Class a motorhomes aerodynamics

[freebeard]

I'm losing the context. Are you thinking of something like a tail box with a drop leaf?

The fiberglass rods could store into tubes when not extended.

4ft extension would be 36ft overall and 11ft from the rear axle. Either wheely bars or a swiveling fifth wheel that can be raised and lowered.

[sregord]

I know I need to build a scale model. It may convince me that no extension is doable. I get back to my shop next month.
No argument that its a long ways back there from the drivers seat with even move wag, but...
When I see things like this quite often, hanging off the back of RVs
https://letsgoaero.com/blackbox-slid...losed-carrier/
It seems that +32" suspended a foot from the RV..(=44") is an exceptable extension... attach it high enough to provide the 10-degree SAE 'departure' angle. I'm just putting on a "roof" the shape of The Holy Template.

[sregord]

YIKES...well over 4 foot.

[freebeard]

That doesn't gain much. You want tper in plan and a square to round transition:


https://external-content.duckduckgo....5b1&ipo=images

[sregord]

No, the long boxy square on the skoolie does not. Shows only that an extension length is possible with an exceptable departure angle. I have no plan to go that long.

The geometry of the square to round transition is neat. molding in the curves of Moby's corners, and the Template's<22* top & sides & ~10* bottom will be a challenging fine tune. very 3D shaping.

an answer to your earlier question:"Are you thinking of something like a tail box with a drop leaf?" Yes...lets say 1st half of the square to round transition be ridged/attached to the rear of Moby. A later 2nd half could be a drop(or uplifted) leaf.

[j-c-c]

Originally Posted by freebeard

Center top: Vortex Strakes



Downforce burns fuel. Lift also burns fuel.

How does the "high momentum mudflap" do anything beneficial besides reduce spray?

[j-c-c]

Over in "The Lounge" forum I shared a bus conversion I am starting. Its a combo RV/internal race car hauler. Bus is 40' so I have enough internal space, but Florida allows 45' max overall length less safety devices (mirrors?), and has an exemption for additional, unrestricted I believe, additional length for "approved" aero devices. Not finding how anything what/how is approved, listed or specified, whether individually or by design or manufacturer or whatever.

I can design the car hauler part so tail end of race car sticks out the back maybe up to 4' ft, that would give an addition 4' internal living or storage space, I have the skill set to fabricate a Carbon Fiber/kevlar top hinged (functions as mini canopy) rear aero hollow tail, that would enclose the rear of the protruding race car, and be the width of the bus. It would be a partially cored CF build to get the needed rigidity for the large panel areas and be light to facilitate its manual lifting and locking in an open position when car is moved.

It would have to incorporate road lights and a tag, as in order to be aero all that equipment would need to be relocated, Can't see much gain here unless I get at least 5-6' extension, with a Kamm style tail (bus 96" wide, Car is 70"? wide @ 44" extension), meaning in 6' I could go from 96" width to say 56" in width which feels too much, and I need the state to consider it an aero device to get past the length exemption. Good thing IMO is the shape can be almost anything as it will be a lost foam mold one time design. My concern is the bang for buck regarding mpg. Or I can just make a simple reduced sized functional cover to primarily cover the rear of the race car, and don't relocate lights or tag. Most everything I need above is already on the shelf except the foam for molding.

[freebeard]

j-c-c -- That's the only entry on that chart I haven't seen anywhere else.

I have seen notched air dams that provide a central jet in the underbody.

I would speculate that it gathers the turbulence coming off the rear wheels and collimates it.

[j-c-c]

Originally Posted by freebeard

j-c-c -- That's the only entry on that chart I haven't seen anywhere else.

I have seen notched air dams that provide a central jet in the underbody.

I would speculate that it gathers the turbulence coming off the rear wheels and collimates it.

Maybe a benefit for "convoys"?

[sregord]

https://fleetengineers.com/shop/aero...amic-mud-flap/
I suggest this is what is implied.