Streamlining. More important, the front or the back?

[Grant-53]

Only if the gun turret is facing aft

[Cd]

In other words, is that Kamm-back helping even a teeeny bit, since the flow from the windshield is a total mess !

[Frank Lee]

Heh- the idjits put the roof on sideways.

[aerohead]

Originally Posted by Frank Lee

Yeah, but to answer the question, would an H1 and H3 with a bubble front end best .24 and .12?

It's a really good question and I'm gonna go back to 1922 to begin to answer it.
*Jaray's 'bubble-front' half-airship',
'pumpkin seed' car was measured at Cd 0.13 in the Zeppelin Work's wind tunnel by Klemperer,based on a streamline body of Cd 0.045.
*In 1933,Walter Lay did his model research,and using 'Hucho's' optimization of leading edges produced Cd 0.12 without the 'bubble nose,'on a longer 'car.'
*About 1938,Koenig-Fachsenfeld and Kamm duplicated Lay's model and measured an identical Cd 0.12.
*In the 1970s,when Hucho was at Volkswagen,they found that they could achieve essentially as low a drag as the 'ideal' nose on the Golf/Rabbit just by softening the leading edges of the car,any further rounding showed no drag reduction.
*The same thing happened with the Vanagon.A 'BUG' nose as on the Schl'o'r pill-bug car would show no drag reduction over what went into production.
----------------------------------------------------------------------
All of this is at zero-yaw.
-------------------------------------------------------------------------
Later in Hucho's book,back in the chapter on commercial vehicles,we find that the 'bubble-nose' demonstrates the lowest drag in crosswind conditions,which is statistically where we do most of our driving.
I believe that GM/VOLVO published that we could expect the equivalent of a 7-8 mph crosswind component on any given day of driving.
------------------------------------------------------------------------
To your question:
*The H-1 with bubble-nose would see closer to Cd 0.12 (of course it would need a belly pan and close up some of the major gaps 'n such)at zero-yaw.
*The H-3 with bubble-nose would see no appreciable drag reduction at zero- yaw.The wheels themselves would have to be better integrated into the body to go below 0.12,as we see with Honda's Dream solar race car series,NUNA,and this year's Cambridge University Eco-Racer (CUER) for examples.

[freebeard]

"If you don't have attached flow at the front, will improving the back matter?"

Overheard on the Salt*

"It isn't the hole you punch in the air, it's the hole you leave in the air"

*actually at a table outside a Mexican restaraunt in Wendover.

[viio]

Confession - I haven't read all of this thread, but I'm computing the OP request now.

[viio]

As requested, 10 foot long tear drops, 3 dimensional (round). Wind speed is 50 mph.



Let me know if you'd like any more.

By the way - thanks, my wife now thinks I'm making sex toys on the computer.

[sendler]

[QUOTE=viio;385657]10 foot long tear dropsQUOTE]

Thanks. Is there something on that screen shot which shows the total cd for each?

[sendler]

[QUOTE=sendler;385682]

Originally Posted by viio

10 foot long tear dropsQUOTE]

Thanks. Is there something on that screen shot which shows the total cd for each?

We actually don't even need to know the cd for each since they all have the same frontal area. Nor any actual value for the drag force. Just the relative drag force between the different shapes.

[Patrick]

Originally Posted by viio

As requested, 10 foot long tear drops, 3 dimensional (round). Wind speed is 50 mph.



Let me know if you'd like any more.

By the way - thanks, my wife now thinks I'm making sex toys on the computer.

The top one looks similar to the CAP 21 symmetrical airfoil for aerobatic planes: CAP 21 (TraCFoil) (cap21c-il)

It uses straight lines on both surfaces from about 20% chord on back.