Flat bottom /tunneling

[nebulous]

Gentlemen
I would like to findout about tunnel design ,and anti lift resulting from their use.
 I agree with blue about departure criteria,and effort to study it is important!
Thanks Jack Costella

[Glen]

Jack, look at the rear engine modified roadster that Chavin Emmons built I believe it has a tunnel and two years ago it spun for over 1/2 mile and stayed on the ground. It should be at Speed Week. The front engine roadster had some ground effects as well. Both cars very fast. See ya in a few days.
 

[mike mendoza]

Gentlemen
I would like to findout about tunnel design ,and anti lift resulting from their use.
 I agree with blue about departure criteria,and effort to study it is important!
Thanks Jack Costella

[dw230]

Thanks Mike

DW

[mike mendoza]

saw the underside of the elec. machine at Bville from the college: looked like an hourglass

[Rex Schimmer]

Jack,
Get a book called "Race Car Aerodynamics" by Joseph Katz and a similar named book by Simon McBeth, both provide good information related to tunnel design. Down force generated by tunnels is efficient but not free, it does require horse power.

Rex

[Jerry O]

Jack;   I worked about 15 years on several Indy car teams and IMSA GTP teams that use tunnels. These devices can create a lot of down force if designed proper. I think tunnels would work very good on your cars, because your cars ride very close to the ground and the lower the car the greater the down force.
We would set the ride height on a Indy car at the speedway to be at zero when it was at speed. We used skid plates on the bottom of the cars to keep from grinding the body away. The car would just skim the track surface. As any device used to add down force, aero balance was very important. I once built a oil pan using a similar design as a tunnel for a NASCAR team. As a test to show the team owner how effective it was, I placed the pan on a flat surface at the ride height the car would race at. I then had a large fan blow air under the pan and then ask the owner to try and lift the pan off the surface. He could not get the pan to move off the surface. So tunnels in the bottom of the car can be a great way to create down force. Feel free to contact me any time if you have any questions.  

Jerry O

[The wonderful One]

I know this is the same Jerry O. VERY SMART BUILDER. I remember when he got his liner picked apart last year by someone who did not like the way he mounted the cage. That is why he quit posting. To bad. He has a lot to offer. I hope he is back. He will be a help. The Wonderful One

[SPARKY]

I also hope he continues to share.

It isn't like we don't have a lot of opinions---  With all of the opinions and comments I encountered with my "UGLY Betty"  Ratical 

I learned to seek out the fair and level headed  SCTA inspectors and board members
--most are--get their opinions, then proceed.  Please remember the reason so many of us are attracted to LSR the CHALLANGES  (on and off the track)  and the FREEDOM to persue our ideas. 

A lot are like me, don't have a lifetime of being around race cars--we don't have the knowledge base pull from we make simple choice mistakes about the way we do things that can have big consequences

[ironwigwam]

Might be interesting to look at a Porsche 962? not sure if I remember the correct number, car model that shows the interuptors over the rear wheels with the diffuse angles at exit?

[interested bystander]

Anybody bothered to check out the Mormon Missle underbody, or from a couple yeas back, the Haas entry (BGS?) or the Eyebal Engineering Electric and the later Dempsey Electric from ten years ago?.

Those designs, by Gerald Arivett, had FRONT and REAR tunnels, and the cars run relatively low but not flat. The electric designs were tested in the now defunct Galcit wind tunnel.

 Bill Scott's quick and dirty built lakester had a large tunnel out the underside and when originally built by the Arivett Bros., had the exhaust dumping into it. (Like today's Formula One). BILL DIDN'T LIKE IT BECAUSE HE COULDN'T HEAR THE ENGINE!!???! There's a Harnick picture from a few years back at Elmo of Bill in the traps and a HUGE dirt cloud pouring outward and upward from the tunnel. Look it up!

The Missle used the Arivett/Haas molds slightly modified.

Don Ferguson owns the molds for all but the Eyeball car, which is an Arivett/Scott Knight aluminum body.

Besides the excellent book by Dr Katz, people overlook Forbes Aird's (interseting name!) book Aerodynamics for Sports and Racing cars.  Not math heavy and Aird explains aero   phenomena in understandable terms.
Read the dissertation on Drag Race parachutes - surprising in the conclusions drawn! He has an example or two and opinions on LandSpeed "chutes.


Incidentally Gerald has two 1/4 scale models in development for  wind tunnel testing currently.

[Jonny Hotnuts]

My concerns with using DF is that it works all fine and well with intended forward motion but as soon as the vehicle gets a little out of shape the forces that once held the vehicle down now radically change*.
(*resulting in just a loss in drive traction or other?)

A tunnel also creates an area under the vehicle for pressure to build under the vehicle with no ablity to bleed laterally and will act in reverse (as originally intended) if the vehicle was to spin....and very likely causing the vehicle to take flight.

Obviously this would be dependent on the vehicle and application.

[akk]

Once a very serious guy asked my opinion of his ground effects tunnel...it was not pretty...I thought it had very high potential drag...my comment was that they do not award down-force trophy's out here...lead works real good and is dragless...dragless down force....unless you are going over 350..

Akk 

[Anvil*]

My concerns with using DF is that it works all fine and well with intended forward motion but as soon as the vehicle gets a little out of shape the forces that once held the vehicle down now radically change*.
(*resulting in just a loss in drive traction or other?)

A tunnel also creates an area under the vehicle for pressure to build under the vehicle with no ability to bleed laterally and will act in reverse (as originally intended) if the vehicle was to spin....and very likely causing the vehicle to take flight.

Obviously this would be dependent on the vehicle and application.

Unlike a wing, a tunnel can work while traveling backwards. It would drop off dramatically then return and drop off (repeat) through a spin. If allowed a tunnel would be preferable to a wing, but like others have commented, after investigating options for adding ballast. And I agree the best compromise would be vehicle/application specific.

[debgeo]

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