Quote:
Originally Posted by KamperBob
I'm a little confused here.
1. BigDave, I thought you had a 3/4-ton diesel. Am I confusing you with someone else?
2. Phil, Dave feels 17-deg slope is too steep but that's less than 22. Any comments on that?
I'm not sure if filled or open sides would be better. If you can compare both and report results, that would be awesome!
Thanks
KB
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KB,this is going to be all speculation on my part and here's how I'm looking at it.
If we place Dave's truck under the template and look at the slope of the tangent at the tailgate,we might find that,while short of Mair's 22-degree maximum angle,we're to 'soon' along the template line to support 17-degrees.
If you look at Mair's boattail in the archives,you'll notice that he doesn't hit 22-degrees until at least a full diameter ( 2-truck body heights ) behind the point of max. roofline camber.
So 17-degrees may be two 'fast.'
As far as the sides are concerned,I'm going out on a ledge.They should behave exactly like a roofline excepting that the flow is less energetic and cannot support as radical a divergence as the roof and even with a windtunnel,would require very careful integration so as not to introduce attached vortices where they 'blend' into the roof sides.
The other thing is the fact that Dave's will be an 'open' structure,something we don't have a lot of published data on.
I do have Ford's patent for their bi-wing spoiler and they go into the aerodynamics of it's performance.Even though their spoiler has 'open' architecture it can still develop some tasty bound-vortices which are capable of modifying the outer field flow in a beneficial manner.
I've found about a dozen cars which have used the 'multiple-rear-facing-step' backlight cover and it appears that they take the bound-vortex from the macro,to the micro level.
I have a very strong suspicion that Dave will see a benefit but I have no way to put any quanta with it.
When Lamborghini,Ferrari,Porsche and others adopt this technology as they have,you've got to figure that they did not arrive at the decision in a haphazard fashion.I've no crystal ball but I'm giving it my thumbs-up.
One upshot is that Dave will 'know' at some point and have something to report.