Class a motorhomes aerodynamics

[freebeard]

Weight added that low, below the center of gravity, will benefit road dynamics. But not by much.

[j-c-c]

Typical insulation foam 3/4"? from Home Depot with just a single layer fiberglass cloth per side is pretty robust and light for indirect air flow tasks, You will have to pick a suitable binder for the foam, polyester resin or epoxy. Limited shapeable with simple bending in 3D. Easy to repair, no rot issues. But itchy/mask requiring when cutting, and spare me the anti mask rhetoric.

[freebeard]

Sounds like a lot of [itchy] effort and expense.

Polymetal is inert and prefinished. Stiffness equal to 5/8" plywood, no more expensive than Birch pywood. Available in 5x10 or 4x12 sheets.



These samples were sheared, rolled and braked on a hand-power bench tool.

[aerohead]

Originally Posted by freebeard

Call it Meredith Effect then?



That's really sad, local to me BRING recycling is flooded with diamond plate and architectural aluminum sheets in 4x4ft and larger sizes. Priced in the hundreds of dollars.

I just scored three 10ft corrugated steel sheets that have holes around the edges but none through the field so new you can see the Zinc crystals on the underside. $24 each, and I'm going to try spot welding two sheets together to reroof the breezeway.

-----------------------------------------------------------------------------------
It was more useful, although it's usefulness was extremely contextual:
* Let's say, you're a Tuskegee Airman, flying B-17 Bomber escort in your 'Red Tail' P-51 Mustang.
* You're operating at 30,000-feet, at a maximum 437-mph, air density = 0.000891 slugs, with your Allison V-engine rejecting 25% of the fuel's energy as cooling system heat, to outside air which is from -40F, to -70F, and a delta-T = 200F across the Bauman-scooped, belly radiator core.
* Compared to a Corvette ZO6, at 85-mph, at Furnace Creek, Death Valley, California
A) the max-Q for the P-51 is 990% greater than the Chevy is experiencing.
B) the delta-T is 256% greater than the Chevy.
C) the delta-V is 514% greater.
* The Mustang is 'transonic' within compressible flow.
* The Chevy is 'subsonic' within incompressible flow.
-------------------------------------------------------------------------------------
The only reason the Meredith Effect can produce thrust off the radiator exit is because of it's velocity and flight conditions, which could never exist for a road vehicle, in ground proximity.

[sregord]

Originally Posted by freebeard

Sounds like a lot of [itchy] effort and expense.

Polymetal is inert and prefinished. Stiffness equal to 5/8" plywood, no more expensive than Birch pywood. Available in 5x10 or 4x12 sheets.



These samples were sheared, rolled and braked on a hand-power bench tool.

Where do you get Polymetal? in those sheet sizes.

[freebeard]

Thanks for asking.

I got those scraps from Mulicraft Plastics. The materials is used for signage. So sign shops might be a good source.

I've seen generally three price levels (retail wholesale and distributors?}. Competitive brands are

PolyMetal:

https://www.nudo.com › products › sign-panels › polymetal
PolyMetal Sign Panels | NUDO Products
Product Description. PolyMetal sign panels are comprised of a recycled thermoplastic core sandwiched between two sheets of finished aluminum on one or two sides. The recycled thermoplastic core lends itself to resisting moisture. PolyMetal panels also feature the ability to digitally print direct to the panel,

Alumapanel:

https://economysignsupply.com › product › alumapanel
Alumapanel - Economy Sign Supply
Alumapanel are flat panels consisting of two thin aluminum sheets bonded to a PVC core. These sheets are frequently used for external cladding or facades of buildings, insulation, and signage. Additional information. Thickness: 3mm, 6mm. Size: 4' x 8', 4' x 10', 5' x 10' Color:

Grimco MaxMetal.

https://www.grimco.com › Catalog › Products › MAXmetal
Grimco | MAXMETAL™
MAXMETAL is the standard in ACM, or aluminum composite material. Comprised of two, pre-painted .15mm aluminum panels bonded to a solid polyethylene core, it is lighter and more durable than MDO and solid aluminum panels. The low mineral core makes MAXMETAL™ easy to fabricate, and its low

I just found another that claims fire resistance.

https://www.alucobond.com › products › alucobond-plus
ALUCOBOND® PLUS - 3A Composites GmbH Website (EN)
ALUCOBOND® PLUS is a panel with two aluminium cover sheets and a mineral-filled polymer core that meets more stringent fire safety requirements. It offers flatness, formability, weather resistance and ease of processing, as well as various colours and finishes.

Your cautionary tail is the

en.wikipedia.org/wiki/Grenfell_Tower_fire
The fire was started by an electrical fault in a refrigerator on the fourth floor.[note 1] This spread rapidly up the building's exterior, bringing flames and smoke to all residential floors, accelerated by dangerously combustible aluminium composite cladding and external insulation, with an air gap between them enabling the stack effect.

[j-c-c]

I see little likelihood of "stack" effects in our automotive applications, but the effect is real and a fire multiplier nevertheless, IMO. Additionally, many seem to ignore, aluminum is quite flammable if the needed temp it is exposed to can be reached, and a flammable core in a composite does promote that condition.
Regardless, for either of the conditions to be achieved in an automotive scenario, there are likely many other much worse problems at hand to be dealt with.
A steel or stainless cladding would negate nearly all the above flammability concerns.

[Piotrsko]

Aluminum melts at about 1100 degrees F, steel about 2000, stainless up to 3500 depending on how it's alloyed. None of them are fireproof with a plastic or organic core. None of them burn on their own, most don't odidize any faster at temp.

More going on in a car than fire retardance, but they burn pretty well direct from the factory. Probability of an air flow panel causing your vehicle to burn is rather miniscule compared to all the other flammables and explosives in and on the vehicle.

I thought Grenfell was caused by a faulty clothes dryer, but that was back in 2018 when I was there visiting, so thanks for the update.

[j-c-c]

Originally Posted by Piotrsko

Aluminum melts at about 1100 degrees F, steel about 2000, stainless up to 3500 depending on how it's alloyed. None of them are fireproof with a plastic or organic core. None of them burn on their own, most don't odidize any faster at temp.

More going on in a car than fire retardance, but they burn pretty well direct from the factory. Probability of an air flow panel causing your vehicle to burn is rather miniscule compared to all the other flammables and explosives in and on the vehicle.

I thought Grenfell was caused by a faulty clothes dryer, but that was back in 2018 when I was there visiting, so thanks for the update.

Not sure anyone was discussing anything being fireproof. My point was aluminum is on the lower end of the temperature achievable destruction range I suspect in typical automotive fire environments, and alum will contribute/self-sacrifice quite actively when that temp is reached.

[freebeard]

I mention that for full disclosure. I think it's more important that it is prefinished. That saves a lot of work compared to fiberglass (yuck) or wood. So long as it doesn't get marred and scratched during fabrication.