hand lay up of coracell m foam

hi all,I've ordered some m foam and plan on using it for some interior parts of my small boat.I've tried the search function and it comes up with nothing.
so i have some questions,do i spread plain epoxy on the foam then apply the glass same as i would for plywood?or is there a better way to limit the amount of resin used?I will be using 6 oz glass and epoxy resin.


thanks

 

The foam will not absorb any resin, since it is close celled. It works nothing like a sponge. You just wet the foam, stick the glass on and then maybe wet the glass, though with one layer of 6 oz, you probably won't even need to do that.

 

thanks Cat.after i coat the foam should i let it tack up a bit before applying the glass?

 

No need to let it tack at all because you want to saturate the little tiny dimples in the face of the foam as well as the glass and all areas in between the foam and glass. If it tacks off, you will have less free liquid to saturate the glass, using more resin, IMO.

Works best (in my practice) to simply use an epoxy roller and load the foam up so it's a little excessively wet. A big film on it. Then, stick the glass on.

The glass then starts absorbing some epoxy from the underside, making a very reliable bond between foam and glass. Before it kicks, I then wet out the top of the glass too, let it go 100% clear, then use a squeegee to pull air bubbles out.

Of course, this is for 1150g/34oz triax, so it's a little more to wet out.

When I've laminated a single layer of 6oz cloth to foam, just wetting the foam out liberally, then sticking the glass has been more than enough resin to work properly.

Letting it tack off a bit is more of a wood/balsa technique to seal off the wood before your lamination. With foam, there is no air escaping from the core. No breathing. No reason to need a hot coat or tacked off coat before the final layer. It's a lot easier to use than wood, actually. No pin holes.

Do you have the M foam in hand? Once you do, you will understand right away... you'll notice it's not even close to porous.

 

ok thanks for the help.

 

Recently, I tried to epoxy 4oz cloth to foam - it formed bubbles all over the sheet - from ten cent to 12 inch size. You couldn't even work them over to the edge. The first half of the sheet I just epoxied straight onto the foam, the second half of the sheet I applied a layer of epoxy to before the f/glass to see if that would help.

I thought it was the peelply wrinkling the cloth, and tried a smaller test patch with 4 oz glass alone. The bubbles still formed, despite careful squeegeeing.

I found that if I pricked all the bubbles, then the cloth would lay flat. The trouble was, on a large sheet, getting every bubble was just too difficult.

The next sheet, I used 6 ox cloth with peelply. It tried to form one bubble, which I popped easily, and then the rest worked fine.

I can only figure that the very fine cloth has a lot of air trapped between the fibres, and the outer layer of epoxy stops the air from escaping to the surface, and starts pooling under the f/glass.

The bottom line, if you see any non-transparent spots under the glass, just prick them with something sharp.

 

i've read a few posts that say to add a thickening agent to the first coat of epoxy to help level out the foam let tack up then apply the glass.would this maybe help deal with the bubbles you speak of?

 

Yes, I have read this too.

If I ever have to try light FG again, I will give it a go.

Its what they recommend for say, Vynilester, so it should work with Epoxy too.

 

You can indeed use epoxy loaded with silica and glass micro-spheres, and use it as some kind of primer putty. It will fill the open cells on top of your foam with something less dense than unloaded resin (and the cuts if you had to do some to fit the foam), but you will have to do a bit of sanding afterwards. You will have a nicer surface to work on, but obviously it adds the sanding time. And your boat will be lighter overall.

 

I would imagine that you could put a layer of peel ply on it, to leave a good surface for the FG. I have forgotten the brand of the foam I bought, but it was very rough on the surface so there would be a good depth of 'goo'.

Better yet, do it all wet - so there is no intermediate stage

this is an excerpt from West Systems receommended method of repairing foam cored hulls

"4. Wet out the contact surfaces with a 105 Resin/hardener mixture. Then apply a liberal coat of 105 Resin/hardener mixture, thickened to the consistency of mayonnaise with 406 filler, to one contact surface. Apply enough thickened epoxy in an even layer to bridge all gaps between the two surfaces. This alternative is recommended for larger repairs.
Or, especially with smaller core areas, apply a liberal amount of Six10® Epoxy Adhesive, dispensed through the static mixer, to the core contact area. Spread the adhesive to a layer thick enough to bridge all gaps between the two surfaces.
5. Press the core material firmly in position. A small amount of thickened epoxy should squeeze from the joint around the piece. Clamp the piece (or pieces) with plastic covered weights or braces, if necessary, to hold it in place. Shape the excess thickened epoxy into a fillet at the core/panel joint and remove excess epoxy before it begins to gel. Allow the epoxy to cure before
removing clamping.

6. Wet out the bonding surface of the core material and panel with a mixture of resin/hardener.
Squeegee a thin layer of 105 Resin/hardener mixture thickened with 404 or 406 filler to the consistency of mayonnaise over the core and exposed panel bonding area if the surface is heavily textured. (Or, use Six10 Epoxy Adhesive, especially for smaller areas.) The thickened
epoxy will fill voids on the surface and provide better contact with the first layer of cloth.
7. Center the largest piece of fiberglass fabric over the reinforcement area and wet it out with epoxy.
You may find it helpful to hold the fabric in place with pieces of masking tape. Squeegee any excess epoxy from the surface, but make sure the entire piece of cloth has been saturated."

 

thanks guys,my foam is in transit,so when i get it i'll do some tests.

i think i'll try the peel ply and even mylar over the wet glass and see what happens.

again thanks for the help.

 

Remember to apply epoxy to a warm surface and let it cool as it cures to reduce out-gassing.

 

Testing is the key.

You will be pleased with either method.

Mylar is a bit of overkill if you have to scuff up the surface for painting or varnish.

 

I've used $30K worth of Corecell in the past 12 months. Trust me, you don't have to do any of this extra stuff.

Just slap the epoxy on the Corecell at any temperature and stick your dry glass over that wet epoxy. Work out any bubbles. Apply peel ply if desired. Done.

It is closed cell foam and the half spheres that make up the "craters" in the surface of the foam are smaller than 1/4 of half of a ball in a ball point pen. They are on the order of the size of a few needle points clustered together.

There is no porosity and it (sorry Hoyt, not trying to be annoying) does not outgas even a little bit with varying temperatures because it is close celled. (Wood, however does outgas terribly in the way Hoyt is describing)

Well applied peel ply over this (load up more resin for it on top of the glass) will leave you with a surface that can go straight to primer, if you apply it well.

This is dead simple. Just lick (with a roller) and stick it.

 

i now have the foam and i see what you mean Cat the surface is quite smooth.
So onto some tests,i plan on spreding some resin lay some glass more resin and glass again.roll out flat let cure.i'm gonna use a piece about 1'x1' any ideas on how to rig this up so i can test how good of a bond i'm getting to the foam?if i leave enough dry glass overhang i'll have something to grab onto but how do i secure the foam so it stays put?if that passes then i'll do the other side same way then test it for strength.other then wack it with a 20oz hammer what would be a good test?if its strong enough i will use the foam for all my interior parts of a small 12' flat bottom square ended driftboat.So strong enough to handel a 240lb drunk guy.This boat will be hand loaded onto a roof rack of my truck.