[That1guy_tim]

Originally Posted by eimarshall

"Quick" update. I wrapped the tire blockers in CF vinyl and love how they look. They match the fenders significantly better.
Attachment 1148205

I also ran some test lay ups of CF on foam core samples in preparation for the splitter and was surprised by my results. My test block was a 4"x8"x1" block of 4lb/sqft closed cell foam with a 1/2'' radius on the top edges. I put 2 layers of 3K 2x2 twill weave CF fabric on both the top and bottom of the block. The block was placed on sheet of glass to get a mirror finish on one side.

The goal was to try out different lay up and vacuum bag processes and see 1. How easy it was, 2. How successful it was, 3. The weight of the final product, 4. What extra considerations I needed to take into account.

Trial 1. I tested using resin infusion and quickly realized the glass side was not getting sufficient resin flow. The resin essentially race-tracked around the edge of the part where the edge of the foam/CF met the glass. the infusion mesh ensured the top got resin but the bottom did not. I tried to fiddle with it while it was infusing and accidentally broke vacuum next to the feed line. failure all around.

Trial 2. Resin infusion again. this time with perforations through the foam every 1.5" and infusion mesh only over ~half of the block. This infused much more successfully. I thought an air pocket was still getting trapped but it filled in better than I thought. I 3D printed a port for both inlet and outlet and those proved much more robust than just gum tape on the lines. I had the feed line above the part and that led to gravity pulling too much resin into the corner. Final results were cosmetically sound but the mesh definitely left a pattern. Final weight was about 100 grams after trimming. A little heavier than I was expecting but a good result. I was still worried on how well the bottom of a large panel would infuse.

Trial 3. Wet lay up and then vacuum bag. The layup is a bit more frantic and messy since you are on the clock as soon as you mix the resin. but once its wrapped the bagging and such is a little easier. cosmetically this was an improvement over the infusion since there was no mesh to cause an imprint and the final weight was about 60grams. I was very surprised how much lighter it was.

Both block 2 and 3 felt equally solid but I was curious why the infusion was so much heavier. I had perforations on both but maybe the infusion filled those holes in more completely? I grabbed a hack saw a chopped both test pieces open. the infusion block was significantly more saturated with resin despite the closed cell nature of the foam. and the perforations were full.

I was expecting the infusion piece to be lighter, and maybe if I got the process more efficient, it would be. but for simplicity and reliability I think I'm going to go with a wet lay up for my final splitter build.

Materials ordered and templates cut. Hopefully I can post the results in a couple weeks!!

Might need another order from you man. These look great!

[eimarshall]

CAD(Cardboard Aided Design) modeling the new splitter!

I wanted to make some slight adjustments to my splitter design, so with the use of some large pieces of cardboard I tweaked the shape slightly. The basic shape is essentially a 5 inch extension of the SS 1LE lip. I made the whole thing about 2 inches narrower(1 inch each side), and contoured the corners to match the curve of the endplates I picked up from AJ Hartman.




On these pictures with no bumper, you can see where I am planning my mounting points. I also have AJ Hartman's rear Camaro mounting brackets. For now I am planning on keeping it removeable, but that may change once everything comes together. We'll see.




If you look closely, you can also spot some red lines where I am planning eventually mount the splitter tunnels. That may not happen for a while though. I am kind of rushing to get the big stuff all buttoned up before baby #3 arrives at the end of April....

I did quickly throw on an LT2 intake I had sitting on a shelf since last summer. #Thatwaseasy

[eimarshall]

Full Carbon Splitter-Part 1: Assembly!

My first splitter was ½” premium plywood and angle iron for structural reinforcement. It was removable and could be taken on or off in about 3 minutes. I felt pretty happy with the way it came out, but I knew I could do better.

I picked up a couple of ½” sheets of 4lb/sqft PVC foam and cut them to match the template from my previous post. I then set about contouring them to provide a slight wing profile to the whole splitter. The foam is rigid enough that I could just hit it with my orbital sander and carefully taper the body of the foam core to the rear. I got the trailing edge down to around ¼” and felt going thinner might start to tear apart the foam.

I also perforated the core with a 1/8” hole every ~3 inches. The would allow resin to bleed from one side to the other and allows the bridging to help strengthen the whole panel.

I then profiled the leading edge for a nice, rounded taper. A vertical leading edge can cause turbulence and airflow separation. The rounded taper promotes attached airflow and will help the air accelerate under the splitter, using Bernoulli’s principle to create a lower pressure region on the underside of the splitter. Splitters don’t really work by generating high pressure on the top of the splitter. I mean maybe a little, but largely the faster airflow under the splitter provides a suction or downwards force.






For the layers, I decided to go with 2 layers of 6K 2x2 twill for the top of the splitter, so that it would be have a nice finish without needing too much resin to fill the fabric. On the bottom, I chose 2 layers of 12K 2x2 for strength and rigidity.

Since I settled on a wet layup and the whole part would take some time to perform the layup, I bought a resin with a pretty slow hardener(2+hour). The downside was that this resin really needs heat to cure and harden. So I built a low temp oven out of plywood and insulation sheets. Its capable of ~150 degrees using a smoker heating element in a sheet metal box and a couple of 4 inch duct fans. I actually built a smaller version first when I was experimenting with CF stuff last year, but the big splitter needed a bigger oven.

I used a sheet of melamine plywood as my surface and cut the peel ply, bleeder cloth and vacuum bag to size. I then waxed and coated the melamine in a release agent so the resin wouldn’t stick.

The bottom layer of the layup would end up being the top side of the splitter, so I started by coating the melamine board in a thin layer of epoxy. This would have given me a perfect finish on the top of the splitter had I not accidentally offset the first layer of CF by about 4 inches….. I had to peel it back up and that created some little air pockets. I then used a squeegee to saturate the first layer before adding the second. Rinse and repeat. For the core, I put a skim coat on each side of the foam. Each layer of CF was cut about 4 inches larger than the core, so I could wrap the fabric from the top (bottom during layup) down over the edge. I then draped the first layer of 12K on top and saturated it with resin using the same squeegee method. Next, I made sure it was tucked in nice and tight to each edge of the core.



I didn’t get any shots during the actual layup as I had my hands covered in resin and I realized I only had a single pair of rubber gloves after I got the first layer down.
After the last layer of 12K, I added the nylon peel ply and then the bleeder cloth to absorb excess resin. I then taped the vac bag down to the board and pulled vacuum. I quickly sealed a couple of obvious air leaks but my vacuum gauge only read ~-25psi, so I probably had a couple that I couldn’t hear or find. I made sure all the edges were still nice and tight around the core and dropped the whole board into the oven. I let it sit at ambient temp for a couple hours to make sure the resin didn’t start to cure before the excess got squeezed out by the vacuum pressure. Then I turned on the oven and fans and closed the whole thing up to sit overnight. After 24 hours at 150 degree F, I turned off the oven and left for a week long vacation.



The dots of resin saturation are where the perforations in the core allowed resin to bleed from the bottom of the layup through to the bleeder cloth. Which means the top was pretty saturated and the perforations were an excellent idea.

[eimarshall]

Full Carbon Splitter-Part 2: Assembled!

Upon return, I cracked open the oven and pulled the board out. I pulled the vacuum bag off and peeled the bleeder cloth and peel ply off the splitter. The release agent also made for a painless separation of the splitter from the melamine board. I dragged the rough splitter outside and washed off the remaining release agent. It was looking pretty good!




I trimmed the edges close to flush with a Dremel and then sanded them smooth. The results were fantastic!





The only defects were tiny imperfections on the surface from peeling up the first layer, and a couple of mysterious silver stripes around the edges. Eventually I realized those were from the silver sharpie I used to delineate the approximate shape of the core during cutting and layup. Whoops.




I was still considering making the mounting system sort of a quick release, but finally decided against it for the sake of rigidity and simplicity. I bolted up AJ Hartman's rear splitter mounting brackets and made a quick cardboard template to drill holes in the splitter. His technique of keeping the brackets loose until attaching the splitter was quite handy! I mocked up the lateral and front splitter rod mounts and drilled holes for them. I mounted the Professional Awesome splitter rods to the splitter and reused their titanium splitter pucks for the front most mounts.

[eimarshall]

Full Carbon Splitter-Part 3: All the CaRbOn

I after tracing the 1LE lip, I added an air dam using plastic corner guards from Amazon and wrapped it in leftover 3M carbon vinyl. Lastly, I added the end plates/tire blockers and a couple more splitter pucks from AJ to protect the nose and forward most lateral points.




A quick weigh in shows the splitter and all associated hardware clocking in at a svelte 12.8lbs!



One last mounting and she's good to go!!




Overall, I'm extremely satisfied with the splitter, it's decreased weight, contoured shape and increased rigidity are vast improvements over the plywood one I ran last year. Of course it probably cost 4x as much in materials alone, but I think it will be worth it.

Of course I had to really test it….

https://youtu.be/SnYfajusQNQ

[kropscamaro16]

hot damn good work man i wish i had skills like this haha

[That1guy_tim]

Great job man!

[eimarshall]

Thanks guys! I can't wait to get it out on track! Unfortunately that likely won't happen until late May, seeing as baby #3 is due next week....

[khcoaching]

Very nice!

[SSEssence]

That came out amazing! Great work!

[RamAir02]

Incredible thread! Love the build.

[eimarshall]

Because I am located in the cooler climate of the pacific north west, I haven't experienced any real cooling issues. Obviously these cars have a ton of cooling capacity but it has always irked me that the hood vents are so covered up and restricted. The factory hood vent for the 16-18 SS might appear 15" long and 4" wide but the vent insert cuts that down to only a couple inches in both directions.

Aerodynamically, the vents are fairly flush but all that air that goes through the radiator needs somewhere to go. Mostly, I imagine, it dumps down underneath the car past the headers. Great for header cooling but not so good for generating downforce. Plus causing the air to mostly stay in the engine bay(or at least have to fight past all the things in the engine bay) will increase the air pressure on the aft side of the radiator, restricting flow. Restricted flow through the radiator generally means less cooling and more drag. Both things I feel I could improve.

Initially, I had removed the vent inserts last year during a hot PNW track day(air temp around 95) as a precautionary measure. Over the winter I thought about adding a set of Racelouver's hood vents or something but never bit the bullet on a set since cooling has never been an issue for me.

Aero however is something I am playing with. I figured if I could make a little ramp or kick up in front of the existing vents, they could generate a small area of low pressure that could draw air out of the engine bay, decreasing the air pressure behind the radiator and thus decreasing the drag on the front of the car. Racelouvers has a ton of data on their website show this if anyone needs to sate their inner nerdiness.

So rather than just buy something, I decided to design and 3D print a little ramp that could clip onto the front of the vent. There happens to be a nice little hole at the front corner of the vent, and the curvature of the hood isn't soo much that I need to compensate for it.

I snapped a pic with a reference measurement and threw together a quick CAD design in Onshape. I designed the piece to be about an inch tall, with a nice smooth ramp and some cool looking reinforcing strakes on the front and on the underside to help direct airflow. The edges are just slots with a gap of 0.04", approximately the thickness of the hood. I added a nice chamfer along the leading edges and sent the design over to my 3D printer. I also utilized the little bolt hole in the corner as a locating pin.




The first test piece matched up pretty well, but I tweaked the dimensions and reprinted 2-3 times before everything fit perfectly.



I thought the blue actually matched nicely, but because this piece would be seeing some pretty high air temps, I printed the final version in PET-CF. This material is supposed to be heat resistant up to 205 degree Celsius or about 400 degree Fahrenheit!






I like the look but might still do something to hide the blue edge of the hood that got revealed when I removed the OEM insert. The ramps look cool though!! Hopefully they are functional too.