Hypothetical Situation: Drag Truck Aero Cap?
 

I was thinking of a hypothetical situation today. What if I were to build a street legal drag truck, and rather than putting a spoiler on it I used an aerocap that also functioned as a spoiler? Do you all think it would help the fuel mileage and rear downforce?

I know you are all probably against gas guzzling trucks and racing but thats why this is hypothetical :D

Well as it turns out you can have yer cake and eat it too. Read this and tell me if it does not say that you reduce lift by a lot, and reduce drag by a lot, together in one easy step. Just build a cap with an 8° slope. See page 85, then branch out from there.

This 7° cap would just help reduce the fairly large lift that is inherent to the design of a pickup, making it essentially aero neutral.

If you want to create some down force (a Negative Coefficient of Lift -Cl) without a bunch of drag, yer going to need to add something like this I suspect.

http://i43.tinypic.com/14j7136.jpg

And you get this. Dunno how legal it would be.

http://i41.tinypic.com/162ioz.jpg

You could take off the "Stinger" and have a real fuel saver here.

Now I imagine other factors would creep into the equation, such as just how powerful an engine are we talking here? Where do you risk breaking traction? How fast do you end up going at half track and end of run for either aero efficiency, or downforce to play a critical role? All these things would have to be fairly understood I think before deciding what to do.

hypothetical
 

It's one of those 'it depends' kind of situation.
Power-to-weight ratio tends to dominate in drag racing unless you're talking about Top-Fuel,where 300 mph is obviously impacted by drag reduction.
The 'aero' kit on my T-100 added 820-pounds over curb weight, and allowing for the weight addition and stops along the trip route,worked out as 40% mpg benefit.So your cap it certainly going to help your mileage.
As to drag racing,even though I was 300-pounds heavier than stock,I out-accelerated the stock pickup and reached a higher velocity as well,and this was on damp salt which was costing other normally-aspirated cars 13% in top speed.
So I think,that if you have the power,even in a 1/4-mile,that you'd probably outrun your present truck.

poetic
 

Love those words. :)

I might have to try making an aero cap for a S-10 or an even bigger more ambitious project of modifying a S10-blazer. Thanks for the input though!

You have to watch the size of that rear spoiler, my first one was overkill. I had to cut it down in half after a week.

The rear tiny lip of the funny cars is perhaps a little too tiny for your application. Perhaps start as high as my rear spoiler and cut it down if it's more down-force than you like.

Also says a front chin spoiler 6-inches from the ground will reduce front lift by 36%, but this will also add a little to the frontal area. Recommended on race cars and on vehicles operating on slippery roads - so they say.