Casting Fiberglass In A Silicone Rubber Mold! 

you lost it with the puddle of resin with the randomly dropped-in pieces of glass cloth. try this: #1 cut pieces to FIT the shapes they are going in to (as in tailoring them). #2 stipple thin layer of resin on to the gel coat surface then lay the pieces in place, overlapping fairly generously. #3 (v important) use a multi-wheel roller to press the cloth in to the resin (or stipple it in with a stiff brush) keep stippling til the resin starts to come thru the cloth #4 paint on next thin layer of resin #5 more cloth #6 good roll /stipple etc etc. this will ensure you don't get the blobby edges, and you should have a lighter, stronger piece

@@raymondo162 Hi Raymond, thanks for your excellent suggestions. You obviously know what you’re doing with composites; I only occasionally dabble in them.

I settle for a pale approximation of perfection every time.

Great project, lots of fun to do!

Already in the works!

I appreciate it Mark, thanks!

The whole point is to have fun! Thanks for watching.

Thanks Max. I appreciate your nice comment!

Thanks for watching Paul!

Glad you find my videos helpful. Thanks for your nice comment!

Great idea. It’s on the list of future projects.

Definitely. I'm also very interested.

It’s a very useful tip.

Glad you found the channel Lorrie, thanks for watching!

I was thinking the same thing, but then I realized this guy has probably been doing this for a long time and is still kicking. Still though ....

It was epoxy, as long as you have an open room with some good airflow you're fine.

its the polyester resin that will fume you to death haha

@Island Mike ive done epoxy in the house all the time its not that bad

​@@jimmyokawa6800yea I only use the respirator when mixing huge 3-5 gal buckets worths where I'm standing over it with no airflow.

That’s because I bought that drill back in the Cretaceous.

Thanks for watching and commenting Roger!

There will definitely be more Fiberglass videos in the future. Chop fibers are good because it’s fast to work with.

Thanks for watching!

Thanks for the nice comment Errison! I appreciate you watching my videos.

Welcome Joel. Thanks for subbing and commenting! 👍

Thank you George. I appreciate your kind comment. Be sure to let me know if I can help you with any projects have have going.

Definitely I will! I'm a new fan of yours! got a lot to watch and learn :)

Early 80's Porter Cable. Bearings are a little tired but it almost 40 years old.

I’m a sculptor. My freelance work is prototyping toys for the entertainment industry.

How many castings you will get depends on the kind of resin you are laminating with. Epoxy resins are very aggressive and it would be necessary to use a parting agent or a barrier coat to preserve the life of the mold. In this video I forgot to use it but because I was only pulling one copy out of the mold I was not worried about it. It’s very hard to make generalizations about mold life because there are so many variables. The best thing is to make a small sample project and see how many castings you get out of the combination of materials you are using. When choosing materials for long production runs mold life becomes an important factor.

Great idea! I will cover that in a future video. After trimming the part with the bandsaw I cleaned it up on a 20 inch sanding wheel, followed by hand sanding. So it finished up fairly well.

Thanks, glad you enjoy the channel!

It’s a epoxy resin Gelcoat E-108GC and an epoxy laminating resin E-108SP from www.silpak.com.

Yes, the process would be very similar to this. By the way, I got a comment from a viewer much more expert in composite casting than I am and he pointed out everything I did wrong! There are good channels on RU-vid for doing fiberglass work, much better than mine. You might want to check those out.

For most projects the gel coat is used to give the final color to the project. Laminating resin is typically clear; it lacks the pigments or fillers to give it color. I also believe that gel coats are more sand-able or otherwise easier to finish than laminating resins are. But I am not an expert at composite casting. I only do it occasionally. I chose I chose this method to make this mold just to demonstrate different ways of doing it. I have done other videos with a brush on rubber mold and shell.

"Gel coat" in composites normally refers to a formulation that take a longer time to cure, so that it is still in the gel state when you layer your other materials (e.g. fiberglass and laminating epoxy). There is usually a higher concentration of waxy particles that will form a shinier skin on the surface compared to other epoxies. As Robert points out, it is also the layer that holds to base color for most composites, because it is used for the surface layer. I would justify a block mold for this part because : 1) You want a level surface for the layering, and block molds are self leveling 2) The difference in volume is small when comparing a block mold and brush on, and that is directly proportional to the material cost. 3) The time cost would be higher with a brush on mold.

Test a small spot of rubber on your car. I rather doubt it will stick but there is always that possibility.

Bigg Nasty Bassin Hey Gabe, the wax carver (pen) is from Foredom Tools. Beeswax I buy online from Camden-Grey and sticky wax and blue sprue wax I buy from Freemanwax.com

Anytime after the gelcoat has set. Thanks for watching.

@@RobertTolone thank you for taking the time to get back to me, once again, your channel is awesome. Happy Holidays!!

I am not really a composite shop. For instance I have never worked in carbon fiber. So I have never explored vacuum bagging my parts. It’s a fascinating process and there are some great channels on RU-vid devoted to composite fabrication.

No, I don't think it is. It's E-108GC Black Tooling Gel Coat and E-108 Laminating resin from www.Silpak.com. Both are epoxies.

I would use a 2-part mold with the parting line around the edges of the cup. The attachment point of the cups to the arms of the anemometer might have to be drilled and tapped after casting. Not sure how your particular cups attach.

You should be able to switch to a lower price resin.

Yes, this piece required 7 layers of resin with about an hour and a half curing time in between. Pretty labor intensive. Thanks for watching.

👍

I don’t do much composite work so I’m no expert on fiberglass. I use it mostly for making mother shells for molds and in that application I prefer cloth because the final product is easier to handle than shells made of chopped strand. So I keep cloth on hand. I have used chopped strand in large projects where the casting is fiberglass backing up a gel coat.

I believe it was a 4 ounce cloth.

My experience has been that it is roughly 1/10 of the life of urethane casting - the epoxy tends to find ways to grab the mold, and silicone will wear out (usually becoming easier to tear) from the heat of casting and leaching of the softening oils. Most fiberglass casting in done with a rigid mold and the part is removed while it is still green. Often the part will be cured outside the mold, but some pieces need the mold to cure in the correct shape.

You want to end up with a hollow resin casting of a balloon? How big will it be?

Yes, not massive....maybe about 6" around the fattest part. BUT I want to make segments....eventually it'll be a model of an air balloon. Like a child's mobile. I have a method for the basket, but not the balloon

I would be inclined to sculpt the balloon model then brush on a silicone blanket and mother style mold. Then hollow cast the model on a rotational molding machine.

Thank you very much! :)

I have never made a price comparison. Generally speaking, the smaller the container the higher the price per ounce. This is true of most things and is especially true of rubber and resin. For me the sweet spot is 5 gallon buckets. Buying materials in small quantities is extremely expensive.

@@RobertTolone How much was it? I don't see prices on their site. 🤷‍♂️

The resins I use, including these epoxy resins, are metered out by weight. No conversion is necessary as long as the units are the same. So for 100 pounds of resin you use 29 pounds of hardener . With 100 grams of resin you use 29 grams of hardener. I use grams for most of my smaller projects and my scale is in grams. Grams are the most convenient because the units are small. The math is more complex using when using pounds and ounces. For example, if you weigh out 1 pound of resin how much hardener do you need. 1 pound x .29. What’s that? 😳 Well, there are 16 ounces to a pound so it’s 16 x .29 = 4.64 ounces. How are you going to weigh that accurately? On a gram scale 1 pound is very close to 454 grams. Multiplied by .29 is very close to 132 grams. More than accurate enough for a casting shop. If you needed more precision than that you would have to go to laboratory equipment. If you are converting units there are 28.35 grams to the ounce. But I strongly recommend using a gram scale. If your question was about calculating ratios that’s a separate problem and I have it on my list as a subject for a video.

I’m definitely going to try this. Thanks!

There are much better RU-vid channels about composite casting than mine!

@@RobertTolone i liked your explination very much and how easy you make it look i will continue to do research surely. thank you for your video

It’s not. It’s actually 6.06060606061 to one. 13.5 x 6 = 99. So a six to one ratio would be one percent off. Most resin mixes are simple like 10:1, 2:1, etc. And they are usually a little bit forgiving about accuracy. I haven’t done tests to see how sensitive this resin is to mix ratio. But my theory is that it must be sensitive or the manufacturer would not specify the ratio with that degree of precision. Otherwise they would just specify six to one. But they didn’t. They specified 13.5 to 100.

@@RobertTolone Ah! No wonder my muffins don't rise. You do make it fun though. Great lessons always.

Me too.