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

[aerohead]

This one is a tough call for me.
All the current research was done within the context of DOT length restrictions.
And what you'll see are forms optimized within this restricted length constraint.
4-feet for rigid,and 5-feet for inflatables.
Fachsenfeld did the most interesting tail I've ever seen,and that was under contract to the Omnibus Company in Germany around 1936.It is an 'extensible' tail.It's depicted in Hucho's book in the commercial vehicle chapter.
It is very close to the 'Template',and the bus measured Cd 0.159 as a model in the Stuttgart tunnel,before Fachsenfeld moved to the FKFS under Kamm's directorship.The Reich Ministry saw his patent and created a shotgun wedding where Fachsenfeld could design as a 'nobody' under the skirt of Professor Kamm's credentials.At one year before the start of WW-II,the German gov't may have been leery about I.G.Farben's ability to provide enough fuel to prosecute a war.They lost WW-I because they ran out of oil.
If I had a motorhome,I'd build a boat-tailed trailer,since there are no length restrictions with trailers per se,and could be left at a campsite area for short excursions until time for the real road trip.
Your existing tail seems very much like GM's 'Optimum tail' investigated by Texas Tech'd Aero Lab and may be performing so well that a very costly redo wouldn't really show at the pump.Diminishing returns as they say.
I'll scratch my head for awhile.We need more case studies!

[orbywan]

Originally Posted by aerohead

This one is a tough call for me.
All the current research was done within the context of DOT length restrictions.
And what you'll see are forms optimized within this restricted length constraint.
4-feet for rigid,and 5-feet for inflatables.
Fachsenfeld did the most interesting tail I've ever seen,and that was under contract to the Omnibus Company in Germany around 1936.It is an 'extensible' tail.It's depicted in Hucho's book in the commercial vehicle chapter.
It is very close to the 'Template',and the bus measured Cd 0.159 as a model in the Stuttgart tunnel,before Fachsenfeld moved to the FKFS under Kamm's directorship.The Reich Ministry saw his patent and created a shotgun wedding where Fachsenfeld could design as a 'nobody' under the skirt of Professor Kamm's credentials.At one year before the start of WW-II,the German gov't may have been leery about I.G.Farben's ability to provide enough fuel to prosecute a war.They lost WW-I because they ran out of oil.
If I had a motorhome,I'd build a boat-tailed trailer,since there are no length restrictions with trailers per se,and could be left at a campsite area for short excursions until time for the real road trip.
Your existing tail seems very much like GM's 'Optimum tail' investigated by Texas Tech'd Aero Lab and may be performing so well that a very costly redo wouldn't really show at the pump.Diminishing returns as they say.
I'll scratch my head for awhile.We need more case studies!

Thanks for the reply. It's not so much a costly redo as a time-consuming redo. If the other mods brings the mpg up significantly I'll probably leave it alone.

On the other hand, once I get it fairly well dialed in, if I have the time I would be tempted to test the heck out of it, get a solid data base, and then take the current boat tail off and build a new 'template' version just to see the difference. That would be fun. I think we need to create an 8th day of the week for projects only. : )

[KamperBob]

Phil, thanks for the update on your T100 projects. I can't wait to see what develops.

Orbywan, perfect is the enemy of good enough. Your RV tail reproved that. You picked the low fruit. Baring the tree may be diminishing returns indeed.

Guys, if my travels pass through either of your neighborhoods again I'd happily lend a hand if you want. Meanwhile, rock on!

[aerohead]

Originally Posted by KamperBob

Phil, thanks for the update on your T100 projects. I can't wait to see what develops.

Orbywan, perfect is the enemy of good enough. Your RV tail reproved that. You picked the low fruit. Baring the tree may be diminishing returns indeed.

Guys, if my travels pass through either of your neighborhoods again I'd happily lend a hand if you want. Meanwhile, rock on!

Thanks Bob!
I'll be busy with Femme-bot's projects 'til April,when I'll rejoin the mad-scientist work.
I'll be on-call for work,but with a little prior notice I can schedule some time to play hooky.
Whether we work together or not it would be nice to catch up on your travel stories and catch a meal together.On me!

[KamperBob]

Originally Posted by aerohead

Thanks Bob!
I'll be busy with Femme-bot's projects 'til April,when I'll rejoin the mad-scientist work.
I'll be on-call for work,but with a little prior notice I can schedule some time to play hooky.
Whether we work together or not it would be nice to catch up on your travel stories and catch a meal together.On me!

I'd really like t catch up this spring. It all depends how my travel plans play out. My life has other moving parts (plus weather) so I'm not predicting yet. But I'll definitely give you a heads up WHEN (not if) I mosey through your neck of the woods again.

Rock on!
Bob

[aerohead]

Truck's been dead since 4-weeks ago today(we think it's ignition somewhere) and I've had a LOT of time to spend with the calculator doing forensic engineering with the 2012,and 2011 trip results.
I constructed a Road Load Horsepower Table based upon Hucho's Fig.3.11,'Influence of aerodynamic drag on top speed.'
I represented the T-100 at it's original Cd 0.44 and 28.925 sq-ft frontal area(estimated) and at 10% drag reduction increments.
Estimating a driveline mechanical efficiency of 92% you can just pick off a power requirement at any velocity or power setting.
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I took the closest mpg data sets between the two years,between the Salt Flats and Carson City,Nevada and back to best eliminate grade effects.(the boat-tailed T-100 and T-100 pulling the Viking were within 1.31% of each other on this round trip portion).
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I took Hucho's low-ball radial tire R-R coefficient and calculated the horsepower requirement to overcome Viking's tire drag,then added 8% to degrade it to a bias-ply tire performance.
Using a BSFC of 0.408 lbs/bhp I isolated the aerodynamic drag portion from the trip mileage of 31.330 mpg.
With the R-R out of the picture Viking would have indicated 32.991 mpg as just a boat tail.
Compared to an estimated 23.8 mpg @ 65 mph,the mpg indicates a 68.355% drag reduction [at 5.65% mpg per 10% drag reduction (interpolated from GM Research Labs)]the drag reduction would yield a drag coefficient of Cd 0.1392.
Due to the density altitude at the elevations I was driving at we have to discount the Cd by 9%,yielding Cd 0.151.
I'm going to include the elevations between the Salt Flats and Carson City so you can appreciate the implications of the trailers additional weight.
This simple 'look' at the data suggests that the trailer is performing as Hucho would predict.A wind tunnel would best measure the actual values,but for low-buck eco-modders it at least demonstrates a trend.

[aerohead]

Here are elevations for way-points along the trip:
Salt Flats Sinclair Station/Cafe--------------------------------- 4,189'
Wendover 'Hill'------------------------------------------------- 4,482'
Silver Zone Pass ---------------------------------------------- 5,490'
Oasis --------------------------------------------------------- 5,873'
Pequop Summit ----------------------------------------------- 6,987
Wells --------------------------------------------------------- 5,630'
Deeth -------------------------------------------------------- 5,341'
Halleck ------------------------------------------------------- 5,230'
Elko ---------------------------------------------------------- 5,116'
Carlin --------------------------------------------------------- 4,905'
Emigrant Pass ------------------------------------------------- 6,114'
Twin Summit -------------------------------------------------- 5,672'
Dunphy ------------------------------------------------------- 4,639'
Battle Mountain ----------------------------------------------- 4,482'
Valmy -------------------------------------------------------- 4,511'
Golconda Summit ---------------------------------------------- 5,154'
Winnemucca -------------------------------------------------- 4,317'
Mill City ------------------------------------------------------- 4,232
Imlay --------------------------------------------------------- 4,226'
Humboldt ----------------------------------------------------- 4,226'
Oreana ------------------------------------------------------- 4,163'
Lovelock ------------------------------------------------------3,969'
Fernley ------------------------------------------------------- 4,212'
Silver Springs ------------------------------------------------- 4,209'
Carson City --------------------------------------------------- 4,764'
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PS the mpg for this route includes an overnight stay in Winnemucca,with a cold-restart the following morning which typically would be a no-no for testing.

[aerohead]

I've just photo-enlarged "Tangent running cost on grades",one of 4-tables of Fig.4-3,Pg.115,HIGHWAY ENGINEERING,by Clarkson H.Oglesby & R.Gary Hicks,4th-Edition,1982,JOHN WILEY & SONS,INC.,N.Y..
It's too small to work with in the book,but preceding the table is a comment on page 114 under 'COSTS RELATED TO GRADES'.
They mention that on downgrades flatter than 2%,the energy demand lowers and costs decrease roughly the same amount as the increase on upgrades.
Then,'There is,however,little if any further cost decrease on downgrades steeper than 2%,since braking is required.'
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In the context of today's hybrid vehicles I think we'd have to rewrite this part of the chapter,however with respect to the Viking trailer,this explains why I'm experiencing lower than expected results.
Added weight of the trailer will induce runaway speed if not compensated for with braking which kills otherwise useful kinetic energy.
Without the trailer,the little air drag present is enough to discourage runaway,and I don't lose fuel energy to braking.
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As a 200-pound plug-in hybrid battery range-extender trailer,with 400-pounds of extra Li-on batteries, the trailers inertia and momentum could be 'harvested' with an EV.
Not so as a pull-behind micro-RV caravan.Weight's go to go!
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I'll have a look at the 'new' tables 'n see where that goes.

[euromodder]

Originally Posted by aerohead

Added weight of the trailer will induce runaway speed if not compensated for with braking which kills otherwise useful kinetic energy.
Without the trailer,the little air drag present is enough to discourage runaway,and I don't lose fuel energy to braking.

In this situation, you don't really lose fuel energy or efficiency to braking.
There simply wasn't anything to be gained when you can come down the mountain using engine braking or aerodynamic braking with the engine off.

But you still had to drag the trailer up the mountain first.

As a 200-pound plug-in hybrid battery range-extender trailer,with 400-pounds of extra Li-on batteries, the trailers inertia and momentum could be 'harvested' with an EV.

There's a limit to that as well - the uphill part would have drained them to as low as the conditioning software will let it, but once the batteries are full, the harvest is over.

And these batteries too, have to be dragged up the mountain first.

[HighMPG]

I been following your T100 for quite some time, took a vacation from ECOmodder and now I see you have a trailer now! Keep up the moddin'!