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Old 01-07-2018, 11:03 PM   #1 (permalink)
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How to best improve an overland camper

Seeking wisdom from the experts over here.

I'm in the final design phase of an overland camper build. I have a design that I feel is structurally, mechanically, and ergonomically well put together. And while the vehicle has been built to travel anywhere, it still spends most of its miles on long stretches of highway. And so, I feel it's important that it's not shaped like a box

I've played with overlaying a variety of streamlining templates over the model, scoured the webs for similar shaped vehicles in wind tunnels, and tinkered with the overall shape until it stopped being ergonomic.

The vehicle is driven between 50-65mph, normally a few hundred miles at a time.

My research points toward the most gains from:
  1. Fairings between cab and camper
  2. Arched roof
  3. Modified boattail

The dry weight of the box will be comparatively light, less than 800lbs. The entire structure is constructed of fiberglass reinforced panels (FRP), foam for the exterior and PP honeycomb for the interior. Similar construction methodology to many boats.

And so, studying the attached model, what would you do and why?

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Old 01-08-2018, 02:24 AM   #2 (permalink)
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Welcome to the forums!

Radiased/rounded edges will be yer friend...especially at the front/nose of the camper.

Don't fergit to allow enough of a gap between the camper and the vehicle fer the times the frame flexes and the gap closes...especially at the top. You wouldn't want to find out that yer camper nose gits cracked or sheered off if it contacts the vehicle, right?

Keep in mind that yer gonna have to make decisions on what to compromise on so yer camper best fits yer needs.

Is there gonna be any kind of frame to keep everything tied together or are you gonna depend on the corner joints to be able to withstand the road forces? A frame would be highly recommended fer the top as it will encounter severe forces that will easily peel the FRP or foam right off the camper.

Have you inspected the other commercial camper tops up close and personal fer any ideas fer yer build? Does the top expand/raise up fer extra headroom when yer parked?
Mechanical latches that keep the top securely locked in place are a good idea.

I'm guessing yer measurements are in centimeters? So 1 cm is about .394 inches.
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Old 01-08-2018, 03:25 AM   #3 (permalink)
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Spotted this one in late June 2015 in front of a synagogue in my hometown. Even though it's not a Tacoma, might eventually serve as an inspiration to your project.

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Old 01-08-2018, 12:05 PM   #4 (permalink)
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The radius of the vertical leading edges would be a tenth of the camper width.
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Old 01-08-2018, 12:38 PM   #5 (permalink)
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BamZipPow:

A T100, great truck! I almost sold my current platform to get the extra width and stronger frame. Alas, it would have set me back in excess if $15000 in upgrades. Next time I suppose.

Lots of great questions and considerations! And yes, all measurements are in metric. I gave up on imperial for construction almost a decade ago.

All of the outside edges have a 4cm (~1.5") radius except the front which I'm experimenting with different molded noses.

The camper sits on a rigid subframe that is isolated from the chassis with a modified four-point torsion free suspension. I'm not sure similar the roof of the T100 is, but the roof of Tacoma has a lot of curvature side-to-side and front-to-back. The closest the cabover sits to the roof is above the 3rd brake light at about 3cm. From there outward it increases to more than 6cm in the sides and front. The frame has been boxed the entire length of the C-channel in the rear. I think with the reinforcement and the short length of the cabover it's improbably that even fully flexed the cab can contact the camper.

My design has no exoskeleton as you may have observed in similar one off builds. The exterior panels are constructed of a sheet of 17oz woven roving glass, 50mm (~2") of foam, and a 34oz WR exterior. The panels are joined with dowel and epoxy resin. After it sets, the edges are routed, layers of carbon fiber and fiberglass are laid up to reinforce the joint. The inside is filleted to similarly join the panels. I have some testing to do with the panels, joints, etc, but I suspect this will be more than sufficient.

I have done a couple years of research, taking a page here and there from mostly individual or smaller builders. There are not many similarities between this and the commercial 4WC or Phoenix pop-up other than the size.

It does expand, with folding rigid panes, to an interior height of ~6'4". The roof lift is hydraulic - both supporting and locking it in place.

I've attached an expanded model.

Cripple Rooster:

I think I've seen photos of that vehicle. Yes, there are some similarities, especially being a smaller vehicle. Very clever pop-up in the sleeping area on that one! It all comes down to knowing what you need and what you can live without. Or maybe more importantly, what your partner can't live without
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Old 01-08-2018, 12:47 PM   #6 (permalink)
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I see a theme here... leading edges.

This has been mentioned here MANY times, but once more doesn't hurt:
https://history.nasa.gov/monograph46.pdf

Within it you'll find not only the often mentioned "Dryden van", but also the image below (p. 28-29). A 30% improvement due to the leading edge treatment!

I often post in truck/trailer/RV posts. If you search my username, you'll find LOTS of posts about the subject.

With the pop top, you have done one of the best things you can do aerodynamically, reduced the frontal area.
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Old 01-08-2018, 12:56 PM   #7 (permalink)
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Quote:
Originally Posted by Grant-53 View Post
The radius of the vertical leading edges would be a tenth of the camper width.
Can you please explain how I'd use this information in designing the nose or fairings. I was thinking something along these lines in the front. Is there something that would be more effective?

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Old 01-08-2018, 03:05 PM   #8 (permalink)
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Quote:
Originally Posted by ennored View Post
This has been mentioned here MANY times, but once more doesn't hurt:
https://history.nasa.gov/monograph46.pdf"]https://history.nasa.gov/monograph46.pdf
Wow, what a wealth of info. I'd stumbled across what I suspect was an abstract from some of the independent studies, but that in its entirety is very helpful!

Thanks!
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Old 01-08-2018, 03:26 PM   #9 (permalink)
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Your [minimal] box van has particular requirements. The Template is a Procrustean bed, ignore it. Look to U-haul rental trailers for guidance on front radii.

What is the purpose of the detail in the frame rail between the bumper and rear tire? It looks like a dump-bed hinge.
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Old 01-08-2018, 04:35 PM   #10 (permalink)
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Tires+

Unless you have a hard requirement for A/T tread for lots of mud, for example, then street tread is not only quieter on pavement but wears better. I've been on the road 6.5 years and 130k miles. Once my stock LRC P-rated tires wore out I went to LRE LT tires. The trick in my case was bumping from 265/70R16 to 75 aspect ratio for market availability of LT choices and LRE rating. I went Michelin LTX2 (no regrets) but other choices abound. My truck's always loaded so I can run these 60 instead of 45 psi. It feels the little bumps more, yes, but the truck handles better and rolls along easier with a bit better MPG. And they're wearing favorably - slowly and evenly. The 75 tires were a couple percent larger OD than 70 which also corrected the optimistic speedo cal. so that was a bonus. As for street tread I've only been in soft sand, dry washes, rocky canyons, slushy snow and dicey ice a minority of times but I've never had a problem with traction. I also hope 10 ply rubber plays Murphy insurance against roadside assistance; and so far, so good, knock wood.

As for box design I did my share along similar thoughts before and during this chapter of my life. I even had a four-wheel pop-up on my Tacoma before it was suceeded by a Tundra. But I set off full timing with a trailer camper. And while I've stuck with the Scamp brand I downsized from the 19' fifth wheel to 13' std hitch, mostly for bed cargo reasons. I still noodle over slide-in designs but at this point (early fifties) I'm less enthused about a scratch build. In my future I can see a Bigfoot slide-in but on a heavier duty truck with larger/dual fuel tank for extended range. I'm less obsessed with record MPG and more focused on the happiness meter. YMMV

Any RV is eco friendly compared to houses and even apartments or condos. And micro campers leave the smallest footprints. So my advise is to think through YOUR use cases to develop the requirements that best meet your needs and wants. Shaving box width or height, tapering rear, and rounding front edges are excellent ways for less less wake and drag on the road. Just make sure that once stopped to enjoy the world, that you're not too stooped or cramped, for example. Make sure you budget enough weight and space capacity for food, clothes and gear you really want to enjoy. The more of those corners you can see around now, the better things can go later. I also hope you thoroughly enjoy the build. Right now that's probably the fun part.

...and keep us posted - before, during and after!

All the best
Bob

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