Cargo trailer drag estimating

[Hersbird]

I've seen some $2000-2500 mid 60's, need floors, too long (28' or more), Airstreams on Craigslist. A rear end damaged one would be even less but normally they are front damaged. A tree or snow damaged one might work too. In a few weeks I will finally have the money to start something but I may take my time looking and planning still.

[freebeard]

Originally Posted by Hersbird

That was the idea I was thinking with cutting up an Airstream, just overall a little taller, wider, with the front part being stock Airstream and then boattail the back like on that Papoose.

I'm not a big fan of this idea. How would you cut it up and have it come out taller and wider? I'd get a generic mid-bath, strip it down to the deck and build back up from there. I had a 1952 Silverstreak Clipper years ago and I replaced 1/2 the deck and floor joists successfully but I needed 3x8' of aluminum siding and what was sold to me was not aircraft grade material and it went all wavy because it wasn't tempered correctly for trailer siding. I lost heart and didn't keep it.

Here's someone else's [similar] Silver Streak:



Both ends and the top are a half-circular. Can you say Iron Man?

Nowadays I live in an off-brand (Mobile Industrial - Santa Fe Springs, CA) 35' R-license park model. It's an aluminum tube with fiberglass end caps. I believe the Argosy has steel end caps.

FWTW here's a Bowlus from the same video:




Search Youtube for the title in the upper left. There were some amazing trailers there.

[Hersbird]

I didn't mean I'd make the Airstream taller and wider, just that an Airstream is taller and wider then the Papoose.

[slowmover]

". . Those older long airstreams are better priced than the shorter ones, I figure why not just shorten a long one and improve the trailing end while I'm at it. . . ."

One doesn't improve mpg wth this trailer type by decreasing size. Not in any significant way. Acceleration events and long grades may make increased weight more noticeable, but a properly-sized trailer is the point to the exercise of laying out trailer spec. IOW, the cost of time, labor and materials won't produce a mpg payoff. Given two identical rigs I can produce better mpg through other avenues. However, there is something to be said for better combined rig stability if aero is improved.

" . . I'm also trying to decide on a tow vehicle. I kind of want 6 passengers plus 2 dogs and a 6000# rating or so. Ultimate would be a new Ram ecodiesel but more likely will be 98ish conversion van which means I'm starting under 20 mpg without towing.

The new EcoDiesel is rated for up to 9,200-lbs. Close enough to haul my 35' Silver Streak. Capable of 30-mpg solo highway without really trying. And with a smaller cross-section Airstream of the 1970's is seeing 18+ towing (again, without really trying) in the hands of one man I know. Careful trip planning and favorable conditions could see one at/near 20-mpg. A combined rig of around 13,000-lbs with a 28-30' er.

A full-size passenger van with a diesel engine would be worth trying to locate even if it needed a new longblock and trans. FORD and GM each made them in the past twenty years. THe first generation DURAMAX has been the only mpg competitor to the CUMMINS. But one must be aware of any problems (and avoid altogether 6.0 and 6.4L FORD). Worth investigating as solo miles predominate 60/40 or better.

The short rear overhang of a van (rear axle center to trailer hitch head) makes this type highly desirable for cargo/passenger space efficiency versus overall length AND being resistant to trailer sway.

Also, there are those us of looking at roof area on the tow vehicle for solar panel installation and a van is excellent for this. Plus the battery bank can be located in the van. A minimal battery weight for the trailer. Same for adding a BIG propane tank. A 3500-series van with a diesel is insenstive to weight additions up to around 1,000-lbs. I'd look to keep van weight at 80% of tire/wheel/axle capacity once fully loaded with passengers, gear and additions of the sort mentioned here.

Generally speaking it is better to add weight to a trailer versus the tow vehicle. But a Clipper can be pulled by a range of vehicles. I'd keep it simple if for no other reason.

But were I trying to make for all weather accommodations for six I'd stick with a 1980's Airstream, Silver Streak or Avion. In particular a tridem 34' rear bath Avion where twin beds ahead of the aft bath can be converted with overhead bunks. The front lounge with a sleeper sofa and convertible dinette can sleep an additional two, three or four people. (The triple axle keeps tongue weight low, at 10% versus 13-15% on a tandem).


1980's AVION

My previous Silver Streak: A 1983 3411


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[slowmover]

The Airstreams are so valuable that you'd want to have a high confidence of the outcome before you took an air nibbler to that beautiful sheet aluminum.

Several tens of thousands made. Not "valuable" in the sense stated.

Are there wrecking lots with damaged Airstream and Argossy trailers?

Yes, COLAW in Missouri is one. Argosy is a bit rare and not worth fixating upon.

Were this my approach -- modifying an all-aluminum trailer -- the early 1950's Silver Streak Clipper freebeard shows above would be the ideal candidate as the shell itself is already a very good shape. I sincerely doubt a home-made project OR existing trailer mod would offer any significant (measurable) improvement. And let us also consider that proper weight balance is already inherent. This FAR outweighs mpg "fun". And that changes require an engineer. At what point is engineering expertise required is central. I say, stick with what is already engineered.

One will have ones hands full with re-building an antique like this (pipe frame and floor rot) so facilities to do a shell-off restoration are needed. Expect that years will be required. One man is looking at all his spare time from a career job even with outside help on occasion. There are far too may examples of this in resto threads elsewhere. Trailers are not simple taken as a whole.

(Sorry to hear of that aluminum sheet fiasco, freebeard)

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[slowmover]

In the above pair of posts I realize I've gotten pretty far from the title of this thread. It is that I note that, for general purposes, the "thinking" about fuel economy in re travel trailers is that light weight and small size are seen as fundamental.

But the numbers are otherwise.

A turbodiesel tow vehicle and aerodynamic travel trailer (where ALL edges are radused) is the winner. Lighter weight due to materials AS WELL AS low center of gravity are also what matter, but true aero is king.

We can find dozens if not hundreds of examples where a small gasser pickup and pseudo aero trailer fail. And fail in space utilization primarily, fuel economy secondarily. What good is 15-mpg with cramped accommodations for four where the mpg is the same for six with room to spare in a far larger rig? With better on-road stability? And higher solo mpg. And that one can carry more gear for weather or hobbies as well as the ability to stay put longer once parked. Etc.

Six people is a far cry from just two. The economics of RV travel are far more than fuel cost, the other big expense is ground rent. Ten nights of full hookups at $45/night = $450. Over a month if one can cut this to four nights the savings is $270. At 16/mpg (as on mine) the distance covered at $4/gl diesel is 1,000-miles. So, how long I can park "free" on BLM land, for instance, is directly related to the trailers capacity for water, waste, food and propane.

The longer one can stay in one place without external inputs of any sort is a larger context than worrying over fuel cost (and then compounding that problem with years of time and effort).

One can play with this sort of thing quite a while. There are those who in retirement move once monthly versus once weekly to keep expenses down. $3000/monthlly is something of a bottom figure for RV travel. Those who say they can do it cheaper usually leave out considerable areas of concern (tent travellers, for example). There is a subsidization by the tow vehicle in that (very high relative miles). And lack of all weather shelter. It is possible, after all, to be sick or injured. Insects, vermin, the damp, etc, are all contraindicated in such (general purpose, in my view).

There is a ratio to be explored, here, would be the point. My starting point is two weeks of full independence as a goal for least expensive travel. Choosing where I park in order to minimize ground rent is just as important as fuel economy.

And that an RV so spec'd is also shelter for ones family when the lights go out back home. Expand the usefulness beyond being just the infrequent vacation (seen over a decade).

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[slowmover]

First linked resto/mod thread is by a formerly full-time sailor and his wife. Beautiful work, and a thread with literary quality. This is the size, age and "cool" factor beloved by those at vintage rallies (Franky, it is about impossible to top the cool & useful factor of this particular Airstream both in model year spec and owner modifications).

First she had to take a ride on a boat -- 1957 Caravanner

Second is a family of seven who have converted their second TT to a "bunkhouse" and with real skill, I might add. The addition of a dishwasher is worth noting. Uses less water, ha! Sold me on adding one to mine (as the "utimate" setup on mine is for two couples). This family used to use a 7.3L FORD diesel van.

Our 1986 32' Excella Rehab -- from rear bedroom to bunkhouse with two bedrooms

The quality of work, as well as material/appliance choices, is VERY high in these two threads. Cheaper is generally not better . . . and these trailers are good for another few decades without any real work.

(Joining AIR is free, and one can set page preference to 100-posts/page for easier reading).

As a comparison, the 2015 25' Airstream highly optioned is around $130,000. And a BOWLUS at $110,000 (one buys these not as a car but as a second house under terms of mortgage: low monthly payments over 20-years or more). A post-1996 Airstream is the best buy for least amount of work, and a 1980's model and later avoids some of the failings of earlier years. The 1950-1963 years are highly coveted and expensive to buy, repair and operate despite "ideal" size and shape.

There are a number of well-known shops specializing in Airstream resto, but it is $$$$ work. An excellent condition candidate (let them locate and buy it for you) is priority one in keeping costs down. Otherwise expect that, with the decision to buy or build your own -- starting today -- one is around five years out from using it to travel full time.

DIY has huge setbacks not usually well-examined. But the Internet has made possible reasonable comparisons. Two years for a good one bought today needing limited work (can be used in the interim, but full resto over a longer period) is a good approach.

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[ennored]

Do we know the drag coeffcient of a typical (any?) Airstream trailer? Google hasn't yielded one for me yet.

A little better than a sphere (≈0.47) maybe? Worse due to awnings, A/C, and other stuff?

[slowmover]

FWIW, I bought both trailer and truck in my sig for just under $30k, but expect to spend more than double that amount over time (this is my home, after all).

So lets look at a vacation for two or more people where access to a major national park is the point. Spend the time there in various activities. And a bit of other driving around for fishing.

From South Texas to Rocky Mountain National Park is 1,200-miles. If I stay two weeks at one location (paying the premium this area requires) and my daily fuel consumption is divided out by the number of days of the entire trip (or, say 2,500-miles to be conservative) as against ground rent we can come to a daily rate of fixed expenditure.

Who among us wouldn't want to spend two weeks in the Rockies during the summer? And to see the reasons our great-grandfathers chose such a spot for a national park.

I can easily carry three weeks worth of food for two as well as have enough water + propane before setting out. Call this zero daily travel expense. Quality food bought and frozen, etc. Wine, beer and spirits on sale. Like the trailer and tow vehicle it is not trip dependent. (my propane capacity for a trip like this almost isn't relevant even using the furnace nightly and cooking twice daily; an advantage of "big").

$3.25/gl diesel at Denver as of today. Same here at home.
2,000 miles at 15-mpg = 133/gls. $430.
200 miles at 9-mpg for summertime mountain traffic; $72.
300-miles of solo at 18/mpg = $54; or,
$560 at an overall trip fuel burn of 172/gls = 14.5 mpg.
21-days = 8/gls diesel/day, or, $26

At $4/g diesel, $690 or $33/day fuel cost for the trip.

At one of the RV parks closer in to RMNP: $600 for two weeks of full hookups.

$33/day for diesel, and $45/day ground rent.

$78/day over 21-days to go on vacation

Overnights en route -- sans utility hookups -- at truck stops, rest areas, WalMart or other is zero daily expense. And I still take a hot shower, cook meals and have electricity for general purposes. Stream a movie, read a book, you-name it. (This also applies to boondocking in the main).

With full utility hookups: two 15k BTU A/C, run the microwave/convection oven, dishwasher, hairdryer, espresso machine, home theater w/ surround sound, WiFi hotspot, satellite radio & television plus amateur two-way radio and clothing washer/dryer, etc. Mine really is a rolling condominium. But not a 7-mpg Class A motorhome or obese fifth wheel.

The adherents of this sort of travel call it "glamping" [glamorous]. With a separate genset I could do both. There are now hybrid solar/gensets that can keep both to a smaller footprint & weight and can run an RV most impressively. Using these other devices is a choice, not a requirement. (I don't have all the above, but could and likely will as the goal is comfort for two couples. Not all places are shirt sleeve weather and one can have the need to hunker down somewhere for an extended period).

So, $1100 to $1200 for a three week trip to cover fuel and ground rent. Short of fees for access to park amenities one can see that ground rent can be fully half or more the cost of a trip. 50-cpm in fixed expense plus food, propane and other.

Fuel cost isn't the problem given good vehicle spec at the outset. Figures above are conservative as I believe I could actually do better than this. A different trip to other locations in Colorado off season would still be about the same given the occasional need to replenish and refresh at an RV park, plus the mountain driving would cause a drop in towed mpg. Call it five days of hookups at $50/day. Or, $250 + fuel.

$1200 is a good number, IOW. Increasing mpg by a small percentage isn't going to change this trip. KamperBob does a more minimalist type of travel, and I recommend his blog, not just his advice (which is very good).

OTOH, I took up the challenge from Diesel Dave to try and see if my solo city-only mpg could be increased from 18-mpg. Over an 1100-mile test I averaged 23-mpg. That, alone, pays for around 5,000-miles of Interstate towing. Free fuel, boys & girls, if my then annual average miles savings were applied to vacation fuel costs. Just cutting annual miles by combined trips will do this without any hyper driving.

Focusing on the trailer isn't the payoff some expect it to be. A turbodiesel tow vehicle is where the money is. The right aero TT is the economical choice because it tows so well and lasts so long. Terms of independence from outside supply is the key, here, since trailer size is a negligible fuel cost given proper design, not low weight or short length.

Combine the two in a smaller package than mine (SUV or sedan + 23' TT) and fuel costs are better on average by 4-mpg -- for the trip above -- to 135/gls. Call it forty gallons ($160) or $7.50/day. A meal at McDonalds. But it may be easier to park somewhere (and at home) and has a lower utility cost overall, but at the expense of payload and water/propane capacities. Trade-offs abound. Etc.

60,000 miles is about the lifespan over ten years of a conventional plastic box RV. 25-years and 250,000 miles for an Airstream type TT . . . and then you rebuild it instead of tow it to the landfill. Run the fuel economy numbers against this time/miles framework.

An OLIVER as mentioned previously, is going to have most of the same benefits. Over 20' for a regular bed and good bath size is a minimum for extended travel in my opinion (and that of many others). I also prefer a tandem axle trailer as they pull so much better.

Make the SUV in the pic below a 3L DODGE EcoDiesel. For a new rig without the cost of an Airstream (the Oliver ain't cheap, though) long term ownership and operational costs would be near to best as could be. 20-mpg highway should be do-able given attention to lash-up details (a PRO PRIDE hitch).



Okay, Bubbas & Bubbettes, more than you want to spend. I get it. But see where the money actually goes. Don't overemphasize one aspect at the cost of others. Ain't nothing cheap to buy in vacation areas. Not to mention the time to track down inferior goods that takes away from being away. That'll kill any putative savings in fuel if more fuel and time is necessary to keep going when supplies run out.

Find out what is state of the art, now, and make good choices per your time as against being able to travel today. Five extra mpg five years from now doesn't seem so smart to me. KB's SCAMP 5'er does 15-mpg behind his small Toyo gasser pickup. It is of a size with decent capacities. And purchase price had to be low, lower than my low purchase cost I'd wager. As well, the ongoing cost of ownership on both vehicles (repairs and maintenance) will be lower as well. But not the fuel cost as it is barely $100 less for the same trip using conservative numbers. (I could re-arrange the type and number of miles to meet or beat his rig with mine as solo is higher for me). See?

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[freebeard]

Were this my approach -- modifying an all-aluminum trailer -- the early 1950's Silver Streak Clipper freebeard shows above would be the ideal candidate as the shell itself is already a very good shape. I sincerely doubt a home-made project OR existing trailer mod would offer any significant (measurable) improvement...

The Clipper has that optimal shape (on the outside, inside there is less overhead storage), but the construction is an outer skin of aluminum, aluminum C-channel ribs and the inner skin in steel. The additional weight isn't a problem as much as the combination is galvanicly active.

One will have ones hands full with re-building an antique like this (pipe frame and floor rot) so facilities to do a shell-off restoration are needed...

They all have floor rot. That's why I like shipping containers.

(Sorry to hear of that aluminum sheet fiasco, freebeard)

I'm over it. If I'd made that work, I would never have lived in the geodesic dome. That was good as it ever got, for me.