Other Advice needed:Tips for making molds with general materials

Roseand

Roseand

The Weaponizer
Site Supporter
Location
Wisconsin
I'm planning on making my own ride plate from a stocker, so I can experiment with different shapes of d cuts, v cuts, etc. Also I'm going to try and make a nose piece for my square, and also try to make a mold out of the footholds that I'm modifying. So basically what I'm asking is for tips on making the molds, and also on what materials I am going to need. For example, what can I use for a mold release besides PVA, and basically what I have to do for a really basic mold. Like, can I do alot of stuff without using tooling gel coat and buffing out a mold every single time? Can you have a successful mold without doing that?
I really like working with fiberglass, and I've got a gallon of epoxy resin and plenty of cloth+biaxial, and I'd like to start getting creative. And for making molds the cheap way, using bondo polyester resin is fine right? Also, I should add I'm doing this on an 18 year old's budget, and it's just for fun.

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MikeyB

MikeyB

H2O-Addict®
Location
Michigan
Ive made a couple small molds so I can add a little bit to the topic. I made a quicky rideplate mold that turned out pretty good using polyester glass and bondo. I started by covering the ride plate in green 3m tape (expensive but worth it) because it was so roughed up on the bottom. After that I brushed on partall paste wax and buffed it off by hand using a clean cloth. I did this 3 times and then brushed on pva mold release. Spraying would have been better but I would have to surface the mold later anyways due to the texture of the tape and imperfections in the original plate.

After the plate was prepped I mixed poly resin with a lightweight body filler until it was of a brushable consistancy but not too runny. I brushed a heavy coat on the prepped plate after it was waxed and the pva dried. After the first coat started to set I threw on a second and then mixed straight poly resin to apply a few reinforcing layers of mat. I also cut some plywood crossections and glassed those in for more reinforcement. After removing the plate I cleaned off the mold release and started sanding down the mold surface with 80 grit paper.

The resin/bodyfiller milkshake sands pretty easily, I worked up in grit to 220, then primed it and sanded again up to 400 then sprayed some gloss black paint on. This provided a quick, cheap and easy mold although it is not very durable. Ive thought of making a plug of this mold in order to make a more durable one later on with tooling gelcoat.
 
motobehrens

motobehrens

X
Location
Gilbert, AZ
I'm not the most knowledgeable on this subject, but this is what I've learned from making small molds/parts with epoxy resin:

You can use meguiars #8 or Partall #2 as a release wax.


If you are making your mold with epoxy resin, just brush on a thickened(fumed silica) epoxy mix over your waxed plug/part, then start laying your glass after the thickened epoxy mix has had some time to firm up, but not quite dry. The better the finish is on your plug, the better the mold turns out.

Make sure the part you are copying has a positive draft, so you will be able to separate the part from the mold.

Ride plates are a good usuable part to learn how to make. You can also add a colorant to your resin if you want to make a couple different colored plates.
 
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tom21

tom21

havin fun
Location
clearwater FL
you can do it on the cheap but just realize the quality will be less than perfect and probably take more work vs using the correct materials and doing it the right way.

without gelcoat your glass will have air pockets in it. that has to be filled. when you sand gelcoat you get smooth glecoat. when you sand glass you get exposed fibers. holes need to be filled, fibers need to be coated. so you essentially do the work 2 times.

your mold will suffer the same problem so all the defects in it will also be in your part.

you can make a nice mold, fix it sand it, modifiy it etc. re gel if you need to and then all your parts come out nice. and even if your mold isnt perfect if you use gel on it and your parts, they can be fixed more easily since they can be sanded.

trust me I know about being a tightwad! as you get older time becomes worth more than the money you save. .02
 
Vumad

Vumad

Super Hero, with a cape!
Location
St. Pete, FL
Yogurt cups can save you a lot of money on mixing cups. Butter tubs work great for larger mixes. As long as you don't melt them, the dry stuff pops right out and you can use them over and over. This is mostly, but not completely, true for mixing foam too, which will stick to and ruin almost any other kind of mixing cup.

Visqueen or other dense plastic works good for pour foam. Pour foam, cover in plastic, use your hands to push the foam into a basic shape, it sets up quick. Might want to wear cloth gloves, the foam can get pretty warm right before it sets up enough to stay put. Probably wont hurt you, but it's uncomfortable.

Harbor freight sells bondo cheaper than anywhere else I have found.
 
speedysprocket

speedysprocket

Alex
Location
Chesapeake, VA
I made a ride plate for my Foot Rocket, which is a little bigger and more complex than a super jet, by using cellophane as the release. I laid a layer of glass on the inside of the ride plate. When it dried, it was still a little flimsy, so I put a layer of carbon on to stiffen it. Then separated the new piece and added my layers of glass to the outside of the plate. Stock plate is maybe 1/4", my new plate is maybe 1/16" or slightly thicker and I've had no issues with it breaking. It's my short flat water plate though, so doesn't take as much abuse as a longer one would when riding surf. I've used this same procedure to copy my Foot Rocket foot holds as well and for a coupler cover, I used a gallon iced tea jug that had the size and shape I wanted to use as a mold.
I guess my point is good luck, have fun, and don't over think it.
 
motobehrens

motobehrens

X
Location
Gilbert, AZ
tom21 said:
you can do it on the cheap but just realize the quality will be less than perfect and probably take more work vs using the correct materials and doing it the right way.

without gelcoat your glass will have air pockets in it. that has to be filled. when you sand gelcoat you get smooth glecoat. when you sand glass you get exposed fibers. holes need to be filled, fibers need to be coated. so you essentially do the work 2 times.

your mold will suffer the same problem so all the defects in it will also be in your part.

you can make a nice mold, fix it sand it, modifiy it etc. re gel if you need to and then all your parts come out nice. and even if your mold isnt perfect if you use gel on it and your parts, they can be fixed more easily since they can be sanded.

trust me I know about being a tightwad! as you get older time becomes worth more than the money you save. .02
Click to expand...

I've made several smaller molds using epoxy resin thickened with West System 404, and had it come out as smooth as gelcoat w/ no bubbles. That shouldn't be an issue. Once the OP decides whether or not he likes working with glass, then he should graduate to gelcoat and poly resin for the mold. We don't want to overwhelm him and think he needs 500$ in materials and equipment to make a rideplate.

You only need a handful of items to start making molds and parts.

Quality is going to be mediocre on the first parts he makes, regardless of what materials he uses.
 
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tom21

tom21

havin fun
Location
clearwater FL
agreed, the point was to try to start off with some kind of surface agent to keep from having a poor surface at every step.

you made your own coating so obviously we are agreeing on finding a way to start with a smooth surface. a gallon of gelcoat or primer or 404 is hardly 500$

I was just looking at the cost of a epoxy vs gelcoat.
make cheap parts or practice with less expensive materials like poly then make your good parts with the epoxy.
although epoxy wont shrink as bad as cheap poly resin.

whatever floats your boat, I dont care to argue about something we basically agree on and I did qualify my post saying it was just my own opinion. there are countless ways to go about it and more materials come to market every day. ive made rough shapes off of cardboard. dont try and tell me about saving money! I have stir sticks for my resin older than some of you. lol

in any case, I defer to your wisdom mr motobehrens. please accept my apology if I have stepped on your toes in any way. you have the floor sir.
 
motobehrens

motobehrens

X
Location
Gilbert, AZ
I'm the rookie, and you are the pro, Tom21. I'm not questioning your advice. Anyone who can build a complete hull, hood, and miscellaneous large parts has my respect. Of course your method is the better way. But I wanted to emphasize you don't need an air compressor, spray gun, poly resin, gelcoat, carbon, etc, etc, to build a small mold and part. It can also be a little less intimidating only having to get used to the epoxy resin and fillers vs having to learn the characteristics of the poly, the gelcoat, the pva.

If the OP doesn't like working with glass, then he won't have all that extra stuff laying around when he decides it is too much time and itchy scratchy work to make a couple rideplates.

I would love to try out that FX-1 of yours. I wish you were on the West coast
 
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