Maximum angle for boat tail?

[bombloader]

Originally Posted by evolutionmovement

Part of the reason I want the fin is the visual link to vintage endurance cars and aircraft (hence also the sliding canopy), part to run a vertical taillight up it as the asymmetry should get more attention

Kinda cool then actually. I think its good when someone can make aero mods visually appealing. Probably see it more in production cars if engineers and the guys drawing the pictures talked more.

[evolutionmovement]

That's my plan. I went to school for industrial design and recognize the importance of appearances. If it costs me a little in drag to make it far more appealing to the average person, the sacrifice is worth it to get the idea of the importance of aerodynamics into the average person's head and show that aero-efficiency might mean different, but doesn't need to mean ugly. The few of us with "weird" or too radically different looking cars won't change an industry and a populace resistant to change, but something that's different, yet familiar and drastically efficient can slowly turn around the huge oil-tanker-with-a-weak-rudder that is the thinking of the populace. The fact that the car will be faster than stock on top of efficient will also help sell since, even if most people never use the power their cars have, they like the idea of it anyway. The only issue of practicality I'll have is being only a single seater as there's no way to fit 2 tandem, but the idea is to get people thinking. The other vehicles I was thinking that would allow the 2-seats, I don't think I could make look appealing enough without costing way too much in time and money which I could use to build a car from scratch instead.

My 3-wheel tadpole designs follow a similar principle in utilizing the familiar proportions of famous tail-dragger WWII fighters.

Sorry to go so far off topic.

[Cd]

Originally Posted by MetroMPG

A useful template is this image:




(Ironically, the EV1 is farthest from fitting the template, yet it's the most slippery production car built, at 0.195.)

I think the reason that the EV-1 looks like it has the 'wrong' angle to its' glass is that the sides taper in. As an example, look at the apparent angle to the slope of the Corvettes back glass from this angle :


And now look at the apparent angle on the Intrepid, which has barely any side taper at all :

[tomi_k]

Anyone have following article:

"Reduction of base drag by boat-tailed afterbodies in low speed flow" by WA Mair, 1969 ?

[freebeard]

My search engine of choice did not find it. All I have is this:

[aerohead]

Originally Posted by tomi_k

Anyone have following article:

"Reduction of base drag by boat-tailed afterbodies in low speed flow" by WA Mair, 1969 ?

Yep.

[tomi_k]

Aerohead : Possible to get it, please?

[aerohead]

freebeard's #75 (permalink) shows Mair's schematic.
NOTE: the drag curve values represent pressure drag only. The friction drag component has been removed.
Long ago I posted a 1991,full reconstruction of Mair's wind tunnel model, and total drag profile, as a function of truncation.
The model is a streamline body of revolution, similar to a 16%-thickness fuselage, with an overall length equal to 6.2- diameters, ogival nose section of 1.3-diameters, cylindrical section of 3.0-diameters, and boat-tail of 1.9-diameters.
The fully-boat-tailed body is Cd 0.066 in free air, at supercritical Reynolds number.
It's Cd 0.204 without the boat-tail.
Mair uses a zero-to-22-degree transition over the primary 52% of tail length, then holds a constant 22-degree downslope for the 48% remainder of the tail. ( Toyota has been using this transition profile for their Prius-II-through today's current model. McLAREN is using it on it's Speedtail. Among others.
It's been lost to the PhotoBucket kidnapping / ransom scheme.

[aerohead]

Originally Posted by tomi_k

Aerohead : Possible to get it, please?

I'm looking right at it. I lost all 770- images ( $ 770 in scan costs alone ) in my PhotoBucket account, so I don't have access to those anymore. I'll see what I can do.

[freebeard]

I lost all 770- images ( $ 770 in scan costs alone ) in my PhotoBucket account,

https://duckduckgo.com/?q=flat+bed+s...ng&ia=shopping

Canon Canoscan (I used to have one of these) are under $100.