Fiberglass casting materials and techniques

[tubachris85x]

So I can't seem to find specific information, so asking here

Probably looking to make molds of the Agent Kallus armor I built for my buddy last year. Figure the best way to go about this for now is to produce fibgerlass casts of his stuff. I've considered vac-form but don't have access nor am I in the market to build (another) one.

The extent of my fiberglass knowledge is use of the stuff from home depot. I know it's not "quality" for producing castings (making mother molds, sure ) but not entirely versed.

Key questions:

-Recommended brand/type of fiberglass materials. I was thinking of grabbing some from a local West Marine store..

- Better, cleaner casting techniques.

As for Gel coats, the understanding I have is that you can generally use any kind of resin as a "gel coat," is that true? Additionally, I've seen on other's work, where it looks as though they applied another, thicker layer of resin to cover the matting/fibers. Is that what they're doing to seal it?


I guess I'd like to get a good understanding of a process to yield quality results...thanks

 

[Shotzy]

I've seen people use "glass fabric" to capture details pretty well; http://www.jamestowndistributors.co...Ol2mngtxRy73uwbudLzZFkNUgRCzobf47RoCwGbw_wcB#

I've personally only made mother molds with it, have you thought of maybe using plasti-paste? Maybe its putty like texture would be good at capturing detail?

https://www.smooth-on.com/product-line/plasti-paste-series//

 

[brandomack]

First off, what environment would you be laying up the fibreglass? Do you care about it stinking? If not use a waxed polyester resin, if you do care about it stinking then use west system epoxy (more expensive).

Your gel coat is what is going to capture any detail, and create a smooth paintable surface, use real gel coat.

If you are wanting something lightweight yet flexible then you can use fibreglass cloth, if you want it sturdy then you will need fibreglass mat (chopped strand)
Both Gel coat and your resin are catalysed with MEKP Methyl Ethyl Ketone Peroxide.

buy silicone brushes, it cuts down on waste.

wash equipment clean with acetone.

Also, if you ever want a good filler, add gel coat with Cabosil (small glass bubbles) to create a consistency similar to cake frosting.

I use these guys exclusively. They are the one stop shop for the film industry here in Vancouver. The USD/ CAD exchange rate can be your friend.

www.fibertek.ca

 

[tubachris85x]

I've seen people use "glass fabric" to capture details pretty well; http://www.jamestowndistributors.co...Ol2mngtxRy73uwbudLzZFkNUgRCzobf47RoCwGbw_wcB#

I've personally only made mother molds with it, have you thought of maybe using plasti-paste? Maybe its putty like texture would be good at capturing detail?

https://www.smooth-on.com/product-line/plasti-paste-series//

I've actually used plasti-paste already before for a previous project. I don't necessarily have an issue with it, but found it to be brittle and not as easy to work with.

Thanks for the recommendation for the fiber too, looks like something I'll roll with for this

First off, what environment would you be laying up the fibreglass? Do you care about it stinking? If not use a waxed polyester resin, if you do care about it stinking then use west system epoxy (more expensive).

Your gel coat is what is going to capture any detail, and create a smooth paintable surface, use real gel coat.

If you are wanting something lightweight yet flexible then you can use fibreglass cloth, if you want it sturdy then you will need fibreglass mat (chopped strand)
Both Gel coat and your resin are catalysed with MEKP Methyl Ethyl Ketone Peroxide.

buy silicone brushes, it cuts down on waste.

wash equipment clean with acetone.

Also, if you ever want a good filler, add gel coat with Cabosil (small glass bubbles) to create a consistency similar to cake frosting.

I use these guys exclusively. They are the one stop shop for the film industry here in Vancouver. The USD/ CAD exchange rate can be your friend.

www.fibertek.ca

So can you clarify this for me then?

The gel coat is clearly the first layer, then you lay down the fiber cloth before the gel coat cures, then you're applying the epoxy as the final coat over top the fiber cloth?

I'm trying to really understand the difference between what a "gel coat" compared to an epoxy resin is.

 

[brandomack]

The gel coat is a much better starting surface material to use. It is very much a "gel" when being applied. It is not merely a first layer that is referred to as a "gel" coat, but a differently formulated material called gelcoat.

If you have ever sat in a hot tub or a fibreglass bath tub, what you are sitting on is gelcoat. It has a colour, and depending upon the smoothness of your mold it can come out as smooth and shiny as glass.

Check out the fibertek website and look through each of the catalogue pages to get a better understanding of what things do.

Your order of operation for laying up fibreglass is this..

1. Apply a release agent to the mold to save it from deteriorating.

2. Mix gelcoat and hardener in correct proportion and carefully apply to mold

3. Allow gelcoat to partially cure, poke with a toothpick and when it has hardened to the point where it doesn't make an imprint then you are ready for your glass.

4. Mix a batch of resin and brush into mold (this just gives the glass something to stick to, dont slop on too much)

5. lay your fibreglass over your mold and begin pressing it into the center, working outwards ( a fibreglass laminating roller is good for this step) be sure to avoid creating bubbles or voids during this step.

6. Immediately mix up another batch of resin and apply generously to the center or the mold and work it outwards, try to keep excess resin away from the mothermold as this will make it difficult to demold.

7. Allow to cure for 24 hours before you attempt to demold.

8. Trim excess glass and flashing with a grinder or oscillating tool

9. Sand edges to avoid sharp edges

10. Prime and paint to suit.

I've actually used plasti-paste already before for a previous project. I don't necessarily have an issue with it, but found it to be brittle and not as easy to work with.

Thanks for the recommendation for the fiber too, looks like something I'll roll with for this





So can you clarify this for me then?

The gel coat is clearly the first layer, then you lay down the fiber cloth before the gel coat cures, then you're applying the epoxy as the final coat over top the fiber cloth?

I'm trying to really understand the difference between what a "gel coat" compared to an epoxy resin is.

 

[brandomack]

Just updated wih an order of operarion.

 

[tubachris85x]

Just updated wih an order of operarion.

Thank you so much!! That's what I needed!

 

[Duncanator]

Brandomak has given really good advice. If there is anything I would add, it is that you should be sure to use compatible resins for your Gel-coat and lay-up resins.

There are basically two types: Polyester and Epoxy. Polyester is the stinky type, and Epoxy is the expensive type. Gel-coat and Lay-up resins come in both varieties.
Both work well, but it's a good idea to use the same type so your finished part doesn't risk delaminating.

I have used the West Systems epoxy resin, and it works great.

 

[Darth Lars]

I have got the impression that Gel Coat is nothing more fancy than resin with pigments and additives (such as colloidal silica) that changes its viscosity.

Also, if you ever want a good filler, add gel coat with Cabosil (small glass bubbles) to create a consistency similar to cake frosting.

I thought "Cabosil" was a brand name for colloidal silica. The small glass bubbles are commonly called "microballoons".

When mixing putty/filler, I use:
* Colloidal silica: Prevents running. If you have enough, it will have the cake frosting consistency.
* Microballoons: Just fills space. Makes the filler lighter. Different varieties are white or reddish brown
* Talcum powder: Makes the filler easier to sand.

West Systems has a ready-made powder mix with the powders above in pretty good proportions for a general-purpose putty.
There are also "microfibres", but that is for epoxy when the filler needs to also be an adhesive and be very strong -- the opposite use of talcum powder.

 

[brandomack]

Cabosil is light weight, low density fumed silica powder additive for use in all types of resins and gelcoats although, when used to thicken polyester or vinylester resins, creates an excellent medium sanding, non-slumping compound

Glass bubbles is a hollow silicone dioxide powder. It is a non-absorbent additive used to extend all types of resins and gelcoats. it can be used in resins alone; however, its main use is to be used in conjunction with other fillers to create easy to sand compounds.

 

[tubachris85x]

So then here's my other question-

If I am wanting to do cold-cast, would the same logic of mixing the metal powders as I would for an epoxy resin be the same?

I know I have to use a specifically "clear" resin w/ tinting for non-fiberglass casting.

 

[brandomack]

So then here's my other question-

If I am wanting to do cold-cast, would the same logic of mixing the metal powders as I would for an epoxy resin be the same?

I know I have to use a specifically "clear" resin w/ tinting for non-fiberglass casting.

It depends on what it is you are casting. In my experience, (using smoothcast 300, and Smoothcast 65D) You add in equal parts A, B, tint and metal powder then stir and pour.

keep in mind, this is with a low viscosity resin, the higher the viscosity, the thicker it will become with metal powder added.

Smooth-On product are your friend in this case.

 

[cavx]

There is a series of 5 videos where a guy makes a mold and then casts a fish. His technique is outside the normal molding/casting, but this might help as he uses gelcoat and fiberglass for the whole project. I'd say he only had access to these materials and used what he had.