Matthewp's Off-Road Design (Critique requested)

[matthewp]

I have been floating around the issue of improving camping sleeping conditions for my wife over a year now (Kristy loves going out to the woods to experience nature but her one and only hold-up is the desire for a good sleeping platform). Finances finally allow me to get serious about it. I was in serious contemplation of a teardrop style trailer versus putting a custom camper on the back of a full-size truck (A la Earthroamer).

After weighing the pros and cons, we decided on a trailer. Our reasoning was my familiarity with trailers, the ability to "drop" our base-camp somewhere while we explore, and the cost issue of the build AND having to buy, register and insure another prime-mover. With that dilemma solved, I seriously sat down and designed the trailer. I had had an idea "sketched" in my head (and a few scribbles on paper) for the longest time. After doing a LOT of research this and other websites, I finally hammered the design together.

I HAVE to give proper credit to Elizabeth C. and her husband Jim for their beautiful Crowswing (the realization of a few ideas in my head that they so wonderfully hammered out, in addition to the wonderful advice and recommendations Jim has given me on design), and Stomper XJ who had the exact shape I was looking for. I also have to thank each of them profusely for great build threads to walk a novice like me through the process. For anyone interested in building a "sleep-in" trailer, please take a gander: Jim & Elizabeth's Crowswing (viewtopic.php?f=50&t=47781) and Stomper's Sawtooth XL (viewtopic.php?f=27&t=24959).

The basic planned specs are:

5' X 9' 6" trailer with room for a double mattress in the sleeping area.
Battery power with solar, shoreline, and tow-vehicle recharge.
12V and 110V capable
Marine refrigerator
30 to 35 gallons of water with electric water pump.
Awning with privacy enclosure on the curb side for showering, changing, etc.
10 gallons of extra fuel for the tow-vehicle and propane for our BBQ.

Please, I want your recommendations, critiques, etc. on how I can improve this design. Thank you! Forgive the prehistoric pencil & paper method of design:

[Irmo Atomics]

If you put as much into the build as you did the design, I'm sure that it will turn out great.

And now for your comment: " Forgive the prehistoric pencil & paper method of design"

If yours are prehistoric, mine are Precambrian:

torp_plan.JPG (145.2 KiB) Viewed 4474 times

[Chuckles]

Wow I built my house and workshop and I didn't have plans this detailed! I am more of a design...build...design...build some more kind of guy. And most of the design is in my head!

This is going to be one fantastic build.

My only thought is that you might be able to skip the upper metal portion of the trailer frame and build it out with wood to save some weight. Also, the slide out table could be attached to the side instead to reduce the number of potential places for leaking.

What's your time-frame for building? I hope to start mine right after deer season (late November) and finish it by May. I swore to my wife I am done sleeping in tents unless its on a wilderness canoe trip.

Chuckles

[matthewp]

Thanks for the compliments folks!

My only thought is that you might be able to skip the upper metal portion of the trailer frame and build it out with wood to save some weight. Also, the slide out table could be attached to the side instead to reduce the number of potential places for leaking.

My worry about making this a one level frame only is that the sleeping floor is suspended and I'm concerned it won't have enough support. Maybe I'm over-designing. I'd like to be able to figure out some weights to see what the difference would be. It would save me money as I have to have the local welding shop build the frame! Thanks for the thought, you have my mind working again.

EDIT: I just did the math and the upper frame adds about 150lbs minus the weight of the siding on the bottom 12 inches (between the upper and lower frames).

A detachable side table would save me a LOT of engineering too, now that you mention it!

What's your time-frame for building? I hope to start mine right after deer season (late November) and finish it by May. I swore to my wife I am done sleeping in tents unless its on a wilderness canoe trip.

Chuckles

I'm looking at starting the build early to mid spring due to the fact my house doesn't have a large enough garage.

[droid_ca]

This looks to be a good design if your building skills are anything like your design skills your going to knock this out of the park

[myoung]

Have you considered increasing the headroom at the front by reducing the amount of the chamfer or its angle. These trailers are small and hide behind the tow vehicle when going down the road so having pronounced sloped fronts are more aesthetics than aerodynamics. You might welcome the chance to sit up in bed with a comfortable backrest and adequate headroom.

Just a thought...free too...so weigh its worth...okay, not much.

Nice design. You're going to enjoy the adventure.

[myoung]

Also, 300-400 pounds of water is a huge amount to carry about. Have you measured how much you might actually use over the number of days you expect to spend between faucets?

[mezmo]

Consider adding hitch receivers at each corner of the frame/chassis.
They can come in real handy to attach awnings, extra table/counter
space etc. I think forum member Oasismaker has the best thread on
that if I am recalling correctly.

Cheers,
Norm/mezmo

[matthewp]

Have you considered increasing the headroom at the front by reducing the amount of the chamfer or its angle. These trailers are small and hide behind the tow vehicle when going down the road so having pronounced sloped fronts are more aesthetics than aerodynamics. You might welcome the chance to sit up in bed with a comfortable backrest and adequate headroom.

Having no familiarity with how these trailers tow combined with the concern about the large frontal area, I was worried about the aerodynamics. I would like to get a little more area up front. Thanks for the advice!

Also, 300-400 pounds of water is a huge amount to carry about. Have you measured how much you might actually use over the number of days you expect to spend between faucets?

I've been completely unsure of how much water to carry. I could get away with 20 gallons now that you cause me to think about it that way.

Consider adding hitch receivers at each corner of the frame/chassis.
They can come in real handy to attach awnings, extra table/counter
space etc. I think forum member Oasismaker has the best thread on
that if I am recalling correctly.

Cheers,
Norm/mezmo

I like that idea! I have been tinkering with putting one at the back but don't really have a reason why. Your idea to have the capability "just in case" is good! I never thought of it that way! Time to do some searching!

Thanks very much folks!

[myoung]

If you ask around you might get some idea about how much mileage to expect for combinations of tow vehicles and trailers of various sizes and shapes.

To start the ball rolling, my trailer with a frontal area of 6 x 6 feet with just a small chamfered top-front edge angled back about 20 degrees is towed behind a Dodge Durango SUV with a 5.7 liter Hemi. I routinely get 17 mpg driving all around the deserts and mountains of AZ and CA. My trailer floor is only 14 inches off the road, while yours is quite a bit higher.

Depending on how hefty you decide to make your trailer, it might approach the weight of mine, which is 1440 pounds.

[Bikerman]

IMHO, much of your framing design will depend on the suspension of the trailer, leaf springs, with or without shocks, air bags, T bars, or what have you. That will influence how the trailer frame reacts to the terrain and the twisting and flex that will be transferred from the frame to the framing of the cabin. You have a 6" drop toward the rear where it says electrical access. With two differnt plains acting at different moments and suppoted by the upright 6" or so pieces. How those are connected as well as other framing connections will matter. If this is steel or aluminum, welded, I can see that being sufficient. In wood, short members are weaker in a vertical manner, depending on the size of timber and methods of connection. I'd keep things supporting weight in a straight line or plain and build any lower compartment off from the vertical plain, just a false box without any structural significance to another part of the cabin.

You may also want to look at diagonal bracing front to rear and side to side to help reduce twisting.

Didn't notice the connection between the cabin and the trailer frame, but you might consider a three point mounting system keeping the trailer and cabin seperate (or four points), allowing the trailer frame to twist some without playing on the cabin.

A trailer from Harbor Freight for example will be on the shy side of stout, IMO, if you are using 2 or 2 1/2 box steel, you may have very little flex. Steel is stronger than wood or Fglass, so the joints made might be kept to a minimum, as the steel will work against the weakest parts. Thinking in three demensional terms.

While a curve or arch is stronger than two different plains joined together, I like your overall design, the Sawtooth is one of my favorites.