The Buchka 242 Fake Racecar

[mikep]

My eyeballs are not worthy of the buchka vision.

 

[Alex Buchka]

Thanks everyone! Karl and I are super happy with how this is coming out, it really gave us a boost of motivation to get the next round of tooling built up.

Awesome work! Does you materials already come with UV protective or is that a final added stage?
I assume the whole car will be painted? Or gonna leave some areas exposed? Or fully exposed?

Thanks! Epoxy has pretty awful UV resistance so anything we want to keep exposed carbon will get 2K polyurethane clear. The hood for my white 242 will get painted to match the car with the inside clear coated to flex on people at cars and coffee. The race car bodywork is also going to get mostly painted and/or wrapped. Not really a fan of the full blown exposed carbon look on an 80's car, it also requires extreme care when laminating since literally every defect of the weave becomes glaringly visible.

I want one of those bad enough to willingly pay actual money to rent the tooling and deal with the logistics of getting it to my garage and back to your shop (slightly less unrealistic than begging to buy one…probably).

Looks fantastic.

We're really not in the business of selling this stuff, frankly I'm also a little nervous about "renting" the tooling out since it's pretty easy to mortally wound a tool like this without the right care and feeding during layup. The tool will definitely be for sale at some point since we don't really have room to store a bunch of bulky items like this.

 

[bobxyz]

You need to design a stylish composite 240 cup holder, and figure out how to mass produce it, to offset the costs of your stunning one-of-a-kind body panels. Either that or do a limited edition run and auction them off to the top 10 bidders.

 

[mikep]

I could use 245-shaped endplates for the C.O.T. wing i want to mount on my 245. I’m willing to pay too much.

 

[towerymt]

I could use 245-shaped endplates for the C.O.T. wing i want to mount on my 245. I’m willing to pay too much.

Too good for torch-cut steel?

 

[mikep]

Too good for torch-cut steel?

well.. I DO have an extra mower blade..

 

[towerymt]

At $1 per man-hour spent, are we closing in on the $1millionDollarBuild?

This self-guided internship program of building this entire car continues to be fun to follow and impressive to watch.

Fingers crossed for a Nissan Pulsar Sportbak inspired wagon attachment, in carbon fiber.

 

[go240go]

What now - carbon fiber fenders?

 

[Karl Buchka]

What now - carbon fiber fenders?

Fenders, doors, trunk, roof, floor, bumpers, splitter, diffuser, wing, ducts. You know, just a few parts here and there.

 

[Karl Buchka]

At $1 per man-hour spent, are we closing in on the $1millionDollarBuild?

This self-guided internship program of building this entire car continues to be fun to follow and impressive to watch.

Fingers crossed for a Nissan Pulsar Sportbak inspired wagon attachment, in carbon fiber.

Our time is either priceless or valueless. Not sure which.

 

[poulrais]

This hood made me cry...

 

[HiSPL]

How does this build just keep getting more and more epic?

 

[Jack]

Fenders, doors, trunk, roof, floor, bumpers, splitter, diffuser, wing, ducts. You know, just a few parts here and there.

Needs carbon fiber sunvisor!!!

 

[propav8r]

Fingers crossed for a Nissan Pulsar Sportbak inspired wagon attachment, in carbon fiber.

See, now that's the forward thinking that we need around here.

 

[Alex Buchka]

The slog continues.

Laid up and infused a second copy of this quick part to keep the momentum going. It's a turning vane for the radiator inlet duct.

Next up was the race car hood. This was a much more complex laminate than the last hood; four plies of 200gsm plain weave on either side of 1/4" divinycell H80 foam core.

Some background jargon: Each ply is rotated 45 degrees from the last one except for the pair sandwiching the core which are parallell to each other. This makes what is referred to as a "balanced, symmetrical, quasi-isotropic" laminate (really rolls off the tongue). In short it means no single direction in the part has more fiber weight than any other - balanced, each group of four plies are mirrored across the mid-plane of the part - symmetrical, and the fiber orientations are spaced evenly 45 degrees apart - quasi-isotropic. The end result of this rigmarole is the part has pretty even strength in all directions and will be less susceptible to weird thermal distortions. A layup like this is sometimes derisively referred to as "black aluminum" because it doesn't really take advantage of the directionality of carbon fiber but has huge upsides in how simple it is to analyze the performance of.
TLDR: It's heavier but behaves kinda like metal so it's easy to predict the strength and stiffness.

This is getting painted so I didn't spend a ton of time making the visible ply perfect or putting the lap joint in a "nice" spot.

First four plies bagged up and infused.

Carefully stripped the consumables off and got ready to bond in the core

The core sections were cut and chamfered with some laser cut aluminum templates. We sandwiched the core between the templates and sanded the edge flush with both pieces of metal. This left a really tidy 2:1 chamfer on the edge. We have cut these by hand in the past with a razor but this method was much faster and more precise.

The core got bonded on with laminating resin thickened with glass microspheres. We buttered up the core with a notched trowel, placed it on the hood and covered it up with some perforated release film and strips of breather cloth. Clamping was done with a new vacuum bag.

Here's the core bonded in. The weird triangular cutout in the center is a clearance notch for some chassis tubes over the engine. The side pieces are relieved for openings that will get cut in the hood for radiator outlet ducts.

First of four additional plies laid down over the core.

Managed to save the bag from the core clamping op so it was re-used here to reduce waste. There was really only one small pinhole so it worked out pretty well.

All finished up and pulled from the mold

There were a couple small cosmetic boo-boos in a few areas but not overall it came out really nicely. It is possible to infuse the whole part, core and all, in one shot but I did get burned on the last part I tried this on so we decided to go for a two-shot. In the end I'm glad we did this since the hood is quite large, considering the cost of carbon fabric we weren't ready to accept the risk of scrapping so much cloth to save some time and consumables.

Untrimmed weight of this hood is about 13lb and it feels plenty stiff for the application. It's definitely possible to trim a couple pounds off this with a different layup schedule but the additional durability and ease of analysis is worth it to me.

 

[Alex Buchka]

The slog continues.

And it just keeps going. Did I mention how much work this is? Follow along the pain train:

Next on the chopping block is molds for the radiator outlet duct. The general workflow for this is much the same as the process for the hood which I covered in a previous post. The main difference here is that there is no physical part to pull a mold off of so that has to be created. This is referred to as a "plug" or a "pattern". We decided it was easiest to split the duct into two halves to simplify the layup and vacuum bagging process. The part was split in CAD and got some extension flanges and trim guides added on. These plugs were then divided up into bite size chunks that could be 3d printed and bonded together.

The plugs then needed quite a bit of filler and block sanding to remedy various surface modeling boo-boos on my part.

Here are the plugs after primer, rough blocking with 80 grit, and one more round of filler.

We then sprayed another thick coat of polyester surfacing primer as the "final coat" which was carefully sanded over dozens of hours, stepping up one grit at a time from 80 to 1500, then polished.

These are now ready to be bonded to some melamine sheets to make up the lower flange and go through the mold making process (mold release, gelcoat, and fiberglass).

Since hand laying glass is kind of an ordeal we decided it would be most convenient to make molds in batches. The next plug that needed made was for the rear wing. This is currently undergoing the same process as for the radiator ducting.

Here's the printer churning out airfoil segments. These were designed to be stacked five wide on some sticks of tubing to line them up correctly

All stacked on tubes and glued together with epoxy.

The segments had a bit of weird shrinkage that varied over the build height. This required lots of body filler and block sanding with 40 grit to get a fair shape that was also straight and consistent

Wing plug with a coat of surfacing primer on all sides, ready for more block sanding.

This is now at present day for the wing. I fully expect another round of filler and primer to get the shape really good and to have confidence there's enough primer to allow for blocking up to 1500 grit and polishing.

 

[blyat]

God i love all the 3d printed stuff in your project. Definitely an inspiration

 

[t8fanning]

Sanding all those prints to your smoothness requirement has to be an absolute nightmare. Incredibly impressive work as usual.

 

[Alex Buchka]

Sanding all those prints to your smoothness requirement has to be an absolute nightmare. Incredibly impressive work as usual.

Thanks Tate! It's definitely not the most stimulating job in the world but there is real satisfaction in finally getting to polishing and seeing the surface gloss up right before your eyes. Also definitely noticed that I'm getting better at efficiently applying filler and sanding. Turns out this is a skill just like any other, even though I truly never, and still don't, have any desire to build this particular skill

 

[adomz]

Oh my! You boys Rock!