Reverse Belly Tank Design

[FABRK8R]

...

This was an Electric Rig from the 70's.
http://www.gregwapling.com/hotrod/land-speed-racing-history/land-speed-racing-silver-eagle.html

At first I thought hey, run a spoiler & it would be good to lay down as far as possible without stretching the tank. Watched this video:
https://www.youtube.com/watch?v=ftq8jTQ8ANE
 & thought 2 1/2 times the drag on an XF/GL rig is bad.

How would you make this set up work?

[fordboy628]

How would you make this set up work?

Uhhhmmm, well, you can't.    Unless you have 2.6^3 bhp!!     There isn't much you can do to reduce 2.6 X drag, EXCEPT, not have it in the first place . . . . .  

This is why I keep telling guys NOT to try and re-invent something.

Being an "ornery old cuss" with your own ideas is one thing.    If the idea is a "poor" one, what does that make you?  

You can    forever and the speed remains the same:   0 mph

"Does paying attention to all the little details matter?   I dunno, but I think you should ask the guy who finishes second . . . . . ."
 
Fordboy

[ronnieroadster]

To make it work looks like it needs to be reversed. The air foil design is hard to beat if only we didnt need to add so much stuff inside to propel the vehicle this stuff would be so easy. And then everyone would be doing it.

[Stan Back]

I guess my memory's really slipping.

I'd always thought that Archie Ary of Colton built that car.  Jack Reed was his regular driver of the AA/FD when he wasn't "indisposed".

And the great thing was that the motor was incased in a "black box" -- borrowed from the Navy in Vallejo -- having something to do with a submarine.  And not to be inspected or opened.  And to be instantly returned upon the completion of the runs.

Might not be a word of truth in my story, but it's more fun than the corporate version.

Stan

[FABRK8R]

fb,

Thanks for the reality check   , there are those "rare" moments when the guy that throws the box away...


... when asked by the principal if the glass was half empty or half full, I told him it was either neither or both,... and then I got thrown out of his office! (true story)

 

Ronnie,

That was some of my thinking is packaging. Everything fits quite neatly in a rear engine set up with the tank the other way.

Stan,...

Interesting.



Question#2,

If applying the airfoil as intended in WWII,... would you or would you not flat the bottom? I got old man Newt & Bernoulli's take,... & the concept of lift I understand. what I am asking is if you leave the bottom curved: "do you compress the air below you when only inches from the ground(not in an unlimited space above below wind tunnel scenario), causing the very effect you are trying to avoid? Or does the airfoil adequately displace the air around the design,... mitigating this effect?"

http://www.flatfire.com/

[FABRK8R]

... & would stickin' your head out the top w/or w/out a canopy be higher drag then flipping the tank?

[Milwaukee Midget]

... when asked by the principal if the glass was half empty or half full, I told him it was either neither or both,... and then I got thrown out of his office! (true story)

It kinda depends on if you're pouring or drinking . . .

[FABRK8R]

 

[fordboy628]

... when asked by the principal if the glass was half empty or half full, I told him it was either neither or both,... and then I got thrown out of his office! (true story)

It kinda depends on if you're pouring or drinking . . .

Ahhhh,   doesn't the former need to be done first?     Then the latter can commence?

Just sayin'

[Skip Pipes]

I’ve also pondered the notion of reversing a belly tank. Seems to me orienting the larger diameter rearward (reversing the tank) makes sense for what we do. I’d also flatten out the bottom as the CAD suggests. There are examples of successful tanks with flattened bottoms (insert joke here). Also, reversing the tank pushes the CP rearward.  Weight will overcome lift. The problem I see is how to be clever when Stan challenges; you don’t know front from rear. 

Skip

[Sumner]

I’ve also pondered the notion of reversing a belly tank. Seems to me orienting the larger diameter rearward (reversing the tank) makes sense for what we do. ...

Think 'teardrop' shaped and which way it should be oriented to the air...



As Porkpie always says, "it isn't how you go into the air it is how you go out of it" (PP hope that was close  ).

The long taper on the rear if you can achieve it is going to let the air close back in at the back of the car with the least turbulence (drag).  If you have the rounded at the back you will have much more turbulence and a larger low pressure area.  The low pressure area is actually trying to suck the car backwards into it so you need more HP to stay out of it,

Sumner

[Stan Back]

I'd only guess that the military probably thought about the shapes a little before they bolted them onto a plane.

On another note -- it's been said that the tanks were mounted a radius below the wings or bodies to not cause any effect when jettisoned.  One motorcycle liner was constructed using this theory years ago but never had the funds for proper development.  Just a thought.

[jacksoni]

in addition, boundary layer changes increase to the rear, effectively increasing frontal area. Nature has had a few billion years to figure out what works best and you won't find any birds or fish or such that are bigger in the butt than the front.

[tortoise]

you won't find any birds or fish or such that are bigger in the butt than the front.

Look at some Google images of flying geese.

You will see some fairly successful streamliners, like Costella's.

If you ARE going to run a tank backwards, cutting off some of the back, (formerly front), Kamm-fashioned, might be a good idea.

So much of lakester drag is the wheels, that some decidedly non-optimal body shapes have set a bunch of records.

[jacksoni]

I am not disagreeing that there are successful cars with larger area in the rear. Microscopic total frontal area helps. But if you have a given frontal area to work with, either packaging of the contents (Costella) or the base skin defined ( a belly tank) the total aero package will favor putting the larger area in the front. There is no advantage to making a tiny front with a big rear compared to  the same total frontal area biased to the front.