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Starting on the next build. A 10t style single piece carbon fiber frame build. Let’s see if I learned enough to make a more complicated piece.


Already it’s more complicated due to the shape of the tub. The curves just don’t lay down fabric well at all.

Check that 10T with a straight edge and make adjustments to make sure it's straight and level first.

Mark Westerfield wrote: ↑Tue Jun 21, 2022 1:43 pm Check that 10T with a straight edge and make adjustments to make sure it's straight and level first.

This is an attempt at a 2 step process.
The chassis is not straight or level. The non-uniformity and holes are filled with clay.
The fiberglass in the picture is going to be epoxy coated,flattened, and smoothed.

I'm a bit worried that if the part is made too flat I won't be able to de-mold the bottom.I know I'll need to flare the tub sides. I'll have to try it and see.

A bent chassis has incorrect anti-squat angle, Incorrect front kick-up angle, and possible side to side tweak - which would permanently carry over to your carbon fiber chassis.

I'm really surprised I haven't seen anyone just 3d print a mold to make a carbon fiber chassis yet.

Contact Jerry Hellström on the Facebook group RC10 Vintage Mania for help and advise, he's been working on making carbon fiber chassis's too.

Using fiberglass resin on the mold. I have yet to succeed with this but it’s an order of magnitude cheaper than epoxy so if I figure this out I can go after more projects.


It’s pretty neat how the fiberglass become translucent. With the resin applied. There are LOTS of bumps in the fabric. I plan on sanding things down flat cutting out the bumps and adding one more layer to smooth things out

The shape of this tub is just hard.

I have a first pass of an outer layer for the mold and I am not sure if I can get it where I need it to make parts.

The camera is being absolutely brutal with the images. It looks a lot less rough in real life.

I have no doubt I could make a solid , flat and properly angled piece from nose to tail curve off this mold. So that’s something.

The sides of the tub are just hard. When I lay down cloth on the bottom of the chassis, the inside radius bubbles up. Literal air bubbles under the fabric.

For the flat sides I can just slice them off with a knife. The curves I am shaping by sanding into. Some parts are straight though the mold.
I am going to reinforce the mold from the inside now with some fiberglass cloth and chopped mat.

I think it may actually be less work if I build a mold entirely from scratch. I’m going to try to make this one work to see what I can figure out. If I get a mold going I can cast a few pieces before I need to make a new one.

It’s just about 97 outside right now so it’s not the best time to pour resin. Going to have to wait for the next pour.

Only the inner and outer layer are cosmetic, so why not cut strips to make it look good and cut the "bulk" layers to make it lay flat and shape nicely?

RC10th wrote: ↑Sun Jun 26, 2022 11:03 pm Only the inner and outer layer are cosmetic, so why not cut strips to make it look good and cut the "bulk" layers to make it lay flat and shape nicely?

That is the plan so far. right now this is the buck that the carbon will be molded on and it's still challenging to get the curves right even doing that.

Wet Sanded from 180-2500 grit, polished and coat 2 of wax. Almost ready to cast. After glass mat reinforcing the inside the thickness is 6mm.

So far so good. I put release on the mold and was and added the bottom 2 layer of carbon fiber. I ran out of the cosmetic carbon fiber so the tracers are visible.

The 2 layers together are between .5 and .6 mm depending on where I measure. It looks like I had good bonding to the angles in the front and the curve in the tail.

I used a bit too much epoxy. And wound up with some glass smooth areas on what is going to be an internal layer. I’ll have to sand it down before I move on to adding the sides of the tub.

I made the first part of the side.
3 layers of carbon fiber that are wrapped around to the bottom with relief cuts. That should be about .75mm, about 1/2 the finished thickness.
So far it looks good. The resin is taking much longer to cure than I am expecting.

If this turn out I’ll hit the other side. I am running out of resin so I may have to stop soon.

Edit:

So 24 hours later the resin has not cured so I have to peel this all off and try again.

My guess is that I either didn’t get the ratio right on such a small batch or I didn’t mix it well enough.

A good looking failure I saw a few posts here from a decade ago where people were able to get vacuum bagging with a food saver to work so i tried it again

That part seemed to be ok.

I think there was some contamination in my mix cups or my resin or hardener was defective. I mixed the resin properly this time. I double bagged the part since the first bag developed a leak.

The part look good. A few wrinkles but over all a good looking effort. But the resin didn’t harden over night. I had this happen before and thought it was improper mixing.

I’ll have to wait on future efforts until I get new resin and hardner. The shipping on hazardous materials is slow. It may be a month or 2 till I get back to this.

I will try drying the material and see that hardens it enough to pull off as one piece. This may work as a shelf piece but it won’t be strong enough to drive

So I decided to bake it, and that absolutely worked on setting the epoxy. It also melted the wax mold release i was using causing a the piece to not release well. I would up with about a dozen .1-.5 mm CF splinters in my hand while trying to demold this.

However the inside looks like a proper finish. I think I can recoat the mold and try again.

So instead of all of that in the last post I mixed up a new batch of resin, sanded down the top spots on that chassis and bagged it again.

The bags failed but the important thing I learned is that the cure continues on for days so you can correct molding issues.

I was able to remold the piece, then reinsert the mold and use clamps for 24 hours to hold the shape pretty darn well.

My pictures aren’t good but this is in much better shape with no finishing than my last project was.

I built up the sides higher than necessary so I can trim to clean edges.

I This chassis is much thinner and had more flex than my last one so this is just a bit stiffer than stock.

Before any trimming this is 5 oz vs the stock at 7.2 I have some time today so I might finish this out.

Trimmed up and drilled up. The weight is down to down to 4oz