Does front matter or just the tail?

[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.

[kach22i]

Generalizations can be dangerous, perhaps citing for example two pick up trucks each fitted with bed aero-caps against each other would be one such example.

Assuming the beds were fleet style and not side-step or sport-step and the frontal areas and ground clearances the same, then a comparison of the front cabs/headlights/fenders could be taken into account.

Real life side winds may also be an interesting factor verses traditional Cd and frontal areas alone.

[stillsearching]

Well i'm wanting to assume that the sides are about the same, frontal area about the same and similar... i'm just wondering whether it's better for the air to just take one big jump out of the way (some of the 'teardrop' looks have somewhat blunt faces sometimes) or if taking several steps to get there makes any difference for instance.

It's most relevant to research i'm wanting to do to haul stuff - modern cars are pretty smooth and are already made to be aero. Things like pickups, vans, and even larger stuff like semi trucks are not until very recently and could use some serious improvement. The generalizations for boattails, underpans and such seem to apply pretty well for the rears and underside I mean, does anything approach generalizations for the front end? (other than send the air to the sides on a tall vehicle because it doesnt' have as far to go vs going up for like a semi)

I'm wondering if the best shape would favor a fairly slow ramp (like the Airflow Bullettruck), a fairly sharp point (even if not likely to be obtained, similar to the tail treatment on the front), or if even fairly blunt/flat nosed is fine so long as the rear is set up to not leave much wake.

[ChazInMT]

It is like a 25/75 thing, the front can gain you 25% by optimizing it, and 75% of the gain potential can be had in the back. The reason is because even with a lousy front end, the air tends to build up and form it's own shape which is fairly decent. The back requires a careful shaping to keep air from forming pressure imbalances and to try to minimize pressure drag. Air does not form it's own shape their and improper shapes will upset the airflow which cannot be undone thus creating drag.

In a nutshell.

[Frank Lee]

Does front matter or just the tail?

Every guy has his own preferences...

[redpoint5]

Originally Posted by frank lee

every guy has his own preferences...

lol :d

[Dirtydeeds]

Interesting topic. I have a truck that could use a lot of help. Front and back. It's a cabover and the back has a roll up door though that I'm rather partial to.



Ideas?

[KamperBob]

Originally Posted by Dirtydeeds

Interesting topic. I have a truck that could use a lot of help. Front and back. It's a cabover and the back has a roll up door though that I'm rather partial to.



Ideas?

If interior cargo and rear door access are requirements then utility trumps aero so mods seem limited. Tuft testing the sides (and roof ideally) could reveal if bow splash is a problem. If so, fairing the front could yield returns by maintaining attached flow. (Why artificially thicken height or width to set up rear taper for a cleaner wake?) Collapsible boat tails becoming more popular with truckers seem like a pragmatic approach.

[Dirtydeeds]

Originally Posted by KamperBob

Collapsible boat tails becoming more popular with truckers seem like a pragmatic approach.

Had something like that in mind. I need the rear door - but I don't need to back up to loading docks.

[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.