Author Topic: Teardrop bellytank downforce question  (Read 10674 times)

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Offline Brad54

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Teardrop bellytank downforce question
« on: August 25, 2012, 01:18:49 PM »
I've searched, and there's a lot of info on tear-drop belly tanks regarding ride height/flat-bottom/round bottom and airflow/down force.

I've got a question that I haven't found addressed:
With belly tanks, how much of an issue IS downforce? I realize it changes and becomes more of a factor the faster you go, which depends on the engine class you're running, and that this is an amazingly open-ended question...

-Brad

Offline SPARKY

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Re: Teardrop bellytank downforce question
« Reply #1 on: August 25, 2012, 01:38:59 PM »
In my opinion virtually none  you are going to have more lift than downforce
Miss LIBERTY,  changing T.K.I.  to noise, dust, rust, BLUE HATS & hopefully not scrap!!

"Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoiding danger is no safer in the long run than outright exposure. Life is either a daring adventure or nothing."   Helen Keller

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Offline Brad54

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Re: Teardrop bellytank downforce question
« Reply #2 on: August 25, 2012, 01:47:17 PM »
In my opinion virtually none  you are going to have more lift than downforce

I should have worded it oppositely. How much of an issue is LIFT, and how big a problem is NOT having enough downforce with a tanker?

-Brad


Offline kiwi belly tank

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Re: Teardrop bellytank downforce question
« Reply #3 on: August 25, 2012, 03:52:36 PM »
First of all, stop calling it a "tanker".
  Sid.

Offline panic

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Re: Teardrop bellytank downforce question
« Reply #4 on: August 25, 2012, 04:52:03 PM »
With a top/bottom symmetrical shape, and no way to limit air going under the body, air is always going to flow across the upper surface faster. Result: low pressure above = lift.
Should really do a search rather than just ask, but if the wheels are still open has anyone experimented with a front dam and skirts?

Offline SPARKY

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Re: Teardrop bellytank downforce question
« Reply #5 on: August 25, 2012, 04:57:30 PM »
my old lakesters nose was shaped like a V shaped air dam with a 1.5" spliter on it that and getting rid of 3" scrub radius helped stop the wandering
Miss LIBERTY,  changing T.K.I.  to noise, dust, rust, BLUE HATS & hopefully not scrap!!

"Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoiding danger is no safer in the long run than outright exposure. Life is either a daring adventure or nothing."   Helen Keller

We are going to explore the racing N words NITROUS & NITRO!

Offline Brad54

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Re: Teardrop bellytank downforce question
« Reply #6 on: August 25, 2012, 05:27:44 PM »
With a top/bottom symmetrical shape, and no way to limit air going under the body, air is always going to flow across the upper surface faster. Result: low pressure above = lift.
Should really do a search rather than just ask, but if the wheels are still open has anyone experimented with a front dam and skirts?
I did do a search. As I said.
I didn't see a direct answer to my question, as it specifically applies to tear-drop style belly tanks. (Is it okay if I call it a "belly tank?" I see that "tanker" is frowned upon...)
I was asking the guys who have experience with them what the lift and down force characteristics are with these specific vehicles.

I've read a bunch of opinions on flat-bottom versus round bottom, and how that's dovetailed in with ride height, but that isn't what I was looking for. Just looking for a little help and direction for my planning stages.

-Brad

Offline maguromic

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Re: Teardrop bellytank downforce question
« Reply #7 on: August 25, 2012, 06:00:32 PM »
If lift is a problem for your combination you could run a keel and a splitter like this lakester. But you would need some good data to optimize everything. Tony

“If you haven’t seen the future, you are not going fast enough”

Offline Dr Goggles

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Re: Teardrop bellytank downforce question
« Reply #8 on: August 25, 2012, 06:42:59 PM »
Don't get your tats in a tingle over it.

Tanks don't get airborne when they go tail first like many "sports cars " do. And, by the time you are going fast enough to do it, if you do ,you'll have a plate full of other concerns. The major one will be traction and how to transfer the huge amount of power you are making to the salt.................

You will find that the majority of those who weigh into the argument about tanks as "wings" see them as a two dimensional object because they drive cars with doors on them. Build it big enough to fit all your crap in it, build it heavy and if your spider senses tell you that there's more weight at the back than the front then stick a tail on it. By the time you've made the effort to get that far someone with more smarts than you will stick their head up and say " can I help with that?" and they may be just what you need.

This is just based on my experience of building one and seeing others run through the relentless hail of advicefire....some make it, god bless 'em, but many don't.

If you are taking on partners in this make sure they are up for the long-haul.


PS. That was a beautiful tank Tony, the splitter work was gorgeous.....in that pic though something is missing....

Few understand what I'm trying to do but they vastly outnumber those who understand why...................

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Offline Brad54

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Re: Teardrop bellytank downforce question
« Reply #9 on: August 25, 2012, 06:46:12 PM »
If lift is a problem for your combination you could run a keel and a splitter like this lakester. But you would need some good data to optimize everything. Tony



That's one of the vehicles that made me go down this thought trail.

-Brad

Offline Glen

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Re: Teardrop bellytank downforce question
« Reply #10 on: August 25, 2012, 07:04:32 PM »
Most of the early tanks had swing axles and caused spins. However a lot of them were very fast in the day and many lessons learned,the same problem occurred with rear engine modified roadsters and many crashed. Today both type vehicles have much better designs and handle very well. Good luck with your build.
Glen
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South West, Utah

Offline Jonny Hotnuts

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Re: Teardrop bellytank downforce question
« Reply #11 on: August 25, 2012, 07:06:48 PM »
With a symmetrical shape lift will be generated due to ground effect. With equal amount of air flow around all sides of the vehicle the pressure going under has the ground to 'push off of'.

IMO having the nose apex lower then center is ideal by decreasing the amount of air going under and increasing the amount over. This will balance the higher pressure going over with the lower pressure + ground effect will help make the vehicle aero neutral (no lift or df) and will make a more stable vehicle at any speed.

Good luck....


~JH
jonny_hotnuts@hotmail.com

"Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully."
*Andres Segovia
(when Im not working on the car, I am ususally playing classical guitar)

Offline Jonny Hotnuts

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Re: Teardrop bellytank downforce question
« Reply #12 on: August 25, 2012, 07:24:35 PM »
....oh, and on the other hand....

People that try and limit 100% of the air from going under the car end up creating a situation where high pressure is on the outside of the vehicle and low pressure is under. The problem is that there is no possible way to 'seal' the bottom of the car with the salt and the low pressure under the vehicle will try and equalize at any area that is the point of least resistance (likely the sides of the vehicle). The pressure trying to equalize generates significant drag (viscous drag) and turbulence along the lower sections.

~JH
jonny_hotnuts@hotmail.com

"Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully."
*Andres Segovia
(when Im not working on the car, I am ususally playing classical guitar)

Offline Tman

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Re: Teardrop bellytank downforce question
« Reply #13 on: August 25, 2012, 10:52:28 PM »
Brad, re-read Dr Goggles thread here and there is much discussion pertaining to your questions.

Offline Kiwi Paul

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Re: Teardrop bellytank downforce question
« Reply #14 on: August 25, 2012, 11:42:07 PM »
Brad, you may be overthinking this. Markley Bros and Johnson/Shipley went very fast with no aero mods to speak of. Jack Kelly`s tank was no slouch either. What do your plans entail? Blown KB of V4F?