Aeromod of a 1964 Saab 96

[JohnAh]

This is the result from last time I made a Frankenstein´s modification of a Saab 96. It´s nearly 20 years ago. (it´s the same car in both images)



I´m not a person of visual perfection but I do aim for a more sophisticated result this time! Here´s what I have for the moment:



The blue Saab is the 1964 two-stroker with "Fred Flintstone floor" and the red is the 1974 V4 four-stroker. After these photos I have cut of the front from both cars and the next step is to put the 1964 nose on the 1974 car. After that it´s time for the roofjob. The 1964 have smaller front and rear windows and looks much better in my opinion. After this I´m free to do whatever madness that comes to my mind!

Those who dares to see more of the ugly-saab i made 20 years ago can take a look here:
Fulsaaben, Snabelgalfen

[Superturnier]

Hey, I remember the Snabelgalf!!
I saw it on the Trafikmagazinet tv show maybe 20 years ago. I quess I still have a video tape somewhere of that tv show.

I think ecomodding of a Saab 96 is very interesting, since it is already has a bit "teardrop" shape. Actually I've been waiting to see somebody improving it's aerodynamics.

The V4 engine is also familiar to me, since it is originally a Ford engine and was used in the car model I have. "My old ford" has just 2 cylinders more.

I look forward to see how your project will continue. I sure understand that it will take time. I myself always have too little time and too much to do.

[aerohead]

Originally Posted by JohnAh

Concerning the kammback I have read different figures about how to design it properly but I´ve got the impression that a slope of maximum 20 degrees on each surface is a good start. In some places I have read that the teardrop-shape should continue for at least 3/4 of the length of a full teardrop. At other places I have read that the area of the flat end should not be more than 50% of the maximum projected frontal area of the entire car.

If this is a good route to follow we can easily look at the streets to se that few car manufacturers follow this recipie. I guess this can be explained by avreage people not knowing what difference it can make and that most people still would find such a shape too extreme to feel comfortable with.

If I look at the Volkswagen L1 concept car instead I find it almost perfectly following the recipies of Kamm with a nice diffuser. Since they have obviously tried hard to get a one litre concept car (1l/100km) I guess they couldn´t afford to cheat with the body shape just to make it look cool. What we see is probably the naked truth and that is what I will try to copy!

The 50% value is contextual in nature and has to do with model wind tunnel studies at FKFS,with Koenig-Fachsenfeld and Kamm involved.
*Their model was straight-sided,no camber,no tumblehome,no plan taper.
*At 100% boat tail,the model only achieved Cd 0.21.
*At 38%,Cd 0.25
*At 46%,Cd 0.24
*At 54%,Cd 0.24
*There was so much vorticity drag with their models you can see that continuing the tail all the way out would net them very little for their trouble.
*In contrast,Paul Jaray's 'pumpkin seed' model of 1921,which had body camber,tumblehome,plan taper,and generous edge radii achieved Cd 0.13 with a relatively steep aft-body slope of 26-degrees.
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*Fachsenfeld appreciated the low drag value of an extended tail and in his patent drawings you can see how he ended the 'rigid' portion of the car body at 50% (where it was going to strike the ground in an urban driving environment),then filled in the additional 'beneficial' portion of the tail with an inflatable 'extensible' boat-tailing device for use on the open road.
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Our cars have a chance to see coefficients of aerodynamic drag on the order of Cd 0.13-.12 with the long tail.It's up to the individual to determine what is 'practical' for their particular driving situation.

[JohnAh]

I´m trying hard to sober up and not start a heavy modification before i have the car running in standard shape. -It´s hard though...
When the car is street-ready I can make a cardboard prototype for the Kamm-back and meassure the difference in fuel consumption. I have a similar "longnose" V4 for family car but I don´t want to lower it´s "WAF" by strange mods. It´s better to wait until I have my personal experiment vehicle.

But a sober thinking doesn´t stop me from dreaming:

This looks really nice! The sloping back is 15 degrees and the final area is a lot less than 50% of the maximum projected area. One problem with this design is where (and if) to put the rear window(s). My dogs won´t like the size of what´s needed to get a proper view on a sunny day, but they will definitely like the extra space!

[JohnAh]

A little update and some thoughts:

Since the last update the blue 1964 have been cut to fragments and seized to exsist as a car. The 1974 body is stripped from doors, windows etc and I have welded the 1964 "shortnose" front to it. Then came the winter...
A cold garage means lot of time to think however!

I see three ways to proceed:

1: Put the car together as a functional vehicle just to get it out in the streets with minimum effort and continue my thinking for a later modification. Since the resulting car will be much the same as my everyday 96 V4 except for the 2-stroke engine and the short nose I don't expect a sensational experience. Some of the work will also have been for nothing when I later start modifying the body.

2: Stay with the original body and later make the aeromods as pure attachments (like a hitch-ball extension).

3: Go "all out" from start, or at least do something wild. Modifications are welded directly to the body. This is the most exciting alternative but I have to make it right and efficient. The front can be left in original shape to a later modification and I will concentrate on the rear end.

I've been playing with "The Template" and if that is to be followed the car will either have a very long tail or the roof needs a long extension forward covering the entire bonnet/hood. I don't like any of these alternatives so the question is how good or bad it can get if I just stretch out the tail about 1-1½ meters (3-5ft). I then see a risk for detached flow all over the roof due to the steep windscreen and sharp bend over to the roof.

I need to play some more with the idea of moving the rear window to replace the windscreen, but it seems like a good idea because it har nicely rounded corners that I hope vill reduce turbulence and low pressure along the door windows.

I've tried to attach three images based on the "longnose" 1970's V4 body.
Two of them show how "The Template" fits (or don't fit). On the thirs image is my idea of a front splitter/spoiler that follows the same line as the flat belly of the Saab. My idea is to stir up the airflow under the belly as little as possible and have most of the air compressed by the frontal area pushed to the sides and over the roof. -Is this a good or a bad idea?

If the ground clearence is raised a lot I guess more air could be allowed to flow under the belly without increasing the drag. If the body is lowered instead, any extra air would increase air velocity and increase drag. A well designed airdam/splitter would cure this i guess, but I have no idea for how to choose the best method.

Blocking off to much airflow under the car would give a low pressure behind the air dam, causing air from the sides to be sucked in under the belly behing the front wheels. I don´t want that at all since the lower sides of a Saab 96 are realy sharp.

[JohnAh]

Here´s a quick attempt to use a 1970's (larger than the 1960's) rear window as a windscreen. The windscreen on a 1964 is made of tempered glass so there´s no legal problem to use a rear window as windscreen on a 1960´s vehicle. The 1964 windscreen is also quite low so I don´t think a rear window will block off too much vision.

The car looks quite bizzarre now! All that´s missing is a bunch of little green men in silvery suits...

[elhigh]

Hi,
I grew up in a SAAB 96, a 1970 with the constantly balky overrunning clutch. I learned to drive in that thing, four-on-the-tree which made the driving examiner's eyebrows go up.

Your rear window as windshield idea looks...very strange. Not bad, just strange. I think a lot of the readers here will tell you that you're mostly filling up stagnant air space and not going to experience a big improvement, but if you've already got the plasma cutter fired up...

The tail treatment looks beautiful. Subscribed.

[JohnAh]

Your rear window as windshield idea looks...very strange. Not bad, just strange. I think a lot of the readers here will tell you that you're mostly filling up stagnant air space and not going to experience a big improvement

I guess it´s a common misstake to judge aerodynamics from a sideview only, or from any limited views you get from photos. I too guess there will be almost no aerodynamic improvement to the air flowing over the roof. What I hope (not...) will happen is that the softly roundes sides of the rear window will reduce turbulence/detachment of the air that otherwise travels around the A-pillars to the door windows.

A much less radical way to smoothen the A-pillars is to shave off the rain gutters but they still form quite sharp corners. When driving at highway speed the low pressure zone at the door windows can easily be felt by reaching out a hand around the mirror.
Except for the A-pillars forming a rather sharp corner, things probably get worse by the side in-sunk location compared to the roofline and A-pillars. It´s a big difference compared to a modern car but I may need to post some detail photos to make it clear to those who are not familiar with these cars.

Honeastly, I don´t like the UFO-look the car gets from the rear window windscreen. I actually hope that it´s not worth the effort but it feels like a rather good idea after taking care of the rear end properly.

[JohnAh]

The front fenders are another part of the car where I got stucked in my aerodynamic reflections. The Saab 96 have a narrow body with an even narrower track width. The front wheels are located deep into the fenders.

On a car with wheels flush to the fenders, putting on smooth hubcaps is probably all that needs to be done. (and can be done). With the weels deep into the fenders I guess a fenderskirt is the best solution, but since the front wheels move a lot, the skirts must be hinged. The Saab 96 fenders are also fully open below, but that´s an comparably easy thing to fix.


I have tried to learn more about the best way to treat the air between the car and the road. An airdam seems to be the standard solution but I don´t think this is the best approach for the Saab 96. From what I have understood, an airdam is actually a quick-n-dirty-fix for an ugly looking belly! The Saab 96 is almost as smooth as a baby butt so I guess there´s no reason to avoid air from getting under the car.

My amateur assessment is that it´s better to deflect air captured by the lower parts of the front to the sides than compressing it under the chin of the car. This is why I thought of a splitter instead of making a softly rounded chin. If I make the chin sharp without a splitter I guess this will create turbulence under the belly.

How would it be to have a thin and sharp horisontal splitter in exact level with a flat belly? How far needs a splitter to protrude to avoid too much leakage over it´s edge? -I´m perfectly happy with the babybutt belly but the car would look realy silly if it has to wear a bib too...

[JohnAh]

Here´s a nice view of a 1964 Saab 96 "shortnose": http://www.saabisti.fi/wp-content/up...6-1964-top.jpg

The car I´m building will look like it´s based on a 1964 "shortnose" but it´s actually based on a 1974 V4, and so are the photoshopped images I posted earlier. I find the "shortnose" way more attractive than the later models from 1965 on, and I believe the shortnose is also slightly more aerodynamic.

A problem with the shortnose is that the front actually ends abruptly where it meets the bumper. If you remove the bumper there will be nothing but an ugly hole behind it. The shortnose "chin" is also sharp and ugly, even worse than the later "longnose" V4.

On the other hand, this leaves a great opportunity for some creativity!