Hiker Trailer Inspired 5x10 Foamie Design

[Falco-4]

I'm continuing to work on the trailer frame, bit by bit. I got the front and rear bumpers mounted on Sunday and assembled and attached the tongue yesterday. The only minor issue I ran into is that the instructions are unclear where to start subs of the measurements, which made the tongue mounts a tight fit without moving things, but it all went together in the end.

As I was wrapping up last night it occurred to me that the cross member attachments didn't look like I expected. I had assumed that the cross members would sit flush at the top with the upper side rails. Instead, they seem to be about an inch lower (I didn't measure yet). Also, the span between cross members will be anywhere during 2-3 feet. Lastly, with the brackets, washers, and bolt heads, I think I'll want to built 1"-2" wider than 5'. The frame is 5' from outside of one rail to the outside of the other.

All that to say, my first big decision is going to be how to build, support, and attach my floor. I'd like to avoid adding any extra height above the side rails, so want build weight on the frame. I feel like 2" foam sandwiched between 2 layers of 1/8" plywood should be plenty strong for the spans but don't have wood or foam purchased to give that a try yet. I'll either need to fill the gap between the to of the cross members and to off the side rails, or raise the cross members.

I'm lean towards the later. I think that I could flip the cross member brackets, drill new holes I'm those and that should make it level, I'm just not sure how much of be undermining those brackets by flipping them.

I'll have a bunch of time to think because I found a guy seeking scratch and dent test doors from Hiker trailers (42" x 42") for$40, so I'm making a long drive to pick one up. It's over 4 hours one way, but the price feels too good to pass up. I also found a nice set of roof bars for really cheap that I'm planning to pick up next week.

 

[Falco-4]

So I had a thought or 2 on my frame issue and could use some feedback of anyone sees issues. Since following the instructions will leave my frame rails approximately 1" above my cross members rather than flush, I thought I could:

a) Run a 1x2 down the inside edge of the frame. These boards could attach to the mounts, then the cross members could attach to the boats.

b) I could flip the mounts over and then drill/screw the cross members into the mounts. The only issue I see is the L shaped brackets would hang rather than resting on top of the lower frame rail (see photos)

Normal mount position. It's hard to see, but there is a gap between the top of the mount and the upper frame rail.

Mount flipped upside down. Tails would need attached to the higher surface which doesn't have mounting hinges.

Also, I went and picked up the rear door and also lucked into finding side doors! They were over 4 hours away, but I was able to get all three doors for $140! The side doors have been installed and they're are a few surface scratches, but nothing that can't be touched up.

 

[Falco-4]

Finished up the trailer assembly this weekend with some help from my dad. I ended up deciding to just install the cross members as designed, I was worried changing too much would weaken the construction.

You see I've been contemplating how I'm going to do my floor attachment with the recessed cross members. I found some 1x2 cedar boards at Menards and think I'm going to go that route. My sandwich floor will sit on the cedar spacers and on the outer frame rails.

I'm at a bit of a standstill as I haven't bought foam or plywood yet, so I started buying together a battery/electrical platform that will eventually go in my tongue box (that I also haven't bought yet).

Here's my general setup so far.

 

[Falco-4]

I found a good deal on Marketplace and picked up a toolbox for the tongue last weekend. After setting it on the frame, I was worried it might stick out to far. But after a quick test, I can turn full lock to lock and still have about 8"-10" between the box and the TV. It would hit if jackknifed, but I think it's enough clearance to be fine.

Should give lots of addition storage for a low weight penalty, since the box is aluminum and only weighs 35 pounds.

I also weighed the frame using a bathroom scale and adding the two tires plus the tongue. I came up with 485 pounds, which is 85 pounds more than I'd budgeted.

 

[Falco-4]

Been on hold for a bit while I wait to get foam and plywood purchased. In the meantime, I did purchase some stainless steel wire and get my hotwire cutter working. The wire has more flex than I would like but I think I'll be able to tweak the voltage and amperage to get it to cut well. I'll also need to build a few different wire cutters to use.

This is the wire I bought. Seems to work well, if a little more flexible than I'd prefer.

I'm using my rc battery charger. I have a computer power supply I've modded to power it, and the charger has a dedicated hot wire mode where you can set the voltage and amperage you want to output a well as a timer for it to auto stop.

This is what I built for a cutter, modeled after @ghcoe . I'll build a few different ones for the cuts I need. I think with my charger being variable I could shorten my wire length, but figured I'd just start with something I know has worked for others.

I only made a couple test cuts, but it seems to work fine. I plan to experiment a bit with different settings to see what will cut the smoothest. I'm not sure how to do a cutter for the long cuts, but most of them should be straight so might be fine snapped with a box cutter.

 

[ghcoe]

Been on hold for a bit while I wait to get foam and plywood purchased. In the meantime, I did purchase some stainless steel wire and get my hotwire cutter working. The wire has more flex than I would like but I think I'll be able to tweak the voltage and amperage to get it to cut well. I'll also need to build a few different wire cutters to use.

View attachment 2495598
This is the wire I bought. Seems to work well, if a little more flexible than I'd prefer.

View attachment 2495601
I'm using my rc battery charger. I have a computer power supply I've modded to power it, and the charger has a dedicated hot wire mode where you can set the voltage and amperage you want to output a well as a timer for it to auto stop.

View attachment 2495602
This is what I built for a cutter, modeled after @ghcoe . I'll build a few different ones for the cuts I need. I think with my charger being variable I could shorten my wire length, but figured I'd just start with something I know has worked for others.

View attachment 2495603
I only made a couple test cuts, but it seems to work fine. I plan to experiment a bit with different settings to see what will cut the smoothest. I'm not sure how to do a cutter for the long cuts, but most of them should be straight so might be fine snapped with a box cutter.

When I built my first hot wire jigs, I used longer wire to act as a rheostat since I was working with a battery charger that had now output control. I could clamp onto the wires at different locations to control the heat in the wire. I used .035 welding wire, still do. I now use a Variac to control the heat output. Since your charger has a hotwire option, similar to a variac, you probably don't have to use as much wire and sticks to wrap the wire around.

When I set my temp to cut foam I want a slow cut, and I use gravity to keep the cut smooth. I use L flashing for a track for the cutter to move along, set up the jig and then turn on the variator until I just start to see the jig move. That is hot enough.

I have a large array of hot wire jigs that I have made through the years. Seems there is always something unique I need to build for some cut. Luckily, they are quick and easy to make. You can see some of my different cutters in this thread #2. Just be careful around those hot wires, they cut through flesh just as easy as foam. That is why I always run them as low a temp as possible. Oh, and don't breathe in the smoke either. Not very healthy for your lungs.

 

[Falco-4]

Since your charger has a hotwire option, similar to a variac, you probably don't have to use as much wire and sticks to wrap the wire around.

That's what I figured was the case. I moved my clamps down and tried a few different settings. I definitely charded my bamboo sticks with the wire coiled. So I was running too hot! I can set both voltage and amperage on the charger, as well as playing with wire length, so I expect to experiment a bit to find what works. I also think I need to make a bow style cutter like your photo in #2. Overall I think I'll be able to get nice dado style cuts and channels for wiring with it.

 

[Falco-4]

I made the next big purchase: foam and plywood. I had originally planned on 2" foam and 1/8" plywood interior, but the windows and doors I was able to get for great prices are all 1.5", so I decided it was worth the simplicity to go with foam of the same thickness. Meanwhile, the 1/8" plywood was all special order and more expensive than the 1/4" luan (actually 5.2mm, so less than 1/4").

Unfortunately I got caught in the rain with the plywood but I got it all stacked and dried out and it looks like wrapping is minimal.

I did get time to cut my three sheets of foam for the floor. I glued the first two sheets together with a simple butt joint with Great Stuff. I taped the joint well with painters tape and it looks perfect on one side and minimal expansion on the top side. The plan is to sandwich the foam in two layers of plywood for the floor, but if I glue up one side and it's strong enough I might just do PMF over the foam on the underside.

Finally, I decided to use cedar 1x2 as spacers between the cross members and the floor. The edges will sit on the trailer frame rails and I'm going to use a rolled adhesive foam for truck caps to give some isolation from the metal. I don't plan to take it off the trailer but want to be able to if ever needed for maintenance or repair.

 

[Falco-4]

Continuing to make some progress. I got plywood laminated to the top side of the floor. I need to decide if I'm going to do a later on the bottom side as well or just do PMF over the foam on the bottom.

I also got the left wall foam panel cut and glued. I laid out the door and window and dado cuts for the galley wall, bunk wall, and bunk shelf. My hot wire is working great. I built a bow cutter and a dado cutter that have been working great.

The other decision I need to make is when to cut my door and window openings. Since I'm laminating plywood inside, I need to glue that before putting the walls up, but would like to keep the walls solid until the are up. I'd welcome any opinions anyone might have.

 

[Falco-4]

Worked on some dado cuts and taped up the side and front panel to get an idea of the size and layout.

 

[KCStudly]

Continuing to make some progress. I got plywood laminated to the top side of the floor. I need to decide if I'm going to do a later on the bottom side as well or just do PMF over the foam on the bottom.

View attachment 2506129

I also got the left wall foam panel cut and glued. I laid out the door and window and dado cuts for the galley wall, bunk wall, and bunk shelf. My hot wire is working great. I built a bow cutter and a dado cutter that have been working great.

The other decision I need to make is when to cut my door and window openings. Since I'm laminating plywood inside, I need to glue that before putting the walls up, but would like to keep the walls solid until the are up. I'd welcome any opinions anyone might have.

If you cut the foam out of window and door openings before laminating ply, be aware of a few things. 1) Foam does not make an acceptable router template for plywood, but plywood makes a very good router or knife template for foam. 2) Be very careful handling foam panels after cutting out, the relatively thin areas above window and below door will be weaker and could potentially break if not yet reinforced with ply. 3) When you do laminate the ply to the foam, if openings in foam are cut but not in ply, or if the ply edge cantilevers past edges of foam, make sure to mask the cutout plugs of foam with packing tape or plastic sheeting and put them back in their holes, otherwise gravity clamps and/or vacuum bag pressure can try to push the ply down into the empty hole, prying it locally away from the foam, lifting it to separate the joint around the opening. In other words, the edge of the opening becomes a fulcrum point and weight or pressure placed on unsupported ply over the opening can tend to lift the ply away from the foam surrounding the opening. I used 5mm ply, and for me this was a real issue.

 

[Falco-4]

If you cut the foam out of window and door openings before laminating ply, be aware of a few things. 1) Foam does not make an acceptable router template for plywood, but plywood makes a very good router or knife template for foam. 2) Be very careful handling foam panels after cutting out, the relatively thin areas above window and below door will be weaker and could potentially break if not yet reinforced with ply. 3) When you do laminate the ply to the foam, if openings in foam are cut but not in ply, or if the ply edge cantilevers past edges of foam, make sure to mask the cutout plugs of foam with packing tape or plastic sheeting and put them back in their holes, otherwise gravity clamps and/or vacuum bag pressure can try to push the ply down into the empty hole, prying it locally away from the foam, lifting it to separate the joint around the opening. In other words, the edge of the opening becomes a fulcrum point and weight or pressure placed on unsupported ply over the opening can tend to lift the ply away from the foam surrounding the opening. I used 5mm ply, and for me this was a real issue.

Thanks for the tips! The fragile sections is my biggest concern. I think I'll end up with everything cut out on foam any ply before laminating to avoid your point 3, which I wouldn't have considered. I'm seeing that it's going to be a bit of a jigsaw puzzle getting things put together in the right order!

 

[ghcoe]

The other decision I need to make is when to cut my door and window openings. Since I'm laminating plywood inside, I need to glue that before putting the walls up, but would like to keep the walls solid until the are up. I'd welcome any opinions anyone might have.

I wouldn't cut the door out till you glue the wall to the floor. If you cut the door out before gluing to the floor you could have the distance bottom distance of the door too narrow or too wide if not careful. I had that issue when I did #1. Now I just cut the doors into the wall, so I don't have to worry about that.