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Old 12-10-2009, 11:31 PM   #21 (permalink)
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Your protractor doesn't lie.

The reason I can get away with 15 degrees is because of the gentle curvature at the back of the roof & upper surface of the hatchback leading up to that final angle. Also, the "shoulder" of my Kammback has a generous radius, permitting flow to transition from the sides without tripping.

If you use a "sudden" 15 degree angle/transition from your cab roof to the aero shell, you could end up with separated flow and dramatically reduced effectiveness of your hard work.

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Old 12-15-2009, 12:49 PM   #22 (permalink)
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Hey ccrider, how's it going on the aerocap for your tacoma? I'm looking forward to seeing your finished project. I'm still dwelling on my design and hopefully use a bit of what you've done for inspiration.

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Old 12-15-2009, 06:43 PM   #23 (permalink)
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i only get to work on it on the weekends with it getting dark so early. i didnt get any time to work on it this past weekend. i am hoping to work on it this weekend. at least i am getting more gas log data so i will have a good base to see how much it improves the mileage. the only problem i am always moving stuff with it so it throws the mileage off. but i am getting around 30 mpg on the highway at 65mph now. it would be nice to get 35mpg out of a truck.
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Old 12-15-2009, 09:14 PM   #24 (permalink)
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The angle of that wood looks pretty conservative. Is that 10 degrees? I've never made a pickup cap or anything, but it feels like it could be more steep. Look at the rear window of some very aerodynamic cars.
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Old 12-15-2009, 09:46 PM   #25 (permalink)
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winkosmosis it is 11 degrees. i dont know much about aerodynamics just listening to people on the forum with more knowledge than me.
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Old 12-15-2009, 09:58 PM   #26 (permalink)
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I think it's just an optical illusion making it look shallower
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Old 12-19-2009, 12:50 PM   #27 (permalink)
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Old 12-19-2009, 01:14 PM   #28 (permalink)
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here is my progress today. i have 2 more supports made that go in the middle of the bed. i will cut them depending on how much i can bow the upper piece of wood up to make it rounded. i hope to get it to bow up 1 1/2" in the center of the bed. if you notice the front support is rounded on the top and the back one is flat. the 2nd support back(that is not in the picture) is going to have a very little round to the top and the 3rd one is going to be flat like the back one. also the side angle lays down as it goes to the back of the truck. this was done so that the top piece of wood remains the same size all the way to the back of the truck. i am going to run the top piece of plywood 6" past the rear support to create a kammback and so when i pan off the bottom of the truck i will pan it off to the back of the bumper so the kammback will end at the same point as the bottom pan. the sides pieces of plywood at the top of the piece will be the same 6" past the rear support and the bottom of the piece will be cut back to the tailgate making a pie shape from the side.

feel free to give me advice.i would rather change it now than after it is built.
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Old 12-19-2009, 01:15 PM   #29 (permalink)
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Old 12-19-2009, 02:44 PM   #30 (permalink)
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I can see the shape you are looking for, and I like it.

Next order of business is two or three intermediate supports for the sides.

Have you thought of this? Build essentially a topless top and use a commercially avaiable rollup toneau cover as your "roof." This way you get the aero advantage and the flexibilty a pickup needs.

Your wood frame would be the perfect support for a mold to make this baby out of fiberglass.

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