CPES

[DudKC]

dh -

Just bought my 105/207 today for the camper. Do you have any advice? I've watched all the videos and have looked through the manual, I'm surprised that it says to sand non-porous surfaces with 80 grit sandpaper. I have oak and birch plywood, which both seem rather non-porous. If I sand those with 80 grit, will the epoxy take care of the scratches or should I just sand it lightly with some 120?

[madjack]

...ply is not non-porous...non-porous in this sense refers to metals and such...a little lite sanding with fine sandpaper won't hurt but you are gonna be sanding between coats...arencha..................
madjack

[mikeschn]

Plywood doesn't need sanding for CES. If you are trying to clean up some scratches or something, use a random orbital sander with a fine grit. Otherwise just slap on the epoxy.

Mike

[DudKC]

Thanks for the sanding help, I'll just touch up some spots and slap it on. The manual says if you don't let it cure, you don't have to sane between coats. Says to wait until it is just about as tacky as masking tape and apply the 2nd coat. Then a little sanding with fine grit after the 2nd coat cures and apply the poly and I'll be done.

[schaney]

Yes, the preferred method for doing multiple coats of epoxy, is to wait until it's in the "Green" stage of curing, fells like masking tape to the touch and no epoxy comes off on your finger, then apply the next layer. This make a chemical bond where the layers actuals become one. If fully cured between layer, you need the sand so the epoxy has something to bite into because you are depending on a mechnical bond.

[dh]

I would give a trial run on some scraps first, get comfortable with how much time you have till it gells. Maybe set up a scrap vertically, applying unthickened epoxy vertically is a PIA. If a coat sets up too fast on ya, sand it so the next coat kan key into it.

[DudKC]

I was hoping not to do any epoxy while the walls were vertical. Should I attach the walls before I epoxy for any reason?

[doug hodder]

On a woody, I do as much of the "build up" while the walls are laying flat. They do however, get a couple of coats once up and vertical. You just need to roll it on thinner and it takes more time to build up thickness. You can't just "mop" it on.

I've also done 2 painted tears as well as boats and the walls were coated out with them being vertical, no horizontal application on the epoxy. I also let them cure completely and sanded between coats. That's how you get them really flat. Epoxy will fail on a really hard 90 degree corner. They have to be eased. Others opinions may differ. Doug

[dh]

What Doug said. I just figured I'd throw that in there just incase.

[Larry C]

I sand all wood with 80 grit with a Random orbit sander before applying epoxy. I feel plywood, especially hardwood plywood is too smooth for the epoxy to get a good bite. The ROS will not leave scratches that will show.

Also, what Doug & Dh said about 90* corners and epoxy failure. I would incorporate some type of radius where the sides and top meet. Plus....I would glass these edges with bias cut strips of 4 oz. fiberglass cloth (not tape). The bias cut strips cloth will be easy to bury in epoxy.

The fiberglass on the joints will help keep edges from delaminating, and prevent the top/side joint from opening, and allowing water in. The minor extra steps of rounding the corners and adding fiberglass to the corners will save you a lot of heart ache down the road.

$.02

Larry C

[dh]

If ya go with cloth, watch the weight. A 6oz or lighter cloth should dissapear, a 9oz will not. 4oz like Larry sugested will be easier to burry. Just throwing this in, if painting, a 9oz tape will work, just fair it in with 407 mocrobaloon filler instead of trying to burry it with 'neat' epoxy. Again, practice the cloth on scraps. I was able to obtain some small off cuts of various fabric weights/weaves from a local fiberglass shop. Not enough to do a tear, but enough to get a feel for thier properties/application, all I had to do was dig through the scrap bin.

[dh]

It just hit me, your using the 207. I have to come clean, I'm not %100 sure if 6oz, or even 4oz fabric will dissapear in the 207. I have 207 and 209 extra slow, and have only tried fabric with 209. It should, I just don't have first hand experiance.

[DudKC]

I am using the 207, but I plan on using some wood trim on all the edges. If I used the cloth on the corners, then put some wood trim over it, the cloth would disappear wouldn't it?

[Larry C]

It just hit me, your using the 207. I have to come clean, I'm not %100 sure if 6oz, or even 4oz fabric will dissapear in the 207. I have 207 and 209 extra slow, and have only tried fabric with 209. It should, I just don't have first hand experiance.

Cloth will go transparent when saturated with 105/207

This canoe has the Wests 105 resin with the 207 hardener, 6 oz plain weave cloth:


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Larry C

[Larry C]

I am using the 207, but I plan on using some wood trim on all the edges. If I used the cloth on the corners, then put some wood trim over it, the cloth would disappear wouldn't it?

If your putting wood trim on the edges, you probably don't need the glass. I assume you are going to epoxy the trim on. If your just going to bed the trim in some type of caulk, I would still glass the seams first.

I am glassing all exposed surfaces not just the seams, even if I decide to use wood trim on edges.

Larry C