4X8(ish) Benroy Build

[Wobbly Wheels]

With my 'big' foam-and-glass trailer build on hold until I move into a place that has more room to work (prob in the spring), I figured I'd try and do something a little more modest. After some time with a sketch pad, I settled on the Benroy profile. I went with a simple 36" radius on the back and 18" on the front.

I did up a composite floor of wood and foam rather than sheets of ply. This gave me a stiff floor while keeping the weight down, and decent insulation to boot.
I started by ripping 2X4s for the perimeter frame to accept the 1/4" ply skins. I also ripped a notch to accept the bottom 1/4" of the sidewall skins so that the end grain of the ply would never be exposed. It will also give more glue surface for a stronger wall-to-floor corner joint. Due to a gaffe in setting up the saw that I didn't catch until I had made the second rip, the space for the insulation was going to be 3/4" instead of the 1" I had originally wanted.
I mocked up the floor to wall joint with some scrap pieces - the 'thousand words' is no problem for me, verbose as I am, but a pic still beats it:

The upper floor skin in the pic is 1/4" scrap rather than the 5mm ply I'm using so it isn't sitting proud the way it is in the pic. On the right is the 1X2 wall stud (on the flat) and outer skin, but what it doesn't show is the lower sill plate of 1X2 that will be glued and screwed to the 2X4 frame below, exactly the way the walls are secured in building a house.

I forged ahead and continued ripping the rest of the 2X4 with the new dimension after coming up with plan B. Locally, I can only get Korolite (XPS - white beaded styrofoam) sheets in 3/4 - EPS (the blue and pink) is available only in 1" and up. The internal spars I had ripped 1" wide from 3/4" stock, so I could lay them on the flat and use the 3/4" as the height instead. I could have laid in 1" blue foam and longboarded down the 1/4 in a flurry of pink or blue snow, but opted to just use the Korolite instead. I didn't like it in the floor in the other build, but that was because my top skin was too thin and didn't spread the loading out enough so the foam was crushed in spots, creating voids. With 1/4" ply and internal framing (which the other floor also didn't have much of in the name of saving weight) I doubt I'll have the same problem.

The main reason I went with a perimeter frame rather than just sandwiching the framing between the skins was because my trailer's frame rails are 48" apart inside-to-inside, so a 48" wide plywood sheet had to 'grow' a little wider to fully bear on them. This is the donor I'm starting from:


I didn't start taking pics right away, but I did get a couple of the floor going together. The frame is assembled with mitred and screwed corners and the lower skin is pinned on. I'm using TBIII on the wood joints and latex contact cement on the foam. Glue is dry and just about to put the rest of the foam in:



The upper skin is on as well now and I've got the sidewall skins profiled and cut out. I ripped all of the 2X4s to the same dimensions, so it grew in length as well. That's not a problem for the trailer because it's longer than I need, but it does mean that the wall skins need to be 'stretched' a bit to run to the outside of the frame rather than to the inside like the floor skins which will happen at the door cutout.

I waffling between having the leading edge (hinge side) of the door set either 12" or 18" back from the nose. I like the look of 12" on paper, but 18" means that a square-ish door can be taller without needing a radius at the front top corner to match the profile's radius. My major consideration, though, is ergodynamic with respect to getting in and out of the trailer and bed. I don't want to decide on one way and then wish I'd done it the other way, but such is building...and life

I am starting on the wall framing today - gotta wrap this up and head out to pic up the 1X2 and the undercoat and carriage bolts for the floor...
Because I have to minimize the amount of time I have a trailer 'under construction', I am pre-fabbing as much as I can in flat panels in the basement. I figure I'll frame the walls right onto the skins, leaving space for the roof spars. That should also make it easier to assemble the whole thing on the frame.

..."should"....

[Wobbly Wheels]

Well, I picked up the 1X2 yesterday - a bundle of 10' that will each provide two roof spars and a bundle of 8' that will provide 4' lengths for wall studs. When I broke open the bundles, they were far too wet to use so they are stacked and stickered and I'll check em again next weekend...I think I'll grab a couple more bundles and get them drying as well since I think I'm going to lose a lot after cutting out knots and checks.
Cue the ranting about declining quality of lumber and how 'standard' or #2 isn't anywhere near what it used to be...

I did get started transferring the layout onto the side walls at least. I grabbed the windows out of storage and, besides needing a good cleanup and some new screening, they are in good shape. I've got a couple of jalousie (slat) windows for the cabin sides and a vertical slider for the head of the bed on the curb side. I want to put a long horizontal window on the front above the tongue box with a stoneguard that opens to a hard awning, but the ones I have are too long for the trailer's width. I'm trying to use parts and materials I've already gathered to keep costs down but I'll figure something out. I do have a 12" Bomar marine deck hatch I could use...

Here's a side panel showing the profile:


When I did the layout, I started with a horizontal line 3/8" from the bottom. That's the depth of the notch in the outside of the perimeter frame and will serve as datum for subsequent measurements. I laid out the door's hinge side at 18" from the front to get the corner of the door out of the front radius. It will also give me room for the vertical sliding window that I wouldn't have if I set that measurement at 12". The foot of the bed is set at 75" + the framing thickness of the front wall (1 1/2" from the inside of the outer skin + 1/8" for an inner skin).
With its current wheels and no spring compression, the top of the trailer frame sits 17" high. I added the thickness of the floor and subtracted that from an arbitrary 32" target for the counter height and got 13" height for the foot of the bed. With a 24" deep countertop, the footwell of the bed is about 10" deep, plus however deep I make that cabinet.

Since I'm just using a 2 burner propane cooktop, I'm thinking I'll mount it on drawer slides under the countertop like a keyboard shelf. I should have space for an LPG hose to curl out of the when when it's closed and I'll need to rig a lock (or use a locking drawer slide). That way, the stove can be plumbed permanently to a 20lb bottle on the tongue but not taking up counter space when not in use. Another thought is to mount it so that it swivels out 90 degrees to the counter with a drop down leg. Of course, there's always the K.I.S.S. option of just using a cannister stove that I can move to the picnic table...which is probably what will happen, at least at first.

With the framing on hold while the wood dries (grrr...), I rounded up the pieces for my electrical system so I can start fitting them into the layout of the tongue box.
This is the heart of it:

I have about 200A*h of battery (50-100 useful A*h), a battery switch, an isolator for charging, an AGC fuse panel (though I may go with a Blue Sea 5025 ATO panel instead) and a 1kW inverter. Not shown is the charge controller for a 60W solar kit made up of four 15W panels that will maintain the batteries while in storage. I've got 12V flourescent lighting for the galley, dome and reading lights for the cabin, and LED courtesy lights to provide some ground lighting for answering the call of nature in the middle of the night.
I'll also have a circuit for a cabin fan and I'll run the wiring for a Fantastic Fan as well, though that hole will be filled by a standard 14" roof hatch for the time being. A car stereo should round out the DC side of things, unless anyone can suggest something that they wish they had allowed for...

Since I have so little electrical load, I figure I'll run 8AWG wire from the batteries to the switch, inverter and DC panel. From there, it'll be 16/2 boat cable for ease of pulling and abrasion resistance - boat cable has two insulated wires inside an additional jacket, like an extension. All wiring will be tinned marine wire to avoid corrosion, the 'creeping black death'. Everything in the pic above will be enclosed in the tongue box to keep cable runs short, except the fuse panel. That will probably go inside the cabin somewhere. I already have the tongue box in 3/4" ply, though I need to make up new lids for it. I figure I'll mount the electrical under a false bottom so I can use the space above for storage. The lower battery compartment will be vented so that batteries can off gas. There should be just enough space in front of it that I can mount a 20lb bottle and a jockey wheel on the bridle.

[Graniterich]

I like your planning. Where are the courtesy lights going?

[Wobbly Wheels]

Thanks Graniterich. I have a bunch of stainless steel exterior LED landscape lights intended for steps etc. They are 12V and they daisy chain together so, while I'll have to figure out the exact placement later (but before the inner skin goes on), they are thinner than the wall framing and require a simple 1" round hole. There will be a couple in the cabin that I'd like to run off an illuminated switch, but I mainly want them pointing down under the doors and galley to light up the ground there. I might put one in each side of the galley as well, facing inwards. I figure that, since I've already got 'em, I might as well use 'em

[pchast]

On drying that wood. Stickers are not enough.

I hope you weighted a flat board on top to hold things in place. Otherwise its
not uncommon to have wet wood twist and warp as it dries...

[Wobbly Wheels]

Thanks Pete - yeah, I got pavers on top of the stack to keep 'em straight. Good call.

[Vedette]

Hi Brian
Great to see you are building!
And making great progress from what I can see.
Would love to see you up and running by next camping season, and maybe at the Farm Gathering!
Keep going hard man!
Good Roads
Brian & Sandi

[Wobbly Wheels]

Thanks Brian, good to hear from you !
By posting it here, I'm committed to seeing it through now
I've got a month off over Xmas, so I'd like to have the bulk of it done by the time I go back in mid-Jan.
I'm definitely in for the Gathering at the the Farm, but I'd love to get this thing done and darken your doorstep before then.
Can't wait to meet you guys and see Miss Piggy in person (and Kermit, whatever stage he's at)

[Wobbly Wheels]

So, tonight I figured I'd round up what framing lumber I had and start making some sawdust while the other stuff dries out a bit.

I got the section forward of the door laid out, including the window (which will be on only one side) The idea is that I can use this as a master frame and just duplicate it for the other side, adding things like the AC inlet etc as needed. Piece of cake, right ? We'll see....

This is where I got to - nothing's glued up yet.




Now, these are my options for hatches: the one is a marine hatch that I need to get a replacement window for (about $30) and the other is a solid aluminum hatch that is ready to go, short of riveting the hinge back on and some paint.

I'm thinking I want to use the aluminum hatch, cut out the center ring, and use some marine glazing adhesive to glue in a piece of plexi...but I dunno yet...

[pchast]

Talk to some others for an opinion... But ... you are using a lot
of framing maybe more than you need, IMHO. Especially in a 4x8...

Please look at some more designs and "think aircraft instead of
house frame." In most cases the skin is the strength.

[Wobbly Wheels]

Thanks Pete - I'll give it another look before making anything permanent

[Vedette]

You obviously have some woodworking skills!
We are all confident that you will be camping with us sometime in the 2015 camping season.
Glad to hear that the Farm Gathering is on your proposed schedule.
Thanks for posting pictures ...... wish I could get some up from my project.
Stay tuned for a TJ B.C. Chapter update.
We just got two new members in as many days!
Good Roads
Brian & Sandi

[Wobbly Wheels]

Heya Brian,

I'll be eagerly watching my email, especially now that things are up and running again on my end. Looking forward to the update

You obviously have some woodworking skills!

If they're anywhere near the tin-bashing prowess you showed building Miss Piggy, I ought do ok.
Seriously dude - there's what....3 cars welded together into the porcine masterpiece ? That just blows me away....

I started laying out the back half of the framing (galley) and glued up the front half, restricting it mainly to just what I need for nailers for the ply panels.

[Graniterich]

Thanks Graniterich. I have a bunch of stainless steel exterior LED landscape lights intended for steps etc. They are 12V and they daisy chain together so, while I'll have to figure out the exact placement later (but before the inner skin goes on), they are thinner than the wall framing and require a simple 1" round hole. There will be a couple in the cabin that I'd like to run off an illuminated switch, but I mainly want them pointing down under the doors and galley to light up the ground there. I might put one in each side of the galley as well, facing inwards. I figure that, since I've already got 'em, I might as well use 'em

I had brand new leftover 12v yard lighting as well! I took them apart, and found 3 led cluster in a 5/8 inch circuit board. Drilled six holes, 4 inches apart, in a 1 x 2 and glued a module in each one, thinking about using as cabin or galley light. I have a couple of rolls of led lights with adhesive on back coming form china. The are about 15 feet long with 300 leds. They are waterproof, bendable, and can be cut up to any length I want

[Wobbly Wheels]

Granite, that sounds like a great idea for an under cabinet light ! I was playing around with some of those cheap aluminum flashlights a while ago, thinking I could take the heads off and inset them in a similar way, though they are running on 4.5V (3xAAA) so it would take a dropping resistor or some such to run them off 12V. There are also inexpensive LED replacements for auto bulbs like 1155's and the sockets are cheap - one could put lighting into just about anything that way.

Made some progress on the trailer, getting the frames done and the skins cut down. I need to 'stretch' the plywood skins a few inches to allow for the floor's perimeter frame. I made the frame to accept full 4X8 sheets (you might recall that my trailer's stringers are 50" apart) so the plan was to have one piece forward of the door and one piece from there back. I will scab in a short piece to fur out the header on the doors to the same plane as the skin.
Don't you love it when you build something in pieces and, when you assemble it, it aligns perfectly with the marks ?
I fully expected to have made a few mistakes because I'm kind of pushing to get this done, but so far so good. I'm going to start design furniture for IKEA next I think



The small diagonal braces you see are temporary - the top end is the frame for one of the jalousie windows I'm putting in. On the left, you can see a short vertical length of fir 2X2. I need to pick up some more, but there will be another one on the other side and the hatch hinge spar will be mitred into them. I have some clear red cedar planks about 12' long, 3/8" thick and 2" wide that are left over from planking a boat. I am going to rip them in half and laminate them into the hatch spars. The outer skin will be two plies of whatever 1/8" material I use for the roof skin and the hatch won't have an inner skin.







It's assembled dry right now so I can take it apart and carry it up the stairs in pieces from the yard to the driveway where the trailer is. I want to get the panels as complete as possible so I can take them upstairs and assemble them with as little construction going on in the driveway as I can manage. I am thinking about using polyester resin and 3/4 oz mat as my outer finish, so if I can have the skins on the frame, I can glass them and then glass the seams when I put it together. I'm using TB3 on the wood joints and probably PL Premium to bond the skins to the frames. We don't have much selection for lumber here, so glassing will let me go with luan or something for the roof since it's really just a backer for the glass. We'll see....