Teardrops n Tiny Travel Trailers

I built my first camper years ago and since I used 1/4 inch plywood for the interior and exterior walls, the camper is heavy. Also the paint didn't hold, sat outside too long, rotted, yada, yada, yada, it's time to build a new and improved camper.

Since I'm going the way of FOAM this time, I have a couple of questions about the canvas.

I have canvas drop cloths from Harbor Freight. I've read about shrinkage after washing so I have concerns.
1) Do I have to wash the canvas before applying it to the foam?
1a) If I do wash it, air dry or dryer?

After applying the canvas to the foam with the TB2...
2) Should I use TB2 to fill the canvas pores or Glidden Gripper, or exterior latex paint, or do I layer all three?

I'm sure that these questions are already answered somewhere in the archives but after many hours studying the past posts, I figured I'd just ask.
Thanks everyone,
Dave

I use HF tarps on my builds.
1. I do not wash them. I think the shrinking as you apply the canvas helps to make a tighter skin. You will have to work out some of the wrinkles, but most roll right out.

2. I mix my TBII 50/50 with water and apply the glue to both the foam and canvas and then roll them together. When applying TBII to the canvas I make sure all the pores in the canvas are filled. By applying glue to the wall and canvas you avoid the glue up from being too dry. I do recommend applying a coat to fill in the pores on the exterior as well. I use the 50/50 mix on the outside too. I have used thinned Gripper at about the same ratio. Applying Gripper or TBII full strength does not allow it to wet the canvas properly and could cause the canvas to rot at a later date.

I did a few write ups on how I did my layups on my build. You can read them starting here. I have changed some of the technique. Now I use 50/50 TBII for the glue ups and not the mixtures mentioned in the write up.
http://tnttt.com/viewtopic.php?f=55&t=54099&start=405

Good luck, George.

Dave re:
1. Seems all canvas shrinks a bit , it expands when it’s damp , shrinks when it dries out , and even glued it will move with the shrinkage … On long runs you may want to leave at least 6” around . for allowances… We had a long run on the FoamStream roof , allowed 4”extra and still came up short another 4” … ( see pic )
2. Lately for Foam to canvas gluing , we’re now recommending totally using the Gripper for everything , and Both surfaces must be completely coated , then joined while wet , smoothed out and trimmed . The outside gets coated with another coat of the thinned Gripper( see George ^) , or two …then Painted . That seems to make the best job for our Rainy climate , if you’re a lot drier place then no worries … use the T2 .. JMHO

Ps , and we like to go over the outside Gripper coat with a plastic bondo spreader to force the primer deep into the weave , leaving a smooth and level surface … As much as we do for our oil paintings …

Psps… Drip edges are not a bad idea !!!

I can see where some shrinkage is a desirable feature. The notion is that it makes a stressed skin that contributes to the structural stability of the canvas foam composite.

However, there have been several posts lamenting their experiences with warping of unassembled panels due to this stress. I believe after an earlier misadventure, Mike succeeded in applying canvas to panels by covering both sides and clamping to a flat surface during glue drying: http://www.tnttt.com/viewtopic.php?f=55&t=70578. He did not say whether he used washed or unwashed canvass.

I am wondering whether unshrunk canvass is more desirable when covering an assembled foam box. When covering panels that will be assembled later into the final structure as Mike did, pre-shrinking the canvass may help prevent bowing and warping of these components?

Tom

I used canvas drop cloths from Lowes, heavy duty ( or at least not the thinnest stuff there). Glued on with full strength TBII, rolled on thick with a paint roller. I did not wash them and did not notice any shrinkage except in one place. (the inside on the curves on the ceiling, and only if I pulled it taut when pressing in place)
I coated the outside with 2 coats of gripper primer, then acrylic houseplant. Nothing has come loose or blistered in the 2-1/2 years since, sitting outside in the sun and rain.

Oh yeah, in case you don't know, scuff or sand the foam to give it some tooth before gluing the canvas on!

Thanks guys,
I'm starting to get a picture of how canvas behaves and how to attach it. Thanks for the advice about roughing up the foam. I'll be sure to do that.
I think that I'm going to have to experiment a little to make sure I completely understand how this is going to work for me. I'll try some washed and unwashed canvas to see if I can avoid having it shrink on my camper. I'll let you know how it turns out.
Thanks again,
Dave

Dave , I wouldn’t worry about all that too much , just leave some extra canvas on the edges ( to trim after dry) and you’ll be fine …

Our 2 cents … If you’re covering the inside panels first , flat on a table , we assume you’re using a much lighter fabric than the outside , so there should be less shrinkage effect … less worries …

Being an Artist , we found out many years ago that if we painted ( a picture) on one side of a canvas panel or Masonite , or thin plywood , then it would warp …the cure was to lightly paint the other side too , usually just with Gesso , ( Artist Primer) so both sides would shrink at the same rate … Paint or Glue shrinks as it dries too ( the water evaporates , the molecules get smaller ) , so it’s not Only the canvas shrinking …

On the trailer side of business, all this shrinking , if allowed for on the edges , makes a taught tight tough covering over foam …the kind of outer Skin we need ...

Bottom line , if it was a really big problem we’ would have heard a lot of whining and complaining about it already … Which over the last 10 years just hasn’t happened... There’s always been a lot of unfounded speculation about Foamies … But hundreds of thousands of miles of Foamie trailer travel have proved them false … or Not really as big a problem as some thought it would be

GPW,
I don't know if you remember my first camper, I called it the pocket knife. It is a folding camper. The roof is hinged and the upper walls fold down. I'm re-making it out or foam this time and making it modular so that the entire thing can come off the trailer and be broken down and stored in my basement when it's not in use. So I'm making it in 11 sections. I know I'm crazy, but I'd like to still use my trailer as a trailer.

I'm very worried about warping, I'll need everything to fit together as it should. I'll canvas both sides of each piece like you said to keep the pressure even.
the reason I'm asking about washing is because blue jeans are made of canvas and we all know how much they shrink after they get wet and dry.
This camper will either be really cool or a complete fiasco.

Very cool design.

Drawings available? Or a build thread?

Thanks,
This is the closest I have to a build thread, but it just shows it without paint.
viewtopic.php?f=50&t=49781

Dave , how could we forget such a Cool camper ... Sorry to hear of the rotting etc. Don’t feel alone . My plywood trailer rotted straight away …Why we went Foam … 
I really believe if you cover one side , then the other side right away , you won’t have to have any worries of warping … There was no way were were going to be able to pre wash 30 yards of 18 oz. canvas so we used it just as it came . On our project we had an inner wooden skeleton to retain the shape … And on our fiirst Foamie we used a thin linen canvas , which was strong and didn’t warp , even though it was a while till we skinned the interior with old bedsheets …

If you want you can use thin plywood or chipboard for the inside skin will certainly help keep things straight and exact …And you can always make up some Test pieces to test all this , see what works best for you …
I think it will be a Very COOL trailer , when you’re done … JMHO

I don't know if you remember my first camper, I called it the pocket knife. It is a folding camper. The roof is hinged and the upper walls fold down. I'm re-making it out or foam this time and making it modular so that the entire thing can come off the trailer and be broken down and stored in my basement when it's not in use. So I'm making it in 11 sections.

What an exciting project. And such an original and interesting design! Do you plan to basically duplicate your original configuration?

I thought about doing a foam rebuild of my Tip Top Tear Drop (link below), but I am not sure that the techniques that work for a fixed geometry are well matched to folding units: Yeah, I can accept that fabric covered fixed joints can be pretty strong, but what about structurally critical joints which must be hinged and/or disassembled? Maybe hybrid joints with some wood or metal at the edges is the way to go, I’ll be looking to see what you do.

Have you looked at the YouTube video in the "Panel Clam Shell" post:
http://tnttt.com/viewtopic.php?f=5&t=64495&start=75#p1212307 (scroll to the "Panel Clam Shell" post). Here is a direct link to the video .
His design has some similarities with yours, and it never hurts to see what someone else did. It is difficult to determine the composition of his panels, I originally thought the outer surface was FRP but then thought it looked more like metal. Note how his panels are hinged and how he has wide gap corners sealed with angled covers - not everyones choice but worth the look.

Keep us posted.

Great video. That guy had a lot of similarities to my camper. The small triangles that he put in the corner, I have that in the galley of mine and the outside corner posts is something that I had too. My walls were attached so I didn't slide them into place. He gives me a lot of hope because he was towing his with a new VW Bug. I want to tow my new one with a Nissan Versa so I think it will be just as light weight. I really liked his prop-up bar.

In this new build I want to be able to get rid of the corner triangles and the corner posts so camp side set up is easier. I just hope that when It's set up at the beach, or somewhere like that, it isn't so light that it gets blown over.
Dave

I am also building a folding trailer with foam sandwich panels, good to meet another folding trailer builder. Subscribed.

My walls were attached so I didn't slide them into place

Yes, his end panel is detached in transit mode (but held down by a strap). However, if you watch carefully (stop the video at 0:58 and 1:12), you will see his side panels are anchored by a double hinged scheme. I used such an arrangement with one of my experiments so the panel moved inward and downward for storage inside (rather than atop) the base. I made the hinge by joining two regular door hinges together with very short bolts to form a 3 flange hinge with two pins either side of the center flange.

In this new build I want to be able to get rid of the corner triangles and the corner posts so camp side set up is easier.

Yes, my biggest grip with his trailer is there are too many loose parts floating around and too many steps for a rainy day.

I want to tow my new one with a Nissan Versa so I think it will be just as light weight.

Wow, I’m not familiar with the Versa, I think most come with a CVT. I currently tow with a Jeep Patriot (2.4 liter, 6 speed auto, trailer 560# empty) and that seems to work quite well (27.1 mpg on last trip of 5600 miles).

I really liked his prop-up bar.

Yeah, me too.