Aerodynamic Streamlining Template: Part-C

[aerohead]

Here is a comparison drag table which might have value in plan-view streamlining contours.
Two of the profiles have particularly low 'signatures' with respect to the cylindrical form.
And you can see a bit of 'phantom tail' where one tail was rounded over like today's blimps,with little if any drag penalty.
Here's the link:
http://www.willswing.com/images/feat...on_600_690.jpg

[Xist]

[aerohead]

Originally Posted by botsapper

I'm sure I'm not the only one who view these 'aero' templates to be very narrow in their scope. The almost '2D' shapes are almost always tested and highly scrutinized with just straight head winds. Pragmatic 'optimal' forms will surely change when these shapes are evaluated with off-center cross winds. The relatively high & flat sides of some of these shapes will go through erratic yaw movements and have straight line instability. Wind tunnel researchers/junkies & especially HPV designers are always mindful of constantly changing cross winds' effect on their designs. I'd like to see wind tunnel smoke trails, tuft testing or CFD flow visualization art created by off-center sidewinds.

Many have questioned the crosswind stability of the 'pumpkin seed' half-body as embodied with the 'Template.'
GM worked on it in their tunnel with the Solaraycer in 1987.
In Goro Tamai's book he addressed crosswind stability of the 'flattened-torpedo' form.Tamai reported that zero lift or negative lift was easily achieved as a function of body inclination.
Crosswind stability was achieved by the use of a simple spine down the roof/aft-body centerline.
The light weight and large relative surface area of these solar racers required much consideration with respect to stability in storm fronts and proximity to the Australian land-trains.
'Normal' vehicle weights might render the issue moot.
Darko Technologies ought to be able to supply lift as well as drag data on the T-100 in September.We should have some hard numbers by then.
The 'seat-of-the-pants' stability meter registered 'stable',on the salt at 105-mph.She felt fine in crosswind at 108-mph in 2007 on the interstate.We've had very strong wind lately and 75-mph in 30-mph crosswind was just fine.
Having the low,slant-back,wrap-around nose and double low fins behind the rear tires (after Morelli,1978) seem to be the ticket to a good ride.

[freebeard]

Tamai ...Crosswind stability was achieved by the use of a simple spine down the roof/aft-body centerline.

In Permalink #31 of Introduction & Cross wind solutions to motorcycle Streamliners? there is dicussion of 'stall strips' which are central ribs on the nose of velomobiles to improve crosswind performance. They needn't be large.

Or maybe something like this?

[euromodder]

Originally Posted by freebeard

In Permalink #31 of Introduction & Cross wind solutions to motorcycle Streamliners? there is dicussion of 'stall strips' which are central ribs on the nose of velomobiles to improve crosswind performance. They needn't be large.

On velomobiles, the top cross section is nearly cylindrical, which is a really high drag shape when seen from the side.

As Aerohead's link shows once more, cylindrical shapes aft are to be avoided at all cost !

[aerohead]

from the 'Spirit of Ecomodder.com' trip to Darko Technologies wind tunnel,it looks like the 'Template' is doing okay.
A redo of the T-100s bed would allow the plan taper to begin behind the cab and the box section morphed into tumblehome and curvature to match the aeroshell.
It would be worth the effort.

[Xist]

Originally Posted by aerohead

from the 'Spirit of Ecomodder.com' trip to Darko Technologies wind tunnel,it looks like the 'Template' is doing okay.
A redo of the T-100s bed would allow the plan taper to begin behind the cab and the box section morphed into tumblehome and curvature to match the aeroshell.
It would be worth the effort.

That must be some great payback, it sounds like a great deal of work!

[aerohead]

Originally Posted by Xist

That must be some great payback, it sounds like a great deal of work!

Yes,and since I remain quite stupid when it comes to estimating how long it would take to complete any project,I'd be thinking of no less than a year to pull that off.
Used T-100 beds at boneyards are fetching $800-$1,000.
There's a damaged one locally that might go for less.
I've got a plywood skeleton of a full-scale aerobed on the Dodge D100.I'm not going to molest that.With enough in the center for plywood and drywall the side 'pods',above and below the bed floor leave all kinds of room for dedicated cubby holes and compartments otherwise un-utilized with conventional beds.Also,the spare tire has it's own 'closet' above the diffuser area which makes it easy to access.
Going below Cd 0.20 would be interesting.Kind of a Mercedes-Benz C-111,III of a pickup truck.

[Xist]

So, you will pie-cut another bed? I wondered about making the sides by getting a block of foam, bending it to shape, and fiberglassing it, although I wonder how well that would handle abuse compared to steel.

What is the widest thing that you have ever hauled in your truck? I was thinking that as long as your bed is four feet wide at the tail gate, you could accommodate a sheet of plywood and that should be wide enough for almost anything else.

[aerohead]

Originally Posted by Xist

So, you will pie-cut another bed? I wondered about making the sides by getting a block of foam, bending it to shape, and fiberglassing it, although I wonder how well that would handle abuse compared to steel.

What is the widest thing that you have ever hauled in your truck? I was thinking that as long as your bed is four feet wide at the tail gate, you could accommodate a sheet of plywood and that should be wide enough for almost anything else.

*For a more painless project
*I'd plasma cut away everything above floor level.
*I'd cut away as much plan-taper as the rear wheels would allow
*I'd fabricate a welded steel tube space frame which incorporated remnants of the tailgate perimeter which 'rolls' into the underside perimeter of the bedcover.
*Gussets would provide some triangulation strength.
*And cut down the tailgate.
*I'd foam panel within the spaceframe
*And glass the foam,providing a stressed skin.
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*Plywood and drywall is probably the largest items I've carried.
*For really large things I have an I-beam and chain-hoist I can back under and just lift off the bed cover if need be.