Kammback assistance, Civic hatch

[greasemonkee]

It's been a while since I've been around, but now I drive 1300 miles a week. I've completed the front end of the car, now on to the rear.

I ordered .125" Lexan for the Kammback, which I plan on painting to protect from UV damage. The piece I ordered may be a bit wider than needed, but I'm confused about how to optimally shape the rear edges. Hopefully the angle is about right. Thanks for any insight.





Note for those seeking results without reading thread - Gains realized by final kammback: 3.0 - 3.5 mpg hwy

Total at 75 degree cruise temps, 10% city driving - 56.2 mpg

[Weather Spotter]

Well I had one on my car for a while. Here is what a Found:

1: start the slope to match the areo template.
2: slope the sides in at about the same angle.
3: round off the transition from sides to top.
4: start planning for a boat tail. Once you try the kammback and find a minimal improvement you will want to add a tail to the car.

5: how are you going to attach the Kammback? those mount points might be good for a tail (add a hitch for the lower point).

[greasemonkee]

Unfortunately the boat tail will require too much time and add too much weight. The must retain it's handling characteristics as I travel through hundreds of curves daily. Nevertheless, I'll be content with a 3mpg gain, thanks for the info.

[Weather Spotter]

My tail has no issues with curves, and weighs under 100 LB. I do not think the kammback will give you more then 1.5 MPg

[Sven7]

Make sure the bottom edges are cut off at a better angle so they don't catch the wind.

A tail shouldn't hinder your car's performance any more than a messenger bag hinders your ability to walk.

[greasemonkee]

[QUOTE=Weather Spotter;266147]My tail has no issues with curves, and weighs under 100 LB. I do not think the kammback will give you more then 1.5 MPg[/QUOTE


The front chin spoiler yielded a solid 3mpg, but some is better than none - only means it takes longer to pay for itself..

[Ultra-Orange]

[QUOTE=greasemonkee;266185]

Originally Posted by Weather Spotter

am I the only one to notice the road behind this pick looks like the template for a kammback?

[greasemonkee]

Not sure why it took me 5 months to continue this. I believe the failed attempt at using Lexan discouraged me so after wasting $70 here it is again, and ABS plastic is the ticket.

So, any ideas on how to shape the square edges to make the best transition? I've still got some heating, shaping, and reinforcing to do, but it's coming together

[aerohead]

Originally Posted by greasemonkee

Not sure why it took me 5 months to continue this. I believe the failed attempt at using Lexan discouraged me so after wasting $70 here it is again, and ABS plastic is the ticket.

So, any ideas on how to shape the square edges to make the best transition? I've still got some heating, shaping, and reinforcing to do, but it's coming together

Marine Plastics,a company which used to operate in Denton,Texas used ABS thermo-form plastic for all its products.They had electric ovens to get the sheet up to molding temperature and then transferred to a airclamp system over hollow wood tooling mounted to a vacuum table.
As soon as the sheet was clamped,the operator stepped on a foot-operated valve which delivered vacuum from a hemispherical storage tank to suck the plastic down over the form.
They had a formed part in thirty seconds,then de-clamp and off to a router trim station to remove flash.
I don't know of a different way to work with sheet material,which is why I gravitated towards FRP construction.
I see ABS garden pools at HOME DEPOT large enough to be a one-piece boat tail or trailer body,but to do them requires a bunch of up-front expense in tooling and equipment,plus shop space.

[greasemonkee]

The status quo around here seems to be a boat tail or nothing. The implications arising from such an extreme mod are a severe shift in the CG which I am not willing to tolerate as I drive through a LOT of tight turns daily on a strict schedule, aside from the fact that I often enjoy a spirited drive.

I've found that this abs plastic is quite easy to work with and have come to this. Hopefully I'll notice the results. Will post when a solid number is evident. Thanks guys