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Ideas Stage

PostPosted: Mon Aug 17, 2015 4:03 pm
by Funluvin001
Hi all,

We're a couple who has painstakingly rebuilt an old trailer, only to have the aluminum contract enough during the winter to get all the new materials moulded to the point of no return and so now we're looking to build anew. We have the trailer stripped to the bare frame and once it cools down enough will be cleaning it up and painting it.

The design isn't going to be a teardrop, but we're definitely leaning in the general area of a foamie. (XPS, not EPS!)

Initial problems with respect to the outter skin: (We're in Eastern Canada and supplies are limited)
1) TBII is available in gallons only at one supplies reseller for a whopping cost of $40.00/gal which is the same price as polyester resin, here. In fact the resin is cheaper by the 5-gal pale.
2) Glidden Gripper is not sold here, and though there is some speculation that a CIL branded variant is the same product, there is nothing to validate that. Also, I've read that it may not be what it once was, and that the jury is kinda out on that one.

Given these limited options, we could build fibreglass/poly resin skins and somehow try to laminate them onto the foam with GS perhaps, though I can't find any indicators of the possible results. (I'm aware that poly resin eats XPS.) Since the weight and consequent tension would depend on size, a down scale test isn't very practical. Like most we're trying to be very thrifty and building full-scale tests, isn't pragmatic, so we're looking for alternatives. Glass is fairly expensive here as well.

A couple of thoughts have crossed our minds - like the possibility of using a 2-part urethane paint as a 2-in-1 paint / adhesive for canvass. Certainly not cheap at $170/gal, but epoxy is about the same and them to have to prime & paint it makes it significantly more costly. Also, Zinsser has a new product out called BondZ, and then I ran across this: Sadly, little information is available about either so I may have some testing to do. Another candidate for testing is this: Since it's spec'd as PVA it caught my eye, but it's my understanding that If it's not crosslinked PVA then it wouldn't have the water resilience of TB2, and it's adhesion to foam is also a big question mark at this point. Dollar wise the Kiltz looks VERY attractive, if it works. I have also read VERY promising things about 3M's Super Trim, on foam, but that would be quite costly as well, and I'd question how well it would work with canvass..

In terms of the design:
We're not planning to haul this any huge distances, but we want to be able to pull it with an SUV, and so weight and aerodynamics are factors, but not absolutely critical ones. Given this we're not sold completely on a frameless design, but rather trying to limit it's weight as much as possible.

The PVC frame-up builds really caught our attention until we went to try to find some locally. Home Depot up in these parts doesn't carry 3/4" PVC and what they do carry is pricey as hell. I was thinking about embedding some 1X2 into the foam glued in using either GG or GS.

(Hint to those who use spray foam as an adhesive, if after a short time of spraying it, you disrupt it's expansion (remove the pieces being glued and putting them back together) the expansion is greatly limited after the fact. This could also be true of GG urethane glue, but I'm not certain.

Have also thought to try and find some 1.75" steel studs which would decrease weight significantly, and being sandwiched between sheets of foam, be very rigid. Worse case, pop rivot them together back to back for middle-of-the wall studs.
Since steed studs are mandatory for all commercial buildings up here, some myths about their strength can be quashed right out of the gate. Built properly, steel studded walls are plenty strong. Impregnated with XPS and sprayed in (carefully) at both ends, the wall would be as strong as hell.

The design of a full pop-up holds a lot of appeal to us for the reduced drag, but a decent DIY lift system still eludes us. Too bad we sold a junked pop-up last year! The Foamstream & Streamline builds also look great to us so we're still wandering around in terms of where to take the build. Hinged pop-ups on the other hand, don't appeal for us, so much. We may be using this well into the fall and so we might have to abandon the pop up ideal because in the winter, sealing for heat loss would be an issue. That's still up in the cloud of thoughts for the moment.

Size wise, 12/13 ft would do us fine, but see attached (I hope) scale of the trailer on graph paper where 1 square = 1FT. We may narrow the whole thing and cut off some of the rear bumper and loose an axle in the process, as it's much larger than we need. The original camper was 15ft with a footprint-on-frame length of 13.5ft and an overall trailer length of 18 ft. We can go longer if necessary but the 12ft length holds appeal in terms of materials VS waste. 14 would be a viable alternative.

Since we have new(ish) leftover aluminium for the old roof, we were thinking of laying out a 2X2 & 1X2 (on end) framing, filling it with XPS spray foamed in place, covering the bottom with aluminium (rodent deterrence) and going with 1/2" ply for the sub-floor. Also worth noting, I'm thinking hard about making it removable easily, from the trailer chassis, for another use.

Another note:
Last year we had 18 ft of snow fall in just over a month.. crazy year but a good benchmark.. so the roof has to be strong enough for some snow loads. My initial thoughts were using 2X6 as trusses and curving them to 2X2 sized, but over the span we have of width to work with, it's not much of a curve.

So far that's where we stand. Any/all discussions/ideas/input very welcomed. I realize it's early but this is the time to plan :D


Seems my attempt to post a pic of the trailer failed. Here (I hope) are before and after proposed mods:

Re: Ideas Stage

PostPosted: Mon Aug 17, 2015 9:26 pm
by pchast
Ask a local professional painter for the best thick latex primer in a 5 gallon can.
You will use most if not all of it. Otherwise you may be able to order Gripper
on line shipped to you for less than that gallon you mentioned.
Here from HD the 5 gal can was 105$ when I got it 3 years ago. Its now listed
at 99.

Re: Ideas Stage

PostPosted: Tue Aug 18, 2015 7:51 am
by Funluvin001
pchast wrote:Ask a local professional painter for the best thick latex primer in a 5 gallon can.
You will use most if not all of it. Otherwise you may be able to order Gripper
on line shipped to you for less than that gallon you mentioned.

I had already planned on using 5'er pales as necessary and I have an account at the local Benny Moore location, but there us a local chain store with a house brand that we find much better. (Home Hardware for those fellow canucks.)
Sadly Gripper isn't sold in the country and so getting it shipped up from The US would be very cost prohibitive. That's why I was looking at the newer Kilz, Zinsser & Circa1850 Prime It! products as possible alternatives. Sadly I dont know anyone who's used any of them, yet, so I may have to buy some quarts and do some testing.

pchast wrote:Here from HD the 5 gal can was 105$ when I got it 3 years ago. Its now listed
at 99.

That's pretty pricey for a primer, but from what I've read, some have used it as their primary adhesive for the canvass? It sure seems to stick to the foam very well. Don't think I've found any results on the long term adhesion effects of such a build yet, though.

I had even debated using a 2-part epoxy marine primer which has both bonding and water proofing characteristics, but it's thick as hell, and very $$$. :cry:

Re: Ideas Stage

PostPosted: Wed Jan 13, 2016 3:50 pm
by KCStudly
Re: cutting arched spars from larger stock to handle snow loads. I would be concerned that you would be cutting the grain short and, depending on the species, setting up the potential for splitting under load. It would be much preferred to have the grain following the arch shape, either by steam bending smaller stock, or by laminating thin slats over a form.

I did see a technique somewhere where the guy was able to maximize the depth of the arch, making it greater than the width of the original stock would normally allow, by planning the layout so that the part removed from the under side could be biscuit (or plate) joined back on to the top completing the arc of the upper cut. I thought that was pretty clever and wish I could remember where I saw it. In other words, if you start with 1x6's and cut a 4 inch high segment out (leaving 2 inches in the middle, you can glue the segment back on the top and have a 6 inch deep arch section that is curved top and bottom. The overlap between the long grains in the bottom segment (now top) piece add back to the long top grains in the now bottom piece.

Another option would be cutting them from plywood.

Maybe this concern is less of an issue if using sandwich construction for your roof, but it was what came to mind.

Re: Ideas Stage

PostPosted: Wed Jan 13, 2016 4:09 pm
by KCStudly
Here's what I mean. The middle is a 1x6 board drawn 5.5 tall by 82 inches long.

The bottom shows the cut starting 3-1/2 inches in from each end (assuming it will rest on top of the walls... this could be less) and arching up to leave 2 inches remaining.

The top shows the segment glued back on top and the upper shoulders lopped off to complete the upper arch.


Re: Ideas Stage

PostPosted: Wed Jan 13, 2016 4:35 pm
by dales133
That tb2 prices sounds expensive.i only paid 30 a gallon in australia.
Id shop around as the place i was going to get it from first was alot more.
I used zinsser super prime and it worked well followed by dulux exterior acrylic top coat