Boat tail mod to my enclosed trailer

[Braebyrn]

Originally Posted by max_frontal_area

sorry i didnt make myself clear, you make an opening at the front of the trailer
where you had your nosecone, all that air trying to push your trailer back will now go inside the trailer into a duct that channels that air to the very back through a hole in the center of the loading door/ramp (which is cool since you are dealing with cars, which tires will ride alongside the hole during loading and unloading) and into the middle of your tailcone which would have to have an exit for the ducted air to go.
now comes the cool part. the ducted air as well as the naturally flowing air from the sides top and bottom flow around towards the center and converge
with the ducted air. and this is what is really slick about it, if this setup is done properly the outside "airs" will help pull along the ducted air and vice versa! this is known as augmentation and the formula 1 crowd uses this phenomenon all day long.

punch a coupa hows in ya trailer?! may seem radical - yes it is, but you will driver father between fillups and perhaps even start a trend!

Thats some work, but would be cool if it did work.

[max_frontal_area]

Originally Posted by Frank Lee

Ducted air is not slick.

If you have room to spare inside for a duct, you are better off chopping the top or reducing the interior

volume by whatever means.

Ducting = more skin friction.

Ducting = more exposure to x-winds vs. smaller envelope.

Ducting = more weight.

chopping:
toy haulers/car trailers frequently doulbe as weekend homes featuring kitchens, showers, workbenches, portable machine shops and the like. afraid hunching over is usually not practical. besides collapsible campers already exist.

more skin friction:
absolutely negligible. riding a bicycle at 10 MPH and then 20 MPH will give the average person only a mild appreciation for the momentous effort required for a vehicle having to displace air for a large slab the size of a car trailer (even if fitted with nose and tail cone) at freeway speeds. air takes the path of least resitance. just imagine instead of being forced to flow around it to be able to go right through. i would go for that!

more exposure to x-winds vs. smaller envelope:

numerous ppl have made the 2 club (entrance into 200 mph club while setting a record at speeds exceeding 200) at bonneville using just this hack. sidewinds are a frequent occurence on the salt. buddy o mine lost one retina when he impacted, quite literally, head on a lead acid battery which was used to power one of the trip lights entering the shot course speed trap. during subsequent events batteries were submerged. if these ducts posed any danger the tech boys would not sign off.

Ducting = more weight:

the idea i have been musing will weigh less than a cooler full of ice n beer and 2 lawnchairs to boot.
by design it is very light yet rigid, features integrated turbulence control, folds and unfolds faster than a teenager can answer a text. now that is what i call slick. tell you what i will do, just for the for the timid among us i will throw in a valve that will allow airlow to be suspended - just in case it gets skeeeeery

so Rick lemme ask you... it appears that you have plenty of room in there to take on a Troll, however it seems there is concern about weight and by the looks of it 'thisone will crack 300 lbs ez!

[Frank Lee]

Destructive? LOLZ

Point me to all that successful drag-reducing ductwork then. Not holding my breath tho.

I should be able to punch out the front and rear ends of a semi-trailer, put the cab and drive unit under floor, and have less drag than not having anything above floor right? Yeah you betcha.

[max_frontal_area]

Originally Posted by Frank Lee

Destructive? LOLZ

Point me to all that successful drag-reducing ductwork then. Not holding my breath tho.

I should be able to punch out the front and rear ends of a semi-trailer, put the cab and drive unit under floor, and have less drag than not having anything above floor right? Yeah you betcha.

1. i intend to provide complete design/build/test data for all to see.

2. a Frank Lee design class "A" truck is a poor example/comparison for more than one reason. besides the cargo bay will be filled most of the time, especially with todays fuel prices dead heading is just bad policy.
now, back to the trailer. for once it would be nice for you to provide some data, studies, instances or the like instead of customarily laying a dark cloud over other ppls attempts.

[Frank Lee]

I already laid out the rationale for ducting to be not as good a solution as lowering the lid.

You don't like/agree with it, go build it, or find data from someone who did, or present some sort of supporting evidence for me being wrong and/or you being right, or even just find something that has been ducted for the purpose of improving aero.

BTW Tempos are freeking awesome; I'm glad they aren't "popular" cuz that means more for me for cheap! One of my '84s has nearly 300,000 miles on it so it can't be that awful.

[JasonG]

Maybe the spitting match about ducts could use its own thread.

If you can make it work that would be awesome.
A few vehicles have put their exhaust and cabin air exit in the low pressure area, how much it helped nobody knows.

For a quick CFD of it look here, http://ecomodder.com/forum/showthrea...html#post73478

[JasonG]

While our trailers don't sit up as high as an 18 wheeler, i wonder how much help one of these would be? Truck Trailer AeroDynamics, LOW COST, Diesel fuel savings




He seems to have reversed the "keep the air out" philosophy and went with "shove more air under it and into the low pressure zone in the rear" philosophy.

http://www.airmansystems.com/work.pdf

[BamZipPow]

Originally Posted by JasonG

While our trailers don't sit up as high as an 18 wheeler, i wonder how much help one of these would be? Truck Trailer AeroDynamics, LOW COST, Diesel fuel savings




He seems to have reversed the "keep the air out" philosophy and went with "shove more air under it and into the low pressure zone in the rear" philosophy.

http://www.airmansystems.com/work.pdf

I think that works fer a loaded 18-wheeler trailer just fine because of the weights and lengths involved. Not sure how well it would work on a lighter trailer...

[Braebyrn]

Looks like you guys have been busy posting. I will get back to this when I get home. Sure wish I had something for the front of the trailer this trip. The winds coming from the west are a killer on fuel economy.

[aerohead]

Originally Posted by Braebyrn

I wonder about the air behind the truck and between the trailer.? If I put scoops to pull the air in and then drop it out behind the truck? I was thinking about that drag.

According to Hucho's book,the gap is responsible for up to 20% of the rigs overall air drag and can mean an extra 10% mpg if you can make it go away.
If you 'rob' the airflow and shunt it internally,you will destroy the surrounding flow,precipitate flow separation,and ruin any chance for aft-body modifications to perform,as they are completely dependent on clean laminar onset flow from ahead.
The partial gap-fillers you see on contemporary 18-wheelers are a proven fuel-saver.
Consider that you want only a single collision with the air,not multiple strikes,then allow the air to decelerate while building static pressure,such that when it finally does separate,it's at the highest possible pressure.