Travel Trailer Aero mods?

[seuadr]

Hi all,

i'm in the ideas stage of building my own motorhome with weight and aerodynamics in mind, in the meantime, i need to learn to fiberglass and save money, so, i'm thinking i'd like to look into what i can improve with my current travel trailer.

with this in mind, i'm trying out that aero template tool - now, i don't wanna intimidate you with my phenomenal paint abilities, i put my pants on one leg at a time just like most of you.



am i barking up the right tree here?

i'm looking in to how the awning attaches to see if i can detach it while in transit and store it inside.

i'm also wondering if, given the gap between the tow vehicle if i should be looking at something more like a bubble on the top like you see on semi trailers?

[aerohead]

Some gross figures from Wolf Heinrich Hucho's 2nd-Edition, Aerodynamics of Road Vehicles, NASA,............
* tow-bar length dependent (gap) alone, can mean up to a 8.67% delta Cd.
* a roof fairing, which brings the tow vehicle roofline closer to that of the trailer amplifies the smaller gap modification for up to a 13.6% drag reduction.
* closing off the gap between the tow vehicle and trailer brings drag reduction up to 27.1%.
* reducing the height of the rear separation point by half brings the entire ensemble to a 63.5% drag reduction.
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Lightweight, compound-curve, pre-preg epoxy carbon fiber fairings, gap-filler, and boat-tailing costs very little in weight penalty. So rolling resistance need not suffer significantly.
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If you want to go 'nuts,' you can lower the drag into negative territory, where pulling the trailer actually lowers 'total drag', and you actually increase range when towing. We know this from NASCAR.
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These are just talking points. You're the 'Captain.'

[seuadr]

Originally Posted by aerohead

Some gross figures from Wolf Heinrich Hucho's 2nd-Edition, Aerodynamics of Road Vehicles, NASA,............
* tow-bar length dependent (gap) alone, can mean up to a 8.67% delta Cd.

i'll have to do some measuring - but it seems like the length is pretty short already.

Originally Posted by aerohead

* a roof fairing, which brings the tow vehicle roofline closer to that of the trailer amplifies the smaller gap modification for up to a 13.6% drag reduction.

could it just be on the top of the vehicle and not need to be around the sides? i could probably work something out that would attach to the roof rails..

Originally Posted by aerohead

* closing off the gap between the tow vehicle and trailer brings drag reduction up to 27.1%.
* reducing the height of the rear separation point by half brings the entire ensemble to a 63.5% drag reduction.

i am assuming this would be the combination of some sort of tow vehicle fairing and whatever i do to the front of the TT?

Originally Posted by aerohead

Lightweight, compound-curve, pre-preg epoxy carbon fiber fairings, gap-filler, and boat-tailing costs very little in weight penalty. So rolling resistance need not suffer significantly.

yeah, and i want to learn how to use these kinds of materials anyhow, so, it makes a lot of sense.

Do you think that a belly pan under the front makes sense also, given that it is simply cost of materials and time?

from what i've been able to gather, the boat tail is probably going to be the simplest to implement since i don't have to worry about clearances between the trailer and vehicle.

the exterior heigth of the camper is 78 inches, the durango is 70 inches, so, that shouldn't be particularly complicated to overcome.

Thanks for the input!

[aerohead]

Originally Posted by seuadr

i'll have to do some measuring - but it seems like the length is pretty short already.



could it just be on the top of the vehicle and not need to be around the sides? i could probably work something out that would attach to the roof rails..



i am assuming this would be the combination of some sort of tow vehicle fairing and whatever i do to the front of the TT?


yeah, and i want to learn how to use these kinds of materials anyhow, so, it makes a lot of sense.

Do you think that a belly pan under the front makes sense also, given that it is simply cost of materials and time?

from what i've been able to gather, the boat tail is probably going to be the simplest to implement since i don't have to worry about clearances between the trailer and vehicle.

the exterior heigth of the camper is 78 inches, the durango is 70 inches, so, that shouldn't be particularly complicated to overcome.

Thanks for the input!

* the shorter the 'gap' the better, so that's good news.
* on the roof is way out ahead of nothing. technically, you'd follow NASA's lead, creating an interface between the back of the tow vehicle which 'blended' to the leading edges of the trailer. An inflatable structure attached to the trailer face, which deployed while underway, could do this hat trick.
We want to think of the T.V. /Trailer as an aerodynamic singularity ( you'll never see 'gaps' in commercial airliners, submarines, kayaks, torpedoes, or dolphins ).
* any 'belly' modification is worthwhile ( my truck is fully belly-panned, as well as all my trailers ). They're designed with diffusers as well, the trailer being a natural extension of the truck' diffuser geometry.
* yeah, if you learn how to do composites, there'll be no limit to what you can create.
* it doesn't hurt to know how to do 'upholstery' as well. Retired gear-drive sewing machines from old high school home economics classes can be had for a song, and they're capable of fabricating extremely lightweight, aerodynamic structures.
* any 12-VDC HVAC blower out of wrecked cars or trucks is ample for inflated aerodynamic add-ons.
* The boat-tail needs as good a quality of onset flow you can give it. If you can clean up the flow coming to it, it will reward you with the best performance.

[freebeard]

In this thread, in this post I posted this picture:

I failed to link to the actual implementation that Hersbird did, but Tinypic broke the pictures he posted. ecomodder.com/forum/showthread.php/camper-build-using-old-hi-lo-31219-2.html

The whole thread is worth review: ecomodder.com/forum/showthread.php/enclosed-trailer-nose-suggestions-37938.html

[aerohead]

Something from the past which never took hold.
http://https://ecomodder.com/forum/m...l-trailers.jpg

[aerohead]

even though we're surrounded by streamlined semi-trailers using NASA's 1980 technology, when it come to RVs, a wall of cognitive dissonance seems to emerge.
While good enough for Roger Penske, it's never been good enough for Penske fans who drive their RVs all across the nation to follow the racing series.
http://https://ecomodder.com/forum/m...18-wheeler.jpg

[aerohead]

this goes back a few generations, but illustrates some of the challenge to streamlining an ICE underbody, compared to a BEV underbody.
http://https://ecomodder.com/forum/m...y-bellypan.jpg

[aerohead]

https://ecomodder.com/forum/member-a...ion-plates.jpghere's the original box-cavity, by Continuum Dynamics, financed with a Defense Advanced Research Projects Agency (DARPA ) / Small Business Administration' ( SBA ) innovation and research grant.
You may notice how 'shallow' the vortices are, captured along the spans of the four longitudinal panels.
This mimicks the onset of roof curvature transition 'roof-bending', as seen in W. A. Mair's torpedo boat-tailing. NASA's Project Shoebox. Walter Korff's 1963, Cd 0.20 semi-trailer. R.B. Potter's March 6, 1956 US Patent# 2,737,411. Union-Pacific Railroad's aerodynamic tail-car of 944. Airship Hindenburg. Koenig-Kamm half-bodies of the mid-1930s. Walter Lay's low drag models of 1933. Airship ' City of Glendale, by Thomas Benton Slate, 1929. Paul Jaray's 'pumpkin seed of 1922. Samuel L. Calthrop's 'Air Resisting Train' tail-car of 1965.
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Introducing a more radical change in initial cross-section violates adverse pressure gradient boundary-layer rules emphasized by by Wolf Heinrich Hucho, and his mentor, Dr. Hermann Schlicting, who literally wrote the book ' Boundary-Layer Theory.'

[freebeard]

The nice thing about that stepped box is you can work around the tail lights.