Project, the Third - Now contains collabsible boat tails (1971 VW SuperBeetle)

[freebeard]

If you leave redwood bender-board out in the rain it gets as limp as a noodle.

I have a baja'd Beetle in the barn. With no fenders or rear hood, I can locate right off the back of the frame and produce pieces that will fit pretty much any Beetle. I can make a plywood form for one side that slips together like an egg crate, then dis-assembles so I can reverse it for the other side. Double tapered pieces and vacuum bagging.

But first there's a lot of serious thinking that needs to be done. I'm hoping aerohead drops by at some point.

[aerohead]

I went back to the thread "Chrysler Airflow aero-modded",permalink#1.There's a 3-view image of what they morphed onto the DeSoto Airflow test-mule.
The Cd dropped from around 0.51,to 0.244.
This is where my brain is right now with respect to the VW,since the Bug is quite similar to the Airflow.
If the rear fenders do not enclose the wheels they can be a bit more narrow and integrate easier into the stinger.
I'll keep turning it over in my mind.

[freebeard]

Thanks for your input.

The lower aeroform is a superellipse rather than a body of revolution to better fit the flat-sided wheel and tire. I just scaled it to bury the stock fender completely so there is probably some trimming that could be done there.

I've been thinking I could I could do some tuft testing. I could lash some [paper-faced] sheet styrofoam horizontally to the bike rack with my HD camcorder and see the result on a flat plane just below the air intake. I'm interested in how big a deck would need to be to allow the airflow to re-attach.

The other area I'm wondering about is the bottom. There is an opportunity to have a vertical slot air intake just before the rear wheel, if only to save fitting against the body and running board. And in the rear, any diffuser would have to start its 10° rise at the apron rather than the axle line, unless I remove the apron completely—which racers do for engine access. I doubt a 12" diffuser would do much.

BTW, since you're looking back to Chrysler in the 1930s, I'll mention:

Airflow Prototypes [last 3 pages]


And one of my favorite stories:
SIA Flashback – Mopar’s Star Cars

It almost happened that when I was in high school the used car lots were full of 5-cylinder radial front-wheel-drive cars. Wouldn't that have been something?

I'll keep turning it over in my mind.

Me too.

[aerohead]

I found a copy of that Hemmings in Fayetteville,Arkansas,which led to a 'Forty Years of Chrysler' book which had the side-view photo of the streamlined test mule.
This car was the original 'Kamm-back',as one iteration was a perfectly vertical truncation of the boat tail.
This modified Airflow,while too 'fast' in profile nonetheless had remarkably low drag for its day.It would be a candidate for museum safekeeping.
The back resembles the Beetle very much.

[freebeard]

I found a copy of this periodical:


Maybe a little of the Volkhart-Sagitta in there?

For context:


The way they handled the rear fender reminds me of the Bowlus Papoose:

[some_other_dave]

Originally Posted by freebeard

Back in the 50s, someone raced a Porsche that had the exhaust pipe on each side in the center of a high-bypass duct that pulled air through the engine. No mechanical fan. [citation needed]

For sprint races, individuals have done lots of different things for cooling over the years.

I think it was in the 60s that Porsche experimented with "Jet Cooling" or something like that. No fan; it used some odd effect of the exhaust or something. They dropped it because it was VERY VERY LOUD.

-soD

[aerohead]

Originally Posted by some_other_dave

For sprint races, individuals have done lots of different things for cooling over the years.

I think it was in the 60s that Porsche experimented with "Jet Cooling" or something like that. No fan; it used some odd effect of the exhaust or something. They dropped it because it was VERY VERY LOUD.

-soD

Any 'jet' of high-velocity will have low static pressure.
A stationary fluid exposed to the jet will be induced to flow towards it in an effort to achieve pressure equilibrium.
This goes back to Daniel Bernoulli and his venturi which the French perfume industry latched onto,which was also the premise for the carburetor and syphon-feed spray gun.
In HVAC work,some hydronic systems will use a forced-air venturi to induce airflow mixing across the heat-exchanger before discharge into the conditioned space.
Also,venturis can be used for refrigeration.A compressed air source is all that is needed.With no moving parts,a venturi can provide reliable cooling.One of my brothers did a stint in a steel mill,cutting yellow-hot steel as is moved from an extruder.He wore an aluminized 'spacesuit' which incorporated a venturi cooling system to keep his bacon from frying.
It is this venturi effect which causes the wingtip contrails on jets.As the wingtip pressure differentials spin up into the vortex,the core pressure falls to a vacuum.Upon passage,heat of compression is released as in an expansion valve in an air conditioner,moving the air below dewpoint,causing the water vapor to condense into visible droplets.

[freebeard]

Here are two more proposals. Aerohead likes Carl Breer's work at Chrysler, so the one in the back is a superelliptic stinger, with the fenders flappin' in the breeze, to mimic that design.

In the front is a boat-tail that's very aggresive in taper. But at the tip are vertical Coanda nozzles that have hot engine cooling air routed to them. It's a toss-up whether that would pull more air through the cooling system, or offer additional back pressure.

[some_other_dave]

You probably know this already, but just in case:

The Bug gets its cooling air from the top side of the motor. Either around the engine lid, or through the slots on the rear deck. Once the engine has warmed up the air, it is dumped under the car.

So, unless you have some significant ducting going on that isn't obvious from your image, your nozzles will be for incoming cooling air--not warm exhaust air.

-soD

[freebeard]

It never hurts to check.

These are works in progress. I do need to deal with air ingress. Two of the designs in #post343378 address this. In fact you could combine the second of those with the ducted design just above.

I lean toward harvesting the air as it spills over the drip rail and tries to form a vortex.

Have you seen the route air takes in the Type III Notchback? In just below the backlight as on a Beetle, but then out to the sides, back through the fenders (where the Squareback picks it up) down to a plenum in the rear valance, and then forward into the engine.

Just today I found this (Wikipedia, I think):
I'm looking at it and thinking about a rear partial belly pan. I have a trailer hitch that reaches from the torsion bar housing to the back bumper, it might make a good foundation. It's certainly heavy enough.