Travel Trailer/Camper help
 

Ok guys... this one may be a bit trickier, BUT, after reading and such, I don't really know where to head with this thing. Here is a link to someone selling a camper just like mine:
2005 Kz Sportsmen 2404 BUNKHOUSE, Travel Trailers RV For Sale in Canton, Michigan | HW Motor Homes | RVT.com - 70317

My truck is a Dakota, as listed in my information. Pulling it is no problem weight wise, but the aerodynamics KILL me when up at speed. Especially last year, when there was a wind storm. I was fighting 50 mph wind gusts that I was headed straight into. My truck was brought down to a crawl on any hills. It wasn't good at all. I"m still working on the truck, and it shouldn't have a problem pulling, BUT, the aero on the camper can obviously be improved.

My thoughts: Some sort of boat tail, even minor should be a huge improvement. There is some damage and leaks to the roof, so this may actually prove to be beneficial. If not the whole way around, perhaps a little "wing" type as you see on some SUV's and such. QUESTION: Is there an optimal angle/length etc. for this and how do i find it?

The underbody will be smoothed, as it is already most of the way.

Anything else I could work on while i'm hacking it away?
I will be redoing the flooring and the master bedroom as well, mattress and all that got wet as well. Roof is now a single roll of sheet with some tar around all the stuff sticking out like the A/C etc.

Thanks for the help guys! I can use any improvment that would be worth the time and effort, and I promise to document!!!!

(Also revising my grille block and air dam on my truck to write up quickly for ya'll)

Mechanical baseline is critical. And, while an aid to mpg, it is central to vehicle performance and component life.

Combined Rig RV MPG

Orbywan's threads are to the point:

Aero RV Boattail

Aero RV Bellypan

And Skyking's design underway:

5th Wheel Design

I'd have a long look at how many miles per year, and expected lifetime use (number of nights of use) to see what benefit aero changes will make. A few thousand miles per year may make it more of a demonstration versus a $$ savings.

I believe you'll want to conduct some tests on road horsepower demand (coastdown, etc) as your trucklet is hard pressed to pull that square white box.

The best TT's are aero in shape, but also feature low ground clearance, low center-of-gravity and torsion arm suspension (independent). A sway-eliminating hitch (such as Pro Pride) is also going to be a help from the aspect of control, and from reduction of steering inputs.

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10 degrees is great. air will reattach if it gets tripped.

apparently 20 degrees is livable, but about the upper limit.

trailer
 

The boat tail probably won't help until the nose of the trailer is corrected.
The lack of side radius is costing you up to 18% mpg,and the gap between trailer and truck another 8% mpg.
If she had a nose like the early Airstreams you'd see up to a 26% improvement.
The 'Bullet' trailer was compared to one like yours,behind a Town and Country minivan.
A 16',2,990-lb trailer like your's got 11.8 mpg @ 60 mph.
The 32',5820-lb 'Bullet' returned 13.2 mpg at same speed,same tug.
And the 'Bullet' nose is in no way ideal.
The side radius has been reported as a source of sway.Fibrelock Fabric Ltd.,England,who marketed an inflatable 'Airstream' nose (trailer dome) in 1982 claimed that their unit reduced pitching and snaking.
The worst part is that your trailer nose will exhibit the highest drag increase in a crosswind,whereas an Airstream will exhibit the lowest.And it's windy most days.

Aerohead, do you mean to indicate the postwar Curtiss-Wright Clipper nosed vehicles (shared by both Silver Streak and Airstream)?

1953 Silver Streak "Clipper" (More images in link).

http://www.vintage-vacations.com/53clipper23S.JPG



Or, as with the later 1959 Airstream "Overlander":

http://images01.olx.com/ui/1/10/13/8090713_7.jpg

Also, does The side radius has been reported as a source of sway need to be corrected to the lack of . . .?

Thanks

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SlowMover: Thanks for the good insight! I don't believe i'm going to be doing a full boattail. As for the amount of use, we just bought the camper, but the idea is to go a minimum of 3 trips a year. Our typical spot is a 4-5 hour drive. Last time we took this trip, my basic stock combo got 12+ mpg there, and 9+ mpg on the way home. Why so much worse coming home? Wind storm. One that had a lot of tornadoes in the mid west. We didn't know it, but we were driving right into them on our way home.
Now, I have a Cold air/hot air intake (switchable setup for purposefull driving) a grille block during the wintertime, and a chin spoiler. Hopefully an electric fan coming soon as well, but I have a boat i'm trying to work on and sell.
As for the camper itself, I'm going to repair the things that need to be repaired, and if in doing so I can improve slightly, I will.

drmiller: Thank you for that. I am thinking of simply doing something along the top and perhaps the sides on the back for 6-8 inches. Similar to the mercedes trailer.
Mercedes Trailer tail

AeroHead: When you said, "The side radius has been reported as a source of sway.Fibrelock Fabric Ltd.,England,who marketed an inflatable 'Airstream' nose (trailer dome) in 1982 claimed that their unit reduced pitching and snaking." did you mean that MY camper is prone to sway, or the airstream is? It is worded that a side radius creates sway, which you have also told me improves mpgs. Then you tell me that this company claimed to reduce it? I'm confused.

On another note, my propane IS in a nose cone, not like the one shown there. I'm sure it improves slightly, but I can't find a picture of it. I really need to go through and find some pictures because due to work I can't get over there in daylight to take one of the real thing.

So... If I made a front for my camper such as this:
Camper Link here would that be much of a help, or would that not really be enough. Anything more than that I probably wouldn't do it as it would be really hacking into this thing. If a project takes a month or long to do, I can do it during the winter inside my friends shop, but I would need to do that next year.

Also, moving the camper closer to the truck you said would improve mpgs by 8%. I don't know where you got that number, but are we talking an inch or two, or like, a lot? I don't think there is a lot of flexibility there, sadly, even if i drilled another hole into the hitch. It would be about a 2" closer max and then I would be afraid of hitting things anyways.

Thanks again guys!

Curtiss-Wright
 

Yep.They have some advantage at zero-yaw,but from graphs Hucho published in his book(s) they really dominate low drag under crosswind conditions,which is what we have much of the time.
If the gap can be closed as well(which is responsible for almost all crosswind drag) we pick up even more savings.
The 1982 'trailer dome' by Fibrelock Ltd. did both operations and was credited with up to a 26% fuel savings.After working with Hucho's material on trailers and commercial vehicles I believe it.
As to crosswind stability,Fibrelock claimed that their unit actually reduced pitching and snaking.
If the gap is closed off the yawing moment will be killed.You'd feel some 'push' but that's to be expected when you are pushed from the side.
If we watch our load distribution and tongue weights we ought to be okay.

Here is a picture of my actual camper front
I attatched it - front of my trailer. I don't know how good it is, but it's better than the one I actually posted. You can see a little bit of the damage up top. It's not significant, but if i do nothing, the water keeps coming in. It currently isn't leaking due a bunch of tar but needs to be actually fixed.

As for the back, i will probably do something like the mercedes trailer listed above previously just to help. i would think that it actually helps in the way of stability as well, AND, i am thinking of making it some sort of storage. I don't use the shower outside attachment that is there, so i plan on eliminating that and reworking that. We will see how projects advance. It may end up being more of a back end than I had thought before!

found the links for a boattail on an rv as well. i only wonder if doing something like that is even legal because it goes over and past the bumper.

Blu3Z3rg, see if you can get a copy of Hucho's book. If not for purchase maybe borrow from your local branch via inter library program. That's what I did last year. The section on trailers compiles data from others and connects some dots. For example, the effect of nose slope on sway is covered; think face pressure and tongue weight. Of course Cd reduction and hence MPG gain. From the wind tunnel pix a big win came from taming bow wave splash from trailer with too blunt a leading edge. There is also some data showing effect of edge radii including rear not just front. Roof deflector too. It will be time well spent I'm sure if you can get a copy. Good luck!

side radius
 

It is confusing.Hucho will have a drag table showing the lowest drag with a semicircular plan form ( like AIRSTREAM),but then warn that these are subject to yawing forces when in a crosswind.
Then Fibrelock advertises that when you install their trailer dome, that the trailer is more stable.
Your trailer nose should not create the effects that Hucho's mentions.
Personally,I would be willing to see.
If the gap is closed off so is the cross-flow which would create the potential yawing moment.
The gap is dead,you've got the bulbous nose,and at the gas station 26% less often.
I looked at a CM Trailer Co. rig last night.It is 94.5" wide with a 19-inch radius on the vertical leading edges of the nose.8" radius @ top edge.

Google Books: January 1982 Popular Science for pic of Fibrelock press release.

Now that is an excellent idea! Modifying the nose of the trailer is otherwise counter-productive as it is almost always the "lounge" or sitting area of a trailer and outward visibility from there is crucial. The rear -- bath or bedroom -- would be easier to mod (removable boat-tail) as use of the space is different. A detachable inflatable "nose" would be outstanding.

Interesting about Airstream. One of the men who worked the Airstream in-house Carvanner Insurance Co years ago stated that, by contrast, that flat-faced travel trailers tend to have a resistance to sway due to that face (nose). Experience of most all aero aluminum trailers is, however, that cross-wind resistance (yaw due to winds) is far greater, so the Hucho statement doesn't make sense. In fact I'd be hard-pressed to find anyone, owner or RV hauler, who would agree with that (as there are those with several hundreds of thousands of miles of experience, in nearly all kinds of weather, climate and terrain). I can see the amount of wind pressure varying on a rounded trailer wall, say, versus the increasing loads against a flat-walled trailer accounting for this given some time/distance stuff. (I'll request the Hucho book via interlibrary)

Closing the gap between TV and TT is without remedy (as I see it) for the majority of us. Not at all knocking anyone who tries. On my rig that gap is a full 60". I see treating each vehicle separately, mechanically (rolling efficiency) and with some aero as being most fruitful. A 5'er is more likely to see gains with truck/trailer gaps addressed.

I'm going to assume that the CM Trailer Co. in question is not the one in Oklahoma (who make an otherwise nice trailer I'm told), but cannot find otherwise a reference to these dimensions.

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That pic bears a nice resemblance to the AWARD line of trailers. Note the V-shaped roof:

http://www.berrylandcampers.com/rvph...19/ta02025.jpg

We are going to buy a travel trailer that will be built to order. I would like to tell the builder to put a wall air conditioner into one of the walls instead of putting a big honking air conditioner on the roof. I am sure the aerodynamics will be better. Comments?

Anything you can get off the roof will help. I have a custom design cooking in my head that will be flush fitted everywhere, with no awnings or vents protruding.

Put the vents, the TV antenna, and all the "uglies" on the back wall where they won't ruin the slipstream. The refrigerator vent has to be whereever the refrigerator is, but that screen does not protrude significantly.

It would be preferential to have the "crank up vent" and the "fantastic fan" mounted on the ceiling, though. The hot air absolutely is up there at the very peak. The TV antenna would not be aimable if it was on the back wall.

I'll have a fan system at either end with a flush hatch like an aircraft landing gear door. One will clear out the bedroom area and the other, the bathroom/kitchen.

The advantage of the RV roof air conditioner is:

a] simple to mount & install
b] centered over axles
c] easy to service
d] great air distribution

The last is the critical piece to address. The cost, complexity, etc of other types keeps them relegated to small trailers, overall due to cubic volume and distances. That is not enough to overcome what is not that great an aero penalty.

This comes up on RV forums. Look up Smokeless Joe on Airstream Trailer & Motorhome Owners Community for a custom installation that will be of interest to you.

Here's an introductory thread:

Ducted AC?- Crazy idea? - Airstream Forums

The split mini is what I'm going with. It will be located right in the middle of the living space so no ducting needed, just like a roof air unit. The compressor/condenser is 75 pounds light, and can go at either end. I especially like not having a huge hole in the roof, it is one of the more common starting points for leakage and rot.
The most common one is the old crank up antennas. They are often installed poorly.

I installed a mini-split system two years ago. Don't be afraid to tighten those pipe fittings! I tried to follow the "torque spec" in the manual and put them on too loose. I had to pay to have the system recharged. It did not need to be evacuated, though.

Use two real wrenches, not adjustable wrenches, and tighten them enough that the nut grabs the tubing and starts to twist the tubing with it.
***
I am still not sold on the roof top AC. Perhaps an aeromodder could build a teardrop shaped fairing that tapers back for a long distance.

It occurred to me that a minisplit AC may not have the vibration rating that a real RV AC needs. If you go that way, I would recommend shock absorbers on the axles.

I'll mount the compressor unit on engine shock mounts, and use a flex line from the compressor over to the trailer frame. The copper lines from there will be fine, as that is what all the gas piping is on trailers. This will also reduce transmitted noise from the compressor.
The cool thing about the mini splits is the inverter tech on the motor. It does not have that huge locked rotor amperage of a conventional unit. This means a 2000 watt generator will start it fine, and it will be fine on a common extension cord.
It is a 12,000 BTU unit and will work well on the smaller trailer I am designing. It will have plenty of passive heating and cooling features to help out.

I am so used to pitching a tent way back in the campsite under the trees. Now, I am going to have to put up with sleeping in a tin can that has been in the sun all day. That's the way it will have to be if we want to camp out in the Sierras or the Smokies with our precious aminal.

So long as you all stay out of the deep South or desert West in summer I'd imagine any of those split systems will work.

On a trailer like mine, from 28' on up in size, a pair of A/C units is practically mandatory if one wants the interior to cool to below 80F. My next trailer will be a 32' or 34' and conversion to 50A service with dual roof A/C units is a given. Aero fairings will be on the list to investigate (around here is an example shown). I just need to find a tin bender who'll work with me.

As my roof will also have solar panels, an antenna farm, plus the usual assortment of vent openings, I've decided not to worry over a "clean" roof but to minimize the drag of each component as I go along. Utility will count over the small FE gains.

I would think a removable boat tail for a TT would trump all these roof concerns given a production model RV. Same for a nose cone of some sort.

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A/C
 

orbywan has fabricated a streamlining fairing for his A/C unit.You might want to check out his RV build thread.

Hucho
 

I think that the concern is that around a radius,sideways lift might be generated which would induce a yawing moment affecting stability,whereas with the sharp-edged corner,it's always in separation and somehow will not create the moment.I don't have the paper Hucho refers to so I'm at a loss to understand specifically where the fear is generated.

I'd like to understand this. Is it in reference to crosswinds hitting the trailer and "lifting" it 90-d to the direction of travel? That seems to be my misunderstanding, here, as my impression of that is that the wind does not "pile up" against the trailer sides as it does with a sharp-edged trailer.

If we speak of winds in the direction of travel I'm still at a bit of a loss. Yes, a square-front trailer has some "built-in" anti-sway (sheer resistance to direction of travel) over a "shaped" front (radiused edges) . . but I'm having a hard time with the claim that it is significant in trailer directional stability. Experience, etc, all otherwise mitigate this claim.

Maybe . . that even a bit of anti-sway via hitch rigging is enough to offset any tendency of this sort.

That's as close as I can come.

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the way the relative wind leaves a body has far more bearing on drag and lift than the way it arrives. In a crosswind situation the relative wind will stay attached a bit on the downwind side of a radiused trailer. I would speculate that this departing effect is not nearly as strong up front, in the shadow of the Tow Vehicle (TV), but more pronounced farther aft.
I don't think the flat face has any real bearing on it, compared to the aft downwind side.
A square trailer will have a long aft downwind side break that will cause a yawing force aft of the pivot(trailer axles) , in the downwind direction.
This force will steer the nose of the trailer into the wind, and consequently the nose of the TV downwind.
So that gust that seems to steer you so hard downwind in your truck is truly the "tail wagging the dog".
Now with your rounded trailer, this is not nearly as pronounced. That is why your experiences with the radiused trailers are what they are.
The relative wind over the downwind side stays attached just a wee bit better in your case. Because the trailer is radiused everywhere, it performs equally better in all conditions.
The wind does not push your trailer around, it pulls it around.

Not push, but pull. Okay, that makes more sense. Thanks for the time in laying that out!

Any Time :)

Pull not push is a great explanation! A larger and/or more blunt the rear surface basically acts like a bigger drag chute. A lot of people think this new camper is aerodynamic.

http://lilsnoozy.com/images/gallery/DSC_4000.jpg

Well it is a bit more aerodynamic. most folks confuse entomo-dynamic with aerodynamic. If it collects fewer bugs then it must be good :D

Coleman "Low Profile" rooftop units and Dometic Penguin and Penguin-2 units are ten inches high. Low profile roof top units may be the best I can do. Carrier had a low profile RV AC, but they quit the RV market. Low Profile Air Conditioners on Sale - PPL Motor Homes

Sherwin Williams sells paint that reflects 90% of the sun's energy back into space. I am going to buy a trailer with an aluminum roof and paint it. I specified a 90% reflective membrane roof for our sun room remodeling project a few years ago. I doubt that is what the RV makers are using for roofs. If they were using a cool roof, they would promote it.

Any rooftop unit that is faired in on the downwind side will be much better. So I'd leave your current unit in if it works, and do what orbywan is doing here.
http://ecomodder.com/forum/showthrea...tml#post250241

It can be screened or louvered to keep the flow attached but allow flow for the AC to work.
you could spends some $$ here for aero and end up saving, vs getting a new AC unit. A complicated electric door system would still be less expensive.
Many thanks to orby here.
Edit: sorry about that bad link.

Well it is a bit more aerodynamic. most folks confuse entomo-dynamic with aerodynamic. If it collects fewer bugs then it must be good

Too funny.

Sure does sell those cab roof deflectors . . and for the guy who ran his hard tonneau cover open and propped up.

I imagine that any TT, 5'er or other RV is subject to potential aero improvment. Too few of them actually travel enough miles annually for it to appear to matter. But if one looks at the 10-year mark -- 5k annually x 10 -- a few mpg over 50,000 miles really would pay well.

Today's word is "entomo-dynamic"
 

^We expect to tow our trailer 50,000 miles or more after we retire. Our last trip to Montana put 5,000 miles on the Cobalt, all in three weeks.

I don't have a trailer yet. We are going to specify a custom built trailer; I am debating whether to have the builder put an AC on the roof or as a wall unit. This brand has not done wall units as far as I know and I might meet some resistance to the idea. I also have to run the idea past the "aesthetics committee", the other member of which is my lovely wife.

If I built an after-fairing for the roof top AC, I would want to epoxy it to the aluminum roof. I am loathe to drill holes in the roof. Epoxy can be unbonded with a heat gun. It would leave some rough edges if I had to unglue the fairing.

I like bonding too. I used all sorts of epoxies in boat and now my truck bed construction.

What are the goals? There are owners of 25' and shorter Airstreams using Euro turbodiesel SUV's and some other who are seeing in the low to mid 20's for mpg while towing. Plenty of both new & used. No need to re-invent the wheel in other words. Not to mention standard building practice and nationwide service, tens of thousands of other owners, etc.

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It's gotta have a cat box in it! We went to the RV show for the first time a year ago and, frankly, we were not impressed with the products. Floor plans and kitchen designs were not efficient. There were workmanship problems with most of the brands, such as adhesives coming unglued, panels that did not align, etc. For that matter, most brands have slide-outs, which seem like a heavy way to add a modest amount of floor space.

We discovered Taylor Coach - Welcome and attended their camp-out where we toured a dozen of them. The product costs 40% more than the typical brands but there are no workmanship problems. They also feature lightweight framed cabinets instead of heavy cabinets made of chipboard. They are light in weight. They pan the bottom. Customers pay more for more features. The manufacturer will build it to order with the features we want, and that is why I call it a custom product. I expect to spend $21,000 for a 22 foot trailer that weighs 3100 pounds with full tanks.

Please tell me about the European turbo diesel tow vehicles. I had imagined that a Sprinter diesel would be a great tow vehicle, but that product is not really sold to typical motorists in America. At this point, I would buy a pickup truck with a V8 engine and expect 12 mpg towing and maybe 20 mpg driving in my patient and ponderous manner.

new, a euro diesel rig will cost upwards of 60K barebones. Personally, the nightmarish stores I read about fuel system failures in the late model VW/Audi diesels has me totally biased against them. They can and do fail and the manufacturers are blaming fuel contamination for everything, voiding warranty. The repairs go into 5 figures.

Plenty of examples of folks using Porsche Cayenne, BMW M5, Mercedes 350, VW Touareg, etc over on Airstream Trailer & Motorhome Owners Community See all threads by JFScheck for recent experience with Euro TD's.

Here's a big dollar rig: a 30' A/S pulled by an ML320.

Still others using VW Jetta, etc. Still more using Cadillac sedans, Honda minivans, Jaguars, etc. A truck is hardly necessary (unless desired).

Here is a thread on the Eurovan as a TV.

Weight is not your concern when it comes to towing. If I can pull a 34' travel trailer and am still below some others at 16-mpg with similar 28-34' TT's weighing from 8k to 11k, it's about aerodynamic resistance being the determining factor.

As those little boxes in your link above are as non-aero a TT as I've ever seen then its' other virtues had best be quite high. White pine framing and corrugated aluminum is about as cheap a trailer construction method as there can be. Length of service is a real concern.

For $20k there is a big number of aero aluminum TT's that can meet the goals espoused in re 50k miles through retirement. My folks bought their TT new and used it 27-years spending next to nothing on it for repairs. The gulf between aluminum trailers and conventional white boxes is wide and deep. Used is fairly meaningless as a term.

Unless already in process I highly recommend looking around more. Ask here or PM me or others, I know I'd be happy to help hunt down some examples (discussion threads) of suitable TT's.

Finally, here is a thread asking about higher mpg tow vehicles for Airstream.

Taylor Coach
 

Here is our new travel trailer. We could have afforded an Airstream, but we didn't want the complimentary NRA membership.