Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Advice on aero-cap shape

hat_man · 03-15-2012, 08:10 PM

T vago...That is the shape I had envisioned to start and then changed to increase the slope on the sides. I know nothing about aerodynamics and generally fly by the seat of my pants. The image you posted looks like the vertical angle at the top (nearest the cab) reamins fairly constant all the way down the sides. I "erased" some of your image and came up with this. With my bed being 10" wider at the cab than at the tailgate I'm not sure it exactly matches our "combined" picture. But if I made the rear match the tailgate width and the front match the cab width and kept the vertical side angle (still looks like 60* to me) the same for the lenght of the bed, and then the 4* slope for approx. 30" (in bed length) and then 6* more for the remaining 42", [whew, gotta catch my breath] how does that sound?

I'm not sure what the green area is, but it sure would make a nice cut out to be able to see the 3rd brake light.

Chaz and T vago...just to open up some discussion...I thought gradually sloping the sides inward (from 60* to 15*) would allow the air to flow better off the back. I remind you both that I know absolutely nothing about aerodynamics. It just looked "swoopier" to me. (You can both laugh now.) What about maybe like Chaz says and transition from 60* at the cab and graduating to 30* at the tailgate? The graduation being at the point that the top slope changes from 4* to 10*. I'll mark it with white spots on the pic. Is the problem with the air from the top (moving downwards) and the air from the sides (moving rearward) meeting up and causing problems? Does keeping the side angles at approx 60* for the full length of the bed negate this? I don't have a clue.

It sounds like I have the top slope pretty well worked out. Now the question is on the sides. I'd love to hear what you two think or anyone else that is interested. The more the merrier. Maybe someone else will be watching this thread and beat me to the punch and finish before me. LOL

And are there any thoughts on the other pic? If I keep the cover square and leave the 5" overhangs over the bedrails will this cause problems with trapped air or anything else? Or is my tapered idea better?

Thanks again to all.

p.s. Chaz...I tried the degree symbol thing and as soon as I hit the 1 it jumps to the top of the page. ??? Maybe the * will have to work for now.

p.p.s OK got it now. Grrrrr. Gotta use the number pad and not the numbered keys above the letters.

03-15-2012, 08:10 PM	#26 (permalink)
hat_man Master EcoModder Join Date: May 2010 Location: Illinois Posts: 475 Oh Deer - '03 Ford Ranger XL 90 day: 33.97 mpg (US) Thanks: 55 Thanked 91 Times in 72 Posts	T vago...That is the shape I had envisioned to start and then changed to increase the slope on the sides. I know nothing about aerodynamics and generally fly by the seat of my pants. The image you posted looks like the vertical angle at the top (nearest the cab) reamins fairly constant all the way down the sides. I "erased" some of your image and came up with this. With my bed being 10" wider at the cab than at the tailgate I'm not sure it exactly matches our "combined" picture. But if I made the rear match the tailgate width and the front match the cab width and kept the vertical side angle (still looks like 60* to me) the same for the lenght of the bed, and then the 4* slope for approx. 30" (in bed length) and then 6* more for the remaining 42", [whew, gotta catch my breath] how does that sound? I'm not sure what the green area is, but it sure would make a nice cut out to be able to see the 3rd brake light. Chaz and T vago...just to open up some discussion...I thought gradually sloping the sides inward (from 60* to 15) would allow the air to flow better off the back. I remind you both that I know absolutely nothing about aerodynamics. It just looked "swoopier" to me. (You can both laugh now.) What about maybe like Chaz says and transition from 60 at the cab and graduating to 30* at the tailgate? The graduation being at the point that the top slope changes from 4* to 10. I'll mark it with white spots on the pic. Is the problem with the air from the top (moving downwards) and the air from the sides (moving rearward) meeting up and causing problems? Does keeping the side angles at approx 60 for the full length of the bed negate this? I don't have a clue. It sounds like I have the top slope pretty well worked out. Now the question is on the sides. I'd love to hear what you two think or anyone else that is interested. The more the merrier. Maybe someone else will be watching this thread and beat me to the punch and finish before me. LOL And are there any thoughts on the other pic? If I keep the cover square and leave the 5" overhangs over the bedrails will this cause problems with trapped air or anything else? Or is my tapered idea better? Thanks again to all. p.s. Chaz...I tried the degree symbol thing and as soon as I hit the 1 it jumps to the top of the page. ??? Maybe the * will have to work for now. p.p.s OK got it now. Grrrrr. Gotta use the number pad and not the numbered keys above the letters. Attached Thumbnails Last edited by hat_man; 03-15-2012 at 08:26 PM..