https://ecomodder.com/forum/member-a...nes-engine.jpg
Quote:
Originally Posted by Piotrsko
That is an ugly section. How are you going to keep it from pitching nose up on the highway?
Let the discussion die, pretty much no one else understood the isssue so hashing out the finer points is pretty much an effort in futility.
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It's only one of many issues I flagged when doing the thought experiment.
This NACA 'Prius' ended up with:
* Height- 56.86"
* Body height- 49.3"
* Width- 70.2"
* Ground clearance- 7.56"
* Length- 230.45"
* Forebody = 34.37%-L
* Aft-body = 65.62%-L
( this is very 'ichtyoid', fishlike in proportions )
* Vergungsverhaltinisse = 3.067
* Af = approx. 25-ft-sq
* Tires are 195/ 60R17
* L/h= 4.05293
* L/h= 4.6744
* L/W= 3.28276
* Ave = 4.00336
* L/ sq-root of Af= approx. 3.84083
* Aspect ratio= 0.3046
* effective diameter ( D )= 113.72"
* effective fineness ratio= L/D= 2.0264
* theoretical minimum drag = Cd 0.0842-body only
* Cd 0.1344, with 1981 VW 'Flow-Body' wheels added
* The roofline contour is 'identical' to that of the GAC ENO. 146, at full-length, then strikes an inflexion point, at 180", then morphing into a Von Mises reflex camber, out to full length, at 230.45".
* In order to fit front and rear seat passengers, the seats had to be rotated by 5-degrees rear-slant, and dragged rearwards in order to allow below-feet, and headroom clearances.
* If this were a BEV, the skateboard would have to be mutilated, allowing shallow footwells for the four passengers, robbing torsional and buckling stiffness from the chassis.
* Allowing 40-degrees of vertical, forwards, outward vision for the driver, places straight-ahead view through a windshield glazing slant of 67-degrees, which might compromise vision due to refraction, plus interior cabin reflections onto the underside of the windshield.
* Both axles occur right at the 'potbelly' of the car.
* With standard wheels and tires, the wheelbase must be no further than 87.9", in order for the belly to strike the ground between axles, at minimum ground clearance.
* Pitching has been mentioned.
* Meeting pedestrian safety regulations might be an impossibility.
* There could be no hood/bonnet/ frunk, nor any engine or electronics access at the nose of the car.
* The ball of the SAE driver's foot is directly over the front axle.
* The steering wheels would intrude remarkably into the cabin space.
* The bodies rear 'knife- edge' would pose a life-threatening hazard to bicyclists.
* There's very little storage capacity inside the car.
* The center of gravity is higher.
* No published section data for the airfoil would be valid on account of it's aspect ratio. A completely un-known quantity ( see Abbott & Von Doenhoff / Robert T. Jones, NACA TN No. 1032, 1946.
* According to Lawrence K. Loftin, Jr., even dust adhering to a fingerprint would be enough to force the section's LBL to TBL, at any point ahead of it's engineered position of minimum pressure trigger. Chipped paint or bug-juice dried onto the leading edges increased Cd by 283%.
* At the same height, the AST-III produces Cd 0.128, before wheel fairings.
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Aerospace engineer, Matt Van Leeuwen's 'Sylph,' 3-wheeler, experienced a 2,100% drag increase compared to that of the NACA 66-Series, 6% thickness section he based the vehicle on.
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So far, I'm just not seeing any upside to laminar sections in ground proximity, Earth's turbulent boundary-layer, and 3-D flow regimes.
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PS
With such a low aspect ratio, there's little facility for dealing with edge vorticity.