Boat tail project based on a single wheel trailer...

[wyatt]

Originally Posted by 01FordCrew

I would love to see your pictures but photobucket says temporary unavailable. I just slapped one together for a 1900 mile trip and it saved me 5 mpg us and gave me room for more stuff. Looks like a win win. Now I want to make improvements.

Do you have a picture of your setup? Everybody likes pictures :-)

[aerohead]

Since the debut of the Cybertruck,and the TFLcars 'Gauntlet',Tesla/trailer towing tests I've been running numbers on trailers.
I did a twenty-hour proof,based on the 1969 Dodge Charger Daytona,in a 2-car draft,using the original research by Chrysler Corp.,plus a road test on the car by CAR and DRIVER,conducted at the same proving grounds where the Daytona was originally developed.
Starting with the NASCAR,two-car draft,step-by-step,I reconfigured the Charger trailing car into a pop-up RV trailer.
With a roof-delete,cooling system delete,mirror-delete,addition of a full belly pan,with diffuser,full wheel skirts,underbody 'hour-glass' delete,'features drag delete,Hoerner' streamlined railroad tail car boat-tail,and articulated,'accordion',full gap-seal,the trailer came in at Cd-negative 0.0835,giving the 'rig' a Cd 0.2315,@ 21.8 sq-ft frontal area,with the trailer at Cd 0.01597,15.60 sq-ft frontal area,and 4,251-lbs.
I reverse-engineered a coefficient of rolling resistance for the tires,at Crr 0.01672813,from the CAR and DRIVER road test at Chelsea,Michigan.
At this configuration,pulling the trailer,while adding 4251-pounds,improves the mpg @ 70-mph,from 19.884,to 19.9972 mpg.
This is with the original Good-Year bias-ply tires.If radials were substituted,we'd see a minor mpg increase.
It's an interesting thought experiment,essentially doubling the weight of the vehicle,adding cargo space,while improving fuel economy.The technology dates to 1922.
I'll be running the numbers specific to BZP's Dark Aero.The preliminary data look pretty tasty.This coming October I hope to verify this concept at A2.

[MetroMPG]

Originally Posted by 01FordCrew

I just slapped one together for a 1900 mile trip and it saved me 5 mpg us and gave me room for more stuff. Looks like a win win. Now I want to make improvements.

Welcome to the forum!



I'd like to see pics as well - I just adjusted your postcount so you can upload without restriction.

[Tahoe_Hybrid]

Originally Posted by freebeard

This was my attempt:

that is a totally illegal trailer wheres the tie chains and brake cable and your reg plate?

[wyatt]

Originally Posted by Tahoe_Hybrid

that is a totally illegal trailer wheres the tie chains and brake cable and your reg plate?

Non-articulating trailers fall under a different category, and are treated as a part of the vehicle frame.
Also, even if it were articulated, some states do not require a tag for light trailers, and don't require trailer lights if you can see the lights on the vehicle.

[freebeard]

Yeah.... what he said.

Also, that was a mockup of a retractable boat tail. The stored position is hung on a bike rack, the lowered position is on a cardboard box.

If it were implemented, the wheel might fly at a low altitude like a [castering] wheely bar.

[aerohead]

During the 20-hours I spent on the Charger Daytona pop-up trailer, I discovered a rabbit-hole in CAR and DRIVER's original reporting.Had they reported 'gear-limited' top speed,I could have saved over two days,chasing my own tail.None of the numbers jived,as I was under the impression that their data reflected a drag-limited top speed.It's makes all the difference in the world!
Having solved the C&D mystery,working through BZP's Dark Aero was a relative breeze.25-lines of calculations,to solve for 17-parameter solutions.Here's the rundown:
*All performance is for 65-mph,with the A/C 'on.'
*Naked,from the factory,Bam's T-100 was good for 19-mpg,at Cd 0.44,and approx. 29-sq-ft projected frontal area,and CdA 12.76 sq-ft,and approx. 3,800-pounds test weight,Crr 0.012325,and BSFC 0.5745 lb/bhp-hour,1725.1 Wh/mi,and 496-miles range,with a 786.65 kWh-e 'pack' (24-gallons)
--------------------------------------------------------------------------
*with grille-block
*extended airdam
*flush,extended rocker panel extensions
*full,rear wheel skirts
*full,articulated belly pan
*diffuser
*above-beltline, cab-to bed, gap-seal
*and aero-shell
Bam's T-100 drops to Cd 0.277,for CdA 8.033 sq-ft,and 24.93-mpg,@ 4,100-pounds.
--------------------------------------------------------------------------
*With Dark Aero behind the T-100,the T-100's drag falls to Cd 0.2354,for CdA 6.828 sq-ft.
*Dark Aero,Cd 0.3733,solo in the wind tunnel,drops to (-)0.1247,@ 18.7 sq-ft frontal area,for CdA (-) 2.3319 sq-ft,trailing behind the T-100
*The composite drag coefficient for the tow/towed combination is Cd 0.155,@ 29.0 sq-ft (based on the T-100),for CdA 4.495 sq-ft,L/H-4.317,L/h-4.881,at 288-inches total length.
*At CdA 4.495 sq-ft,the combination returns 31 mpg,REGULAR UNLEADED
*35.65 mpg,with MAZDA SkyActiv gasoline direct-injection,turbo engine
*40.3 mpg,with AUDI,TDI engine
*130 mpg-e,with Tesla electric drive,@ 252.1 Wh/mi,and 396-miles range,on a P100D battery pack (3.0509-gallons E10)
*top speed improves,from 96 mph,to 116-mph.
*The Toyota V-6 engine recognizes a T-100 with an 'apparent' 10.215 sq-ft frontal area,about 1/3rd the truck's original size
*As a complete system,Bam's mods add negative 0.285 to the pickup truck.
*By adding 1,350-pounds BZP picks up 12-mpg
*By adding 1,350-pounds BZP gains 20-mph
*By adding 1,350-pounds BZP gains many additional cubic-feet of,weather-tight cargo capacity
--------------------------------------------------------------------------
An unknown quantity remains the V-6's BSFC as the engine load transitions.HOT ROD Magazine recognized a variability in BSFC for a small-block Chevrolet,350-CID,V-8,from 0.49-lbs/bhp-hr,to 0.71-lbs/bhp-hr,depending on load.The ICE is 'island-hopping',all over its map.
And Hucho warns us,via General Motors Research Labs,that unless we properly gear-match after drag reduction,we can lose up to around 30% of the streamlining benefit.Not so if electric powered.The Tesla BSFC-e basically remains right at 0.137 lbs/bhp-hr
I've seen as high as 39.9 mpg @ 100 km/h on three occasions,on REGULAR gas.My 4-cylinder probably has less internal friction than the V-6.A lot of money would tell.

[Tahoe_Hybrid]

trailers suck figure out by using the hitch without a tire as you will be limited to only 55mph max speed

[wyatt]

Originally Posted by Tahoe_Hybrid

trailers suck figure out by using the hitch without a tire as you will be limited to only 55mph max speed

I went 70 with mine routinely. 12 inch tires rated for 55.

[gumby79]

Quite impressive on the math. 1350lbs is definitely worth 12mpg.
---
Regear
Re gearing/trans swap had a 16mph effect on top speed. 87.14mph with 2.44:1 final Vs. 103 with 2.16:1 new top gear.
@2350 the defueling matches the load. And will not accelerate past 103 over a 10mi test at WOT.
----

Originally Posted by wyatt

I went 70 with mine routinely. 12 inch tires rated for 55.

It more of a legal thing many states have a 55 for 3axels OR towing.
Dark Aero beats the when towing but falls on its face on the 3 axel part ,unless the 3rd is off the ground 55 is the limmit.
ID, MT, UT, NV, AZ, NM, CO, WY, and KS over 55, some up to 85mph, is allowed when towing . Im shure there are others but I haven't been there, or don't recall.

Dreem Big Chisel Down To Reality