Making a carbon fiber chassis the beginner way (part2)

[JosephS]

[place holder]

[JosephS]

This is a continuation of part 1 of this project
I had a project last year as well where I made my first chassis that could be run

moldmaking takeaways-

• Large Smooth Ceramic floor tiles are an ideal working surface
• ----
• Car wraps (atleast vivid+) are not compatible with polyester gel coats.
• expanding polyurethane foams are not dense enough for fill
• non-sulfur clay is an ideal fill and molding material
• Aluminum works ok as a wrap
• Wrap is only needed on porous materials- I used one so that a colored gelcoat wouldn't stain original parts
• Make wide flanges on flat parts to avoid bridging.
• fabrics and mat materials need to be cut to size- this avoid distortions
• wet matting will NOT conform to an existing part, clamping force is needed
• colored gelcoat needs 2x the hardener as natural
• gel coats may look fine but need to be 2x
• tooling gelcoat doesn't sand well.

Carbon fiber part making

• Pre-cut materials to shape and size make sure to cut relief in curves
• spray glue should be used on carbon fiber fabric to fix the material before cutting
• vacuum is essential use 2 bags to ensure leaks don't happen
• 7 layers of plain weave 5.7oz 3k carbon fabric builds to about 2.6mm
• Demel Easy lock cutters work well for trimming cured pieces

Resin working

• polyester resin requires a full vent hood or outside work
• 4:1 fast epoxy hardener is better for RC parts I don't need the extended layup time of 3:1
• syringes allow for small volume mixing of epoxy
• Full curing takes nearly a week and substantial rigidity and strength develop.

I noted on my first project
"To get a wet out and a coat it seems to be that the ratio is between 2 -2.5 oz of resin per oz of cloth." [s]A 2:1 epoxy to fabric ratio seems really high to me. I'll need to document this time.[/s] The correct matrix cloth ratio is about 50/50.

[JosephS]

I prepped the mold, washed and waxed with putty put in every edge or defect.

I then made a pattern. I applied some spray adhesive for the carbon fiber to stay cohesive.
note:
Back fabric patterns with cardboard or poster board.

The mold was final prepped with 2 layers of paste wax, and 3 coats of epoxy mold release spray.

I laid up each piece in the mold one at a time.

A total weight of 2.5oz


I mixed up 3:1 medium speed epoxy at 5oz.
Note:
Epoxy fabric ratio should be around 50/50.
I brushed each piece of fabric with epoxy before placing in the mold.

I pressed each piece in the corners as best I could. I then applied some perfed release film. I the. Applied clay to the corners. I am hoping to make crisp corners.Note: clay seems to work for this.
Note:
perfed release film requires backing with breather. Any wrinkles in film will distort part thickness. Not just surface finish.

I bagged the mold In a food saver vacuum bag. I checked the bags ability to hold a vacuum. I missed that on my last gt pull. I double sealed it and now I wait,

I used about 2-2.5 oz of the epoxy I made. I was going to use the excess for my carbon fiber chains repair but the whole pot kicked and melted my mix stick while it was at it . This is inline with the 50/50 resin fabric ratio

Fabric
6 layers of plain weave 3k 5.7 oz with Kevlar tracer
1 layer of 10.7 oz 2x2 6k

Epoxy

Us composites thin resin with 3:1 hardener

Temp ~ 75• f

Release
Paste wax 2x
Epoxy parafilm 3x

Mold
Poly Tooling gel with fiberglass reinforcement
Modeling putty in all voids and edges.

[Dadio]

Fingers crossed

[JosephS]

Great result.
Notes:
This build hit 2.1mm. Target 3.0 mm for flat chassis. 2.1 for tub style chassis.

The resin saturation was good and very few pinholes

I wonder if I revered the resin to epoxy ratio in my notes.
Note: Having consistent resin issues.

Unbagged

The demolding was difficult. I need even more release than was used, some spots of the mold surface peeled off.
Attention needs to be paid to make sure things don’t wrap around edges. Made it harder to release

Note:
Release wax needed to be applied MUCH thicker. As pieces needed to be cut closer to size.

Trimmed a bit.

Looking at this compared to my effort a year ago this is much better. Nearly professional. The clay kept the interior corners smooth and perfect. I think the wrinkles in the interior surface will go away if I use a breather cloth above the release film.

I will see if I can rehabilitate the mold and make another one or two pieces.

The quality of the gel coat piece is excellent but I am not making robust molds. Ideally I would make 10-20 for the effort in making a single mold.
Note: Mold had issue on tooling gelcoat application. Was successful with 3 layers of gel coat.

[JosephS]

Found someone to talk for help on molding parts. This was the shop decoration.

[RogueIV]

Found someone to talk for help on molding parts. This was the shop decoration.

C0F08D3A-3D72-4A11-BEA5-60838C0B3263.jpeg70EDA424-3FE7-49FC-9851-99C4ACB8E899.jpeg75F8B103-4A1A-4F66-9BE1-3C575EE6B7BC.jpeg

I'd say they have some good experience in molding things lol

[JosephS]

Found someone to talk for help on molding parts. This was the shop decoration.

C0F08D3A-3D72-4A11-BEA5-60838C0B3263.jpeg70EDA424-3FE7-49FC-9851-99C4ACB8E899.jpeg75F8B103-4A1A-4F66-9BE1-3C575EE6B7BC.jpeg

I'd say they have some good experience in molding things lol

Yep. They didn't have experience with carbon fiber but they had a lot of beginner advice.

[JosephS]

Well that worked

Full demold no damage

Bottom

Inside

The vacuum failed on readiest bag. I think the chemicals from the process make it impossible to reuse a bag.

The chassis is 2.4 mm thick. A bit dry on epoxy, but that was due to technique. I used a spreader to draw out epoxy. That was too aggressive.

I used 1 thick and unbuffed coat of paste wax,2 coats of man 2300 release and 1 coat of parafilm release.

I misplaced my shears and couldn’t cut the carbon to shape without them . So there are some distortions in the rear by the bulkhead support.

The mold is ready to go for the next one. I can just keep making these now.

I am going to surface finish out the 2 I made and see how well they get to the end of the process before I make more.

[JosephS]

This is requiring a lot of finishing.

I will add a few layers of material from the rear bulkhead back to make rear about 3.0 mm and thicker overall. I plan for it to sit under suspension components.

I was using a rotary tool, but it seems I can use tin snips to remove bulk material and like my t2 chassis I used wet sanding to level the sides of the chassis.

[Dadio]

Good to see your getting better results, mask up if your using a rotary tool , you don't want to breath that sh#t .

[JosephS]

Last attempt on this batch of material.
I went for the t2 I was successful with last year

This mold feels nice. I cast it directly on the chassis which is still scratchless.

I used 3.9 oz of fabric and made 4oz of resin, I think 3 still would have been in excess. I cut a pattern out and used that to cut each layer of material.
I think I would have needed 9 layers of the carbon fabric and I only had 5 so I used 5 additional layers of much thinner fiberglass at the core.

I added a layer of perforated release film backed with breather fabric . I also used some clay to get into the corners.


The vacuum pulled well with the single bag, but I added a second layer to make sure air leaks wouldn’t wreck it.


I can see that I didn’t use a large enough piece of release film and some of the chassis was in contact with the bag. Hopefully this was in the flange area and won’t be an issue.

[JosephS]

Fantastic results. With some room for improvement.

The demold wasn’t to challenging even though I made some mistakes on the layup.
The parts need very little finishing on the outside surface. They have the look and feel of professional pieces.

As well the mold is ready for another piece with no repairs.

I am still having an issue with too much resin. I am using a perforated release film back with a breather, but the excess resin isn’t making its way into the breather. There is no fiber in the excess resin so it is easy to remove with sanding

I am finally at the point where parts are good. I see a few places to improve on this process.

Hopefully I can make a few pieces good enough to sell so I can buy more material.

[Dadio]

That's looking really good

[Mwildmann]

Been enjoying following this, looking great!