Cloth/epoxy technique

[Oscar]

In some places the cloth doesn't stay put.....(Like cmartin's overhead piece.....)

Is there anything wrong with "painting" the substrate, and wetting out the cloth, and then waiting until both get more tacky (start kicking) and then applying the cloth to the substrate. It will adhere much better..... I realize this would only work for relatively small sections.

[Tim]

To a point, yes, but be careful not to let your wet-out cloth really get to the kicking/tacky stage, or you have a high risk of lack improper adhesion/bonding.

[Rachel]

When I re-cored decks from below, I used a few strategically placed strips of blue tape to hold the cloth up while it kicked (I put them right on the wet cloth and ran them across to un-epoxied surfaces adjacent). These were relatively lightweight and small pieces; I don't know how it would work for larger ones.

Another thought that I haven't tried is to use something like waxed paper backed by thin plywood propped up by sticks to the sole (or wherever).

Slightly related to what Oscar proposed (but not related to holding it up overhead), I was just reading where Bruce Pfund showed that cloth (in this case, biaxmat 1708) would adhere to plywood much better in the long run if the coat of neat resin used to wet out the ply initially was allowed to just get tacky before wetting out and applying the cloth (for tabbing, in his example).

I could see myself wondering if it was tacky enough....wondering.... checking...oops, too tacky. I guess a few tests on scraps wouldn't hurt.

Rachel

[jollyboat]

You can also use scraps of wood covered in plastic that hold up the wetted out cloth directly - use wooden dead legs to hold it in place.

[Rachel]

Or you could... "use something like waxed paper backed by thin plywood propped up by sticks to the sole (or wherever)."

;)

(I didn't know the prop sticks were called "dead legs" though; one can always learn something new :)

R.

[jollyboat]

"Dead Legs" is term used in construction, say for example if you wanted to remove the pillars on a front porch, you would slightly jack the porch roof up, install "dead legs" - which then bares the weight load of the roof - and then remove the pillars. For the epoxy project - there are commerically available, small adjustable rods - that can be used with success. The adustment feature keeps trips to the chop saw to a minimum.
Your "waxed paper/plywood" suggestion is basically the same as I suggested. Plastic, wax paper, whatever will be able to release from the epoxy once it has set up.

[Hirilondë]

I always heard of them referred to as a dead man, because he could only stand there and do no other work. Not that a dead man could stand either :) I use them all the time. Hmmm, they do more work than some people I know now that I think about it.

[Zach]

Dave,

That got a good chuckle out of me. Grin.

Zach

[cmartin]

I tried the plywood method today, I'll report back tomorrow with results.

A few notes on my experience so far...

Be careful when snugging up the support/deadmen. I found the cloth shifted a bit as I applied tension. I'll find out tomorrow if I need to redo.

I wasnt sure how long I needed to leave the support in place, so I left it until tomorrow. I'm sure I could just until the epoxy starts to kick, but I didnt.

It's comforting to see cloth in place, to make sure it's properly place and saturated. Plywood pretty much means you are flying blind.

[One Way David]

Just to add to the concept. Cabinet makers might call these spring clamps. When gluing up a large span of ply or formica, long sticks cut to allow some spring in their length are wedged between the ceiling and the project to put pressure where a regular clamp can't be used. Just turn the idea upside down and you could hold something up instead of down. The length of the clamp would be longer than the distance from the floor and the project, 1x2 or similar would work in most cases. Thin ply, 1/8 or Luan (sp?) could be used for a ceiling that had a radius. Dave

[cmartin]

I tried another method today to install a ~3' x 18" piece of cloth. I'm sure larger pieces are possible, considering my previous attempts this was a big piece for me.

I began by laying down a coat of unthickened epoxy when I planned to install the cloth. Next I marked the center of the ceiling and the center of the cloth with a Sharpie. Then I mixed another batch to wet out the cloth. This time I cut out some plastic a little larger than the glass piece. Once wet out I moved the glass with plastic in place to the ceiling.

I planned, a little, ahead and had a spring clamp and a piece of plywood waiting for support. After lining up, roughly, the cloth I clamped the plywood in place over half the material. I then used a scraper, with the plastic still in place, went over the exposed half to ensure proper glass contact and no air bubbles. I then removed the clamp and wood and did the other side.

I am still using slow hardener, not sure this would work with fast, but I then waited a few minutes for the epoxy to start to setup. Slowly I peeled the plastic off the cloth. Of course the cloth moved around a little, but it was easy to smooth it out with the scraper.

Using slow epoxy takes some time to setup so I wont know the results until tomorrow.

[One Way David]

Bet it'll be fine. And you thought it out ahead to do 1/2 at a time. In my haste I'd of wound up grumbling at all the air bubbles when I took off the clamp, plastic and board :)