A tear with no name

[QueticoBill]

Joined in April 2013, first post this past October, so guess I'll start to document progress - or lack thereof. Basically, looking for a small step up from a tent, and a place to stay those first and last nights of canoe or backpacking treks. So, a plywood and foam tent on wheels, simple kitchen more like a patrol box than a kitchen, the "cute" factor is important, kind of like the woody look and love spar varnish as a material when shellac won't work, and still love building and design though hope to drastically cut that back professionally by 2019 or 2020. I set an ambitious budget goal of $1000 all in, and between Ironton 5 x 8 and Maine registration, I'm over halfway at around $550. Probably won't stay under $1000 but for sure I can do it for not more than $1500. So my thoughts and planning in outline so far.

Frame
NT Ironton 5 x 8
move axle and fenders back
invert axle on top of springs
extend tongue 2-3' and make removable for security purpose
modify wiring but use stock lights initially
preserve option to upgrade to 13 or 14 or 15 inch tires and fenders to match
have frame joints welded perhaps
hand pack bearings; find spare hubs and tires

3/4" py deck
5 x 10 - end up around 5 x 9 with 6" cantilevers front and back
apply Chuck’s mix
undercoat bottom side - Fence Post Black Beauty or?
tek screw to trailer frame (no wood frame)
xps and coating under

Walls
sandwich - stressed skin - 1/4" ply - 3/4" ply stick frame w/ 3/4" xps - 1/4" ply
3M™ 30NF contact
Titebond for wood.
“internal cleat” method of wall to floor, with hanging down outside frame
home built doors and Wylie windows
add “trim” frame and rails on exterior
birch veneer ply
spar varnish exterior
shellac interior

Roof
build on top of walls, edges covered by woodie trim
1/8 ply inside - 1 ½" 3/4" ply spars or no spars with 2 layers 3/4" xps or 3 layers 1/2" - 1/8 ply
looking at the marine vinyl/landau car top material, maybe truck bed liner, maybe just spar
light color

Hardware
hurricane hinges for hatch

Accessorizing
minimal or no electrical after required trailer lighting
no built in ac or heat
galley just counter, pull outs, and cupboards
space for cooler and Coleman white gas stove and lantern
begin with double size air mattress (have) - go to memory foam later
plastic bin tongue box or matching TD sides from scrap

 

[QueticoBill]

So here are my first thoughts - actually number 6 in my system of developing a design. Obviously based on the "New Cub" in the Design Resources, with slightly tweaked geometry. The farm is 8' x 5' the plywood deck is 9'+ a little by 5', and th out to out of the cabin is 10'. Basically 4' from bottom of frame to high point.

 

[QueticoBill]

And probably last post for now, I decided I should look a simpler plan, so modeled after the Generic Benroy in design resources is this. I'm not too keen on the straight sections of the profile, or should I say I really liked the all curves of my version of the New Cub, but need to investigate. In common, the Ironton 5 X 8 trailer and a 58" by 80" "floor" or sleep space. At 6'-2", stomach sleeper with arms crossed under my head - I can't do less than 6'-8" which means all but a small cooler does not fit under the counter in this one.

 

[ddc612]

I built the new cub, with a few of my own tweaks. 5 wide, and 10 long on a 5 x 8 frame from Northern Tool. The biggest pain was dealing with the radius at each end. The rear hatch was the biggest pain. But for added space I'm sure it's one the better designs. Compact, light, and still spacious. We've used a few times this past year, and it doesn't feel claustrophobic in the least.

 

[KCStudly]

I really like the way the Benroy gives more interior volume and a sharper cutoff at the galley for better access to the counter; but also didn't like the bland-ish look of the flat sections. So I modified it into The Poet Creek Express profile; added a slight arch to the roof and a "bustle" (outward buldge) on the hatch. This allowed me to use deeper hatch ribs without encroaching on the edge of the counter. Sort of a mash up between a Benroy and a canned ham.

I would seriously rethink the use of the 3M green (30NF) adhesive. A few of us have had less than stellar results leading us to question the high cost of it. Knowing what I know now I would either use epoxy or PL... actually, I would use epoxy. Essentially the same price and no more difficult to master; if you plan to spray the 30NF you will need a respirator anyway, so why not go right to the epoxy? (Yes, this was suggested to me early on, too. No I did not take the advice at first. Yes, after making the switch to epoxy construction I wished I had started there right from the beginning. just saying.)

Also, doing multiple plies of foam is a PITA, takes more time and material expense than just doing kerfs, and you can run into curing issues (unless you use epoxy... which does require certain precautions with foam; i.e. don't use too much in any one spot or it could go exotherm on you). There is a good kerfing thread in the stickies of the foamie forum. The only reason I would ever do laminated foam again was if I just absolutely couldn't get the thicker stuff locally (if you live in a warmer climate they don't always stock thicker sheets.... try insulating contractors if your box store doesn't have the thickness you want).

 

[QueticoBill]

Thank you.

Your comments on the 30NF are interesting, as the people who use it for platforms, shells, and other stressed skinned fabrications all rave about it, especially foam to foam. I was planning on rolling and brushing, not spray. It seems to be the only adhesive that there is no drying problem when enscapulated in foam.

I like the New Cub because of no straight sections so it's bound to be stronger, but I'm still thinking through profiles. Problem is, Everytime I play with others, I'm drawn back to new cub.

Laminating layers of foam is simply to get a solid foam core with good continuous contact with skins. Seems necessary to go sparless and ribless.

 

[KCStudly]

One issue I and others have had with the 30NF was drying time when brushed on. It took much much longer than the label info. The other issue has been getting a uniform and complete bond. The label says to roll with a 300 lb roller (IIRC), and that is just not possible on foam. Even skinning with thin ply, I would expect damage to the wood grain at that pressure.

Sure, I think I got a decent bond for the most part, but I know there are areas that didn't get to full strength; where I cut out my bulkhead for an aux vent, then skin was not bonded well at all.

Kerfing adds air channels that lets moisture/air cured adhesives dry.

 

[QueticoBill]

Kerfing may be the only viable option ultimately, I just hope not. Invariably, the kerfing ends up with gaps in the flats of the foam wedges against the curve of the skins, and makes the contact cement ineffective, done it has no gap filling ability, like PL or epoxy.

Thanks.

 

[KCStudly]

There is another option. I have not experimented with this on thicker foam, but there are some videos of it working successfully. If you use a stretcher to contain the outside of the foam (such as applying a glued on layer of cotton fabric, or a thin metal or plywood "sled") and then bend it over your profile (or other form) you can actually get the foam to bend quite well w/o crushing or breaking (at least small samples... larger sheets might take quite a bit more effort). The sled or laminated fabric layer takes care of the tension side of the bend allowing the compression side to take all of the deformation.

The sample of PMF I did, about a 12 inch square of 3/4 thk blue foam, 10oz canvas TB2'd on one side, could be bent over into a near U shape with no apparent failure. Came back to flat, as well.

 

[QueticoBill]

Very interesting. I need to probably waste a sheet or two of foam to see if it will bend to the radius I hope to get to, which on an ellipse is hard to calculate what the minimum radius is. I thought the 1/2" R-tech would be most likely to do it, but thinnest I can find locally so far is 3/4".

 

[QueticoBill]

Well, I've gone a different way. Decided to go back to the MI original Trailer for Two for inspiration and rather like it. I'm still playing with door and trim but thinking spar varnish on some sort of (inexpensive) hardwood veneered ply. Pretty sure with the gentler radiuses - mostly over 4' - I can get 3/4" to bend - R-tech if not Foamular.

 

[noseoil]

Bill, you can cut the wall weight a bit by using 1/8" Baltic birch instead of the 1/4" you show. It will also bend better on a radius & give a clean look when it's in place. 3/4" ply for a deck is a bit of overkill. 5/8" would probably be fine, depending on your bracing. Remember, 1/2" with 2' centers is the standard in the building industry. We used a sandwich panel for the deck with 1/8" BB top & bottom for our floor, 4/4" poplar frame, insulation in the voids & blocking for hard points wherever needed for fastening & reinforcement. I did kerfing at 2 1/2" centers for our foam on the roof, 2 layers of 3/4" & it worked well.

About the Fastbond 30, we had some issues in aircraft work & the guy doing headliners (raw silk on a formed nomex panel) called the factory about it. It's a very good adhesive, but a word of caution here came from the factory. It needs enough heat & lower humidity to cure properly. If it's cool & damp, forget about using it. That being said, dust is an issue when it's getting ready to bond. We cranked the heat up in that room, then had a sign made which said "Simulated dust-free environment" to put on the door. This is what it took & from that point onward, it worked very well.

We chose the Benroy design due to space considerations & it does give a bit more room front & back for placing things. Looking forward to the build.

 

[QueticoBill]

Thank you. I have about settled on 1/8" (or 0.106 at my store) for both sides of roof. Am considering for walls as well but lean to 1/4" (0.196 actual) with just 3/4" foam.

I might go to 5/8 floor but not 1/2 (7/16) on 24" centers. I think 1/2 is only up to 16" anyway on a floor, 24" on a roof. Plus no wood framing, just ply, including cantilever of 6-12" at ends.

And am planning double 3/4 foam in roof. I understand the precautions of the 30NF - spent a while on phone with 3M as well as fabricators I know.

 

[noseoil]

Bill, on a "floor" for the trailer the load is fairly well distributed by the mattress, & what would be a conventional load scenario for a floor goes out the window. That's why we got away with the 1/8" floor deck. We use a 5" stout foam mattress with a 3" memory foam topper, so the weight is fairly well spread out once the trailer is finished.

I did take precautions when working inside on wiring & stuff, used some 1/2" OSB as a liner while kneeling & moving around, since the 1/8" panel would hole from a point load like a knee cap. No problems so far with our system.

 

[QueticoBill]

Good point. (What - no water bed? ) I can probably go to 5/8" but using two sheets of 3/4", I had planned on using what was left for ripping into the framing. Leftover from 5/8 or 1/2" seem not useful for much - maybe cabinets. I also don't fine 5/8 hardwood veneer and in a birch veneer the half inch is only a few dollars less. And that coupled with routing and 1/8" off bottom face to get it to sit level on Ironton frame, all lead me back to 3/4". Makes over zealous use of the tek screws to fasten ply to deck a little more tolerant as well, and a little more slop for recesses for the frame bolt heads.

But a lot to think about and I really appreciate you thoughtful posts. After all, a job well planned is a job half done.

 

[QueticoBill]

Update. Chassis is finished. Modified Ironton 5 x 8 as I planned. I keep tweaking cabin design but it will be based on the original trailer for two profile, with a deck that keeps ending up in the 9-6 to 10' range. And I committed to it sitting on top of chassis and being removable.

So chassis drawings:

 

[QueticoBill]

And some photos.

Coupler attachment: Slipped the 2 x 2 through the inverted factory coupler attachment plate - 4 bolts - 2 vertical and 2 horizontal.

The coupler was for 2 1/2" so I added 1/4' steel plate shims on either side - approximately 2 x 4 inches.

 

[QueticoBill]

8' - 2 x 2 x 1/4 tongue attachment - the holes in the Ironton framing were already there so only drilling tongue. I should have used 1/3" or 3/16" max. The worksheet in design resources here said the 1/8" would have been 150% of what was required and the 1/4" was 400%! Overkill - but the price could not be beat.

 

[QueticoBill]

Finally, the change to underslung axle and raising fenders on the frame. Drilling the spindle for the stud on the spring was easy, as was inverting spring bolt. Moving it rearward was harder, because of cutting for carriage head bolts - which was a combination of sabre saw and file.

I (had a friend with a man cave machine shop) modify the fender brackets so the tab for the bolt to frame was down, not up, and of course drilled frame for relocated fender.