Volvo 240 wagon - partial Kammback prototype
 

I'm interested in diesel_john's rear aero treatment.
http://i188.photobucket.com/albums/z...mm_smaller.jpg

The more I look at the full size pic the better I like this back.
http://ecomodder.com/forum/attachmen...6&d=1202433430
I know how hard it can be to do a back when the liftgate / body cut is on the rear panel and not on the side.

Can you please start a new thread with some details on this one? Or if the thread exists and I missed it - post the link?

Here's a pic of what I had for a couple months this past summer. I tore it off when I wanted to clean up the car so it wouldn't look like it was Ma and Pa Kettle's (google it, I guess, if that's not familiar to you).

http://i188.photobucket.com/albums/z...k/100_0027.jpg.

You can see the taped joint at upper right were top piece meets side. Had to be untaped and retaped every time I opened the tailgate. Plus duct tape residue all over the place. As with other mods, no confirmation that it actually helped. But if using a good clean design I think it has to help.

I was thinking today that you could buy another replacement tailgate from a junk yard and build a more permanent boat-tail on that. Then you could just re-bolt the original hatch on when you want to sell it or look normal hehe.

Brucepick - hope you don't mind I split this off into a new thread. It's interesting.

And I agree - I'd like to see a new thread about the Rabbit treatment.

Question about yours: was there much downward taper from the roof line? It may be a trick of the photo, but it seems to be more of a roof line extension, ie straight out.

I like the idea of the junkyard tailgate. I hate to haggle up perfectly good parts. I am neither professional nor proficient enough to indulge in that.

mattW -

Most excellent idea. That's been one of my eee-vile plans. In the meantime, why not try to prepare mock-ups that attach to the tailgate and still form a flush connection to the side and top of the car?

CarloSW2

i'll take a pic when the windchill gets back above 0. my hatch is fully functional. the side plexiglass panels slide into a slot at the bottom which makes them stable on the highway. all mounting screws on the hatch are outside the sealing gasket, so no water can get in the cab.

hatch is functnl,
side skirts are hinged so i can get my lift arms under there,
full belly pan, except under oil pan.

was inspired by Ernie Roger's bug TDI.

My general rule of thumb is no more than 15 degrees change.

can remove wheels without removing tin work now.

can only see a thin line of the rear treament out the back window.

each vehicle is different, tuft testing is the shortest path to success.
start your tail where the separation is pronounced.
i think, bottom is the most difficult to exit clean and the most important.
other pics and posts thur out this site.

Thanks for splitting it off for a new thread. I'm going to take a good look at the other pics of the Rabbit back. diesel_john, please write up as much detail as you have time and patience for. And thanks!

Mine did taper downwards. You can see it in the pic at the right corner where the top and side pieces meet. At center maybe not going down quite as much but it did go down. I was trying to be conservative and not have too much of a downward angle. Roof of course is essentially flat/level as it's a long wagon with flat roof.

diesel_john,

Can you post a gaslog? Or is there one somewhere that we can see? What kind of FE improvement have you gotten with your setup?

When I originally suggested this thread (which was split off from another) my intent was to see more information on diesel_john's car. However this thread got titled with my own car's description. Both cars have a large rear face with the large wake that generally produces.

Anyway, based on the guideline of maximum 15 deg. angle to maintain attached flow, I did two drawings. I didn't measure the drawn angles but I think it's close enough for where I/we are now. You can see that to reduce the rear face appreciably on this car you need a reaaaaaaallly long boat tail.

I don't know if I dare build this thing. It would have to be pretty large, which probably means heavy, and also will have a large side profile to catch side winds, with all the construction issues that come from those issues.

http://i188.photobucket.com/albums/z...ideView400.jpg

Rear view:
http://i188.photobucket.com/albums/z...earView400.jpg