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So one of the projects I have wanted to try is making a carbon fiber chassis. This will have 2 steps: making a mold then making the part.

I had in the past tried creating a 'buck' for molding. I simply lack the skill and workspace to make an accurate enough piece.

I am going to make a cast mold directly from a chassis. I bought a very good condition t2 tub as my base. The t2 tub has an angled bottom and doesn't have many acute curves. I think that this will help when I actually cast a part.

For my prep I cleaned the chassis with rubbing alcohol. Then applied tape behind each screw hole. I then made flanges from paper along each edge. After the flanges were attached I applied melted paraffin wax to every hole and crevice. My goal is to eliminate any place where resin can go and get stuck. I had a heck of a time in the little area where the rear bulkhead attaches to the chassis.

I looked like this at that point I then applied a parafilm epoxy mold release. This prevents the resin from adhering to the part I am molding. Although this is for epoxy I have tested this with Fiberglass resin. I decided to use a polyester resin designed for fiberglass. I am using a combination of fiberglass cloth and chopped mat. I had made some initial molds out of fiberglass cloth and wasn't able to get them thick enough. I purchased fiberglass chopped mat to make a thicker mold with less layers, but they special binders in chopped mat require using fiberglass resin.


I planned to do a normal setup.

I precut 3 sheets of fiber glass with some slices in it to go around curves and angles.

I prepped the resin for 2 batches. An initial 1oz for a first pass and 2 oz started 5 minutes later for the end of the layup. I added the stated ratio of hardener and stirred for 1 minute on each batch.


used a small paint brush to apply the resin directly to the chassis and added the glass on top. I learned that to avoid air bubbles stipple or blot the resin onto the cloth. This let me push out the air bubbles from underneath the cloth. I then applied the second layer. The cloth wasn't cut well enough and I had to cut relief cuts for the 2nd and third layers. I used about .75 OZ per layer. I think I can expect about the same if I was using epoxy.

Everything was ok until I applied the chopped mat. The chopped mat was less flexible so it pulled out the previous layer of glass cloth. To emergency repair this I quickly made a vacuum bag and placed the piece inside. I planned on an open air layup, so it wasn’t prepped properly to go in a bag. I hadn't made a piece this big before, so I had a hard time getting it in the bag. I then removed the air. I noticed that even though the flanges were made of paper they held up under the pull of the vacuum.
At this point my gloves broke and I am covered in unset epoxy and fiberglass strands from the chopped mat.
I need to use a bigger bag next time, if I still have one. The sides started to pull away from the part of the mold where the tabs for the rear bulk head are. I used a set of clamps to pin that part down.

I waited a couple of hours and removed the part from the bag so it could finish curing. The bag pulled away cleanly so that was a good sign. The resin wasn't hard yet so I took the scissors to trim off some of the excess fiberglass. I then peeled off the paper flanges from the inside.

I'll wait till morning to make a full evaluation, but it looks like a pretty good first effort. The wax prevented the resin from seeping into screw holes and there were no gaps. The mold feels pretty thick at this point and when I knock on it, there is a solid sound coming from it.

I'm going to let it cure overnight before I try and remove the chassis from the mold.

So far it seems promising.

there is a pretty great thread here
https://www.rc10talk.com/viewtopic.php?f=36&t=16647
and here

https://www.rc10talk.com/viewtopic.php?f=35&t=35038&start=15
It looks like the author of that thread had good thing going on. He looked like he got a much better mold than I did when I tried my gold pan mold. I am going to go to add extra layers of cloth and I think the t2 tub has a shallower 'draft angle' that was mentioned in the thread.

It looks like I should have used a gelcoat or tool as my first coat. I'll have to see if the fiberglass resin has sufficient surface for being a mold. It looks like I'll learn something out of this.

https://www.fibreglast.com/product/molding-fiberglass/Learning_Center

if the parts get finished I should look at this
https://www.competitionx.com/beginners-guide-to-rc/prep-your-carbon-fiber-parts/

Notes here http://www.chm.bris.ac.uk/webprojects2002/mjames/fromula_one.html state 3-4 layer of carbon fiber make 1mm. So for a 3mm chassis I would need 9-12 layers of CF and 6-9 oz of epoxy.

A successful failure!

The parts remolded correctly and the chassis is not damaged.
Some things worked and some didn’t. Where the resin contacts the chassis all is smooth. No fabric is visible at all from the mold side.

The wax in the holes look like it mostly worked. I was able to scrape the wax plugs off the mold with a fingernail and it was mostly flat. There were voids in the mold. These seemed to be due to bunching fabric, as well the tail of the mold wasn’t flat due to wrinkles in the fabric.

The mold was also about 1/16 thick and should be around 1/4” thick to cast a 3mm part.

The flanges moved inwards and that would make cst parts harder to demold.

Next layup.
Since I know now I will need to vacuum the mold I am starting by attaching the chairs to cardboard with low expansion foam. Seemed like a good idea but even this low expansion foam seem like it may cause more mess than solve problems.

I cleaned up the board and it took less time than I thought
I started with it centered and then it went on to drift off the edge of the board. It’s pretty stuck on so I’m going to have to live with it like this for a while.


Unfortunately I buffed a bit too much and noticed I pulled some of the dye off the anodized metal…

The finish is smooth still so I just hope I can boiled it in some dye and bring the color back.

I was about to say from your last post isn't that chassis a bit too nice to be experimenting with ? Lol.

Best option is to have it re-anodized to restore the color

RC10th wrote: ↑Tue Jan 25, 2022 9:15 pm I was about to say from your last post isn't that chassis a bit too nice to be experimenting with ? Lol.

Best option is to have it re-anodized to restore the color

That's a bummer. The amount of work it would take to make poor condition chassis work for casting would be way to much. It'd be days of grinding to make it smooth enough. All of the processes can be reversed by soaking in chemicals that don't hurt anodized aluminum. It was trying to polish it that messed it up and it wasn't necessary. I can't see myself spending the money to get it re-anodized, when I last looked an few months ago it would be over $200. I probably just not going to build the project it was for.

Maybe look into getting a mold 3D printed instead of trying to make one out of fiberglass?

If your just using it for a mold a crappy chassis wouldn't be too hard, just skim the chassis with a filler of sorts and sand nice and smooth for either a plug or a buck.

Many a mold for RC bodies have been made from plaster of paris.

Phin wrote: ↑Tue Jan 25, 2022 10:24 pm Maybe look into getting a mold 3D printed instead of trying to make one out of fiberglass?

So that is completely possible, but there are a few challenges to overcome.

The chassis mold would be larger than a consumer 3d printer can print, even from a high quality printer I would need to do some kind of vapor smoothing for the surface.

I'd basically be looking at shapeways or similar service.


Not that it couldn't be done. I do eventually want to learn how to design a part that could be used for this , but it would add complexity for me.

A smooth scratch-less piece of tempered aluminum is a good starting point. Basically anything can be undone by soaking the chassis and acetone, then denatured alcohol.

There are a good number of youtube videos showing how to successfully make mold from existing parts, I think I am on the right track,just lacking experience.

RC10th wrote: ↑Wed Jan 26, 2022 12:11 am If your just using it for a mold a crappy chassis wouldn't be too hard, just skim the chassis with a filler of sorts and sand nice and smooth for either a plug or a buck.

Many a mold for RC bodies have been made from plaster of paris.

That was the plan until I found the chassis I am using for this. It becomes a finishing hassle getting the finish right even with filler so I figured that this would save me a bunch of setup effort.

Whoever had this chassis before me didn't slam it into a curb so It has the added bonus of being symmetrical.

JosephS wrote: ↑Wed Jan 26, 2022 11:21 am
The chassis mold would be larger than a consumer 3d printer can print,

Not exactly true. The Ender 5 Plus has a print area of 350mmx350mmx400mm which comes out to 13.77"x13.77"x15.75". This is a consumer grade 3d printer.

Just a rough measurement of a goldpan rc10 chassis is around 12.5" in length. I don't own a t2 chassis to be sure it but I do not see it being over 13.77" in length, but I have been wrong before.

I guess the other way to make a mold would be to vacume form it , not to difficult to make a rough and ready vacume former with a hoover and a hot air gun .
By the way I'm very interested in how you get on , a very interesting project .

The finish from a home printed mold would need so much clean up it would take hours , I love 3d printing but it's just not an efficient method for this type of thing .

LowClassCC wrote: ↑Wed Jan 26, 2022 11:38 am

JosephS wrote: ↑Wed Jan 26, 2022 11:21 am
The chassis mold would be larger than a consumer 3d printer can print,

Not exactly true. The Ender 5 Plus has a print area of 350mmx350mmx400mm which comes out to 13.77"x13.77"x15.75". This is a consumer grade 3d printer.

Just a rough measurement of a goldpan rc10 chassis is around 12.5" in length. I don't own a t2 chassis to be sure it but I do not see it being over 13.77" in length, but I have been wrong before.

Wow. That is far more affordable than I guessed with a larger print volume than I have seen.

Once I get a handle on how to make this work I may look at 3d printing again.