Designs for the TTT Mobile Mango

[MadMango]

(I relocated this from the Build Journal).

I've decided on a 5x8 trailer with full-size 15" wheels. This should get the towing height close to my F150 without having to use a drop hitch. I've got a preliminary design going, but I already see some changes I need to update. I was going to build composite walls from 1/2" plywood, sandwiching 3/4" rigid foam, with a 1/8" interior skin. I would use 1x2" furring strips to stiffen the wall perimeters and internals (staples and glue). After some reading, I am thinking of substituting 1/4" plywood for the 3/4". The floor will stay 3/4" plywood.

I'm not too worried about aerodynamics, I figure the rear of my truck will have plenty of turbulent air to make any rounded corners a mute point. Camper and trailer should weigh around 850-900lb, so it should tow fine.


Isometric top view. I'll use two 14" ceiling vent fans, and mount my solar panels topside.


Galley will have a slide-out for easier access storage. I might change this around and add another slide-out for a cooler, or just secure it to the top of the counter. I need to add little 12v pump for running water. Still working out the details in this area.


I'll relocate the fenders to the camper body, and will probably have to cut them down in width. I want to keep everything within an 81" width. I might also try fitting in a 3" PVC pipe for fishing pole storage on either side, under the camper body overhang.


Building on a trailer with a 12" side rails affords me leg room to sit inside when the cushions are made up like couches. We are going to give ourselves 72" of horizontal space for sleeping, though I may push it to a standard 74", or just create a foot pocket for the extra length. By building on top of the trailer side rails, it also yields 36.5sqft of storage space. I'll also construct a sling/cot (material sewn between 2 closet dowels) for my 4yo that is easy to move when needed.

I searched this site trying to find a similar build (using a trailer with side rails), but I wasn't successful. If anyone can provide links, that would be great. I'm looking forward to any and all feedback! I'd like to solve most of my design issues prior to cutting any wood. I don't have a garage to build this in, so I am hoping I can pre-fab all the wall, floor, hatch, and roof panels first, then connect it to the trailer and store it under a tarp.

Thanks for looking.

[Camp4Life]

Nice, I like it! And yeah, with a F-150 you won't even notice it's there. For the aero though, there's a good drop off the truck's roof down to the bed and then the air comes straight off the tops of the tailgate, at least on the newer models. My 2015 has the newish design tailgate that's almost like a spoiler. You might want to take that into consideration because the airflow will come right off the top of your bed and hit the flat front of the trailer. Probably won't make a huge difference with a truck mileage-wise, but something to consider maybe. Not sure if you can have the angled part come down near the top of the tailgate...

Can't wait to see the finished product!

[BigGoofyGuy]

I think that is a really nice design.

[MadMango]

My wife didn't enjoy the 38" climb to get into the trailer, so I went back to the drawing board.

Side View- based on a standard 4x8 plywood sheet, now with only a 25-inch step to get in.


Top View- still two 100w solar panels.


Front View- it'll be 60-inches wide and overhang the wheels.


Galley- she wanted a lot of counter top space, she loves to cook when we are out.


Galley Extended- foldouts galore!


Doors- angled piano hing with gas spring, seal will be on the door instead of the body. Windows will just be flush mounted, tinted plexiglass.


Door from the Front- should provide shade and rain protection if we need it. The door opening is tall enough to sit and not hit our heads.


Interior- the "bookcase" area will have sliding doors to retain small and light items.


Interior- that's no bookcase, it's a loft bed! Our 4yr old should have several years of enjoyment in this. We are thinking of a 3-inch thick memory foam full-size mattress topper for our bed. We'll have to cut the corners near our feet to fit between the wheel wells.


Storage- shallow, only 8" deep, but should be plenty.


I still haven't decided if I want to build on the HF 4x8 trailer or the NT 4x8, so any opinions on that would be great. I'm also having a hard time figuring out how to latch my side doors and have them lockable.

[KCStudly]

Seems much easier to build.

I have a concern about your doors. The wider you go with a simple ply door the more likely it will warp or wing. The more you cut out of that door for windows, the more likely warping becomes. Just saying, you may want to add a 1x frame around the perimeter to stiffen it up.

You mention that the door is tall enough to sit in, but can you stand up under it when getting in or out?

[OP827]

I agree with KC concerning the doors, especially in combination with additional force on one side from a gas spring ..

[MadMango]

KC,
I'm still investigating the door design. I may add 1x2 frame as well as an inner skin of luan. It will still require one to crouch down to get in or out, but at least you can sit on the edge to get your footwear on or off. I could go with a long gas spring to get the door to open more, I may look into it.

[KCStudly]

I would suggest it.

During my build, at times I have had the cabin sitting down on a build frame at a lower height than it would be when it goes on to the trailer. Just leaning in to pick things up I have clocked myself on the back of the head on the door flange... hard... on more than one occasion... when standing back up. I don't think this will be a problem for me once I'm at normal ride height. I'm just saying, ergonomics count and this wouldn't have been something that revealed itself in a sit test. Consider all of the actions you might take in and around your TTT, reaching in for an item, walking up to the door in the dead darkness of night after a few brews around the campfire, climbing out at night in a bit of a daze (be it from groggy sleep or those rent-a-beers consumed earlier).

Another thing to consider, several people have done gull wing style doors for the cool factor, or to suit certain profile/geometry issues, and, to my recollection, the consensus has been that they are a pain in the arse to close after getting inside.

I'm not trying to discourage the creativity shown in your design. I'm just trying to help make sure that you hash it out well enough that you end up with something that functions well and that you enjoy it in the end.

[MadMango]

KC,
I appreciate the feedback! That's what this space is for, or so I hoped.

I decided on the gullwing door mostly in thinking that at highway speeds, having the hinge sort of on the leading edge would help with preventing water getting inside during a rainy jaunt. I had planned on a pull-handle (just a nylon loop) on the inside of the door near the gas spring that could assist in closing it while inside. What type of latches still have me stumped.

[KCStudly]

That's another thing to consider. Even if your door is relatively rigid, between the hinge and the door latch is essentially a triangle. So if one leg of the triangle is much bigger than the other, then the springiness of the door seal might tend to cause the door to flex a different amount to either side, perhaps enough to keep one side of the seal from compressing fully. I don't know if there have been any cases of this in real life, but it is something that I considered when arranging my hinges and latch; and is a good rationale for building nice rigid (albeit light weight) doors.

You really want to avoid having to have more than one door latch; that would be a pain in the (insert you word for not so ergonomic here).

[MadMango]

I'm not one for wiring and electricity, even though I was an electronics tech (FC) in the Navy. That was a long 20yrs ago. Can someone sanity check this for me? This is what I have planned.

1. I want to be able to switch between shore and solar power. My understanding is that I do not need blocking diodes if I make my connections after the charge controller, as they already have them built-in.
2. I will use a 6-output, 12VDC Blue Sea Systems distribution block.
3. The DPDT switch between shore and solar power is rated for 20A, is that enough?
4. This is a budget build for now, so I will just use an existing battery charger instead of a dedicated and switchable RV style power converter ($$).
5. From your experience, do I have enough 12v outputs?



Thanks!

[KCStudly]

I would look for a simple way to have the power strip run directly off of shore power when connected. Running from 120VAC thru a battery charger/batteries/power inverter is inefficient, and the battery charger may not be able to keep up with demand.

In other words, with the current (pun intended) arrangement shown, you may not be able to indiscriminately run all of your 120VAC goodies w/o draining the batteries, even when connected to shore power. (I assume you will have a high demand based on having two batteries. Are both really needed?)

You want to be able to charge batteries and use 120VAC all at the same time.

[MadMango]

Hey KC,

These are smaller AGM batteries, only 35Ah, not the full-size ~50Ah car battery. I want to be able to be on solar through the night running a few 12v fans and lights, with capacity to spare. Sealed batteries are about $1.85-$2.00 an Ah, having two smaller batteries was more cost effective when comparing $/Ah.

I could always directly run a power strip from shore power, that is what I did in my old '88 Ford Sportsmobile. I was talking to a few RVers, and they were the ones to suggest the battery charger in lieu of an actual power converter.

[KCStudly]

Yeah, I think an on-board charger is a good idea and have one in my plans. The issue is that the typical charger works low and slow so it doesn't work too well as a power supply for active loads. You could be taking it out faster than you are putting it in.

Check out Flboy's circuit diagram. He is building a big CTC, so the system is definitely overkill for a TD, but from my perspective (not being any kind of electrical engineer) it looks to address switching from solar to shore to batteries well.

[MadMango]

Thanks for posting a link to Flyboy's schematic, I would have never thought to add circuit protection in my lines. I just found these inline circuit breakers, and I think they will work out perfectly fine.