Making fiberglass panels

Another thread got me thinking about this.

For purposes of making shelves and bulkheads out of solid glass, what is the recommended most cost effective method of fabricating glass panels, say 1/4 inch thick?

A friend of mine told me he uses a few layers of thick fiberglass mat with thin epoxy resin, sandwiched in between two pieces of plywood with some cinder blocks on top to get even pressure and some squeeze out. He uses wax paper as a "mold release" between the ply and the glass.

How good is this for making panels? Should some roving or else woven glass layers be incorporated between or on the outside of the mat? Can a mat only layup work with, say, polyester resin?

I'm just looking for the most time and cost effective method of fabricating stiff fiberglass panels.

I know foam core simplifies this process somewhat, but for now assume no foam.

 

Parabeam kicks butt, but if you can't get your hands on any, I suggest 2-oz. mat, Coremat, 2-oz. mat. Nothing wrong with polyester for shelves. Not sure if your bulkhead requirements call for something more substantial.

I used to build baffles for Forest Service-style fire tanks out of 3-oz mat, 24-oz woven roving, 3-oz mat. They had a lot of flex. I think you'd be disappointed with mat-only panels.

 

Peterchech,

Most of my fiberglass flat sheet work is done on a piece of 3/4" marlite.

With a fresh piece several coats of mold release wax are first applied before doing anything else. The panel size is then layed out and masking tape applied where I'm going to make my panel cuts. A couple more coats of wax..just to make sure I didn't miss anything. Then I mask off anything that might possibly get spilled or sprayed on outside my lay-up area. Maybe another coat or two of wax while I'm thinking about what to do next.

Next I'll spray a couple of light coats of PVA... I never trust wax alone on my first couple of lay-ups.

Now you can either brush on or spray your gelcoat...it's up to you. So far I prefer the spray option, but brush applications are so much easier when it comes to clean up. Wait two or three hours for the gel coat to cure depending on your conditions.

Your lay-up schedule is going to depend on how stiff you want that panel. A 1/4" isn't going to give you a lot to work with, so you might consider a solid glass laminate or one with coremat.

If it were me I'd do a matte/biaxle lay-up to the required thickness and then rib roll until it was as flat and compact as I could make it. You can substitute roving for biaxle and save yourself some money since it's about a half or a third of the cost.

If it's going to be nice both sides, after it's kicked finish off the top with another layer or two of gel coat giving yourself enough thickness to eventually sand to a smooth finish.

I'm not sure I'd do the plywood press and rely on wax paper as my only release agent...don't get me wrong it can be done, but at least I know that I'm going to have one nice side no matter what else happens.

MM

 

I have done plain fg sheets and foam sheets. Mat on the inside, two outside layers of cloth increases strength more than mat on the outside.

If you need 'see-thru', then foam isn't an option obviously.

If you need light weight, foam is definitely the choice.

I would say that foam is also cheaper - (better strength per $), and better total strength

 

Shelves, stringers ,and stiffeners ,etc etc call then what you like its really shape of the said itam that gives you what you are looking for plus the type of glass you use to make the said itam as well!!. Do you want to create a Eye beam or a ring frame or a stringer or what ? Its what happens when the said piece of what ever is placed under a panel bending load how long will it hold its shape/stiffness/strength before it finally collapses and become completely useless . Have seen a stiffener on the side of the bow panels in a yachts that just somply collapsed underload and when the load was gone reverted back to its origanal shape like nothing had happened . The person was so proud of what he had done and thought it was doing a wonderful job but at the end of the day was completely useless and not doing much at all. Could not comprehend why his beam was collapsing when he saw it with his own eyes !!!a simple L shape of 2 x 450 csm 60 mm in deepth !very light and when fixed in place looked great!!!
Anything on edge over a long distance no matter what it is when the panel bends and the what ever it is, is placed under a load more then it can handle will at best just fold over and most times not even break !! and when the load has gone could revert back to its origanal shape like nothing had ever happened !! solid glass , plywood , anything could simply fold over depending on the height and whats along the top edge and how its formed ( what shape )Foam with glass each side is ok but how thicker foam would you use ? 5mm ,10 mm, 15 mm ,20 mm what about 30 mm?? and what would you run along the top edge ?? What glass would be best ?? slender beam construction is a art form all of its own !! and what you use to make it from and what shape you use all these things are vitally important as to how much load it will carry and how long will it last !!!!