adhesion level of myriad samples

[Dusty82]

Thanks for clearing that up for me, Mike! I'm easily confused as well as easily distracted by shiny objects.

I too am becoming fascinated by the whole "foamie" process and I'm running several possibilities through my mind. Nothing worth drawing up in SketchUp yet, but one never knows.

I'm also wondering if you did anything special to prep the foam before applying anything to it. When I work with closed cell foam in making door panels and such, there's a skin that has to be removed from the foam before gluing it. The glue bonds to the skin just fine - that skin will just pull away from the foam itself over time. Is there any kind of skin on the foam you're using (indicated by a shiny finish,) and if so, did you sand it off before you applied anything over it?

[mikeschn]

I didn't do any special preps to the foam for the test, other than use my roller that looks wicked... I'll post a picture of that later too!

But on the actual walls, I would sand em with a random orbital sander just to rough em up a bit.

Mike...

[GPW]

There does exist the possibility of using beaded foam ... The PVA glues DO stick to that !! The next test .... As with any foam , you can always go Thicker ... and Beaded foam is CHEAP... comes in many weights ...

[Conedodger]

So far the only two finishes that look good to me are the 8 oz canvas on foam with titebond II and the bedsheet on wood with exterior latex enamel.

Once you upload this one i will remake the video with titles

I cant get TB2 to stick to foam so i look forward to seeing this one.

[GPW]

Any more testing , please let the glue/adhesive cure out to it's recommended time .... Please !!!

[mikeschn]

Okay, you guys did it... You made me go out and do another sample!!!

Here's the blow by blow...











Tomorrow night I'll dilute the titebond II and put a layer on top. Then Wednesday night I'll make the video for Cone!

Mike...

[eaglesdare]

hmm, wondering if using the bead board stuff with a layer of canvas inbetween. perhaps is you can't find the 2" stuff, maybe sticking a layer of canvas inbetween the 1" foam.

i have no idea why i was thinking of that, but maybe that might make things stronger with that canvas inbetween foam.

[GPW]

Eagle , going on the conclusion that the "skin is the strength" , a skin on the inside would make the foam a bit stiffer ... but you can get beaded foam in really big sheets and Blocks ...Cheap ... We know "carpenter glue" sticks to it because we used to glue silk, polyester sheath, or light cardboard (non corrugated) to it with Elmers ... making wings for planes ... They were very tough , usually surving all the other parts ...

Let's not discount beaded foam boards just as yet ...

[squatch]

Funny you should mention beadboard. A contractor had a 6"x12" trailer load of the stuff for sale on CL here last week for about $40. 2" thick. I think about 15 full slightly beat up sheets and lots of partials. I was tempted. I figured the extra would go in the garage rafters as insulation. Just didn't have time to deal with it when it was avail. and it would take me about 3 trips to bring it home in my trailer. The other concern for my use was strength. expanded is just not as rigid as extruded and mine will see dirt roads a bit.

Hadn't thought about the glue factor. Beadboard does glue pretty well with just Elmers glue all.

[Conedodger]

Thanks for testing again Mike.

I am sure you have read all i have written about the importance of it being wrapped.

Your Image



Shows what i mean as its not wrapped at all. The loose ends of the cloth must be stuck to something thats porous. So in our case that is wood or another layer of cloth, but not just foam. If its not porous it will simply not dry or bond, if one part is porous it will dry over a long time and bond to one side and slightly stick to the other.

You need very little stick as long as the foam cannot move. All the strength is from the porous to porous joint not to the foam

This is wrapped


I think this is one of the issues with using foam, in that people wrongly think covering foam on one plane with something makes it some sort of super strength composite but is doesn't. Its just keeps the outer skin in place and stops it moving, its the skin thats the strength. Wrapping the foam adds a lot more strenth.

An example:

Paper is week, layer it with a few bends and it becomes Cardboard, which is much stronger. But Cardboard laid flat is still weak, but fold it into a box and it becomes a lot stronger, now fill the box with foam its becomes even stronger, now wrap that box in something and it becomes super strong.

But its still made from paper.

The Chinese made papermache furniture 1000's of years ago and its still around today, putting layer on layer on layer with laquer made it very strong.

In boat building they build up the layers with more layers in points of stress. The areas that have no stress are not that thick.

There is no way a single layer of cloth stuck to foam will be strong enough for some of us, so simply add more layers.

In Eagles build, she added wood and a double layer in places so the single layer of cloth is only in some places. Even those places are foam, TB2, cloth, diluted TB2, undercoat and topcoat all supported by spars and bulkheads.

Eagle admits that if she went out and cut a join she could peel off the skin but is she going to do that, I doubt it.

The fact is that she made a TD in a few weeks and has used it several times. She is already planning another and will change her design. All this in the time most of us are still thinking about it.

I think both Eagle and GPW would agree that the following statement is important.

"If in doubt put another layer on"

[GPW]

Squatch , Good find !!! Bead board is much less expensive ... the trick is just to use More foam (thicker ) ... the skin is still the strength ...


Cone ,

[GPW]

Just another thought .... bead board bends easily !!! No kerfing ...

[Conedodger]

Then Wednesday night I'll make the video for Cone!

Mike...

Done the video with titles Mike (well almost). Do you want to add a title at the start and end to say what its about?

[squatch]

Squatch , Good find !!! Bead board is much less expensive ... the trick is just to use More foam (thicker ) ... the skin is still the strength ...


Cone ,

I found it but didn't get it. Haven't had much spare time lately to invest in this.

Conedodger, Here is one of my recent experiments that validates your above post. When I started reading the original thread before I joined I started a little project. A glue and bedsheet covered cardboard box to carry my camping grill. Coated inside and out with an extra bottom and 2 layers of tb2. Very substantial and rigid. Sorta the poor mans version of a fiber drum case. I still need to finish painting it and install a strap around it. I intend to make a couple of more for other camping gear. I wouldn't sit on it but it's way stronger than just cardboard and wont melt if wet.

A couple of pics.

[wagondude]

Just a thought, I know that when working with epoxy you want to work wet on wet for a chemical bond. With TB2 does this matter at all? What would happen to the canvas to foam bond it you coated the perforated foam with a layer of TB2 than allowed it to dry then recoat and lay on the canvas?

Bill