5th generation civic hatchback - improving aerodynamics

[NeilBlanchard]

In a 1-car crash, low weight is very helpful.

[gascort]

I think the best way auto safety is summed up is:
Size is an advantage in all kinds of crashes.
Mass is an advantage in only 2-vehicle crashes.
Rather than changing the cars, it would be nice to have everyone wearing 5-point seat belts. No, just wearing their seat belts correctly would be nice.

I personally don't think the 2010 MINI cooper performed well in the crash test. Its front end is too short; the crash dummy in the test recorded 48g of deceleration.
The side impact test: 69g

My 1993 escort (16 years older!!) had 42g of chest deceleration in the same test.
(no side impact stuff was around then, so I suppose my car might be the same or worse there... plus I don't have side airbags)

Adding length is great for economy and safety. My Kammback helps rear-ending, and my new air dam is going to extend my front about 0.3m. The SMART fortwo is just plain DUMB for economy and safety. Just "cute" and easy to park. By the way, it had 55g in the same exact test. I don't know what crackhead decided to put its picture on their page for the 5-star crash test rating search page.
Safercar.gov

[Grim]

Originally Posted by 1.5Ldave

Weight has no bearing on how well a vehicle will do in a crash. Size for the most part doesnt either, granted to dont end up underneath one of the collosus vehicles people drive to "feel" safe. Ill choose quality engineering over some big heavy box for safety any day of the week and twice on sunday.

f150 and mini cooper 40 mph crash comparison



Both of these vehicles hit the exact same off-set barrier at 40mph. Now keep in mind that this is not a test of how the two cars would fare in a head-on collision with each-other. This is simply how the cars did versus an off-set crash test. In fact all you have to do is look at the dummy’s legs and you can get an idea of what would happen if you hit a wall in either car. The MINI had almost no intrusion which “indicates that the driver’s survival space was maintained very well” - the F150 on the other hand had “Major collapse of the occupant compartment that left little survival space for the driver.”

Originally Posted by eRoc

I beg to differ with this argument. Weight and size do have a big part of how vehicles do in a crash.

Take the vehicles in that video. Mini Cooper maybe weighs 2200lbs. F-150 weighs approx 5000 lbs (guessing). You wouldn't think that at 40mph the Ford would carry more momentum into the crash than the mini cooper? What if we took an f150 made out of Nerf and crashed it into a wall at 40mph? Do you think it would have the same effect? I doubt it would crumple further than the front bumper.

Size also matters. Take a number two pencil. Snap it in half. Then take that half and snap it in half. Then take the smaller half and snap that in half. It gets increasingly harder each time.

Finding the balance inbetween all of this is why engineers get paid the big bucks.

Physics....

P.S. First time poster. I'm going to post in the welcome forum but I found this thread through Treehugger.com (actually found Aerocivic and there was a link to this thread). I'm intrigued by all of this so I will be posting more often.

-Eric

That generation Ford in the 4 door extended cab variety was rated THE WORST. The body deformed horribly. The Current model ford is actually one of the safest fullsize. Ford took a LOT of deserved beating for that poor crash test and they thankfully did something about it.

Body on frame generally do poor in crash test. Unit body the complete body structure IS the frame so you are sitting in more of a cage. Example. My 86 Previa has a MUCH better crash rating then the full sized 3/4 ton Suburban it replaced.

European vehicles tend to have better safety standards especially over full size Truck based vehicles. When most of the safety standards in the US came into play was LONG after the Germans in particular were building passenger safe cars.

Side impacts is where the main concern is. A large vehicle has the occupants sitting higher. When hit in the side most Truck based vehicles will be hit on or below the door sill then involve the frame approximately where the transmission crossmember is located where the vehicle is stronger. A small vehicle you are involving the B pillar and door where there is a large open span. It takes a LOT of extra material in those location to give strength to withstand the hit and there is NO crush zone to speak of before the occupant comes into contact with the side of the vehicle.

Back to the original Topic

Great read. Thanks for the very detailed post of upgrades and results. You have me fired up to try a few things on my Bean (Previa).

[jime57]

He did do a masterful job. However, I am beginning to worry a bit about some of these boattail contruction methods. The various sheet materials being used for lots of the boattails makes compound bends very difficult. In fact, many of the boattails are essentially without compount curves. That means that it is difficult to envision how one increases angle downstream.

It seems to me that a construction technique which used some type of foam with fiberglas skin would allow the basic shape to be formed with compound curves. Perhaps large strofoam blocks could be glued together in a rough shape, then the complex form could be achieved by planing down with some sort of file such as a sureform. Since strofoam is not tolerant of fiberglas resin, the foam would need to be sealed. I spoke with someone a while back who indicated that simply painting the strofoam before adding fiberglas was effective.

Just thinking out loud.

[robchalmers]

on the safety question.....

http://www.youtube.com/watch?v=qBDyeWofcLY

http://www.youtube.com/watch?v=MzZak...eature=channel

Back ON TOPIC.....

How do get around cooling difference on hot day / cold days I know your seasons are alittle more predictable than here in Blighty. Do you have to open up new holes on hot days?

[animated_zombie]

All I can say is wow! I just joined the other day, and I've spent the morning reading through this thread. Amazing build-up, very inspirational!

[lzyga09]

good read i cant wait to put a belly pan under my civic and do a mini air dam/ spliter!

[Aconrad84]

Originally Posted by Lazarus

Outstanding. I llike the skirt brackets. Are you planning on a mirror delete? Those are huge. Very nice work indeed.

I'm pretty sure that would make the car illegal. My 1990 Civc hatch has only one mirror as sold from the factory... a bonus, but i think the effect of the mirrors on the aero is minimal. Seems like a crx would be the best place to start for this brand. It has a kamm/prius style back design, easy motor swap to a 1.5L too you'd only need the engine mounts the 1.5L sits on in a regular civic, and axles. Also think about how lightweight drives shafts, clutch, flywheel, and other usually performance oriented upgrades will help with fuel economy...less rotational mass = less work for the engine to do. Reducing friction would help to i.e. hypereutectic pistons, and ceramic sleeved cylinders, but thats out of most peoples price range.

[EF TuneRR]

Originally Posted by Aconrad84

I'm pretty sure that would make the car illegal. My 1990 Civc hatch has only one mirror as sold from the factory... a bonus, but i think the effect of the mirrors on the aero is minimal. Seems like a crx would be the best place to start for this brand. It has a kamm/prius style back design, easy motor swap to a 1.5L too you'd only need the engine mounts the 1.5L sits on in a regular civic, and axles. Also think about how lightweight drives shafts, clutch, flywheel, and other usually performance oriented upgrades will help with fuel economy...less rotational mass = less work for the engine to do. Reducing friction would help to i.e. hypereutectic pistons, and ceramic sleeved cylinders, but thats out of most peoples price range.

The 84-87 or 88-91 CRX HF (high fuel efficiency) would be the best place to start. They are the lightest weight (and best MPG) of all the CRX models. It's pretty obvious the 2-dr Insight is a continuation of the CRX HF design philosophy.

[navivovas]

Hello!
Great job...and great patience,i think.Congratulations,Andrew!