RV rooftop air deflector (DIY: Toyota Highlander pulling 4Runner/Apex travel trailer)
 

Just a quicky.
Gilkison phoned last night from Trinidad,Colorado to say that the Toyota Highlander rear hatch which I modified into a rooftop air deflector for his 4RUNNER/APEX travel trailer rig is recording the highest mpgs he's seen so far.
They'll go on to Denver and then home after a family visit,then we'll have about 1,200 miles of round-trip data to digest.
So far so good!
I took a defunct hatch,cut away as much steel as I could without sacrificing strength,then pop-riveted aluminum skin where the glass used to be.It's mounted by aviation grade piano hinge to a transverse 4-foot Harbor Freight level at the front and the rear support struts anchor to a bifurcated 6-foot Harbor Freight level attached in cantilever to another 4-foot transverse level which acts as the rear cross piece.
The deflector is set at the same inclination as the 4RUNNER windshield.As the dual-windshield P-61 Black Widow.

EDIT by admin - added images...

http://i1271.photobucket.com/albums/...2/HPIM1834.jpg

http://i1271.photobucket.com/albums/...2/HPIM1832.jpg

Another success!

Think John could send a photo of the work?

Pics>>>>>must have pics!!!!!!!!!!!

One of my To-Do list items was a cab roof deflector.

http://kamperbob.com/blog/wp-content...or-150x150.jpg

I delayed installation my first 11 months of full-time RV life. I didn't trust the strength of my truck cap. The sawed off aluminum topper covers the front third of my 6.5' truck bed. (The nose of my 5th wheel trailer covers the back third. The middle third gap is mostly filled by a generator mounted on the nose of the trailer.)

Cap strength was a concern because of how it was shortened. After peeling off the skin the under frame was cut down. The frame was originally all welded. I can't weld aluminum so I used pop rivets, screws and bolts. It holds itself together no problem. I'd trust that in a hurricane. What I don't trust at highway speed is additional stress from a deflector. Not until I get around to reinforcing it better.

The original plan was to use the deflector as intended. Eventually replace the fiberglass wing with a solar panel. Last month I (finally) added solar to my rig.

http://kamperbob.com/blog/wp-content...Up-150x150.jpg

I scavenged the deflector for parts to mount the panel. The tilt mechanism was my objective. All this I trust inclined for stationary use but for travel I keep it folded down flat (horizontal). Highway wind loads are reasonably low that way.

What remains to do aerowise is reinforce everything to handle road winds. Whenever I get around to that I'll be in a position to experiment with different angles. It's worth doing but lower than other priorities for me now.

Even then I'm not expecting huge gains. My trailer already has generous radii (circa 12") on the top and sides. By rights bow splash should not be an issue (per work by others). A deflector probably won't do a lot of good if onset flow is already attached. Still, it's something I'll be able to do (eventually) so it remains on my someday-maybe list.

By contrast the friend's Apex doesn't have such generous edge radii going for it. If it has considerable bow splash currently then a deflector seems a prudent addition to the rig.

Here's a link to my blog post with more pix and context on the not necessarily aero facets of my deflector related project.
Solar Project – Part 5 | Recreation Engineer

photo
 

John's probably got some in his Zoom and I've got three in my camera,but they're from before he moved the deflector aft about 9-inches (231mm).
I'll see if Al can help me post what I have,and when John checks in,see what he's got.
It's nothing fancy and it was 101 F when I painted it,so the paint (acrylic lacquer) pretty much turned to dust.
Next time,maybe Homer Simpson will let me spray it in his control room.:p

Apex
 

Yes,APEX is kinda Dark Ages design.There is a sloping and upper radiused nose in elevation,but zero edge radii in plan view.
The deflector has a bit of curvature to the sides and it was thought that some of the source flow could be directed laterally,allowing APEX' nose to ride within it's wake.
Rough without a wind tunnel and no time to do a tuft test.Sucks!
1,200 miles of data will help us appraise it's value.
Bob,sure like the PV/deflector! Two birds,one stone!:)

photos delayed
 

I won't be able to post photos today.
Al has a new computer and is going from Windows XP to Windows 7.And it's not going well at all.I got here at 11:00 AM,it's 2:27 now and the CPU is still grinding away.
I'll try again next weekend,sorry!
P.S. I did talk to Gilkison from Denver and he was happy with numbers.
He'll be by home Sunday when I talk to him next.And we'll have all the numbers by then.I'm very curious about his return leg,southbound between Colorado Springs and Trinindad.This is where the T-100/Viking trailer pulled 47.8 mpg at 65-mph.We'll be looking for some anomaly.

numbers update
 

After 1,571 miles,Gilkison got home.
He averaged 13.08 mpg,up from around 12.5 mpg.
The new 'high' tank is 14.587 mpg,up from 13.7 without the foiler.
So about a 4.6% mpg increase on this trip.
Which is in the neighborhood of a 9% drag reduction (wind averaged).:)

Sorry! no photos today
 

Apologies to all.Al's swamped (that's good for his business) so won't be posting images today.
Gilkison emailed three more.
I'll try again next weekend.:p

Thanks for trying, anyway, Areohead. Can't wait to see those pics! :thumbup:

Quick pix of rig
 

Cross linking pix posted to other recent thread.
http://ecomodder.com/forum/showthrea...tml#post322769

http://ecomodder.com/forum/attachmen...1&d=1345493532

http://ecomodder.com/forum/attachmen...1&d=1345493532

If anyone's interested I can aim for a better profile view going forward.

photos
 

I'll try for images.Forget it!
I do this so little I can't remember from one time to another and if I don't bring the proper 25-pound work with me I leave home without instructions.
I managed to get the images into photo-bucket but I don't remember how to link them to here.
The store will be closed in a little while,I'll try again Monday,Sorry!:(

From photobucket, if you copy the IMG code which will be beside or below the picture somewhere, then if you paste that here it should work.

pasting
 

I remember getting on the image and sliding down to the IMG code and clicking.I'll try a right click.

Clicking it should highlight it, might even automatically copy it, I don't remember exactly. But either way, when it is highlighted, copy it, and paste that code here as if it were text and that should do it. Sorry for the late reply.

Phil: I added 2 of the images from your Photobucket album to post #1 in this thread.

Clever design, by the way.

Also added a link in your "signature" to your photo albums (Photobucket & your albums here on EcoModder). (That won't show up until you post again.) Maybe others here can help out when you get stuck, since they'll have the album links.

http://s1271.photobucket.com/albums/jj622/aerohead2/

http://ecomodder.com/forum/member-aerohead-albums.html

pics
 

Darin,thanks for the inflight rescue!
I did locate my other work-book which had my instructions for Photo-bucket,'n maybe I can function a bit better.
Having access to the Photo-bucket album is really good though,as members can just browse around in there and see if anything strikes them.
Tanks again big-time!:D

3D
 

This rig (SUV w/ deflector + Apex trailer) may be an instructive example.
http://i1271.photobucket.com/albums/...2/HPIM1834.jpg

From Hucho's compendium.
http://ecomodder.com/forum/attachmen...1&d=1346157818
http://ecomodder.com/forum/attachmen...1&d=1346157818

The Apex already has a generous roof edge radius in profile (side) view. In plan (top) view it has pretty sharp edges. Gilkison reported to Phil record high mileage. To my brain all this evidence supports sidewall splash as a likely problem that the rooftop deflector addressed.

It would be nice to see 3D streamlines from proper CFD, or tufted sides of the trailer with and without the deflector, to further demonstrate benefit. I suspect long term FE will show real gain. With real world variability, however, scientific confidence requires more trips, patience for us, and generosity of those involved to share.

Rock on!

leading edges will be next
 

In plan view APEX' corners have zero radius.
I've been collecting large radii structures to use as molds for wet layups.
An awning company could also roll square aluminum tubing and heli-arc it into an Airstream-esque birdcage framework onto which tailored awning fabric could be attached forming a very light,hollow nose cavity add-on.
Awnings stand up to Texas thunderstorms all the time.I see no reason why they wouldn't do fine on the face of a trailer.
Anyway,when time avails itself,I'll get into this one.
We're also going to do a fairing for the rooftop AC unit as orbywan has done.

Huge help, KB!! I've had a hard time with deflectors as the RV world is one in which the desire for better mpg is a constant question. The lack of good record keeping is one hindrance, the annual miles another (for comparison purposes). And more are the differences between rigs (TV & TT).

So about a 4.6% mpg increase on this trip.
Which is in the neighborhood of a 9% drag reduction (wind averaged).

Am looking forward to more as it is available.

.

That shape looks so good, it looks like a 1998 -2005 VW Beetle front hood.
>>> aftermarket fiberglass suppliers or junkyard time.

I think this lays out the future in re trailer towing quite well.

Saw this a month ago in MA.
http://ecomodder.com/forum/attachmen...1&d=1346342773

Less monstrous than Franken Hauler and better than stock flat front with all sharp edges.

this
 

Bob,that's a little sweetheart.Soft edges everywhere,especially up at the top,which seems to be the coup de etat when it comes to blow-overs.
And the footage from Texas Tech showed the 'Nose Cone' to be the best with respect to attached flow.The air just goes around the radius and hugs the downstream surface.
Not quite as good a leading edge as on your rig,but a pretty good add-on.
The fenders would be the thing to look at I guess.

From the Net
 

Here is the White Paper quote:


Did some more digging around last night on the subject of rooftop air deflectors and came up with these from the RV world:

The OP: " . . I need to add here that I used this very same software for recreating an engine explosion on an aircraft while in-flight. This was presented to a group of aviation professionals. They all agreed it was accurate in the way it simulated air flow . . . . "

(Accident re-constructionist)

RV.net: An Animation


Animation, Revised


Continued


From a FORD forum:

Deflector Roof Rail Mounting Clamps


Record-keeping is the real bug-a-boo of the RV world. Inconsistent results, overall, and "general impressions" predominating. Plus, attention to hitch rigging, vehicle steering alignment and proper tire pressures make air deflector gains/losses not much more than "noise" (at present).

But, as with AIRTABs, the wind deflectors are nearly always credited with greater stability in the face of crosswinds, especially as generated by other traffic (semi-tractor trailers).

How well they work is ironically better credited with the "mistake" of leaving a wind deflector in place once the trailer is unhitched (ha!)

For the purposes of this thread, the TT rig in question probably has noise in the system in re proper hitch rigging (applied leverage by the weight distributing hitch) that is, first, only solved by using weight scale data; and, two, proper steering alignment of both vehicles; three, proper tire pressures (weight scale data for the tow vehicle); four, the elimination of brake drag on both vehicles; five, elimination of steering wander by the tow vehicle.

This "noise" can change the FE results "achieved" by the wind deflector completely.

Posts by Ron Gratz on the Towing subforum at RV.net (I use the WOODALLS portal to same) are the best guide in how to set up hitch rigging. This is about the play of under & over steer (induced yaw) and is part and parcel of what the big truck manufacturers speak of when looking at Steering corrections per 100 miles as a factor in FE. Hitch rigging is formulaic. Straightforward, overall.

Quote: (from, Just Got Back From the CAT Scale)


If a friction bar hitch is the present system, it also is a contributor to lesser FE (IMO) due to it's crudity (and needs to be disconnected when on wet roads, etc). The rig owner ought to look at the new ANDERSEN WDH as an inexpensive alternative to what is no better than a doorstop. Ease of achieving proper weight scale values is far higher, besides. This is by no means the "best" hitch, but it's a step in the right direction (and for purposes of adjustments to any component or system to try and filter for FE gains via aero changes). 90% of all travel trailers are incorrectly hitched (industry data). Verify that it is not (should be a first step).

The goal is in remaining lane-centered with no driver input despite extraneous influences.


(Will add some more to this post later)

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Ross, thanks for those links. Dustin's CGI is Flow Illustrator on steroids. The level of detail looks so realistic and plausable. But thanks to Lucas, Pixar and others we need to be more skeptical than ever. In Hollywood the immutable laws of physics aren't. Validate, validate, validate. :)

I thought some of his asides (about air flowing back under the tow vehicle) were certainly of interest. I don't see him selling anything, or acting as a stalking horse. I added these links primarily as being representative of current RV world discussions. I saw no real reason to add ones from Class 8 trucks as that world is pretty well understood by its members (industry leadership).

The RV world tries in re FE, but is short on leadership. Air deflectors have been around quite a while (I certainly remember the discussions after October, 1973), but there has not ever been decent consensus due, again, to record-keeping and accounting for the system noise of a combination vehicle, where (unlike a 5'er or tractor-trailer) some time & care in achieving formula results in hitch rigging can "drown out" aero aids.

There are any of a number of hypotheticals where I believe I could show that an aero aid cannot be separated out where the gain is a small percentage.

It's easy to say it works (and I'm hopeful, not doubtful), but verification is difficult (unless one has worked the numbers necessary). Rigging, alignment, brake drag and steering wander are all to the point. (And new vehicles are not to be assumed correct).

Were I in Colorado, I would take the rig to Transwest Truck Trailer RV in Frederick to start sorting out trailer brake drag, bearing adjustment, trailer axle alignment after a stop at a CAT Scale to get weight scale tickets for the vehicles separately and lashed up; with and without WD activated. (I can provide a fill-in-the-blank chart for collecting all the numbers).

The same basics apply to the tow vehicle. New does not constitute proof of zero brake drag and zero steering wander, much less alignment. Small differences are magnified in towing.

I realize the rig owner may not want someone else spending his money, yet on the other hand the best performing rig may be to his interest. And a relationship with a talented shop is that first step.

My point to this second post would be that there is no downside to any of this. The difference between an "okay" rig and one that has numbers nailed down is night & day while on the road.

This is when the "feel" of an aero aid becomes palpable.

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