Does front matter or just the tail?

[Dirtydeeds]

Originally Posted by majestic

I wouldnt worry too much about the rear end, considering its use and necessary access.

The blunt front end shouldnt be too much of a problem if the corners are rounded enough, and they look reasonable. the truck is so long it should reattach anyways, but still youll want the least amount of separation.

First i would add a fairing on top to ensure flow transistions smoothly to the top and minimizes separation on the roof.

Then i would add skirts similar to those being installed on most bigrigs, coverage to the rear as depicted would be best.

Airdam at the bottom of the nose should help considerably as well, doesnt need to be real low, just enough to get the air flowing down the side of the newly installed skirts instead of the very dirty bottom.

Last i would try to close the gap between the cab and box. should be easy since the truck is all one piece.

KEWL!

That's about what I had in mind. I could probably cover the rear wheels, too. That section would merely need to be removable. I could put that part on a hinge - making it strong enough to be a table/work bench.

The space between the cab and the box would be tricky to match up. Not impossible though. The cab flips forward for service. Best if that part is attached to the box.

[brucepick]

Consider using a Coroplast panel to bridge the gap. Attach semi-permanently to the can and use some Velcro to attach it to the cargo body.

[aerohead]

Originally Posted by stillsearching

Having seen boattail after boattail, underpans, and all the rest, one question in my head that applies to alot of potential future aeromods is... is there some ideal front shape? How much contribution to total aero does the front end make assuming you've done everything possible to slick down the rest as much as possible?

For instance, would a flat nose cabover semi have any advantage or disadvantage vs a long nosed conventional semi. Would one type of pickup (like the new Fords which are pretty slick for coefficient of drag last I checked) have a big advantage over another type of pickup (like late 90's Dodge Rams which are as horrible as they come) assuming both have boattails, underpans, removing all the barbs you can that cause drag, closing off part of the grill, etc etc.

If you'll look at the graphics at #515 permalink (I think) of the Aerodynamic Streamlining Template Part-C thread you'll find a drag table for the streamline bodies of revolution.
In only one source,in 39-years have I seen one of these bodies analyzed for 'reverse-direction,'but Fachsenfeld did it.
So in answer to your question,if you designed by reversing the 'Template',with the pointed end forwards,you could get the drag to within 14% of the drag of the tail pointing backwards.
The big question is about 'caveats.'
'Blunt' noses are actually preferred for 'teardrops' traveling in the traditional orientation.
Fachsenfeld makes no mention as to whether or not you could take any liberties with a 'reverse-Template.
If you can't,then the extreme lay-back angle of the windshield would make forward vision impossible.
That's enough to scare me off.
If you do a 'traditional' teardrop half-body as with the 'Template' you've got a chance at Cd 0.10 as with HONDA's Dream 2 solar car of 1993.Their laminar-wing-based Dream of 1996 scored no lower Cd,although they did better with frontal area (although you cannot get in or out of the 'car' in a traditional manner,whereas you can with the 'Template' [see Bochum University's solar racer]).

[freebeard]

That's about what I had in mind. I could probably cover the rear wheels, too. That section would merely need to be removable. I could put that part on a hinge - making it strong enough to be a table/work bench.

I'm not sayin' forget everything else, but do that!

[stillsearching]

Originally Posted by aerohead

If you'll look at the graphics at #515 permalink (I think) of the Aerodynamic Streamlining Template Part-C thread you'll find a drag table for the streamline bodies of revolution.

I utterly and completely didn't understand a word of that but it sure sounded cool. : D


I guess in part my assumption or what I remember reading in the past seemed to indicate that as long as laminar flow was maintained it didn't matter too much. Some lumpy looking shapes could be had, with wierd things going on, but there wouldn't be much drag - for instance tumbles of air could be happening in the pickup bed behind a truck, but it was a localized occurance, and the air coming over the top of the cab just maintained a separation from the 'tumbling' spinning air, so that laminar flow was never broken.

I mention that because that's concerning things in the middle of the body - if I have a smooth front and a streamlined tail, there's still issues of say pickup-rear to trailer-front to be concerned about.


What I was wondering in specific though was like the Airflow Bullettruck has ALOT of work put into streamlining the front of it. A long sloped nose extension primarily. What i'm wondering is whether one could dispense entirely with that, use a flat nose semi, and just boattail the heck out of the rear of the trailer, and insure a good cab-to-trailer seal, to get better mileage.

[stillsearching]

Actually I better expand slightly because that might come off wrong. : P

Looking at table http://ecomodder.com/forum/attachmen...1&d=1247946422 i'm wondering what happens with basically a flat front, but the long soft tails. Like a cabover flat front semi given the whale tail treatment.

When you were talking about reversal of flow, do you mean something like the Streamlined Body (in that linked attachment) simply pointing forwards with a rounded bulbous tailend? Or something with the points going forward and backward? (no rounded anything) It's possible I wasn't clear that I wasn't seeking to reverse the whole streamliner template, just apply the same sharp point to the front as to the rear, like you might see in a ww2 droppable fuel tank. They don't have bulbous noses and I wondered why.

Is there an aerodynamic difference between "stairstepping" air out of the way (say the Streamlined Body in that attachment is, instead of one half circle in the front, say it was 3x as long in the front, where the long part of the nose moved 1/3 of the air out of the way, then the next 1/3, then the next 1/3... this to me is what the Airflow Bullettruck almost looks like, instead of a streamliner bulbous nose where it's stepping the air up out of the way up to the hood, then the cab top, then the trailer top, which I would think would be less efficient) But maybe it's not a huge difference because the front is only 25% of the drag/matters more in the tail..

[jere]

Originally Posted by majestic

I wouldnt worry too much about the rear end, considering its use and necessary access.

The blunt front end shouldnt be too much of a problem if the corners are rounded enough, and they look reasonable. the truck is so long it should reattach anyways, but still youll want the least amount of separation.

First i would add a fairing on top to ensure flow transistions smoothly to the top and minimizes separation on the roof.

Then i would add skirts similar to those being installed on most bigrigs, coverage to the rear as depicted would be best.

Airdam at the bottom of the nose should help considerably as well, doesnt need to be real low, just enough to get the air flowing down the side of the newly installed skirts instead of the very dirty bottom.

Last i would try to close the gap between the cab and box. should be easy since the truck is all one piece.

That is a good way to go That should help with handling also. I would skip coroplast and start with fiberglass at least for the larger areas. There is a lot more fluid being moved with larger vehicles coroplast wouldn't last too long. I have seen some larger rigs ( mostly from Canada) that have larger panels under the trailers that might transfer over well.

[freebeard]

I utterly and completely didn't understand a word of that but it sure sounded cool. : D

It essentially is a pointer to: http://ecomodder.com/forum/showthrea...tml#post362860. Aerohead doesn't do hyperlinks.

Some lumpy looking shapes could be had, with wierd things going on, but there wouldn't be much drag - for instance tumbles of air could be happening in the pickup bed behind a truck, but it was a localized occurance, and the air coming over the top of the cab just maintained a separation from the 'tumbling' spinning air, so that laminar flow was never broken.

Laminar flow adheres to the surface by definition. Once there is underlying turbulence it's no longer laminar. As for 'lumpy shapes' compare the M-B Boxfish or your typical porpoise to the Template, similar Cd but the 'lumps' are carefully considered.


The Template is seductive because it offers simplification, by ignoring necessary things like the driver's sight-lines, ingress/egress, &etc. A look at the racers at Bonneville Salt Flats suggests the pointy nose offers benefit above 300mph.

I would skip coroplast and start with fiberglass

Consider materials like Polymetal and MaxMetal, both have thin aluminum skins on a 3-6mm plastic core.

[Frank Lee]

What I was wondering in specific though was like the Airflow Bullettruck has ALOT of work put into streamlining the front of it. A long sloped nose extension primarily. What i'm wondering is whether one could dispense entirely with that, use a flat nose semi, and just boattail the heck out of the rear of the trailer, and insure a good cab-to-trailer seal, to get better mileage.

IMHO that long Bullet Truck nose is more of a hindrance than an asset. I think the aero could be just as low drag with a far blunter nose, and that long beak creates ground clearance and maneuverability issues.

[Xist]

Originally Posted by Frank Lee

IMHO that long Bullet Truck nose is more of a hindrance than an asset. I think the aero could be just as low drag with a far blunter nose, and that long beak creates ground clearance and maneuverability issues.

The nose seemed to work for what he needed it to, but I think that it would require even more creativity to make a good boat tail for a trailer. You might drive thousands of miles before needing to move it, but it will always be in the way.