Travel trailer opinions wanted

[Frank Lee]

Put the TV + trailer through a tight turn and a dip in the road too, to look at clearances. My front end angle suggestion wasn't as much for style as it was for closing up the TV/trailer gap, which is an aero BIGGIE.

The height is definitely more important than the shape. If there is excess height in there for the sole purpose of keeping true to that roof arc, it is adding much excess frontal area, not only straight on, but that catches x-winds too. Pick a desired interior height (I'd pick 6'6" but that's me) and lop that roof arch off straight. See what that looks like.

[KamperBob]

Originally Posted by dpero

If I cut 8' off then I would be at 17' which is actually shorter than the Visa. I don't think that would help much. If you mention it simply because of the axle then as I replied to Frank, I can move it easily enough.

I'll probably be tapering the rear more which would center the bed more anyways. If I center it as I drew it, there would not be much room for access on either side. I want 2 bunks for the kids so maybe a bunk on either side in the rear would work better.

I suspect a trailer as long as you drew would need a second axle. If not for weight then handling. Also, your floorplan suggested interior space not fully used.



Bunks can use space well, especially if they fold (partially) for storage and elbow room when not being used. A pair of narrow 24" beds plus skimpy 24" isle to get between requires 6' width, inside.

Fun project. Keep up the great work!
KB

[euromodder]

Originally Posted by dpero

I was able to move the trailer ~20 in. closer to the van.

How about using that 20" to get a more bulbous nose ?
It can be quite blunt and still have good aero, but it'd be better than a flat slab up front.

I threw the axle in there without much thought. It does look too far foreword.

It doesn't look too much forward when seen by a European eye
To me, US trailers with their axle further aft seem weird.

Over here, axles are put near the expected CoG, with low tow hook weights as a result.

With such large side area, it's also important to balance the area fore and aft of the axle.
On the original design, it looks balanced as the rear end is longer, but has less height than the front.


With plans to start building a house, I'm looking for a streamlined cargo trailer

[KamperBob]

Originally Posted by euromodder

It doesn't look too much forward when seen by a European eye
To me, US trailers with their axle further aft seem weird.

Over here, axles are put near the expected CoG, with low tow hook weights as a result.

With such large side area, it's also important to balance the area fore and aft of the axle.
On the original design, it looks balanced as the rear end is longer, but has less height than the front.

I understand US tongue weight is about twice what Europeans use. For two-lane highways at 55 mph max (35-45 including towns) such a "large sail" configuration may be fine. On divided-lane expressways with large semi tractor trailers going 70-80 mph regardless of your speed, good aero and more nose weight keep your family safe first and foremost. Less hard on the wallet is a really nice bonus!

Originally Posted by euromodder

With plans to start building a house, I'm looking for a streamlined cargo trailer

My less-than-perfect-but-better-than-standard-cargo-box trailer (post 65) logged over 13,000 miles moving me cross country (many trips, over a year) with aplomb. Now it's helping build a 1,200+ square foot (plus second story) barn. When I'm done needing it, someone else will enjoy a nice, unique toy hauler.

Cheers
KB

[dpero]

Originally Posted by KamperBob

A pair of narrow 24" beds plus skimpy 24" isle to get between requires 6' width, inside.

KB

True but your upper body would still have a lot of room which may not make it seem so tight.

I just did a quick layout of that; With a 24" wide bunks, and at the current taper of the rear, there's 31" between in the front and 27" in the rear. But, I will probably taper the rear more so it may not work out.

[KamperBob]

Originally Posted by dpero

True but your upper body would still have a lot of room which may not make it seem so tight.

I just did a quick layout of that; With a 24" wide bunks, and at the current taper of the rear, there's 31" between in the front and 27" in the rear. But, I will probably taper the rear more so it may not work out.

Good points. Maybe I should have asked for clarification first what you meant by BUNK beds. If stacked then you'd crawl in/out so I'd want a wide. If not two stacked but just one each side but raised over say storage cabinets then I'd want extra isle to get up/down without catching a knee for example. Now that I think more about it, given reduced headroom in the rear maybe you meant twin beds (normal height). In that case they could be even closer maybe. They could lift up (hinged lengthwise) for storage access. Just thinking out loud some more...

Rock on!
KB

EDIT: Doh! Now it's obvious when I look on the site. Email notification doesn't show pix so I missed it. Clear now!

[dpero]

I see how you got confused. I guess bunks implies one bed above the other.

I did some playing to see how workable that idea would be with cabinets and such. After this I'll have to see how much I can taper the sides and flatten the roofline.

[SoobieOut]

Just a though enter my mind about the gap between the SUV and the trailer. What if you could use an accordian device like on a Articulated bus.


Just a thought.

[slowmover]

As above, the trailer does need tandem axles. The loss of a single tire on a trailer is hairy (to be polite) on a single axle. A tandem just isn't going to create that much more drag or problems. They tow FAR better, and the braking surface increase alone demands their inclusion.

As nicely as the sketches are going, think about systems. Water, alone, needs a fresh water tank, a grey water tank, and a black water tank. Plumbing runs are preferably short, so this is the reason bathrooms were conventionally located at the rear (along with the water heater). The fresh water tank ought to be just barely ahead of, and mainly atop of, the tandem axles. A trailer will also have to account for several batteries, 30A service panel, air conditioning, etc. Propane will also have to be accounted for by two tanks, underbody (exposed) runs to refrigerator, stove, furnace and water heater. The floor of the trailer will be at least 6" to account for tankage/frame alone. I would not assume a frame of less than 5" channel plus outriggers. Other walls should be at least 1.5" and preferably 2" or a little better depending on framing, so wall/ceiling thickness of 4" plus. An 8'6" wide trailer is down to 94" interior width. Etc.

Generally the kitchen, furnace, water heater and toilet are on the port side of the trailer, and the refrigerator to the starboard (same as entry door). Propane lines need to be short and straight.

Storage is compromised by anything other than a roof air conditioner, etc. And the roof is "busy" what with the need for A/C, ventilation ports, antennas (TV, radio, satellite, WiFi, GPS, etc), solar panels, and the need for service. A flat roof.

Windows are even more important. The lack thereof (a low glass-to-floor-area ratio) is a killer for comfort and live-ability. They need to sited to maximize outward visibility from a seated position, to induce cross-flow ventilation and lighting. Sticking a few here and there isn't to the point. Either I feel I am a part of the surrounding landscape, or not. Cheap trailers (plenty of "aero" ones) lack this.

Am stating the obvious that "classic" layouts on trailers still tend to work the best in re space vs accommodations. Check owners manuals or specs from late 1960's AVION and AIRSTREAM as well as STREAMLINE trailers for tank capacities, weight, etc, as your guide. The factory never did add in weight for options like A/C back then, but as a basis for sizing things, it ought to be of help.

Twin beds are 39x80, for instance. The aisle does not need to be 27". If you want folks to balk at a trailer, cut the beds down. The older trailers used to have fold-down bunk beds in place of (or integrated with) storage cabinets above conventional twins.

It's easy to lose space to all of this. Maintaining a 6' 3" head clearance is never as simple as with tube and caps (to describe the early clipper designs).

There seems to be 2 lines of thought regarding the aero; Saftey/towability vs aerodynamics. Finding the perfect mix probably isn't possible so comprises need to be made and I'll have to figure out where to make them.

There is no either/or happening. Most of the FE is in the tractor spec, not the trailer. A trailer needs aero more than weight reduction, but both are important. The order of importance is: livability (for a given size) and then packaged to promote best towing characteristics. Otherwise we'd just load a pickup with a wall tent and all the goodies. But no one wants to set up and break down a camp that takes 3-4 hours for each to have similar amenities.

So the question is about packaging. Unused space is undesirable (especially if it contributes to sail area) as FE gains are far too marginal. The bulbous shape would be better on a motorhome, IMO, where forces acting against the vehicle can be offset by a dual wheel drive drive axle for instance. And a motorhome that is in constant motion, not parked for long periods is where it would pay.

If I can get 16-mpg with a 3.75-ton 34' travel trailer behind a 4.5-ton pickup truck, what gain would a non-conventional shape yield? The same trailer as mine pulled behind a circa 1980 big gasser truck or car would have been 7-8 mpg. Were I to use Andy Thomson at Can Am RV (London, Ontario) to set me up with a Mercedes AWD fully independent suspension turbodiesel SUV I might see 18-19 mpg. With a smaller trailer (25-28'), maybe above 20 mpg.

But not with a cramped trailer . . . let's remember that 20,000 miles per year is quite high for TT use, whether for business or pleasure or a mix of both. I've rarely seen higher than that. The spread between solo driving and towing is classically 30% (or a bit higher). If I can reduce fuel burn by another 10% on a 30-mpg TV I have only gone from 21 to 24 mpg. At the usual 5k annual use, this is (@$3/gl; 208 vs. 238 gals) a savings of $90 per year. Barely a tank of fuel is all my 10% gain accomplishes.

Closing the margin for the TV (tow vehicle) for fuel mileage when solo and when towing is more easily achieved. I've wondered what an aerolid would do for my truck as THAT would increase FE without compromising trailer specification. As the TV and TT need to treated separately for aerodynamics it is the more promising course is the way I read it today.

I think that for a cargo trailer a basic teardrop shape is do-able. And as these are business vehicles by any definition, it is an excellent subject once capacity, balance, handling and clearance issues are defined. The gains would be substantial, are there are many, many very high annual mileage trailers of this sort in use.

But not so much for a travel trailer. Advances there are best left to the TV as the aero basics of TT design were hammered out by 1952 or so. Materials and cost of construction are the real constraints, not design per se.

.

[JasonG]

I've got to agree with Slowmover on most of his points.

An 18' trailer is going to weigh in at 5-8000 lbs. Axles are rated around 4-5000 in the smaller sizes.
having towed single,tandem and tri axles, lets just say I love my tri axle in cross winds
The 41' beast you see below tows better than my old tandem axle 35'.

The propane lines can be run below the floor but inside the belly pan. Yes mine came factory with an insulated full undertray. Its great in the winter. The tanks dont have to be fully outside but have to be in a sealed compartment with an open bottom.

I suggest the fresh tank go in a cabinet inside, under the bathroom sink is common. Balance the black and grey tanks around the axles. The grey will fill up at least twice as fast, trust me.

Storage space is a premium in RVs. Dinetes offer a huge advantage over table and chairs.

All that said, check your vans tow weight and especially the tongue weight.