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Aerodynamics question: Building a '51 Chevrolet 3100

1K views 13 replies 7 participants last post by  boostedbowtie 
#1 ·
Hello,

I'm building a Chevrolet Pickup that will be in the 200mph range. We've chopped the roof and sectioned the hood to get it out of the wind a bit. My concern is actually the back. It's going to have a Prostock style wing but thinking the stock configured tailgate is going to create some serious vacuum. I also remember the GMC Syclone that ran at Bonneville years back had 1/2 of a tonneau cover vs a full for aerodynamics reasons.

Anyone have knowledge or experience with aero issues that could give me some direction or advice?

Thanks for any help.
 
#4 ·
Look at the Studebaker salt flats truck with the whole vehicle rake and large hood scoop that breaks the windshield profile up into smaller pieces.
The box will have a high pressure zone just aft of the cab that maybe could use a small dome to keep it from needing stays to remain in formation.
Bank's S10 uses nothing aft of the tailgate. In fact, every salt flats pickup uses nothing so there must be some rules that prevent aero devices back there.
There is a huge adverse pressure gradient at the sharp body break that needs to be improved.
Starting from the ground up:
  1. A rear diffuser to aid in slowing down underbody air to create higher static pressure to reduce the low pressure zone.
  2. A body extension that tapers back to a dull point. The simplest example is the the 4 flaps on the back of a 53 foot van.
  3. The usual PS style rear body extension with some wicker. This helps the air coming off the bed a bit before it enters the wake region behind the body.
  4. Or, do only #3 like Larry Larson who extended the bed a ways and just added more powah. You'll note he built up the the height of the box to shorten the rear window height and help with the whole body wedge effect.
  5. Don't forget a big chin spoiler to reduce/eliminate front end lift (when the fronts are still on the asphalt.)
In general, the huge wake zone behind the rear of the truck is what helps produce the most drag. Reducing the wake zone is the goal and is also the hardest thing to do when the ideal teardrop form is not practical.
Good luck.



 
#6 · (Edited)
Look at the Studebaker salt flats truck with the whole vehicle rake and large hood scoop that breaks the windshield profile up into smaller pieces.
The box will have a high pressure zone just aft of the cab that maybe could use a small dome to keep it from needing stays to remain in formation.
Bank's S10 uses nothing aft of the tailgate. In fact, every salt flats pickup uses nothing so there must be some rules that prevent aero devices back there.
There is a huge adverse pressure gradient at the sharp body break that needs to be improved.
Starting from the ground up:
  1. A rear diffuser to aid in slowing down underbody air to create higher static pressure to reduce the low pressure zone.
  2. A body extension that tapers back to a dull point. The simplest example is the the 4 flaps on the back of a 53 foot van.
  3. The usual PS style rear body extension with some wicker. This helps the air coming off the bed a bit before it enters the wake region behind the body.
  4. Or, do only #3 like Larry Larson who extended the bed a ways and just added more powah. You'll note he built up the the height of the box to shorten the rear window height and help with the whole body wedge effect.
  5. Don't forget a big chin spoiler to reduce/eliminate front end lift (when the fronts are still on the asphalt.)
In general, the huge wake zone behind the rear of the truck is what helps produce the most drag. Reducing the wake zone is the goal and is also the hardest thing to do when the ideal teardrop form is not practical.
Good luck.



Going to make what looks like a stock front bumper and make it into a splitter to keep the front down. This thing is going to have a full belly pan which is cool but if it gets air under it, it won't be pretty. Going to use shock stroke data to sneak up on it to see if it wants to lift. A 51 cab is pretty rounded, wonder if that will help the low pressure behind the cab?

A bunch of valid stuff to think about. Thanks!
 
#8 ·
.

Sounds way cool, just don't kill yourself!!!

There is or was a guy on here with a pick up running 200 ish.
It was bright red, maybe in the Michigan area?? Anyone know who that was and how to find him??
I bet he has it all worked out, and will save you a ton of dough & headaches??

Good luck. Keep posting as the build goes along!!


.
 
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#12 ·
Far from 200mph but you can see where the air hits the tonneau . I have a sheet of aluminum under it where the air hits it . And you can also see in this pic where the cover sucks up behind the cab . truck also has an aluminum strip under the air damn . Made a world of difference .

This truck is on a rail at 156mph , but also weighs 4600lbs . The weight helps a lot for sure .


Land vehicle Vehicle Car Pickup truck Truck
 
#13 ·
Far from 200mph but you can see where the air hits the tonneau . I have a sheet of aluminum under it where the air hits it . And you can also see in this pic where the cover sucks up behind the cab . truck also has an aluminum strip under the air damn . Made a world of difference .

This truck is on a rail at 156mph , but also weighs 4600lbs . The weight helps a lot for sure .

Wow! Cool picture! Thanks for posting that. That's a pretty killer truck you have there!

View attachment 115426
 
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