Project: ECOfamily Civic and its Aero Hitch Box / Boat Tail

[Fat Charlie]

Nine gallons to recover is cheaper than making a new one from scratch.

[California98Civic]

Originally Posted by Fat Charlie

Nine gallons to recover is cheaper than making a new one from scratch.

^ agreed. Driving any car means mishaps, so once they happen, figure out the best next step and move on. Looking forward to further reports.

[christofoo]

It was a mistake to walk away from something I had made with my hands, when so much of it was salvageable. But that wasn't clear until I had worked out what the solution to the side-wind would look like.

[whatmaycome14]

You and this project have been an inspiration to me about the future of my car. I'm glad that nothing was seriously damaged. Success is at the end of a road of many failures. I can't wait to see further improvements!

[RiderofBikes]

Plus 1 for tie downs+duck tape!
Utilizing this for experimental spoiler, and a host to the Exploding Kamm klub


Also, skool of hard knocks is the best as much as it pains us, we all taste it until we find something better! keep up the work

[Istas]

Lots of really cool ideas and execution! Magnets instead of drilling the roof, something I'm not sure I would ever have thought of. Also, you linked a single magnet but said you somehow bought them in pairs, here is the listing for the opposite-polarity pairs, for anyone interested:

K&J Magnetics - Products

The trunk-moved kammback is how I was thinking of doing it on my first car but never did; your execution is both proof-of-concept and encouragement for my current 05 Accord. Great idea with the magnetic fabric-mat material, very clever on the hinged attachment for the hitch-box. And I highly approve of sheet metal. Your fabrication skills (and tool selection)(and cad/simulation knowledge) are definitely something for me to aspire towards.

[mikeyjd]

Awesome project! I learned quite a bit reading through all this!

[christofoo]

Some quick updates:

I'm contemplating moving overseas for a few years for a job opportunity. If so, most likely the removable mods will go into storage and I'll sell the car.

Magnetic attachment of anything to the outside of a car is no good, according to Utah inspections. The Kammback has been shelved since June.

The AHB latch was left open due to user error and the lid flipped open on the road, damaging some sheet metal. I've repaired it, but haven't added a secondary safety feature yet. See the next post.

I faced a headwind during a trip recently. My best estimates are 28-30 MPG, level ground, ~72 MPH ground speed, 25-35 MPH headwind, ~45 MPH gusts. So that would roughly be my MPG at around 100-105 MPH, if I had a suitable gear. Here are my best guesses on the car's performance parameters right now:
Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com
Cd: 0.30
Crr: 0.12
(Maybe higher Crr right now: we're in winter tire season, they might be a bit higher than the all-seasons. The Crr end of my coast-downs has registered at around 0.12 with the (crappy) Les Schwab all-seasons. So I should be able to reach 45-50 MPG at PSL (neutral wind condition) just by getting some decent LRR all-season tires... on paper.)

So the project overall is somewhat successful: I can get mid 30's MPG trip average in very unfavorable conditions without sacrificing speed, with loads of storage volume. And the tail has proven it's ability to hinge on contact, avoiding damage.

I think the underbody is where I've primarily failed aerodynamically on this project, so far. It looks awful and so far I've left it untreated.

[christofoo]

I had a bad feeling about letting my wife use the car and AHB without me around. In hindsight, I tried to train her on the latch, but didn't put any emphasis on how unfreindly it was. It was possible to get the feeling it was engaged, when it wasn't. So I'm sure it's not really her fault.

In any case, she thinks she was going about 30 MPH when it flipped up and hurt itself. The lid didn't detach, but it bent up the sheet metal in the aft and tore out a number of rivets.



Snipped out the damaged sheet.


Healed it with a new sheet.


And redid the hinges. I hated the piano hinge.


(The hinge actually feeds through the sheet metal's crease, so it's aesthetically pleasing without a big sacrifice in stiffness. But I still sealed it up around the hinge. I liked the way this turned out, but it would still damage itself if it flips up again, most likely. Actually, maybe if I put a foam pad in the right place to absorb the shock, I might be able to engineer it to survive a blow over.)


If I was smart I would make sure to add a secondary latch before I use this too many more times... though the lid actually fits better now, so the latch is less error prone.

[MetroMPG]

I'm sort of following in your footsteps with an 8th gen '07 Civic sedan.

Kammback is nearly done. Starting on the tail extension this weekend. Construction materials and techniques not nearly as nice as yours. Oh, and ZERO added utility/storage.

Ps.. good luck on the job prospect.