Making a carbon fiber rc10t chassis the Competent way

[JosephS]

It’s been about long enough since my last chassis. Since I ordered my sons rc10t re-releases I thought I should make some chassis for them.

I seem to be getting better year over year. Hopefully I can make something meaningful to them. As well if the tooling comes out well I’ll have my oldest make a chassis.

I’ll re-read my previous threads but I already know I need to build new tooling to make a quality chassis.

I am fully sacrificing a nose plate as well as well as chassis that was in good condition to begin with.

This is of course to put off the current build even further. I should be building an edinger I collected parts for years and can finally start on. So here is what I did instead

Sanded to get things flatter

Sits flat on the tile

Using bondo and release

Previous attempt notes here
https://www.rc10talk.com/viewtopic.php?p=540329#p540329

Relevant Notes here
https://www.rc10talk.com/viewtopic.php?f=113&t=48258

The T3 chassis at the end of this thread
https://www.rc10talk.com/viewtopic.php?t=47048&start=60

turned out well and fixed a few issues I was having with the April build. It was a good runner without being overbuild. Did well considering the steel pole I ran it into a full throttle.
though this was a direct pull and not cast from tooling.

Looks like the resin ratio should be less than 1:1
I never solved the issues with wrinkles in cast parts, though on the 2 part made from direct pulls the inside was smooth. I think the wrinkles are partly caused by excess resin.
The wrinkles make the part NG since the finishing is excessive.

I don't have any gelcoat. Given the summer temps. I am not sure that I can use it without waiting for fall.

8 layers of plain weave 3k 5.7 oz fabric should be about 2.1mm thick
Switching to west system from US composite resin. I am also switching to a ultra slow cure resin. It is supposed to be more rigid on full cure than the faster set ones.

[JosephS]

Nothing shows off what you missed in finish better than clear coat.

I think I made good progress. The chassis is flat, the area between the nose plate and the chassis are filled.

I also evened out the sides so the metal lip is smooth.


The clear coat should provide a mirror smooth surface for the tooling.

[JosephS]

Mounting up the tool to an acrylic blank
And waxing

2 coats of clear

6 paste wax of 5

3 coats of man’s 2300

Clay was used to fill the nose and tail as well as to form a bead around the chassis

The width of the nose and tail were widened to that the tooling would not curl or round in those areas

The height of the wall was increased with clay to reduce rounding near the top of the chassis.

The rear bulkhead stay has been a challenge to mold and will continue to be. May just build a wide bulkhead and use shim/washers to build the gap.

[JosephS]

I am out of gel coat and will try using the remaining epoxy I have from my previous batch as a surface coat that will be backed by satin weave fiber glass

Coats will be .4 oz resin .1 oz hardener

Will be applied by brush


This was not successful. I was out of vacuum bagging materiel. Then I decided to use some clay to hold the sides down, completely forgetting that other times I had a release film between the clay and the resin.

I'll have to see if anything comes out of this.

[JosephS]

Have not been documenting,

I went and reinforced the sides of the chassis with additional layers of fiber glass.
resin west 105
the west resin is slower setting and helpful,
Getting the fiberglass to adhere to the side is challenging

mixing 5ml epoxy 1ml hardener

cleaning brushes with alcohol hand sanitizer works and allows reuse.



I can not vacuum bag this material. it consistently punctures the bag, even 2 layers




The side reinforcement worked but filled in some of the mold gaps with resin.
I used a scrap of carbon fiber that I used on one of the sides. It is exceptionally more rigid than fiberglass. This was wet layed and roughly conforms to the sides of the chassis.



After the sides set I have added a nose to tail wide carbon fiber reinforcement on the outside. Single layer of 3k carbon fiber that are edge scraps. Slightly to wide on the nose section. Since I can't vacuum I placed the chassis flat on a ceramic tile. I added a round support in the tail with foil faced clay. I did the same for the nose. I noticed the chassis was not resting fully flat. I added a 10# weight to the center to keep enough pressure to make the mold flat to the chassis.





I am hoping to keep voids to a minimum so that the mold remains still when I cast in it. I want to retain the straightness I worked to create.
I am going to use carbon fiber for mold reinforcement, It is more expensive but seems to what I should be using at my skill level.

I have concerns the cast I made will deform if I try and cast from it.


This technique seems ok for my skill level. I cast what I am calling a fiberglass slipper. It conforms to the surface well, but is still thin and flexible so it can demold without cracking like a stiffer mold would. I then make sure I can demold it, then reinforce it.

I am going to attempt to make a new buck from this mold using bondo. The idea is that it is hard enough to machine and smooth enough to surface. I should be able to shape and sand the piece enough that it can be vacuum bagged without breaking the bag. As well it should be strong enough that it doesn't deform under the vacuum pressure.

This is a whole lot of effort to avoid using MDF . By the time I'm done with the bondo, reinforcement and making a new tool from the bondo piece I could have paid for the tools needed to work mdf.