And aerodynamics?

[oiseautempete]

it is good to continue to shrink the back of a car, whether at the roof or even the sidewalls, from 14 to 15 ° max continuously
After that it is sure that the back does not do it all, the proof with the school, but it contributes to it strongly (like the front wheel fairings apparently )

Hum, 14-15 ° it seems too much, see on a plane is rather to 8-10 °, incidentally it's good because a car with narrow ass is almost unusable (non-existent trunk, internal volume ridiculous) ..
But you can save a lot without changing the shape of the body just by optimizing: retro (replaced by cameras), elimination of body assembly slots, air intakes, extractor cooling air, fairing underbody, fairings of the rear wheels, etc ... besides it is about what Honda did on his Insight (the true one, that of 1999 ...)

[Ca]

The higher the speed, the smaller the angle must be, for our car at 130 km / h max it must be about 14 °.
I was talking turbulators previously, with them we can go up to 30 ° at least for cars, the turbulent flow clinging to the surface.
In the end, there are ways to do beautiful things with these little miracle machines.

[I Citro]

(Follow on the left the aero and aerodynamic lab of road vehicles)
http://inter.action.free.fr/

Welcome to oiseautempete So forum.
The level of your interventions and the links that you relay are fascinating.
I did not know inter.actions but the site is worth seeing.
I strongly recommend reading REFLECTIONS ON THE ENERGY OF ROAD VEHICLES (self-eco) in the section PUBLICATIONS.

[Other]

Hello

By dint of watching the cars pass in the streets I tell myself that they are all more aerodynamic in reverse than in forward

The aerodynamic ideal is roughly the shape of a 12.7 machine gun bullet, fine nose, maximum volume in the middle, narrowing backwards, ass abrupt rupture: and that's exactly what the current cars look like, with naturally the constraints of length ...
It is totally wrong to believe that the ideal form is that of a drop of water: it is more dictated by the force of gravity than by aerodynamics ...

Disagree for the ideal aerodynamic shapes
For having made several bonnet on the planes, for 200 speeds at 260kmh the overly sharp pointed hood are significantly less efficient than the rounded hoods with air intake carburetor motor extentioner, as well as propeller spacer to extentioner forward . The aerodynamic gains are more at the air outlet under the hood than at its front form, the hot air outlet of the engine must remain the rau desoudoud fuselage
the small details like the slits of fins and rudders, simply clogged with adhesive tape we won an extra 18kmh.
I am on the tests now of a freshly built airplane just change the angle of the fixed plane back have is going from 210kmh to 224kmh ..





Note the sheet placed under the hood to get the air under the fuselage, we also notice the slots in the fins and elevator depth.
Just before one's mouths
You have to make one change at a time, then a flight test, full ga zen landing, you have to start with the most important drag, then concentrate on the small drag, otherwise the gains are not measurable.
For the wheels we modify a single fairing and we see if the plane pulls on one side (for the wheels it is more the wheel leg junction with the carenage which is of importance that the carenage itself



Hood not very effective of this recent plane


Efficient rounded hood of this 140 Cessan1946


Aerodynamically this Quikie 2 is very refined with a motor derived from VW 2 liter it exceeds the 300kmh, a rapid acceleration in dive

[oiseautempete]

Disagree for the ideal aerodynamic shapes
For having made several bonnet on planes, for speeds of 200 to 260kmh the hood too sharp pointed are significantly less effective than the rounded hoods. Aerodynamic gains are more at the air outlet under the hood than has its shape before
the small details like the slits of fins and rudders, simply clogged with adhesive tape we won an extra 18kmh.

This is quite debatable: for an airplane the constraints are quite different because it is necessary to ensure the most laminar flow possible behind the propeller and a massive cowling coupled with a small propeller is very inefficient (I know a construction plane amateur with VW engine which was really catastrophic with its big original bonnet and which went very well with a thin bonnet), when I speak of thin bonnet, see the Michel Colomban MC 100 which hits 300km / h with 80cv ..., but a Thin hood requires positioning the cooling air inlet and intake vents very precisely in the overpressure areas of the hood, which makes it possible to make them 2-3x smaller (therefore with less drag) than on large hoods of old "rustic" planes. The flow under the hood is of course also very important because it conditions the efficiency of the cooling: car manufacturers are attached to it more and more.
The hot air that comes out of the extractor under the engine can never be laminar (there is the same kind of extractor on most cars equipped with a fairing under the engine), but indeed, the effects of Slot have a significant influence, very well known to glider pilots who always tape them so as not to degrade the finesse.
The aerodynamics of cars has a huge influence on consumption beyond 100km / h, which does not mean that it is negligible below ...
14 ° of slope on a car at 130km / h is far too much, no aerodynamically efficient car has such important values ​​(see for example the Honda Insight of 1999 or the GM EV1 which all have very soft vanishing lines (Same as the faired bikes that run at 40km / h ...), with the turbulators probably, but this kind of fragile and aggressive devices are not realistic on a car, fins well placed and much more robust are d advantage (see the tiny fin R16 TX whose efficiency was much surprised at the time ...).
But hey, we can spend hours on this subject as it is vast

[Ca]

The discreet but very efficient fin of the R16 TX plays exactly the role of turbulator, it prevents the re-circulations of air that would be as soon as the descent more pronounced of the tailgate if it was not present.

[oiseautempete]

The discreet but very efficient fin of the R16 TX plays exactly the role of turbulator, it prevents the re-circulations of air that would be as soon as the descent more pronounced of the tailgate if it was not present.

Uh, I would compare it to the wingtips of the wings of the ADAC planes, invented by Handley Page in the 20 years and magnified on the Fieseler Storch / Morane Criquet, whose purpose is not to create turbulence, but to guide the air nets in laminar mode to prevent their detachment of the profile ...
The turbulators, whose total drag is lower, are much more recent devices that result from bird watching, especially raptors ... but we are still very far from achieving the same efficiency as birds in all phases of flight ... (variable incidence, variable curvature, variable geometry, variable elongation, leading edge, wingtip and stall-less depression turbulators, etc.)

[Ca]

Uh, I would compare it to the wingtips of the wings of the ADAC planes, invented by Handley Page in the 20 years and magnified on the Fieseler Storch / Morane Criquet, whose purpose is not to create turbulence, but to guide the air nets in laminar mode to prevent their detachment of the profile ...

I think you have to confuse laminar and turbulent flow.
Very often, around the master couple occurs a transition from laminar flow to turbulent flow.
Look at the 11 page of this document:
http://inter.action.free.fr/publication ... nees-2.pdf
A simple illustration all argued is much more informative than me .
You can see on the internet that all owners of model aircraft cut an adhesive tape using sewing scissors (or something like that). They stick their ribbon at the level of the master couple of their wings, sometimes a little before, in order to make the flow of the air turbulent, a regime which delays very much the detachments.
For the R16 TX's fin, I'm pretty sure the airflow after it is turbulent.

[Other]

Hello
Interesting the PDF on page 13 the profile tapered ratio of 3 verifies in practice on certain aircraft (the fuselage etand long for reasons of stability couple on the back rudders) it is difficult to have this report, but in practice to the tests two models of aircraft with the same wing, the model side by side is faster than the tandem model despite its increased frontal surface
J3 and Piper J4 on the Aeronca Champion 7AC and the Champion Chief.
The DC3 builder the first DC2 prototype had a narrower fuselage by expanding it on the DC3 so it increased performance.

For the wing beaks the reason is differrent that for the vortex generators (small piece of metal or plastic that is glued on the upper surface of the sailes) the wing beak has long existed the BF109 had that it allowed a landing around 110 kmh.

Vortex Generator on Wing of Quickie 2


Spoiler profile on a Pegasary


Be cd'aile on Pegasaire unaccoupled automatic output


Junker planks, fins and flaps cleared from the wing this makes a STOL plane (160metre 2,10hp propeller engine)

[oiseautempete]

I think you have to confuse laminar and turbulent flow.

Given my aeronautical training, I know very well the difference, thank you ...
I think you are confusing "normal" turbulent flow and micro vortices created by turbulators: their effect is very different ...
The nozzles I am talking about make it possible to force the air streams to stick to the profile longer in laminar mode, moreover the ulm manufacturer ICP offers machines with turbulators and with nozzles: those with turbulators have less drag in configuration of normal flight are intended for their fast model, but much less powerful than the slats with the large angles (very low speed) of the true "STOL": it all depends on what one seeks ...