Aeromod of a 1964 Saab 96

[California98Civic]

I like the drawings. I do think that the aft angle on the boat tail could be more steep. Seems like it should be, when I think about "the template" so to speak. Others will know better.

BTW, what's the tool in the picture?

[aerohead]

Originally Posted by JohnAh

I'm not skilled with the pen but I played a little with a curvature-whatever (...it's called in english) just to get a hint of what my latest ideas would look like.

The first step is to create something like a station wagon out of an old trunk hatch so it can be detacheable. The upper part of the "station wagon adaptor" will be slightly larger than the rear window to straighten out the bent roofline a bit. Since it will cover the window entirely I don't have to remove the window, but since my large dog have complaints and I don't like the idea of double rear windowns I'll most likely remove it.

The station wagon adaptor will have an entirely flat surface in the rear end, with a small door and a window to make the trunk accessible from outside. The original rear lights will be left in place, all I need to to is to modify/extend the rear fenders to give a flat surface in level with the SW-adaptor.

This modification/attachment should give some Kamm-effect superior to the sofly rounded original 96 design. To really get to the extreme I can then build a second extension that is hinged to the roof of the first extension. This part will be like a fiberglass bucket, or even be a quite massive part with a core of expanded polystyrene. To make the car easier to park I can have a mechanism that allows me to raise the tail extension over the roof, exposing the rear window/door and making the car a lot shorter. If I need to use the hitchball or go somewhere were I can't have the tail at all, it is easily detachable, exposing the original rear lights fully. With the final extension in place, the original Saab rear lights will still be partly visible, mainly from the sides, marking the width of the car seen from straight behind.

The best thing is that I can do this crazy thing in two steps, making the project less complicated.

Here is Kamm's last project car,for the Battelle Institute,a modified DKW sedan.

[NeilBlanchard]

Originally Posted by California98Civic

BTW, what's the tool in the picture?

It's a french curve. There are several different versions that are used to get smooth irregular curves.

[JohnAh]

The "ears" on the DKW posted by Aerohead looks terribly silly. I guess they can improve stability in high speed but they must also incrase sidewind sensitivity. Saab may have been designed by aircraft people, but I have no intention to add rudders and fins.

Except for that, the DKW attachment is quite close to what I plan as a first step. if I remove the rear bumper I'll get two strong lower fixing points and I also plan to install a hitchball. By using a trunk hatch as the base for my kammback extension and combining this with the lower fixing points I'll hopefully get the whole thing stable enough to not need any higher fixing points at all. The small gap between the kb-extension and the car's body must be filled with a rubber seal or some long lasting duct tape, or my dogs will be soaking wet when it's raining...

[JohnAh]

The 1964 "short nose" 2-stroker project have not advanced a bit since my first post here, and I still have not made the slightest aeromod on my 1975 V4. (life has it't priorities) Fuel efficiency have however advanced a lot, as a result of improved driving skills only. The average consumption now seems to flatten out at around 4.6 litres/100km or 50 mpg (US) by extreme "Drive Without Brakes" and "Burn & Glide" with engine shut-off.

I have tried with 7-8% larger tires and noted a 1-2% improvement, but the negatives killed most of the joy. Larger tires should be equivalent to a 5:th gear and should reduce consumption much more, but I guess my driving techniques makes that marginal in comparison.

I think the only way to improve the numbers further, without replacing the stock engine, is to start experimenting with aeromods. A kammback boattail extension would probably make quite some difference, but it's probably also the aeromod with lowest WAF... (wife acceptance factor) I'm therefore thinking of starting with something less radical, an air dam/splitter for example.

The Saab 96 have a flat and smooth belly with few disturbing shapes. Even the engine compartement has a whole floor, except for a square hole just around the oil pan. The lower front edge is slightly rounded but ends with a sharp edge (seen from the side) that I guess will force som of the rammed air to rush below the car as turbulent flow.

Here's a photo of a slightly customized 96 V4 with the front bumper removed:


My idea is to direct all air hit by the frontal area sideways and above the car only, leaving whats below the body untouched. The plan is to make an air dam that drops vertically from just below the headlights, down to the level where it meets the horizontal floor-line. This should direct more air up and sideways instead of squeezing some of it under the car. Since an even sharper edge will probably increase turbulence under the car I will extend the floor-line into a splitter. Such an air dam/splitter will be quite high above the road compared to others.

Since the Saab 96 is unusually flat below, I don't think there would be any improvement by lowering the ride height. I believe it's better to leave the still air under the car than scooping it around.

If I can avoid pressure differences between the belly and the sides I hope the sharp edges between the doors and the floor isn't harmful. Something will offcourse happen around the tires, so perhaps some sort of skirt between front and rear wheels is a good investment anyway? Such a skirt could be made of thick rubber so it won't get damaged over speedbumps etc. Perhaps even a "diffuse skirt" made from a number of brushes/brooms in row can successfully fill this area up?

[JohnAh]

Trucks and busses sometimes have wheel arch brushes. Can that be a nice product for aeromodders in general, both as a wheel arch "filler", for side skirts and even front air dams?

[California98Civic]

I think on the sides brushes might be of some value, but not on the front where the head-on air collision will "brush" them aside, surely. On your tire experiments... the marginal gain might become more substantial if you offset the added weight of taller tires with lighter wheels. In city driving, or any acceleration/deceleration situation, such as on the highway doing "burn&glide, the added weight will limit the benefit of taller gearing. Go for narrower, lighter, taller, all at once. Also, did you calibrate your distance measurements? Taller tire/wheel combinations will make your odometer register less distance. Use a GPS to figure out a multiplier for the odometer readouts.

Nice car.

[elhigh]

I learned to drive in a 1970 SAAB 96, and I loved that quirky beast. I remember noticing, even then, the featureless, broad expanse of the underside of the car. There's almost nothing down there but the exhaust pipe. With a bit of spacers to hold it away you could add a bellypan to the car that would make it truly featureless, or else consider eliminating the muffler and have the exhaust exit at one of the front wheelwells.

That's a daft idea, I know - but I do remember that when the exhaust rotted out it didn't sound much different.

On a long trip from Virginia to Minnesota Dad reported the SAAB was turning in a solid 40mpg; 50 is damned good for modern cars, phenomenal in one that is 40 years old. I'd say you were doing very, very well.

[aerohead]

SAAB offered a splitter-type air dam on late production 96's which would get you on your way

[renault_megane_dci]

Where I work (automotive) it is said that a lower front helps the Cd of a car.
The side view of your car shows the opposite although it is not loaded.

That mod would make for a good WAF and should help aero.

What is the size of the rims ?

I seem to recall Citroen CX had flat stainless wheel covers that would not look too badly out of place (I guess they were 14").