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ChazInMT · 08-26-2010, 02:09 AM

Barna,

Man, That is a SWEET lookin Kamm, your fabrication is great on that. In looking at your car's basic design, it is decidedly unaero in the sense it has very little roundness to the roof line, and the transition at the top of the front windscreen to roof is quite abrupt by more modern standards as well as the rear window to roof, That is a cd killer.

I think you're definitely on the right track with the Kamm thought, but you either need to raise the rear edge a bit, or soften the transition from Roof to Kamm by making the shape of the Kamm rounder. You need something here to create a clean detachment for the air going over the roof. I think now your problem is you still have a rather abrupt change in the air from roof to Kamm and it isn't working.

OK, I wrote the above then went and messed around with drawing things over your pics and those of another Protege I found online.....I have to say I'm stumped, it looks all the world to me like you're at 10° on your Kamm, that is how I'd make it too. It could be a bit flatter, but I can't see that making a huge diff. I wonder if you aren't too aggressive on the sides? I don't know how you could modify it, but if you could make the sides less angled in by making the top trailing edge a few inches wider, it may help. I'm thinking you may have hit a "Sweet spot" (as in bad) for creating a large vortex generator. So by making the slope less steep a tad, maybe raise the trailing edge by 1.5" and wider by 3 inches or so, you'll get the clean air release your looking for without some weird pressure differentials creating a pair of horizontal tornados that you're dragging around.

Another thought is your speeds for testing. Is there someplace you can go to get up to 75 or so to start your test with? Since higher speeds really magnify aero problems / benefits, you may get different results starting at higher speeds. (Of course this is coming from a guy in Montana where I'm road kill if I drive 59 MPH where speed limits on our highways are 75 and cops don't even quit chewing their donuts if you pass them at 80)

And to answer your earlier question, seems like you got the You Tube thing worked out. To post pics without uploading them to EcoModder as attachments, I post them on a free web site called TinyPic. Then I copy the little box on there with the "IMG code for Forums & Message Boards" and paste it right into the post.

Like this

Hint, if you right click any pic then hit "Properties" at the bottom of the pop up menu, it tells you the source of the pic.

Great job again on your Kamm.

And finally (Man, will I ever shut up?) How in the wide wide world of sports did you make the Kamm? I'm considering doing something similar on my 04 Civic. And how much did the plastic cost?

08-26-2010, 02:09 AM	#9 (permalink)
ChazInMT Aero Deshi Join Date: Jan 2010 Location: Vero Beach, FL Posts: 1,065 MagMetalCivic - '04 Honda Civic Sedan EX Last 3: 34.25 mpg (US) Thanks: 430 Thanked 668 Times in 357 Posts	Barna, Man, That is a SWEET lookin Kamm, your fabrication is great on that. In looking at your car's basic design, it is decidedly unaero in the sense it has very little roundness to the roof line, and the transition at the top of the front windscreen to roof is quite abrupt by more modern standards as well as the rear window to roof, That is a cd killer. I think you're definitely on the right track with the Kamm thought, but you either need to raise the rear edge a bit, or soften the transition from Roof to Kamm by making the shape of the Kamm rounder. You need something here to create a clean detachment for the air going over the roof. I think now your problem is you still have a rather abrupt change in the air from roof to Kamm and it isn't working. OK, I wrote the above then went and messed around with drawing things over your pics and those of another Protege I found online.....I have to say I'm stumped, it looks all the world to me like you're at 10° on your Kamm, that is how I'd make it too. It could be a bit flatter, but I can't see that making a huge diff. I wonder if you aren't too aggressive on the sides? I don't know how you could modify it, but if you could make the sides less angled in by making the top trailing edge a few inches wider, it may help. I'm thinking you may have hit a "Sweet spot" (as in bad) for creating a large vortex generator. So by making the slope less steep a tad, maybe raise the trailing edge by 1.5" and wider by 3 inches or so, you'll get the clean air release your looking for without some weird pressure differentials creating a pair of horizontal tornados that you're dragging around. Another thought is your speeds for testing. Is there someplace you can go to get up to 75 or so to start your test with? Since higher speeds really magnify aero problems / benefits, you may get different results starting at higher speeds. (Of course this is coming from a guy in Montana where I'm road kill if I drive 59 MPH where speed limits on our highways are 75 and cops don't even quit chewing their donuts if you pass them at 80) And to answer your earlier question, seems like you got the You Tube thing worked out. To post pics without uploading them to EcoModder as attachments, I post them on a free web site called TinyPic. Then I copy the little box on there with the "IMG code for Forums & Message Boards" and paste it right into the post. Like this Hint, if you right click any pic then hit "Properties" at the bottom of the pop up menu, it tells you the source of the pic. Great job again on your Kamm. And finally (Man, will I ever shut up?) How in the wide wide world of sports did you make the Kamm? I'm considering doing something similar on my 04 Civic. And how much did the plastic cost?