Quote:
Originally Posted by cliffyballs
Hey everyone,
First time post and its gonna be a tough one, but coach said go big or go home...if i have to go home i want to use as little gas as possible!.
I would like to build a boat tail for a 2003 Jetta GLS 2.0L gas engine. I know little to nothing about boat tails other than what they look like.
My plan is to use a trunk mounted bike rack and modify it accordingly.
I want to use plexiglass at least on the top so i can still see out of the back.
I will eventually use trailer lights for brakes and blinkers.
So my question/s:
How long do i need to make it?
What things do i need to keep in mind?
What angles do i need to maintain?
What am i forgetting that will cause worse MPGs?
What do i think i am doing right that is actually wrong?
Any help would be great!
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cliffy,I'll try a go at your questions:
* The length will lock in the drag reduction,so you you might want to target a specific mpg improvement,and from there we'll know how far to go.If you look at the 1st-gen 1999 Prius,at Cd 0.29,and the latest 2011 3rd-gen Prius,you'll notice that by adding only 7.3" length,moving the rear body up to near the boat-tail curvature,along with a few tweaks,the drag was cut to Cd 0.25.Since 'cars' have achieved Cd 0.10,you can see that there is substantial room for improvement.
* As far as 'angles',it's more about degree of curvature.There is an Aerodynamic Streamlining Template here at the aero forum which you could use as a guide for designing your tail.All you need is a decent photograph of the Jetta taken from the side,taken at enough distance from the car to accurately show the current roofline.Also,it's a good idea to get two friends to sit in the front seats when you take the photo,so it will be 'settled.'
* Since the tail needs really good airflow to it in order to perform to top level,I would recommend rear wheel skirts to smooth that lower flow.