Glassing (fiberglass + epoxy?) - clarity, technique...

[Ben Fleis]

If my memory is correct, glassing is basically a fiberglass cloth, impregnated with epoxy, usually done on the outer hull. I was digging through the forum trying to find confirmation, but no luck so far.

Can this be done such that the finished glassing is clear, or near to it? If so, what is needed to achieve it?

Thanks!

-b

[JimConlin]

Glass cloth set in epoxy will be adequately clear if applied carefully and the weight of the cloth is no more than 6-8 oz./yd. The techniques for this are well treated in the strip canoe and kayak books.

If for structural reasons, you need glass heavier than 8 oz., plan on paint.

[capt jake]

Tell your supplier what results you are trying to achieve. They should be able to guide you to the proper cloth for this application. I can't recall specifically, but I think it is referred to as E Glass. It has th flat fibers in the cloth. I have had good luck with the transparent effect with 4oz and 6oz. I haven't tried anything heavier.

What are your going to glass? What kind of structural requirements are going to be demanded from the glass?

[Ben Fleis]

Capt,

I am considering using the technique as part of a slatted panel, in a frame-and-panel style door. I remembered reading about the technique, and think it would work well because it will add some structural value via the epoxy, and maintain transparency (or high translucency) without the weight of actual glass.

It sounds like I need to contact a local boat supply place, which will be no problem at all in coastal maine :) Really if I had been thinking I could have just gone down to one straight away.

Thanks again!

-b

[P.I. Stazzer-Newt]

What "structural value" do you think will be added by the epoxy?

Leaving out the glass means that you are just applying a "goo" which sets medium hard - plenty of varnishes do that, and are better able to resist the effects of sunlight.

[Ben Fleis]

What "structural value" do you think will be added by the epoxy?

Leaving out the glass means that you are just applying a "goo" which sets medium hard - plenty of varnishes do that, and are better able to resist the effects of sunlight.

Imagine a typical frame and panel door. Remove the panel. Add ~20 slim slats, spread out across the width, with gaps between them, in width equal to each slat. Part of the rigidity from door comes from the frame structure in the corner, and part comes from the panel itself. In the slatted version, the structural support from the panel is mostly lost, but by adding an glassed back (a la shoji screen), the panel becomes a "solid" piece again. It's certainly not as strong as a wooden panel but represents what is likely to be a substantial improvement.

Does varnish really dry with strength equal to epoxy? I know that in the end they are both just plastics, but am fairly ignorant beyond that.

-b

[P.I. Stazzer-Newt]

A traditionally constructed frame and panel door - does not rely on the panels for its rigidity - these should be sliding fit or seasonal moisture content changes could well destroy it.


I remembered reading about the technique, and think it would work well because it will add some structural value via the epoxy, and maintain transparency (or high translucency) without the weight of actual glass.

This hints at an epoxy layer - without any glassfibre - which would give no additional strength at all.

If you need additional strength then the glassfibre stays - If you just want a moisture barrier then there may be value in an epoxy layer.

What did you want?

[Ray Frechette Jr]

It sounds like you are contemplating a free floating glass epoxy screen tot he back of the slats.

Likely you will be exceedingly dissapointed withthis result.

6 oz glass cloth bonded to a wood substrate provides some additional strength, but a free floating 6 0z glass cloth fixed in epoxy is fairly flimsy all by itself.

Frame and panel construction relies nearly entirely upon the frame for the strength. As noted the panels typically were designed tobe free floating in order to change and slide in mortise with moisture changes and were only pinned in place at most.

The deep mortise and tenon joints of the frame is what provided the sturctural integrity of the door.

[kc8pql]

I agree with PI and Ray. The panel contributes little if anything to the strength of the door. Just pin your slats in place, one small brad or headless pin in the center of the slat top and bottom, and you'll be fine. If you toe the pins into the corner at the groove, through the panel and into the frame, they'll be almost invisible. If you have a moral objection to nails, a spot of glue works too.

[Todd Bradshaw]

...and for clarification: Varnish is not "nearly as strong" as epoxy. The truth is that epoxy is "nearly as weak" as varnish. Both are just coatings and neither contribute noticable strength when used as such. If your wooden bits aren't strong enough to stand on their own, the application of either varnish or epoxy to them is not going to change that. Epoxy resin-saturated fiberglass cloth, however, can make a substantial strength contribution if the glass fiber-to-resin ratio is in the proper range and you simply have enough of this mixture present.

Just keep in mind that there is a very big difference between the strength and characteristics of plain epoxy and epoxy/fiberglass. One is just a surface coating, but if you have enough of the mixture, you could build Disneyland.

[Ben Fleis]

Free floating is the wrong word here. I want to consider fixing my slatted screen to the frame, which is why I claim it will add some rigidity. I should have said that frame and panel is the basis of the design, but that the panel will not be floating in any sense. Perhaps that clarification is enough. If not...

http://lh5.ggpht.com/ben.fleis/SQNPXWLkyII/AAAAAAAAAP4/eheUZW78c5I/s640/IMG_9009.JPG

This is a picture of the mockup I am working up. I put a piece of tracing paper in there to see how much transparency is maintained. The frame itself will be reasonably strong, but adding an epoxied panel should considerably help deal with racking.

In terms of "triangle" supports, the epoxy, while itself weak, when bridging the gaps, turns 20 1/4" slats with tiny 1/4" triangles into a singular 10" triangle. Even the weakest materials can add substantial strength when used well.

Ok, enough babbling. I appreciate the advice on fiberglass cloth, and plan to head out to the marine shop shortly to buy some. I also don't mean to sound defensive, but I do believe that even a small amount of epoxy in this "paneling" setup will provide some additional strength. Next I need to add it to the real prototype to see how much strength it adds, versus its additional weight.

Thanks again!

-b

[kc8pql]

I'd back the slats up with a piece of 1/8" acrylic, sold cheap at hardware stores for reglazing storm doors. A light sanding with 220 grit and a random orbit sander gives a nice white frosted look. An epoxy/glass panel will be brownish yellow and somewhat translucent if it's not sanded smooth. It will be almost opaque if you want to sand it smooth. Mortice and tennon, or even bridle joints at the frame corners rather than miters will add a great deal of srength to the frame.

[Todd Bradshaw]

You still seem tio be very confused about the difference between "epoxy" and "epoxy/fiberglass composite" and are either misusing the terms or failing to understand the difference in their physical characteristics. You could bridge the gaps between the slats with a backing layer of epoxy saturated fiberglass cloth, in which case the material between the slats with be semi-transparent and wind up looking kind of like screen wire. It will add a bit of dimensional stability to the slat network, but not an awful lot. If you want a solid surface on the fiberglass areas between the slats (without the screen-wire effect) the fiberglass/epoxy would need to be formed into a sheet up against a temporary mold (a big hunk of waxed Formica, for example) and the slats could then be coated and dropped into position on the wet fiberglass and allowed to cure.

A few coats of plain epoxy resin without the fiberglass cloth will neither bridge the gaps between the slats or contribute any strength to the project. Individually weak materials can indeed contribute substantial strength to a project - but only when used properly and in a way that takes advantage of their characteristics.

[P.I. Stazzer-Newt]

Its the age old question.

What do you want?

If you want a transparent panel - one you can see things through - then glassfibre is fairly horrible - better than tracing paper but nothing like as good as acrylic or polycarbonate sheet.

To create a fibre reinforced shhet suitable for sticking to the slatted wooden thing:
1. Prepare a mould (mold) surface.
2. Lay on the fiberglass cloth.
3 "Wet Out" with the resin of your choice.
4 Wait till the resin cures
5 Split the new laminate from the mould
6 Trim and fix the new laminate sheet to the Slatted panel thing.

N.B. Epoxy resins are notoriously unstable in UV light.

[Ben Fleis]

Thanks for taking the time to explain all of this. Sounds like acrylic or paper may be the only sensible options at this point, if the yellowing is that bad. Out of curiosity the UV instability -- is it structural as well?

-b

[kc8pql]

Out of curiosity the UV instability -- is it structural as well?
Yes. First the UV turns unprotected epoxy cloudy, then with time it becomes brittle.

[sdowney717]

the cloth does add small strength
the cloth also allows for a more uniform thickness coating of the epoxy. It is giving you a base thickness to work with. Without the cloth, your epoxy coat will be harder to maintain the same thickness over the whole surface.

when exposed to the sun, the epoxy will eventually totally fail, peel crack and fall off.

[Tom Lathrop]

Do you want to be able to see through the structure or just have light transmission through it. If the latter, I suggest using synthetic shoji screen material made of fiberglass. It's white and looks great in thi kind of application. Passes light pretty well but is not transparent.

If you must see through it, I would suggest something like 1/8" thick acrylic. This will be stiffer and more transparent than any epoxied glass fabric.