AZ911

The Yellow Bird had a tail here is a pic. It also had close to stock suspension to still handel at 200+mph

Noel

A tail will also help your car to run cooler at highway speeds or above due to creating a high pressure zone where the air is fed into the engine bay, which is a low pressure zone on a tailless car. I noticed this when I went to a show this summer and switched back to the non-tail lid. Temps were up.

Also, the difference on the track is significant.

BTW, I have a 1976 turbo tail on my car.

Noel

Martin S.

The Weissach tail in conjunction with the 3.0 Turbo front chin spoiler works wonders at the track and on the road in cross winds. One trip around a track with a high speed sweeper of over 100 mph, with and without a tail...you'll go for a tail every time.

The Duck Tail is simply not enough...hence Porsche brought out the bigger tail for the first Turbo cars.

Some non-scientific reasearch determined that the 964/993 moveable tail had about the same effect as a Duck Tail, ergo, there was lift on the back of the car at speed. The greater the lift, the lighter the car...fill in the blanks.

JackOlsen

Actually, the ducktail was discontinued because of safety concerns in Germany (odd as it might sound, it was considered a hazard to pedestrians). It is ultimately not as effective as the 3.0 Turbo tail. But the Turbo tail has a detrimental effect on drag, whereas the ducktail (like the dimples on a golf ball) actually improves the car's coefficient of drag.

In other words, a ducktail will do most of the work of a 3.0 Turbo tail (maybe a ten pound difference, at 90 mph), but -- unlike the 3.0 Turbo tail -- won't slow you down on the straights. It will actually make you slightly faster.

The 3.3 Turbo tail was better, in terms of downforce (but still bad, in terms of drag). And still: none of the pre-964 tails (Turbo or otherwise) did anything more than reduce some of the lift generated by the car at high speeds. It was the 3.8 RS tail that finally had a big enough effect to create actual net downforce. Add a big wing to the 3.8 RS tail, and you're even further ahead of the game (and check out a Porsche club race, with all the monster wings on 3.8 RS tails to see what the most popular solution is).

The 964 electric spoiler is difficult to directly compare to the ducktail because the overall aerodynamics of the 911 were dramatically improved with the 964 (and later with the 993 and 996) body design. The 964 and later bodies didn't need as much spoiler for the same net effect as the pre-89 models. Even when Porsche put a fixed wing on a post-89 911, it was less dramatic (but more effective) than the old Turbo tails.

hoffman912

personally, i think the cars look best in their natural state.. if it came with out a tail LEAVE IT. if it came with a tail.. keep a tail on. the designers at zuffenhausen knew what they were doing.

ever see a 912 or early 911 with a whale tail? not a pretty site.

on the other hand if youre doing track events.. go for it. but keep in mind, you need the corrisponding front spoiler to counter balance the effect from the rear spoiler.

hoffman912

by the way.. there is a really interesting 911 and porsche world article i have from about 3 years back, called 'A Trick Of the Tail'. it discuses the birth, evolution, science, and technological break throughs by porsche and their front and rear spoilers since they started putting them on their 911s in 73. amazing article everyone thinking about a spoiler should really read and consider.

r911

The 964 electric spoiler is difficult to directly compare to the ducktail because the overall aerodynamics of the 911 were dramatically improved with the 964

Jack, I think you need to drive over to the Skunk works and ask to use their wind tunnel (the low speed one)....

Harry, What's the chance of that article getting posted? Or do they sell back issues? do you recall which issue it was in?

JackOlsen

I'd love to spend some time with a wind tunnel. I would bet my coefficient of drag is terrible, probably in the .44 neighborhood.

Harry, do you have the ability to scan the old 911&PW article?

hoffman912

i indeed have it scanned. im just a little worried about posting it here fro the world to see and pissing off john d and phil raby (the publisher of 911 & p w), who happens to post frequently on the 964 board. its not like its a new article though.. was from 00 or 01.. but i believe back issues can be bought.. (sorry im a journalism major and realize coppyrights are a big issue)

ok found it!! A Trick of the tail 911 and porsche world No. 88, July 2001, pgs 74-82.
written by Philip Raby.

ok, i am sending a PM to Mr. Raby, requesting permission to post this article, in part or full on here. hopfully i will have a response by morning, and if so, will have it posted by the afternoon, and if not then, definitly tomarrow night after 11 or so.

JackOlsen

I would say it falls under fair use, personally (and I write for a living).

hoffman912

ok, i got permission from Phil to post the article. (by the way, please excuse the poor quality of my scanner). However, he only has the copyright to the text, and not the photos, therefore all photo's had to be removed. there are alot of great photo's in this article, and i highly suggest ordering the back issue so you can see all of the photo's and daigrams, as they really describe and illustrate each point of the different spoilers magnificently, as well as how they work. you can order a back issue from http://www.chpltd.com/911_porsche_world/index.html

btw, a thank you to Phil for allowing me to post this.

A Trick of the tail 911 and porsche world No. 88, July 2001, pgs 74-82.
written by Philip Raby.

hoffman912

Adrian

I would like to hear the story of one of these rear and front spoiler installations on a 911SC for my book. I have a section called DIY and I would hope that one owner would like to share his efforts with others. I need a brief write up and good photos through the process.
Ciao,
Adrian
964C4

anh911

Has anyone seen any info on using a diffuser under the rear of the car? My understanding is that a large part of the lift comes from under car turbulence.

A4_Pilot

Following on from what Jack Olsen was saying (by the way I saw your car the other day and it looked fantastic!), it seems to me that the 'ducktail' is an evolution of the Kamm tails that were popular in the late 60s/early 70s.

Dr. Kamm discovered that a sharp up-tail actually reduced drag because aerodynamically it acted the same as a long cone extending horizontally from the rear of the car (creating a teardrop shape). This created a bullet shape that was aerodynamically very efficient and acted like a much longer streamlined body.

You can see examples of these 'Kamm' tails on the Aston Martin Development Project cars (DP215 et al) and the DB6, as well as the concurrent Ferrari 250LM, and 275 GTB and GTB/4 among others.

I believe these were discontinued by all companies because a 'sharp' edged tail formed out of the metal body work was considered hazardous to pedestrians as mentioned in the article posted by Harry Hoffman. At about the same time the infamous 'fan car' was demonstrating what underbody 'ground effects' could do to aerodynamics in Formula One, leading to the exotic underbody trays found on high-end sports cars today.

I hope this helps. Please contradict me if I'm wrong. Thanks --- Antoni