Project Extended Pop-Top Aerodynamic Camper Shell ('99 Tacoma)

[ron]

so was the trip with the foam topper on the truck? 34mpg at what speed, I cant get my toy tec over 23.3 with smooth lexan wheel covers short trip to work and back. Im building one.

[a8ksh4]

That was without the foam top. There was lots of and down (mountain roads), so I could do a lot of engine off coasting and long slow engine braking just controlling speed. That was mostly 15-20mph on the dirt and 40-55mph on paved road. I followed (kept up with) a friend going out to his property last night and only got 22mpg.

What model of Toyota do you have? I don't think that the 22R motors get the same economy as the later 2RZ.

[ron]

its a 2.4L I-4 not sure of the # In an extra cab automatic techoma 2003

[bobo333]

wow great work on the cap so far, that foam look so easy to work with and able to make much nicer shapes than wood or metal, i think if i ever redo mine it will be in foam

keep it up

[CH1cruisin]

ChazinMT. You may have a good idea there. In the early 50s (or thereabouts), both International Pickups and Buick had hoods that could be opened from either side so there is some existing designs out there that could be found and studied.

George

[gone7]

Very nice project, and practical too.

I am wondering about your goals with regard to aerodynamics. It would seem prudent to consider lowering the vehicle or creating proper air-direction techniques (particularly around the wheels) to keep air-flow controlled and released from the vehicle as it moves along.

Which brings me to the issue of the bed area. Except for your particular desires, one does not need to worry about the height of the back portion as long as it is no higher than the cab, because the cab has already cut thru the air in that area. The only concern is where to begin the taper for proper air release after that deflection.

One must also consider the effects of tapering from the sides in helping the overall air-control. (Will that be done within the lenght of the bed or after?)

Finally, with regard to aerodynamics, it appears clear that the frontal area means more than just about anything else. That is where the "push" is, and I believe that push is more difficult than release.

Thanks, and keep up the great work.

[a8ksh4]

Originally Posted by ron

its a 2.4L I-4 not sure of the # In an extra cab automatic techoma 2003

I wonder if most of the difference is from the extended cab (I'm jealous) or the auto trans.


@ Varn - That thing's awesome, however eccentric!

Originally Posted by CH1cruisin

ChazinMT. You may have a good idea there. In the early 50s (or thereabouts), both International Pickups and Buick had hoods that could be opened from either side so there is some existing designs out there that could be found and studied.

George

What's that in reference to?


@Acev - My understanding of doing the curved back (camback/boattail), as opposed to a straight back shell, is that is reduces the turbulence behind the vehicle. I had a regular shell on for a while and it cost me ~4mpg.

It's harder to make changes to the front since I need to see out of the windshield. I'd like to lower it, but it seems like whenever I make big changes to my vehicles (like lowering suspension), I end up regretting it, and I'm off-road often enough that I want to keep the ride height where it is. I do plan on building some kind of air dam/grill block to address the front aero.

I agree that curving the sides in would be a good thing, but I didn't account for it originally in the design of the shell, so I'm a little reluctant to go back and rework it to allow a side taper past the end of the bed. It's a possibility though. Do you think it would make much difference tapering the sides of the last 18" of the bed and shell?


The coast-down testing is going to have to wait until next week... not enough time in the day this week. I'm going to go by TAP plastics tomorrow after work and pick up enough materials to do some testing... might have some good stuff to post after that. I want to measure thicknesses of different numbers of layers of glass and figure out the cure times for the resin I'll be using when I finally cover this thing.

[MetroMPG]

Do you think it would make much difference tapering the sides of the last 18" of the bed and shell?

So as long as you keep attached flow, go for it! The impact you can gain from re-working that last 18" won't be enormous, but if you haven't locked in the design, why not?

[t vago]

Wow! Take a sabbatical from Ecomodder.com, and all sorts of new things appear.

It's nice to see yet another person using this FoamulaR stuff. I have an aerocap made out of this stuff too, but unlike yours, mine just bolts down to the existing tonneau cover rails. Good for my purposes, but probably not for what you want to do.

The Makings of a Pickup Aerocap: T Vago’s Dakota

My thoughts of side tapering are probably not "orthodox," as I have pretty much figured out they may not be as good as what would be expected. My theory about this idea is that the aerocap ought to become progressively more and more like a chord. This should serve to minimize any power-robbing vortices that would form on the rear of your truck. My version 2 cap currently nets me about 10% savings in fuel economy, but I think that I could push the savings up to around 13% or so by replacing the tapers with a more chord-like cap.

[ron]

a proper angled side taper per the template should make a diff. in mpg from what i've read, but you can always finish as is or take some away later