A foam project- Screen and Mastic! New Pics 4/28

Canvas covered foamies (Thrifty Alternatives...)

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Re: A foam project

Postby Nodrog » Wed Sep 27, 2017 11:41 pm

Underneath edge of side.jpg
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Hi folks! I'm baack! Ihave a few more pics, have been working mostly on the edges under the sides,have wood pieces that make tenons that hold the sides, am rolling screen under the bottom edge and stapled it to the wood right in the corner, continuous staples, like 2 per inch, then covering with 3 coats of mastic.... the shiny metal is .050 aluminum for floor under cabinets, about 21" on each side..
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Re: A foam project

Postby Nodrog » Thu Sep 28, 2017 12:23 am

Here's a pic of the hind end of trailer before screen, visible are inset ply pieces (1/4") to mount taillights. Also can see the arch shape of roof, was trying to get max headroom in center, while looking shorter on sides...These pics will magically grow when clicked! 151268
I'll try to add another pic, maybe I won't have to make more posts.....This pic is of inside through door, can see the arch of ceiling, that was a little bit of a pain, roof also slopes lower toward the front, was trying to make it more aerodynamic, I guess...it has 4 rafters, about 2' apart. These are little glue lams, 6 layers of pine, just the thickness of the foam-151267

Now, maybe this is interesting....? On the back, I have added more thin coats of mastic. This will go on very thin, with a very light sanding using the somewhat worn 100# on the palm sander. I used a drywall broadknife to spread just as little as I could, smoothing a little more with the plastic squeegee. This is best done in weather not too hot, I think, because in thin coats can only do a small area at a time, it starts drying immediately! I think this is altogether 5 coats, after the first 3, the coats can get real thin. No use using too much, that just adds weight and costs more money! This will yield a smooth finish without a bunch of sanding and only require thin paint!! 151266 Although the screen pattern is faintly visible, it cannot be felt at all, I think I'll slap a little primer on it to test...Altogether this method is exceeding expectations, smooth and wow! really hard....cannot believe it's just foam with screen and glop!
Here is the drywall tool I have used.....it looks old and rusty, but the edge is good...151265 Thanks for looking, maybe somebody can get something out of this? Later, Nodrog
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Re: A foam project

Postby GPW » Thu Sep 28, 2017 6:08 am

".Altogether this method is exceeding expectations, smooth and wow! really hard....cannot believe it's just foam with screen and glop! “

Nod, welcome to the revolution … :thumbsup:
There’s no place like Foam !
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Re: A foam project

Postby Nodrog » Sun Oct 15, 2017 12:39 pm

Hello again! I have been grinding away, needed to put the project outside to do the top, which is now finished to the point of 2 coats of primer! I didn't really perfect the surface, because it is only visible to the birds! But, it is pretty good. After that have been applying more goop to front and sides....here are some roof pics....also have a weight- at this point I am at just about 650#, think it will double that when finished and loaded- but, we have over 6' headroom, and will have various amenities, so think that is pretty ok. I will do pics, then go take a few more....
Trailer Roof 3.jpg
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Trailer Roof 2.jpg
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Trailer Roof 2.jpg
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Trailer Roof 1.jpg
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Re: A foam project

Postby Nodrog » Sun Oct 15, 2017 1:32 pm

More pics!! The back has a coat of primer. The street side I am calling ready for primer, the front is ready for final sanding, I think. I have been squeegeeing on the thinnest coats, to about 6 total, with light sanding between coats. This fills the dips and knocks down ridges....I will use a total of 8.5 gallons of the mastic, at current price of 26? per gallon that's about $250 although the first batch I bought was cheaper. I have sanded a fair amount off,hahaha! I have a pic here of the edge of a window hole, the skin is on far left, thin gray line...next to the treated 1/2 ply I inset to attach windows....The back with primer looks at least as smooth as smooth drywall....pretty fun! It's great to get the stuff all over hands and tools and just wash with water!.. My 85 year old neighbor says it looks like fiberglass. He is following closely, and really wants me to get it painted, I guess he wants to see it at that stage, it's funny how impatient he is! Soon, Don, soon....! Here are pics- thanks all for your looks and replies, comments are most welcome!! 151406 151405 151407 151408 151409
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Re: A foam project

Postby amandacreiglow » Sun Oct 15, 2017 2:27 pm

Awesome! Good work.


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Re: A foam project

Postby OP827 » Sun Oct 15, 2017 8:34 pm

It is a new choice of cover materials on this forum, thanks for sharing. I was looking into similar mastic material after I came across canvas canoe builds.
Can the mastic be slightly thinned with water for a "skim" finish coat similar to drywall compound technique?
I think using double fiberglass screen is a good decision for better strength on outside.
I see that you have some embedded ribs in the roof, could you share some details of how you did that?
Sorry for so many questions :)
Great project! :thumbsup:
My foldable foam trailer build: http://www.tnttt.com/viewtopic.php?f=50&t=61344
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Re: A foam project

Postby Nodrog » Sun Oct 15, 2017 10:36 pm

Hi OP, and others! I have had a fun time getting this covering on, the mastic is an interesting material...I would not thin it, it will already squeegee out very thin, the coats I am putting on are like real thin drywall mud coats. When I say I put on 6 coats sanded between, we are talking just barely over the thickness of the 2 screen layers, in total buildup. Not very thick! I don't think I would use only one screen layer on a standie trailer, don't know if that would be very substantial. As it is, the panels have stiffened up a lot, which is real good to see. One or two things, watch for accumulations of little fuzzy fibers on the back edge of the squeegee, I just keep scraping that off with a thumbnail, which I wipe on my shirtsleeve. I like the fibers even though they are kind of a pain sometimes, they will add a lot of strength! Also, just as with drywall mud, don't get little dried bits of mastic from the top part of the bucket or other pieces of grit or crud into your work, you'll get yucky grooves etc. The ribs are strips of pine ripped with the bandsaw then surfaced so that 6 pieces together equal the thickness of the foam, I glued them up on a piece of 2x8 with a bunch of little pieces of angle iron screwed to it. I have a drum sander with motorized feed to surface, I will add thin 1/4 ply a little wider than the ribs to support the foam panels... in case it snows an inch or 2...more snow loads might need more roof support, the ribs are @2 feet apart...although each is way stronger than the foam....gotta go watch a show.....Later, gators...Nodrog
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Re: A foam project

Postby OP827 » Mon Oct 16, 2017 8:18 pm

Thanks for answers :), good to know.
What is your plan for the roof interior? I think if you do the same two fiberglass mesh layers on the interior of the roof, you would have a better structural roof strength. Interior skin layer needs to be much stronger than the one on the walls. :thinking:
My foldable foam trailer build: http://www.tnttt.com/viewtopic.php?f=50&t=61344
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Re: A foam project

Postby Nodrog » Tue Oct 17, 2017 2:04 pm

Hey OP- I have already covered the roof inside, before assembly, with muslin applied with primer. Then, to quote my last post "I will add thin 1/4 ply a little wider than the ribs to support the foam panels... in case it snows an inch or 2". To clarify, I meant that ply strips will be screwed to the bottom of the ribs, they will be @ 3 1/2- 4" wide, to allow each foam panel to rest on little shelves, see what I mean? Also, the arch of the roof is 6 inches, which itself adds a lot of strength. We typically only get an inch or two of snow, more and I might have to go out and sweep it off, just to be safe!! I am going to cover inside walls with glued on muslin, which my tests indicate is pretty hard. There will be some cabinet things attached to walls that will provide support for walls.

But, this thread is not so much, in my mind about the rest of the trailer, mostly I am seeking to show the use of the mastic and screen on the exterior to achieve a smooth finish without use of, say, epoxy. I have worked with the stuff, it is useful for so many things, but all the mixing and mess, yikes! Hard to clean up, gloves alll the time...nuts, this is not a boat!! In other words, I would have used epoxy and glass but I'm just too lazy now!! I don't mean to sound argumentative about anything, by the way! I certainly am aware that I might be building something that will never fly... :lol:

One more thing, the mastic dries pretty quickly, I don't think I would have liked working with it in the heat we had in the summer, it had turned a lot cooler by the time I started on the covering. Low 70's or down in 60's....Gotta go put a little more primer on walls...

PS I will add that when applying screen, I pulled it taut, and pinned it every so often at front and back, worked from center to ends, guess that's common sense? Over and out, Nodrog
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Re: A foam project

Postby OP827 » Wed Oct 18, 2017 7:38 pm

Plywood may not be as strong for reinforcement, strips of hard wood would be better with the grain along the stress direction.
Really interested to see how this mastic covering will hold against time, road vibrations, sun and weather. I used epoxy in my build, but would convert to this method if it works..
I am not a great fan of working with epoxy too.
How brittle is the covering after it is set? It is still somewhat flexible or hard as a rock? Please do let us know. Thanks again!
My foldable foam trailer build: http://www.tnttt.com/viewtopic.php?f=50&t=61344
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Re: A foam project

Postby Nodrog » Thu Oct 19, 2017 2:53 am

Good evening! Or morning, whatever! Well, OP good to hear from you, questions are fun! I haven't gotten all that much done the last couple of days, have been keeping terrible hours! We are unsupervised crazy old people who barely know what day it is...Anyhow, the covering is fairly flexible, harder than canvas, I think, but nothing like epoxy/glass. My test from last year can be pierced with a sewing awl, but with quite a bit of resistance. I wanted a surface that wouldn't dent too easily, like when people poke at it. Adhesion seems to be like paint, but again, nothing sticks like epoxy. Still the limiting factor in any coating for foam is, of course, the fact that once you pull a thin layer of foam off, you are undone. But that peeling isn't supposed to happen. I have wrapped the covering around like a sock, as per GPW, so I think it's on pretty snug! . I don't know what the effect of extreme cold would be on this whole thing...like in Canada? Probably ok, but a test through a winter might be good, or a sample in the freezer? Maybe I'll put my test from last year in the freezer for a few days? I feel that for our mild winters in Western Oregon there will be no effect. The mastic does need to be sealed against water, as stated on the bucket. So,I have been carefully doing 2 coats of primer on all surfaces, for a start.
I am using Gripper primer applied with a roller, will use a nice latex exterior house paint. I really love latex or water based anything! Might roll a coat on the pickup, too!!
I don't think road vibration will do anything to the coating, foam should dampen vibration anyway? I think most of the trailers end up plenty sturdy, regardless of method, and on here they vary from tanks to kites! Hey, I started some drawer bottoms a while back, foam with 1/4 ply strips through for reinforcement, might use some of that thin cardboard in the bottoms....so far they weigh very little.
In other words, I don't know much for sure,and am definitely an expert on nothing. Next question?? ok, gotta go...Nodrog
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Re: A foam project

Postby GPW » Thu Oct 19, 2017 7:02 am

NOD , do like we do , leave it outside … you’ll find it’s remarkably durable ... ;)


“ We are unsupervised crazy old people who barely know what day it is “ … "Call us legion, for we are many !” :lol:
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Re: A foam project

Postby OP827 » Thu Oct 19, 2017 9:21 pm

Latex on pickup to match the trailer would be cool... :lol: Anyhow, I think I need to find this mastic in Canada now. HD Canadian version does not seem to carry it..
My foldable foam trailer build: http://www.tnttt.com/viewtopic.php?f=50&t=61344
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Re: A foam project

Postby Nodrog » Fri Oct 20, 2017 2:30 am

Hey folks- GPW, I have suspected we are not alone in our madness, good to hear from one who understands! OP- really, sometimes I wonder about this foam thing, I think it'll turn out ok, but I think I could have used door skins over 3/4 x 1" frame covered with canvas and would have been done a lot quicker,bradnailer and pneumatic staples, oh yeah!! I think it was Dancam? wondering the same thing. But this is light...I am pretty close to weight estimate at this stage, I weighed with a bunch of tools in trailer, maybe I'll weigh them as I take them out, those big c clamps are pretty heavy!
Also....I have had the light shining down the side as I prime the thing in the twilight, and see verry small ripples where the foam was a little rough still. I gotta take it out of it's little tent when the sun comes out again next week...Maybe I should have tested the alchohol /shellac primer on it, looks like the water primer raised the "grain" of the mastic a little. The mastic is latex ( I edited that, I don' tknow what else it would be if it is water based! It says so on the bucket!)....I believe I can touch up on top of the primer like with drywall mud...Probably only shows with light at that angle though.
Am happy at this point to work on the interior, I have a general plan but have details to work out....Am also thinking that for electric I'll pretty much do a solar panel, maybe 100w and a good sized battery, don't want to fool with shore power, really. No AC.
That's pretty much all I know right now.... less than ever, it seems, but ignorance is indeed bliss!....Nodrog
Last edited by Nodrog on Mon Apr 16, 2018 1:33 am, edited 1 time in total.
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