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Old 06-05-2019, 05:49 PM   #51 (permalink)
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Freebeard,

That looks awesome. For my application, where would you suggest ducting from/to?

Everyone,

I am rethinking doing a "hatch" and am contemplating a custom single door, or a tailgate and small micro-hatch/window above. This would be for ease of construction. I am also considering incorporating solar panels into the new roof assembly for alternator load offsetting.

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Old 06-05-2019, 08:41 PM   #52 (permalink)
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I have your attention now? From Permalink #10:





The Clarity (concept?) uses a V-shaped cut line, the Suburban might need curved or straight edges. It would depend on what happens with the lower rear quarter.

Air intake would be the rear side-window openings and a new trough in the end of the roof. Converge in depth and diverge in width to make a slot around the new tail.

I like the Magnum L-shaped hatch, but it might need adding length or shortening the Suburban top. All one color of course, and it could have a tailgate like a wheel-chair ramp.
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Old 06-06-2019, 09:30 AM   #53 (permalink)
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Freebeard,

Apologies, I know in my previous design iteration I had dismissed the idea as too complicated. I am now considering a duct at the rear as a potentially good place to relocate some auxiliary cooling to (e.g. oil cooler). The 2019 Clarity fuel cell/electric/plug in hybrid production model appears to have a much smaller version of the duct shown on the prototype. I am assuming they need it for battery/auxiliary system cooling.

If I were to follow the path of the Golf W12 I would leave the existing major bodywork and structure, tilt the rear side windows in at the back at a certain angle to create the duct, do a similar cut on the roof between existing bodywork to create the duct, fill in internally the outer sides of the duct to create a smooth duct walls, replace or modify the rear doors to provide a place for the air to exit. I believe this is what you are suggesting, correct? Basically, it is an internal boat tail of sorts with the original body lines hanging out in the airflow.

If I were to follow the path of the clarity I would still do a major chop/boat tail to the vehicle, collect air prior to this chop, release the air at the rear of the vehicle in the wake.

Obviously if I put a radiator into the duct to supply auxiliary cooling it will drastically change the function and airflow. Probably wouldn’t work so well integrated with a primary drag reduction (e.g. Golf) as opposed to supplement (e.g. Clarity). I will have to ponder on this.
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Old 06-06-2019, 11:46 AM   #54 (permalink)
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Quote:
I believe this is what you are suggesting, correct? Basically, it is an internal boat tail of sorts with the original body lines hanging out in the airflow.
I'm not saying it's a good idea, just the one that came into my head.

But, you've got it. Minimal structural changes to body, and a clip that includes a hatch and its frame. I'm not sure what goes on behind the rear wheels, but that's where your oil cooler would go.
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Old 06-08-2019, 05:56 PM   #55 (permalink)
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Quote:
Originally Posted by aardvarcus View Post
The 2019 Clarity fuel cell/electric/plug in hybrid production model appears to have a much smaller version of the duct shown on the prototype. I am assuming they need it for battery/auxiliary system cooling.
On the production Clarity, those are rear air curtain ducts. The duct is self-contained in a trim piece that fits to the rear door panels, with the outlet in the rear wheel arch:



I looked into buying the ducts separately, curious if I could retrofit them to my car, but it's only available as the whole assembly, for $175 per side--too rich for my blood.
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Old 06-11-2019, 03:47 PM   #56 (permalink)
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Vman455,

Ahhh, air curtain ducts. Thats what I get for assuming their function, maybe junkyards will have them before too long at more reasonable prices.

Everyone,

Thank you all for your feedback, both positive and negative. I appreciate both.

Due to some of the feedback I have received, I am analyzing alternative ideas to hitting my desired drag coefficient for the Suburban. I have narrowed the contenders down to two maid ideas: the cargo area chop recently discussed and a variation on the fixed tail & folding tail idea.

The cargo area chop is to cut the vehicle and re-taper all the bodywork in the cargo area behind the middle row door.

The new tail idea is to replace the rear double doors with a new single rear door, hinged at the edge of the passenger tail light location (no binding), and will contact the existing weather-stripping to seal. This door is reinforced and is the basis for the remainder of the tail build (e.g. the tail is built onto and swings with the door). Relocate the tail, 3rd brake, and backup lights to the back face of the new door. The door will taper in on the top and sides as it goes back per AST tapers. The back of the door will hold hinged panels to have a deployable tail, with new lights on the tail for deployed lighting on the rear. This is a variation on the previous idea, except instead of an add on piece retaining the stock doors, the new single door makes some of the details (like hinging) easier.

Advantages of the cargo area chop:
No actuators, less weight, no additional length.
Advantages of the door tail:
Retains full cargo volume, not impacting vehicle structure.

I don’t think there is a huge difference in the amount of work between these two ideas, just different types of work and different headaches for both. There are obviously lots of details remaining to be worked out for either selected idea. So what are your thoughts?
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Old 06-11-2019, 04:34 PM   #57 (permalink)
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Quote:
I don’t think there is a huge difference in the amount of work between these two ideas...
It doesn't look that way based on the amount of red in the two pictures. Have you ever chopped a top or replaced a quarter-section of a car body? Beyond the metal work there's a lot of fettling and paint. The Kammback, if it were made out of Polymetal or similar, would require almost no finish work at all.

That said, it appears to address three of the four sides. What about the area from the rear wheelwell to the bumper? Turnpike Cruiser skirts? air scoops for a remote oil cooler? Big-*ss difusser?
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Old 06-12-2019, 09:31 AM   #58 (permalink)
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Freebeard,
The reason I believe the work to be similar is the folding tail has complicated hinges, actuators, and associated wiring that the other project doesn’t have. I am also assuming similar construction methods for both projects. Your point is not lost on me, no I have not chopped a top nor replaced a quarter section of a car body. I do want to learn though.

So the plans for the underside are a complete nose to tail belly pan out of aluminum except not under the exhaust ending at the new rear bumper. Basically flat from front differential to rear axle, sloping up from the bottom of the rear axle back. The exhaust ends behind the passenger rear wheel, that may get relocated straight back to end closer to the rear. I would not want to collect air from below for the oil cooler due to mud/damage concerns but would collect it from the sides if I pursue that project.

Despite having the materials and tools to work on that and similar projects, I am holding off because deciding on the path for the roof and sides in the back has impacts on the other work. As you can probably tell I keep wavering because it is not an easy decision for me. I am equally concerned about biting off more than I can chew as well as shortchanging the project and being dissatisfied with the outcome.
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Old 06-12-2019, 11:08 AM   #59 (permalink)
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I don't know how I missed this before.

https://ck5.com/forums/builds/my-bob...ack-build.324/

Apparently I would not be the first to build a hatchback Suburban.

If I followed this path, I would (potentially) not narrow the rear, cut off the rear cargo area window and above, convert to a tailgate, create mating weatherstripped surfaces to seal, build a hatch, install lexan windows, and install a legitimate roll cage.
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Old 06-12-2019, 01:26 PM   #60 (permalink)
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That makes something like a four-door Chevy Blazer, or Nissan NX.

Bobbing the tail would not help the fineness ratio. Maybe skin the rear quarters and bring the contour straight to the rear opening? Lots of opportunity for skirts and skegs there.

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