Bus roof raise aero

[Keller]

I'm doing a bus build and I am raising the roof about 22"

Now the first image is what most people ha e been going to here lately. And leaving the back a strait up lift. I'm thinking I like the second strait up blunt raise for the front and will slope and transition the rear over my bed room. Or would sloping both front and rear be beneficial?

As I take it the rear would be much more important than the front. A blunt raise would alow my to mount a big screen TV above the driver head. But if its beneficial I could slope the front as well and live with a small screen.

Thoughts?

[oil pan 4]

How much are you going to drive it?

[Keller]

Quite a bit probably. This won't be a "tiny house" its an rv/tow rig ill be using at least once a month to pull my rock crawlers to offroad parks.

Just wondering if the strait up roof rasie would hurt me at all.

[freebeard]

Just wondering if the strait up roof raise would hurt me at all

Define hurt — 10mpg vs 11mpg?

A lot depends on the floor plan of the interior, but your first example has a saddle-shaped curve. The ideal is a bluff prow that transitions smoothly into center section. It's not really bad it's just pointless and robs interior space.

Make it like an Airstream or U-Haul trailer.

Since you posted in Aerodynamics note that the front is only 25-30% of the total drag.



Tow vehicle you say?

[Stubby79]

I'm no expert (hehe), but I'd assume a completely flat front end would just push all the air straight up, rather than guiding it over the roof or down the sides. Rounded transitions would make a lot of difference at speed. The larger the better.

[kach22i]

See the attached rough concept.

If this is for an RV, have you studied or given thought to gutting the raised floor system?

I'm not sure how all the working parts are organized under there besides dedicated luggage areas between the wheelbase, but it seems lowering the floor could be just as labor intensive as raising the roof, plus the "A" in CdA is the same or lower should you taper off the back as shown in concept sketch.

In between the wheels the lower half of the coach interior would be "U-shaped" in cross section but the rest of the time it should just be a rectangle.

Don't think of this as removing the floor, think of it as lowering the floor.

I'm guessing that you are running electrical and plumbing under there for your new layout, leave a service utility cavity but instead of 36" make it 12".

Drive shaft and exhaust pan tunnel raises will be the immovable fixtures to work around.

[Piotrsko]

Do you already have the bus? If not you may consider the round top bluebirds which generally went further between refuels than the flat nosed dittos that I drove.

[kach22i]

You might not be able to lower the floor as much as I was wondering about.

See attached image.

https://www.pinterest.com/pin/356488126734879948/

Maybe there is wasted room in there anyway?

Flat floor?

Minimization of wheel arches in passenger compartment?

[Piotrsko]

There might be as much as a foot of suspension travel you can ignore because youre not dividing time between preschool and high school load weights.

[freebeard]

Originally Posted by Stubby79

I'm no expert (hehe), but I'd assume a completely flat front end would just push all the air straight up, rather than guiding it over the roof or down the sides.

Nor I (I just parrot back what I've heard here) but I'd wager that an air (particle/voxel) is going to the nearest edge, there's twice as much sides as top and the bottom will exhibit vena contracta.

No need to correct kach22i, he did himself. I'd strongly consider shortening the roof to leave a back porch.