![]() |
Spoiler based on kamm-back dimensions?
Hello -
Back in this thread I was given feedback on what a proper Kamm-Back might look like for my car : http://ecomodder.com/forum/showthrea...html#post41152 - Post #16 http://img40.imageshack.us/img40/511...ckteardrop.jpg This led me to this design, which was deliberately limited in length by the distance to the back bumper : http://img198.imageshack.us/img198/2392/ks11full75p.jpg http://img26.imageshack.us/img26/328...eometry.th.jpg I haven't done any serious work on this because I want to maintain rear-view visibilty, third brakelight visibility, the complexity of the gently curved roof shape, and the risk of a "parachute" effect if the top got loose. Then I noticed this from the 1970's Pinto mods : $11 worth of mods plus new tires - Car and Driver improves MPG by 25% http://ecomodder.com/blog/wp-content...oiler-blog.jpg Quote:
http://img34.imageshack.us/img34/518/ks10flat75p.jpg http://img34.imageshack.us/img34/251...eometry.th.jpg From an aero POV, do you think this would help? I am thinking that this is similar to Ernie Roger's new-Beetle Wing Spoiler. IMO the positives are easier construction, good rear visibility because only a "single flat line" of coroplast is in the way, third brakelight visibility, and (hopefully) less risk of a parachute effect. The only bad thing is that I would need to disable the rear-window wiper (one fuse), unless I made a gap between spoiler and the rear-window (Ernie did this for other reasons). CarloSW2 |
FWIW, I don't think that strategy will do as much good on a wagonback as it does on the Pinto hatchback (Edit: and Beetle). My reasoning is, if the Pinto spoiler really does work and promote attached airflow all down the hatch, it would successfully have reduced the wake area at the rear of the car by a large amount... half? But on your wagon you have proposed extending the spoiler up to such an extent that even if you do achieve attached airflow on the top of the back window (or the mimicry thereof) it looks like it wouldn't reduce the area that forms a turbulent wake very much. Now if that spoiler went horizontally out the back for, say, 3', you might have something.
|
Why do people use those aerofoil overlays? The shape of anything you add to your car should be based on the local airflow conditions.
|
I was wondering about spoilers like that one on the Pinto... It seems like they'd trap a puddle of air, and force the air to flow above that, at a shallower angle. I guess that really does happen.
Your angles are much steeper, but since having the liftgate closed on a pickup is more aerodynamic than leaving it open, I'd think your design would help too. |
Frank & Co -
Thanks for the feedback. Three feet would be a good experiment, but I think I'd have trouble when it's parked (someone would thunk into it, probably a pedestrian on their cellphone). Hrmmm. Maybe a three-footer that was retractable? I was hoping that I was "seeing" a good aero shape, but maybe it just isn't there. Because it's a lot easier to do, I may just try it for grins. I could reuse some of the "infrastructure" for future-someday-c-through kamm-back. CarloSW2 |
I think you'd see some gain- say, 10% vs the- say, 50% on the Pinto (turbulent wake reduction, not necessarily Cd reduction or fe increase). My understanding of it is, you can boattail quite nicely, and do things with spoilers re: that airfoil template, but wherever that bodywork ends, you still end up with a turbulent wake. Aerohead has a description of that phenomenon somewhere here.
Yours is kinda the difference between a regular minivan and an Aztek. |
i think the spoiler on the pinto mailny works because it reduces the vortices that come off the C pillars... back in those days a lot of hatchbacks had C pillar angles similar to the pino.
this angle is to steep to maintain attached flow as is pretty obvious, but the airflow comming off the sides will form a large vortex that starts at the top and curves inwards. the spoiler intercepts these vortices and breaks them up. I've seen this sort of bodie style refered to as a "morel bodie" it's for this reason a lot of hatchbacks and fastbacks today still maintain a semi "trunk lid" but todays hatchbacks have mostly a more steep angle; and more boattailing at the rear wich reduces these vortices |
Hi,
http://img198.imageshack.us/img198/2392/ks11full75p.jpg I think something close to the first example would be the best -- it doesn't have to be as extended as you show it to be a benefit. |
wonder
Quote:
|
overlay
Quote:
|
All times are GMT -4. The time now is 04:45 PM. |
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2025, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com