Full-boat-tail trailer with gap-fillers for Toyota T-100 pickup

[orbywan]

Sounds like fun Phil. I'm getting ready to go to an RV show in Indio on Monday, but I can't wait to get back and get on the Aero RV again. After I finish the belly pans and get the wheel fairings done and do some work to the front end, I'm going to try some propane injection with the 7.3 diesel.
Do you have any experience or knowledge of that? How about you slowmover, or anyone? I've already got propane on board, all I have to do is add the regulator and the hose. I've talked to several guys with big class A's that swear they get a solid 10 to 15% with it. I'm running around 16 to 17mpg now, if I can get a little out of the improvements still in the works and then add another 10% on top of that, I'd be RV'n in tall cotton! Still shooting for the big two zero!!

[aerohead]

Originally Posted by orbywan

Sounds like fun Phil. I'm getting ready to go to an RV show in Indio on Monday, but I can't wait to get back and get on the Aero RV again. After I finish the belly pans and get the wheel fairings done and do some work to the front end, I'm going to try some propane injection with the 7.3 diesel.
Do you have any experience or knowledge of that? How about you slowmover, or anyone? I've already got propane on board, all I have to do is add the regulator and the hose. I've talked to several guys with big class A's that swear they get a solid 10 to 15% with it. I'm running around 16 to 17mpg now, if I can get a little out of the improvements still in the works and then add another 10% on top of that, I'd be RV'n in tall cotton! Still shooting for the big two zero!!

M.R.Sharkey's VW Diesel Rabbit Pusher-type range-extender trailer has propane injection.
I believe he recycled a used BBQ grille LP regulator and orifice to make his.I don't have that material with me,but you could GOOGLE his project.I don't recall him mentioning specific mpg results,but I don't trust my memory.I believe Sharkey has email contact info at his site.You might be able to bounce questions off him.

[orbywan]

Wow, that's some interesting stuff, a diesel pusher trailer. Ha! This guy believes propane injection is benefitial in the same ways I've read others state. I don't want to hijack your thread here so I'm going to post some of what he wrote on my 'Aero RV' thread and get some other reactions. Thanks Phil.

[aerohead]

I've been turning over every rock I can get my hands on with respect to information with which to help reduce the trip data on the trailer.
I found what I believe to be an independent verification to the premise,that a trailer could actually reduce the drag of the tow vehicle combination.
The data is from Sighard Hoener's 1951 book,'Aerodynamic Drag,'Chapter 9 (B),pages 166-172,Fig.9.12,'Aerodynamic drag coefficients of a "standard" locomotive,a streamlined engine,and of a power car,measured (9.15) in combination with a tail car.
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Image (b) and (c) depict a streamlined NEW YORK CENTRAL R-R, steam locomotive with angled-roof tender,Cd 0.39,and a streamlined self-powered passenger railcar,Cd 0.42,both pulling a boat-tailed 'Tail Car' of Cd 0.10.
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While the Cd 0.10 'Tail Car' is certainly of interest,it was the streamlined coal tender which struck me.
The Tender is 37.6 feet in length,behind a 57.4-foot locomotive.The body of the tender begins,matching the aft-body of the locomotive,@ 137 sq ft projected frontal area,then at 50% length,begins a constant 9-degree roof slope,terminating at 89 sq ft cross-sectional area ( which matches passenger rail car dimensions).
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In the second paragraph of the chapter,Hoerner explains that the Cd of the locomotive/power-car can be derived,simply by subtracting the Cd of the 'Tail Car (0.10).
This gives Cd 0.29 for the Loco./Tender vs Cd o.32 for the power-car (both Cds are measured in front of a 'train').
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This suggests that the 9-degree 'fastback' Tender is actually streamlining the locomotive down to a lower drag than the constant-section power-car.From the numbers,a drag reduction of 9.3% is attributed to the effect of the Tender (trailer).
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With respect to the 'Tail Car,' it is 48.75 feet in length,with 11.75 feet of boat-tail.76% of the length is just skin friction,leaving 24% of the length as base drag.At Cd 0.10,it's pretty interesting when you consider the majority of constant section and length.
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I'll do the calcs some time to separate out the skin friction of the tail car,and try and get an image posted.Al's pretty busy today,no guarantees.

[aerohead]

Here is a image from Fig.9.12

[ShadeTreeMech]

Originally Posted by aerohead

Here is a image from Fig.9.12

aerohead has a way with making ecomodder porn by accident :P

[aerohead]

I've been living inside Hoerner' and Hucho's world for awhile and have ferreted out some quanta which may shine a light on low drag trailer potential.
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In Horner's section B.1.,'Drag of Motorcars and Locomotives',Fig.9.10,there is a depiction of a self-powered passenger railcar studied by O.G.Tietjens and Ripley,'Air Resistance of Trains and Inter-urban Cars,Transactions,American Society of Mechanical Engineers,1932.
The railcar is credited with a frontal area drag coefficient of Cd 0.08,complete with wheels,on tracks.
This is considered the lowest 'theoretical' limit for drag of such a vehicle.
Within the text of the chapter Hoerner also reports that the "ideal" streamline forebody-drag coefficient is Cd 0.04.
In Hucho's 2nd Ed.,pg. 330,Fig. 8.60'Air drag distribution over vehicle sections for a rounded and sharp-edged front,' if one 'solves' the pictorial algorithm for forebody-drag coefficient,a value of Cd 0.041 is arrived at which is in very close agreement to Hoerner's value.
If we accept the Cd 0.04 nose drag value,we're left with Cd 0.04 for the tail.
Both sections equally share the surface friction component.Wheel drag is reflected.Ground proximity is reflected.
We'd be talking about the Lancair/Legend of railcars.Everything flush,smooth,faired.Completely smooth underside.
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If a wheel fairing package for a trailer were executed as with contemporary solar race cars we might establish Cd 0.04 as a 'talking -point' for the lower limit we could predict for a full-gap-filled,full boat tail trailer of ideal length.
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It's an evocative number.
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My trailer is not ideal in length.I have disparate exit wash velocity issues due to the bed box rear corners.I'm over-built,overweight,and the Viking speedboat hull body is also short of ideal in contour,compared to its integration to the T-100.
The 47.9 mpg between Colorado Springs and Trinidad was a glimpse of what really low drag can do,so I'm in it to the finish.
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A final thought for now for any of you members who are thinking about a project like this.
Kamm's wind tunnel experiments proved the value of plan-taper in the body.If one were to do a full 'Template' style roof contour ( in elevation view) ,without plan taper you're looking at Cd 0.21 capability,versus Cd 0.13 if you include it.That would cost you 38% loss in drag reduction.Yes it's a larger front-loaded investment,but it will pay significant tax-free returns over its entire service life.And when wheel bearings are the only significant moving part that could be a very long service life!