Help me choose a trailer

[da_dt]

Hi all, fisrst post.

I've been reading a while and have seeen some excellent trailer threads on here, but they all had to do with optimizing an existing combination. Since I don't have a combination yet, I'd like to pick it right to begin with so I have less optimizing to do

Only thing set in stone is my tow vehicle (an '06 Silverado) and needing close to 120 sq. ft. of floor space with a 6'6" interior height. I'm towing up to 10k lbs (trailer included), so would prefer a gooseneck, but would be OK with a tag hitch too. I've contacted a couple manufacturers about making me a 6 wide by 20 long gooseneck, but I'm afraid to hear what the price may be. I do want to keep this on really existing trailers, too. Not the "ideal" that we can't buy like that european semi trailer scaled down to my size.

If I do a gooseneck, I think I'd want something like on many of the horse/stock trailers with the front taper like this: [I guess I can't post links yet, but it's the top picture at w w w . g o o s e n e c k . n e t / 2 5 3 7 2 7 . h t m l (with the spaces removed)]. It seems like the bowed roof on that trailer would be better, but on Pace trailer's website they contend that the flat roof on their aerosport would be better.

I guess I have info overload. The setup on that Gooseneck link above seems the best to me, but I'm bringing the question here for the experts. Would it be better to have a square (with rounded edges, of course) front bumper pull with a shell pushing the air over? A v-nose bumper pull cutting its own air? Flat roof or bowed? Or, a tapered front gooseneck like above?

I will be towing over 150k miles/year, so I want to get this right

Thanks

[caissiel]

here is my story.
1. You need a diesel to pull any trailer worth using.
2. The easiest trailer to pull is a 5th wheel style, and not bumper hitched.
3. The front has to be eggshape fibre glass fronts, and not flat curved like the cheaper units.
4. I tow my 15500lbs trailer 39ft long with less fuel then I did the first 24ft 4200lbs pancake low profile model 5th wheel with a Ford Ranger STX 2.9L Standard.
5. Choose a trailer with as high rated tires as posible, I have 110Lbs in my tires.
6. The lower the trailer is to the ground the better it is on fuel mileage. Mine is about 13" from the road and 13'2" high at the front, and next to no wind resistence at 60MPH because of the eggshape front similar to the Truckers.
7. Though I have a long bed the trailer seem to deflect the wind very well. I do slowdown some with cross winds because cross wind affect mileage much more then head wind with a long trailer.
Thats my experience with this new trailer that realy surprises me every trip I do while observing the mileage with my calibrated ScangaugeII.
Did 16MPG in the state of Florida and 14MPG in the hills of Virginia and Pensyvania

[ChazInMT]

GooseNeck.net Page

That should help.

I have wondered myself if anyone has ever put a 6ft taper back on a trailer to see how well it would improve mileage on a camper.

Something like this.



Simple drawing I know, but I think you get the idea, and the sides would be tapered as well.

[turbothrush]

I am wondering if you keep the flow attached and you reduce the wake area by say 20% would the drag be reduced by the same amount and would the mpg increase by about half of that?
I am building a fiberglass/foam truck camper ( profile is done but I can still taper the sides) hope the "areo experts " chime in.

[ChazInMT]

From my understanding, reducing the wake area by 20% is not a linear relationship. It could help you by 5% to 40%, depends on what you begin with and how you do it. The "How you do it" demands that you follow the ideal aero template in tapering the back end of your trailer. I'll post a pic later of what I'd do to a truck camper.

[wyatt]

Originally Posted by da_dt;249556[B

][/B]
set in stone
tow vehicle (an '06 Silverado)
needing close to 120 sq. ft. of floor space
6'6" interior height
towing up to 10k lbs (trailer included)
prefer
gooseneck
6 wide by 20 long
keep this on really existing trailers
bowed roof on that trailer would be better (Pace trailer's website contends that the flat roof on their aerosport would be better)

This is how I understand your requirements. I am guessing that the relatively long rounding on the front will make a bowed roof less effective. The orange on the tail could be a kit you add on, like the Trailer Tail that is seen on semi trailers. If you did one of the steel or aluminum trailers from your link, and just skin the sides of it with something, round up the front edges, add on the "cab topper" (orange thing) and maybe a tonneau cover on the bed, you would be in good shape. It would be best if you can also shield the tires on the trailer (and truck) to the max extent possible, and throw some smooth wheel covers on everything while you are at it. I show the wheels inside the trailer's outer walls, but I understand that may not be possible. The goal is to minimize the volume between the lead vehicle and the trailer, but not have everything smashing into each other. Also, the trailer should be "hidden" from the oncoming air to the maximum extent possible by trying to not make it any larger than the lead vehicle than necessary. The tail should have a maximum of 15 degrees inward slope. Hope this helps.
OH, and throw a smooth underbody on it why don't you? You can put one on the truck too, just be careful to let lots of air through the engine compartment, since we don't want to blow a transmission...

[botsapper]

You got some nice beta examples.
1938 Curtiss Aerocar

[KamperBob]

Originally Posted by wyatt

That visualization of requirements are really nice. Well done!

[wyatt]

Originally Posted by KamperBob

That visualization of requirements are really nice. Well done!

Thanks KamperBob, that means a lot coming from the builder of the FrankenHauler!

I would have suggested sealing the gap between truck and trailer from the truck side too (and some may still be a good idea, like the way a semi truck has an overhang) but I didn't want the pieces to interfere with backing operations.

[aerohead]

Originally Posted by turbothrush

I am wondering if you keep the flow attached and you reduce the wake area by say 20% would the drag be reduced by the same amount and would the mpg increase by about half of that?
I am building a fiberglass/foam truck camper ( profile is done but I can still taper the sides) hope the "areo experts " chime in.

turbothrush,I am without my workbook here and cannot give a definitive answer.
If I had to rely on memory( quite dangerous now! ),I'd say that if you were working with an airship,fuselage,or submarine hull,that the relationship would be basically linear.
Pressure drag,the target of streamlining,is a function of the pressure differential between the vehicles forward stagnation pressure,and the base pressure of the wake.
If you move the separation point back,such that the wake is reduced 20%,you'll be picking up pressure recovery,as the point of separation is now in a regime of greater pressure as the air decelerates down the tapering body cross-section.
The reason you won't get a linear benefit is that along with the pressure drag,your still looking at surface friction drag ( which is actually increasing as you lengthen the vehicle),cooling system drag,induced drag,interference drag,and the rolling resistance drag of the powertrain and tires,which all conspire to overshadow the benefit from the reduction in pressure drag.
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If the vehicle is completely streamlined excepting for the boat tail,then as the boat tail is lengthened,you do see an arithmetic relationship of diminishing return as you approach about 70% of the 'Template' aft-body,for example.Between 70% and 100% there's virtually no change in Cd.