Foamie hybrid thoughts...

[mikeschn]

I'm thinking about foam again. Why, because realistically there's no other way to make a Mad Dash Winter Warrior that is lightweight.

The first time I played with foam I had planned on doing canvas on both sides. I didn't do the outside, and when it got stored for the winter, it got damaged.

So this time around I am thinking about doing a hybrid, 2" foam walls covered with thin plywood on the outside and canvas on the inside. For this kind of arrangement what would be the best way to glue wood to the foam? Gorilla glue? Titebond III?

And while we are thinking about covering the outside of a foamie, has anyone ever tried the FRP from one of the big box stores?

btw, here's a rough draft of what I am thinking...


Mike...

[KCStudly]

Glad to see you back around.

I may be a bit biased in my opinion, but it seemed to make more sense to me to put the thin ply on the inside, away from the weather, and put the canvas skin on the outside. No trim needed, and a monolithic barrier to the elements once sealed and painted. Also, so many people have complained about the complexity of hanging canvas inside after assembly. Even if you were to apply the canvas on the bench, doing the corner strips in situ does not appeal to me.

Also, I have found the combination of 1-1/2 thk foam with the 5mm inner skin to be very hardy. For the box section I would think that is plenty thick. On my galley wing walls, despite the laminated wood as a hard edging (... or perhaps due to them warping?) I have found some instability with the way my hatch fits. At this stage of my build the unsupported portions of the walls seem to bow in with heat and humidity, tho I am hopeful that this will be reduced once the final skin is on and everything is sealed up better.

Re: Adhesion. For laminating on a big area I would shy away from GG. My concern would be that no amount of weights or clamping could reliably thwart the hydraulic expansion, plus being water cured it is difficult to get the right amount of moisture, yet still have a fast cure. The best results I have had is with a thin rolled on layer of TB2, making sure that there are no puddles or roller lines of pushed up glue. The wood has to take all of the moisture in the glue before it becomes sealed by the cure, otherwise any excess moisture will be trapped and the glue won't harden. Experiment with modest (not small) sized test pieces to learn the right amount. Small pieces will give a false sense of the cure due to edge proximity helping with air. In fact, on some of the flatter areas of my hatch where I was using PL300 to laminate foam to foam I added shallow kerfs just to let air in and assist the cure.

I also had reasonable success using 3M 30NF "Green" water based contact adhesive. Even coat so it dries uniformly and let it dry before joining. The tricky thing here, between ply and foam, seems to be having really flat surfaces. They recommend rolling with a small roller and high pressure for best adhesion, which I did not do because I was concerned about marking the wood or local crushing of the foam. I used a makeshift vacuum bag setup with a shop vac and got a mixed result. Where the surfaces are stuck they are stuck really well, but where contact was less than optimal they are not stuck at all (like what I found when I made the hole saw cutout for the fan in my bulkhead), or are only stuck over a small percentage of the contact area (destructive test pieces showed surprisingly few small stalactite like connections dispersed over a large area... still strongly joined, just not as full contact as expected). For foam to foam laminating of 3/4 thk kerfed the stuff worked great because the flexibility of the foam let me get a good press by hand, but the stiffness of the ply seemed to give mixed results; at least for me. Depressed areas of the foam, like where the band of printed info is, didn't take because the contact adhesive has no filling capability to speak of. I did read that one builder makes a practice of applying multiple layers of the adhesive to build up some thickness before joining, but the product is expensive and I didn't try that since it is not what the label instructions indicate. I looked for a while to find a local vendor, but it is not commonly stocked, so they all wanted me to buy case quantities; McMaster-Carr sells gallons and quarts.

[Fred Trout]

I agree, GG is out - it will foam unevenly over those large areas when you don't really want much foaming at all. I did not find doing canvas on walls inside w/ TB II after assembly that bad but the ceiling is a real pain so something done on the flat for the ceiling would be preferable. Really can't help with the "best" glue but not using GG or GS for large ply panels is a no brainer. I found great stuff the best at joining foam to foam and wall base to floor if you can work fast and limit the scope of the glue-up and use positive high pressure mounting points (nylon insert dry-wall-screws, bamboo skewers, packing tape, clamps, etc). Ignore this if you can deal with getting GG to sit flat and foam a tiny amount evenly but I could never get it to foam in some places at all while others went wild and it is very expensive and it is harder to sand vs foam so creates a fairing complication.

I also agree canvas on the outside would be stronger than ply but depends on the look you want really. I think the canvas will be much stronger because of the overlapped corners. With ply over foam, you really do not have any reinforcement against racking unless you use a wood skeleton like KC did. Especially if you do not have a solid box structure because of the separate popup back end.

For speed, depends on how fast you can perhaps do a full-sheet plywood "box" covered by canvas versus a full foam "box". The foam is more forgiving, the ply has inherently stronger joints and eliminates the need to fuss with mounting blocks. Anything involving composite walls, fancy angles, etc just slows everything down.

[KCStudly]

IMO, speed is really not so much an issue of building materials or basic TD design, but rather the methods and style of the builder. If you have mad carpentry skills with years of production experience, and/or are retired or self employed so you can build full time, or if you just bodge it together, you will have something to show rather quickly.

If, however, you are more challenged, work on your project part time (or on TD time), are particular about details and/or have boo boos "that must" be repaired at every turn, then your project will take much longer. (Line forms to the rear.)

There are plenty of examples of all varieties of build styles and types that fit into these categories: fast crude builds, fast glorious builds, fast simple builds, slow crude builds, slow simple builds, and slow glorious builds, foamies, traditionals, standies, etc. etc. So don't assume that all foamies are quick building. The devil is in the details in every build.

[GPW]

We naturally might use 2" foam with canvas outer and chipboard inner ... Lighter cheaper , paint's well .... The thing to decide on , and this is always the Rub... Do you want it to look like a nice Shiny Big Buck RV trailer ( Impress your friends)... or a simple Practical ,inexpensive, easy to store , tow and repair if needed Camping trailer ? (Impress yourself!! ) It always comes down to that ... "the Look" ...

A Hard Tent ... or expensive Playhouse for the inner child ..... or somewhere in between.

Ps. OSB floor(the good stuff) , brings the weight down low for stability.

That is a Nice looking drawing ... great if you're using the more Traditional materials ..

KC's right about the details ... Foamie is no place for slack building ... All the parts collectively working together as a Unit .... A UNIBODY...

[GPW]

Just to be out the box , we've learned from others that applying canvas over plywood really goes a long way to prevent de-lamination and splitting ... especially if it's been treated with "the Mix" ... Had I done that to my first wooden trailer , I'd still have it ... Plywood and Foam is a sure possibility .. the right material for the right job !!! Same old story ...

[mikeschn]

It was really really windy, and raining today. How does a foamie act and feel in those circumstances? You guys have had foamies for a while now, so tell me...

Do you feel your foamie swaying in the wind?

Do you hear the rain beating on the outside skin of your foamie?

Are you worried that the foamie is going to blow over?

What do you worry about in a severe storm?

Mike...

[mikeschn]

Thanks KC,

I thought the GG would be problematic. I'll stick with TBII or TBIII for large surfaces. And I understand and agree with your thoughts on putting the plywood on the inside. Unfortunately Chell doesn't like canvas on the outside. Don't know how to get around that yet.

@Glenn,

Got the heavy floor built out of 1/2" plywood. Stuck now, until the outside skin can be agreed upon by both of us. Chell just found out that the FRP is like 32 pounds per sheet. I think we would need 10 sheets, with many large pieces cut off and thrown away. Still it sounds really heavy. I'm thinking we just ruled out FRP.

@Fred,

Yep, I know the benefits of a canvas exterior. But I can't talk Chell into a canvas exterior. At least not yet. She's looking for something pretty on the outside.

Mike...

[Fred Trout]

Storm ? Depends - if you see it coming you can move along to someplace more sheltered. If it's a after sleep time tornado, you have the option of kissing your butt goodbye or prayer

I have not camped with a foamie yet but have in a tent when a windy t-storm hit. Not much fun rushing to put that up after we beached the canoe and it blew over anyway.

What can you do ? She who must be obeyed rules

[tac422]

It was really really windy, and raining today. How does a foamie act and feel in those circumstances? You guys have had foamies for a while now, so tell me...

We've been in the Big Pink in heavy rain, and some wind.

Do you feel your foamie swaying in the wind?

No sway at all, I put jack stands under the rear and jack the front up until it's level.

Do you hear the rain beating on the outside skin of your foamie?

Yes, you can hear the rain, but it's not loud. We find it relaxing.

Are you worried that the foamie is going to blow over?

Nope, never even close All the weight is down low...

What do you worry about in a severe storm?

A tree branch could puncture the foam, but then I've seen branches puncture regular shingle and plywood house roofs.

You start another one Mike, and I'll finish it ....

[KCStudly]

I would be more worried about stabilizing the standing edges of the side walls and opening of the clam shell lid/hatch. As stated ^, these will not have the benefit of the closed box structure and the sock effect will be greatly lessened.

You can have a perfectly smooth exterior canvas surface. You just have to work a little bit more for it. Careful attention to trimming and terminating your overlaps, perhaps using the corner molding to help with that, then filling with a high build or block filling primer; or even resorting to a full on boat quality epoxy filler and paint treatment. Sky's the limit if you have the patience and budget.

Doesn't the box store FRP have a pebbled texture? I'm good with a little texture in the outer finish, but I can tell you that it is a lot of work to get the flaws out of the foam in the hopes that they won't project thru the canvas. Seems like the more work you do to take them out, the more you end up putting in. Knowing what I know now I would think that it would be much easier when doing canvas over plywood, than straight over foam. Even more now, GPW's suggestion to lay down chip cardboard before canvasing seems like a viable idea. You just have to plan for all of the extra thicknesses and laps so that your door jambs and hatch seals work out correctly.

[Fred Trout]

If you wait a couple of weeks, you should see the result of a novice trying to get the 'fiberglass' shiny look on canvas over foam. I will be using concrete/foundation paint, sanding, filling edges with vinyl spackle, more sanding and more paint.

[GPW]

Two schools of thought ...
1.Fiberglass provides a nice smooth surface , but must be waxed to retain that slick look ... This was proven by many fiberglass boats ... Also , should it get damaged , it is not that easy to fix and blend in with the other shiny finish ... Our ex RV dealer although charging us $120.00/hr labor for his expert work , couldn’t even do a decent job on patching holes in my fiberglass walls ... The repairs stood out like a sore thumb and even a third rate auto body shop could have done a better job ...... I could have done a better job .
2. a Foamie with a canvas covering is already somewhere between Beer Cooler and Tent, and it has a “look” of it’s own ... (Fabric) ... Damage is always localized to one spot , and that can be repaired with a can of great Stuff, a serrated steak knife, and a canvas patch ... A little glue , a little paint , and you’re done , and back on the road... We’ve even made up a Foamie repair kit to bring along just in case.
Can of Great stuff, serrated kitchen knife ,scissors, sandpaper , glue , paint , canvas patch material , cheap brush ... fits in a small box ... like a Foamie First Aid Kit ...

We had a tree branch go through the Jayco roof like it was Butter ... Scary ... Their roof was from top down .... a "membrane” ( in their words) consisting of material the thickness of a dollar store Vinyl tablecloth ( very thin) , 3/32” plywood (measured) , 2" of beaded foam , and a ceiling covering of a wallpaper like textured product . a single limb ( a rotten limb too) went through the roof in 10 places. Makes a good case for Aluminum skin on the roof ...
We’ve watched a canvas covered roof on Foamie #1 in a horrific hailstorm here ... full of dents .... a week in the summer sun and all the dimples were gone .

We also watched yesterday as our gardeners children (schools out) were throwing rocks ..... at the Foamstream ... my whole drive way is Rocks , and little boys LOVE to throw rocks .... checked the FS.... no damage , not even a dent ... THICK 18 oz. canvas ...

Do we care what the wife wants ? .... for me , after 40 years ..... not so much ... Nor does she care what I want . Familiarity breeds contempt !!!

[mikeschn]

Knowing what I know now I would think that it would be much easier when doing canvas over plywood, than straight over foam. Even more now, GPW's suggestion to lay down chip cardboard before canvasing seems like a viable idea.

That's kinda sorta what I was thinking, but I was hoping to do it without a membrane on the outside. Thinking about it more, I'm beginning to realize, I will need a membrane of some kind. So maybe hide the joints under some aluminum edging.

What is chip cardboard?

This might work under a membrane. http://www.menards.com/main/p-1931476.htm

Mike...

[GPW]

Mike , chipboard is just like the stiff cardboard on the back of writing tablets ... ( does anybody remember writing tablets ? ) Available in thin sheets or thick sheets ...
Being an Artist , got mine here : http://www.utrechtart.com/Search/Defaul ... d&Search=+ We used the thick stuff on the front as a panel to cover the inside foam .... and the thin stuff as a wall covering ... when painted it became very smooth (and Washable ) , besides being waterproof ..
Experimenting with some now and “sizing the board “ with poly or T2, both highly thinned out .... In essence making a random fiber marine plywood ..... it’s all Cellulose eh !!!

Ps. Just an after thought , a thick 0.120” chipboard over foam on a roof (safety man) ... there won’t be any limbs going through that !!! The sledge hammer test proved that ...