Teardrop calculation

[David Leikvold]

"if a teardrop is the perfect aerodynamic shape, why are drop tanks not shaped this way?". The original design priorities were very different. The drop tanks were designed to extend the range of (usually) fighter aircraft. Typically in WW11 they would leave England with enough fuel on board to escort bombers all the way to Germany and back, with time and fuel to fight if they had to. When contact was made with the enemy the tanks would be dropped and the aircraft still had full wing tanks, which was more than enough to make it back to base in England, but not enough for the round trip. The drop tanks were still slick but didn't need to aero perfect because with tanks on board the fighters only needed to fly as slow as the bombers so the capacity was more important than the shape. This idea was it until mid air refuelling became a reality.
We, on the other hand, need a belly tank to fit a driver and an engine and everything else, all very different priorities to the original design.

[Rob]

Thanks Dave,

I knew the original intent and modus operandi, I was more curious as to the derivation of the actual shape, particularly as it seems to be almost generic regardless of volume.

From what I've seen, the tanks used on jets are even more slender than the prop versions which makes me think reducing frontal area is more important to minimising drag than a less than perfect aerodynamic profile.

Cheers
Rob

[David Leikvold]

I knew you would but some of our readers may need more. Your point about jet tanks is very valid, the trade off between frontal area and pure shape really matters as speed increases. For our purposes there must come point at which frontal area is more important. The fastest streamliners look nothing like our classic 0.04 tear drop.

[nitro-nige]

it ain't long enough for a V8 AND a gearbox .......

Jess Doc I don't think you're trying hard enough.

Seriously though have you got any pix of your car that show the drivetrain packaging?

[Dr Goggles]

rear plate of gearbox , tailshaft, there is an inch and a half of tube ....

[Lynchy]

Good to see you still have a tailshaft loop in there!

[grumm441]

it ain't long enough for a V8 AND a gearbox .......

Jess Doc I don't think you're trying hard enough. :wink:

Seriously though have you got any pix of your car that show the drivetrain packaging?

Nitro
It ain't long enough for V8 and a gearbox
G

[Rob]

Nitro
It ain't long enough for V8 and a gearbox
G

Not even with a trans axle doc? Just a thought.

Rob

[grumm441]

Nitro
It ain't long enough for V8 and a gearbox
G

Not even with a trans axle doc? Just a thought.

Rob

Rob
It would work with a transaxle
Possibly, Audi, Porsche or Subaru, however, none of these items are really within the Jarman-Stewart budget at this time, and we would still have some issues with final drive ratios and an adaptor for said transaxle.
Then we would need V8 that would get us in a class where a record is attainable with the very limited budget .
G

[Rob]

Rob
It would work with a transaxle
Possibly, Audi, Porsche or Subaru, however, none of these items are really within the Jarman-Stewart budget at this time, and we would still have some issues with final drive ratios and an adaptor for said transaxle.
Then we would need V8 that would get us in a class where a record is attainable with the very limited budget .
G

Rome wasn't built in a day. Keep playing with the V6 whilst asking around. Something may just fall in your lap. I've seen a highly modified P76 run through a Kombi transaxle so they too may be a possible but I hear you RE the ratios.

'Twas just a thought.

Cheers,
Rob

[Dr Goggles]

Wayne Mumford and Russell Mack's "Waza-Vudu" runs a VW trans-axle.
However , taking a rational look at this argument , what are we trying to achieve.

We are running in E class, we could run a 253...we could move up a class...thing is we're happy where we are, the motors are cheap and despite the doomsayers they'll do for now .....What is the argument for a V8?

As for gearboxes, in light of what I just said , sure, we could use a transaxle, CV's, lspend a heap of money getting another final drive ratio , a million parts........gettin' the picture?

We've got an Aussie gearbox and a BW rear end, cheap ,simple, available and have a low final drive........from where I'm standing it's a no brainer.....feel free to point out the weakness in this argument

Going back to the beginning of this thread. If your aero is good you need less power, you can use cheaper parts, more readily available parts......aaaaaaaaaaaaaaaand, go fast........

It's called the KISS principle

[nitro-nige]

In regards to going up and down a class.
The Buick V6 came out has a 3 litre, so that would take you to F class.
If you get the 4.1 litre block you can bore and stoke to 274ci. So that it'd get you up to D class.

I reckon you're onto a good thing.

If you did wanna go V8 I'd look at how the Formula SAE cars do the diff and gearbox. They seem quite short in the rear which would allow for a longer motor.

[Rob]

No argument from me either, I was just responding to Grumm's comment.

Cheap and plentiful works for me in all things perhaps except women...

Cheers,
Rob

[Dr Goggles]

Jack Dolan who built the motors for Vesco's bike liners and has owned many Bonneville records gave us some great advice on the build of the tank, he also has some pretty firm opinions on building motors for landspeed racing.He is still running cars at Bonneville and said

" everyone is obsessed with getting more out of the motor they've got, not many people have the wits to DE-STROKE what they have...think about it"....

he has an RX7 with a Buick V6 in F class....he'll talk all day about the benefits of undersquare motors for LSR, lower piston speed....high revs.

If we were to go for a V8 it'd be without a gearbox, that's do-able, but it's a way down the track....we've got four classes and a quad cam motor( )to muck around with first.....

anyway, this thread was about aero.

[nitro-nige]

My vote would be for a flat bottom.
Cars like poteet & main speed demon look like a good design.



BUT according to the first post a half teardrop has a higher drag co-efficient.
To the bat cave, I mean wind tunnel.