A New Aeroshell- and Lessons Learned

[cfg83]

aerohead -

Originally Posted by aerohead

rrhatbruce,nice work! She's a beaut.With respect to "angles" you might want to check out the "aerodynamic streamlining template".You can see it being used at MetroMPG's "permanent Kammback for the Metro" thread.------- It's really more about degree of curvature which will sustain the final exit angles.Your Tacoma's bed is so short,it may not be able to support such a "steep" angle at the back as 16-degrees,and you may have separated flow,which will frustrate your mpg improvement.

I was thinking the same thing. I rotated the picture of the Tacoma to make the bed horizontal and I *think* I see two angles :



The red "12 degrees" line I show above is based on bondo's F-150 shell :

http://ecomodder.com/forum/showthrea...d-cap-583.html


rrhatbruce -

I rotated a picture of the Tacoma that was not a perfect side view, so my visual analysis may be way off. As others have said, the workmanship is beyond reproach. During your design phase, did you contemplate a "12 degree solution" with a CRX-style vertical rear window?

CarloSW2

[NeilBlanchard]

Hi,

The cap on the Tacoma is curved. If the bed is too short and the angle gets too great, then the cap should not come down to a point? It should have a small vertical surface at the back, instead.

[groar]

So beautiful
I'm a little bit more ashamed about my ugglyback

Wish you to improve your aeroshell and thanks to you for sharing your lessons.

Denis.

[bondo]

Hello Bruce.

I know how frustrating it is to build something with such high expectations and not have it work like you want. Been there, done that, and been there again. Now is the time you must be tenacious.

The photo below is of my first attempt at an aerodynamic lid, the white truck. I too used an existing camper shell I had built some years earier as a starting point. As you can see, the slope of the white truck cap is too abrupt. The silver truck in the foreground is the clay model I was sculpting for the lid I have now. That slight difference in angle makes all the difference in the world.

CarloSW2 and others are correct in illustrating the slope of your lid being too abrupt. My first lid had to same problem and did'nt improve the fuel efficiency of the truck at all! Aerohead explains it best as the air separating from the surface of your lid and becoming turbulent. I hate it when that happens. With a correction in the angle of your lid and development of the back surface as NeilBlanchard and skyl4rk suggest would make a great difference.

On my lid, I got lucky. I sculpted the angle of my lid to what looked like it might work and again, it was dog luck I got it right. I consider myself honored to be in the company of many here on ecomodder that posess knowledge I would love to have. I have learned a great deal about aerodynamics from many here. I can do one thing though, I can make shapes and quickly too.

Bruce, give me a shout at aerolid@aol.com. I may be able to help you on making the modifications to your lid. In one weekend we could knock it out if you would'nt mind driving to Little Rock. I know you are in school, but maybe we can work at a time to get it done.

Bondo

[rrhatbruce]

Thanks for the encouragement everyone. Unfortunately I probably do have seperation. I don't have the mileage logs posted but we took a 150 mile trip yesterday and... no difference in mileage, up or down. Once I'm back from vacation I will do some tuft testing, expecting to find lots of swirlies.

The biggest mistake I probably made was to go so far in building before I was able to test my work. I knew I was pushing the limits but if I have to cut it back apart and raise it up the world hasn't come to an end. (I will have to give my long-suffering wife some attention first though)

CarloSW2: It is really just one angle and that is at 18 degrees. The foreshortening from my photo not being taken perpendicular to the truck is fooling your eye. Also the upper angle you're seeing is the 30in chord radius I used in my attempt to sweet talk the airflow into my steep angle.

Bondo: Thanks for reminding me you had a false start. I still am a fan of aeroshells and have learned a lot with this one. I'm not sure what my plan is at the moment but there are several options ranging from a spoiler at the back, doming the hatch, VG's, all the way up to cutting it back apart and raising it up. I will let testing drive the decision making process. I will probably take you up on you offer in a couple of weeks.

Neil:

It should have a small vertical surface at the back, instead.

Now you tell me!

aerohead: Thanks for the workmanship compliment. Like several in here I work in engineering and really couldn't convince myself to do anything less. (Personality flaw but what can I say) That said 40 feet is about the right viewing distance. Much closer and the flaws really start to show.

Big Dave:

As you know, windows are a complication, and I question just what you can see through rear windows laid over that far.

Not much but it's my shell and that's how I wanted it. Actually it wouldn't be so bad if I hadn't used limo black tinting. With the rework that's already in the future that will probably come off. Then I can use it as a mobile greenhouse in the winter.

[MadisonMPG]

I would paint it black.

[Concrete]

rrhatbruce,

it is beautiful!
do you keep a fuel log?

[aerohead]

Originally Posted by cfg83

aerohead -
Seems like the bed is just too short to allow the cap to "flow" down to the elevation of the gate top without separation.The photo magic really helps visualize what's going on.Thanks!


I was thinking the same thing. I rotated the picture of the Tacoma to make the bed horizontal and I *think* I see two angles :



The red "12 degrees" line I show above is based on bondo's F-150 shell :

http://ecomodder.com/forum/showthrea...d-cap-583.html


rrhatbruce -

I rotated a picture of the Tacoma that was not a perfect side view, so my visual analysis may be way off. As others have said, the workmanship is beyond reproach. During your design phase, did you contemplate a "12 degree solution" with a CRX-style vertical rear window?

CarloSW2

Oops,I put my reply up above in the wrong spot---Heavens to Mergitroids!

[mjboks]

Thought this might be interesting to this thread. I'm also a tacoma owner and followed this thread on aeroshells. Great work by the way. Anyways, if there's one for the H3 truck, the style might be catching on:
Snugtop - Custom Fiberglass Manufacturing, Truck Cap & Tonneau Top Covers, Camper Shells Tops, Customized Truck Toppers, Pick Up Truck Canopy

[aerohead]

Originally Posted by mjboks

Thought this might be interesting to this thread. I'm also a tacoma owner and followed this thread on aeroshells. Great work by the way. Anyways, if there's one for the H3 truck, the style might be catching on:
Snugtop - Custom Fiberglass Manufacturing, Truck Cap & Tonneau Top Covers, Camper Shells Tops, Customized Truck Toppers, Pick Up Truck Canopy

The slant back looks to borrow from the military Humvee which sometimes sports the slanting cover.I suspect there is immediate separation of the flow due to the hard angle,the downstream re-attachment.
Style-driven,rather than science-driven design.
Although,as the late,great,Bob Parsons would say,"It's way out ahead of nothin'".