I also use smooth-on rebound 25 to make my molds. the casting I also use smooth-on 65d. I do a few layers with 65d then fiberglass inside to add some strength to it. I have good luck with this and saved on using a lot 65d per helmet.

there's a lot of u tubes videos on using smooth-on products to check out.

 

[Artakha]

Thanks guys! I had been looking at smooth-on stuff for a bit so I guess I'll take that route. What is the advantages/disadvantages of using resin vs. fiberglass? Fiberglass would make a tougher helmet? Sorry for my naive questions...

 

[Darth Voorhees]

Yes fiberglass is a much stronger helmet. Resin cracks easier and will also tend to be heavier because you'd need to put a few layers of it in to get it to a good strength. Resin helmets will also warp eaiser so they have to be taken care of more cautiously. Like dont leave it in a hot car etc. The screen used helmet was also made from fiberglass.

What Fettfw3 said about using the 65D and then glassing it is also a good option, similar to what i was saying about using the Smooth-cast 320. the 320 is a little more rigid than the 65d, which is marketed as semi-rigid. I like the 320 because it sands easier and smoother IMO.

Fiberglassing takes more time but i feel its worth it in the end as you get a sturdier helmet, whether you use a urethane resin as a gelcoat or not, the fiberglass makes it a tougher helmet.

 

[fettfw3]

your questions are not naïve. I had some of the questions my self when I wanted to cast some of helmets and didn't know how or what to use.

Voorhees explained it out better for you then I could by typing. I have read a lot of his post and " wise he is"

 

[Artakha]

Ok Thanks guys I think I will then go with fiberglass. Would I need wax with the 320 if I was going to use that for the gelcoat? And why is the wax important?
Also would 'bondo glass' work fine for the mother mold instead of the stuff smooth-on sells (which is pretty pricy)?

Sorry for all the questions

 

[fettfw3]

I have never used 320 so I cant tell you anything about using it. I do wrap aluminum foil around the rebound 25 silicone mold after it completely dry's and build my fiberglass mother mold over it. You want to use enough fiberglass to get it nice and strong so that it don't flex any when you are holding it in your hands. I found it takes me 2 sampler packs (2 pounds) of rebound 25 per helmet to make a good thick mold.
check out xXbocephusXx on u tube he does a 4 part video on molding and casting a fett helmet.

 

[Darth Voorhees]

Ok Thanks guys I think I will then go with fiberglass. Would I need wax with the 320 if I was going to use that for the gelcoat? And why is the wax important?
Also would 'bondo glass' work fine for the mother mold instead of the stuff smooth-on sells (which is pretty pricy)?

Sorry for all the questions

No need to apologize brother, this is why we are here!

No you dont need wax with with the smooth-cast 320. That is only for a standard gelcoat made with polyester resin. (which is what the fiberglass resin is, the gel coat is just thicker and opaque colored) Thw wax is so the surface doesnt dry tacky. Since its technically made for making boats the layers usually remain tacky to add the subsequent layers. the final layer wax is added so it will dry tack free and be sanded. In a mold we do it reverse, but same idea.

The 320 is urethane resin, basically the off white stuff you see alot of small parts cast with. I brush in a few layers (letting it cure up between each one) until i dont see any of the mold showing through and then once its cured up i put 2 layers of glass in it. The 320 isnt really made for this purpose and cures fairly quick, so you'll need to use disposable chip (house painting)brushes. i use 1.5" ones. Bondo fiberglass will work fine. Use the fiberglass "matt" rather than the "cloth", so you get more rigidity from it.

 

[Uhbif]

For the form I use Rebound 25, Rebound 25 + THI VEX and Mold Star 30
THI VEX makes silicone thick.
The case for forms - Plasti-Paste


The helmet made from Smooth cast 300, Black Onyx or 65D.

 

[Uhbif]

For fiberglass, you will need a gelcoat as the first layer you put in the mold. You can use a polyester based gellcoat , commonly used for boats. It will need to have wax added, or you will have to add a wax additive to cast with it.

Very interesting. I want to try.

I have not much choice, but I found epoxy and polyester gelcoat. Which one is better? Or there is no fundamental difference?

Didn't understand about the wax additive. It is added into a silicone form before applying the gelcoat?

I also use smooth-on rebound 25 to make my molds. the casting I also use smooth-on 65d. I do a few layers with 65d then fiberglass inside to add some strength to it. I have good luck with this and saved on using a lot 65d per helmet.

there's a lot of u tubes videos on using smooth-on products to check out.

What fiberglass is best for 65D? Polyester resin peels off. I used Novol 720

 

[Darth Voorhees]

The wax additive goes into the polyester resin gelcoat itself. it makes it cure up tack free. The polyester resin gelcoat i have used already had the wax in it. But it can be purchased separately.

I havent used the epoxy gelcoat, so im not sure what the difference would be other than that one is obviously epoxy and one polyester based.

The polyester/fiberglass resin should stick to it fine. Im assuming your laying the fiberglass in it as well...not just the polyester resin alone? Because THAT would just peel or flake off. You need to be adding the fiberglass as well.

Its basically the same thing as buying a rotocast helmet and then reinforcing it with fiberglass. Your just doing it while still in the mold. That said, the only fiberglass resin ive used for this is the bondo brand, which is your standard amber colored polyester fiberglass resin. Maybe the formula is different from what you used? I cant be certain there.

 

[Uhbif]

The wax additive goes into the polyester resin gelcoat itself. it makes it cure up tack free. The polyester resin gelcoat i have used already had the wax in it. But it can be purchased separately.

Please tell me, what brand of gelcoat did you use?
I don't think I will buy one, but I will analyze the composition and application.
He normally separates from the Rebound form?

 

[Darth Voorhees]

I believe the brand was HI-BOND. it was a lesser expensive one. It can be purchased with or without wax, i got the one with wax. I no longer have it now though

The gelcoat separates fine from the rebound mold. Like i had mentioned earlier on, the gelcoat is basically the same thing as the polyester resin used to do the fiberglass lay-up. it is just thicker and an opaque color to give you a nicer finish surface.

 

[Uhbif]

Darth Voorhees, thank you, I think I understand the basics.

Found the same paraffin additive.

I will try, about results I will write )

 

[Uhbif]

First fiberglass Helmet.

Polyester gelcoat and resin. There are voids between the layers, and how to avoid them?

 

[Tottofagrin]

View attachment 95088

First fiberglass Helmet.

Polyester gelcoat and resin. There are voids between the layers, and how to avoid them?

Glass doesn't do very well in sharp corners, it can tend to straighten and make a void underneath. With fiberglass you want as round corners as possible to avoid this. It's also very important to completely wet the matt (fibers) with your resin before laying on the next layer. Don't know if any of this could be your problem.

I've never cast a helmet but my approach would be to use slush cast resin as the first layer to pick up all the details that can be hard with fiberglass. I'd try to get a nice smooth inner layer without with rounded edges and corners. Then I'd start laying on the fiberglass with resin.

About the wax in the gelcoat. To my knowledge it's only when you want to use a gelcoat as a top layer that you need wax, i e topcoat, for instance if you want to repair a fiberglass hull or helmet. Gelcoat doesn't cure fully in contact with air. But as a first layer in a mold you won't need wax. That's what I've learned when it comes to working with fiberglass boats anyway. Please correct me if I'm mistaken.

 

[Rogermaximus]

You guys are friggin awesome hear, lots of knowledge!

 

[Darth Voorhees]

Glass doesn't do very well in sharp corners, it can tend to straighten and make a void underneath. With fiberglass you want as round corners as possible to avoid this. It's also very important to completely wet the matt (fibers) with your resin before laying on the next layer. Don't know if any of this could be your problem.

I've never cast a helmet but my approach would be to use slush cast resin as the first layer to pick up all the details that can be hard with fiberglass. I'd try to get a nice smooth inner layer without with rounded edges and corners. Then I'd start laying on the fiberglass with resin.

About the wax in the gelcoat. To my knowledge it's only when you want to use a gelcoat as a top layer that you need wax, i e topcoat, for instance if you want to repair a fiberglass hull or helmet. Gelcoat doesn't cure fully in contact with air. But as a first layer in a mold you won't need wax. That's what I've learned when it comes to working with fiberglass boats anyway. Please correct me if I'm mistaken. 

From my experience, you do need the wax in the polyester gelcoat for the first layer, because essentially that first layer becomes the exposed layer , basically the same as the final layer when doing a boat hull...its just working in reverse. If you dont add it, (or use gel coat with the wax already in it) the outer layer comes out of the mold very tacky. It then would require an acetone bath and a bunch of sanding before it becomes ready for paint. Alot of work.

I have been brushing a high durometer urethane resin into the molds first as a gelcoat and backing that with the fiberglass and that has been working very well, so i agree with your general slush cast resin for the details and then laying in the glass. You get a nice finish right out of the mold and the durability of the fiberglass.

 

[Tottofagrin]

From my experience, you do need the wax in the polyester gelcoat for the first layer, because essentially that first layer becomes the exposed layer , basically the same as the final layer when doing a boat hull...its just working in reverse. If you dont add it, (or use gel coat with the wax already in it) the outer layer comes out of the mold very tacky. It then would require an acetone bath and a bunch of sanding before it becomes ready for paint. Alot of work.

I have been brushing a high durometer urethane resin into the molds first as a gelcoat and backing that with the fiberglass and that has been working very well, so i agree with your general slush cast resin for the details and then laying in the glass. You get a nice finish right out of the mold and the durability of the fiberglass.

Thanks for your input! When I'm talking about boat hull work I'm talking about doing them in a mold, the gelcoat goes in first then the inner layers so to speak.

Maybe we have different gelcoats in Europe, it's only when using it as a top layer that I know you have to mix in some wax to get it to cure properly.

As a side question, have you tried using epoxy resin for your fiberglass? Will it bond properly to the PU resin? As it's easier to work with indoors that hopefully will be my route.



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