transparent fiberlass layup?

Guys I am needing some info. I need to make a part that is clear see thru. Its part of a boat I build. From doing some reading I believe I can do this using an epoxy and light fiberglass cloth? Anyone have any experience with this that could save me some time and money with trial and error?

Strength is not an issue here its basically going to be used as a deflector type part that attaches to the main boat.

 

There are many boats carrying transparent areas on their hulls, even transparent panels in the bottom for underwater viewing. They are made with tempered glass or polycarbonate, with a series of measures to preserve watertightness. To what extent and in what area you want to implement your idea?. Can you give us some more information?

 

Silane surfboard glass is transparent, but over 2 layers it starts to lose its clarity slowly. Air is the biggest problem. You need to wetout with minimum working and a fill weave coat and finish to gloss/polish.
Also you need UV inhibiters in PE, & epoxy doesnt handle UV which will kill clarity. Styrene in PE ultimately goes yellow.

 

Optically Polycarbonate is the best transparent polymer. It is subject to attack from petrol/gasoline and derivatives which is is major weakness. If you are glassing ie polyester or epoxy, a clear hardener epoxy such as certain Araldites is a possibility. It will yellow very very slightly over time with UV. There are some grades available for aerospace and medical industries.

Polycarbonate can be vacuum formed for shape but be very careful about the grade etc and you may get distortion from forming. It can be glued OK with solvent glues as well as epoxy. Acrylic is a second best but use the extruded type if you vacuum form. PVC is third best but I don't recommend it.

 

It will be a curtain so to speak on a small boat to keep water from coming over and onboard. Have no idea how to go about vacuum forming from plastic and just figured I could lay it up using epoxy and cloth. Maybe not. It will be an oval shape approximately 4ft in diameter and angled to prevent water in the boat.
Here is a photo of what we use now just thinking outside the box at how kool a clear glass one would be.

http://www.waterfowl-works.com/jkalash3.jpg And it would only need to come up about 2" and then angle outward with the shape of the deck about 8"

 

You could always try a Mylar (calendered polyester) 'cloth' instead of the coloured fabric. You won't beat that for light weight. Also you will keep a soft ie tube edge at the outer face, which is a lot more pleasant to handle than a plastic edge even with a return. Worth a prototype I would guess and it will give you a good feel for the visual look of it, always better in the flesh than a rendering.

Only thing to remember is Mylar does not stretch so you can't use a bias cut to take up the slack anywhere. You can double side it and stitch through as in sailmaking. Be careful about stitching and needles, I'm sure some of our sailmakers can advise on best practice to stop tearing.

 

No 'glass cloth or resin system will work for this application. Once you have sufficient fabric to make it stiff enough to be serviceable enough for use, it'll be translucent at best, even with special clear resins.

Polycarbonate (Lexan) or acrylic (Plexiglas) are the only real choices. Lexan is tougher, but doesn't hold up to UV as well as the less tough acrylic. Both are easily heat formed, so all you need is a mold. Lay the plastic sheet over the mold (usually with a sheet of felt between the two) and heat to about 300 degrees. Most of us don't have an oven big enough so a heat gun will do, though keep it moving. At around 300 it'll begin to soften and "drape" over the mold. Continue heating to about 350 and it'll become very pliable. It's easy to over heat, which will make bubbles and blisters, so go slow, keep moving and let the heat do the work. Once formed, just let it cool naturally and once so, pop it off the mold and trim as needed. I've made about a dozen compound curve windscreens this way and it's not hard, just a bit tedious with the heat gun.

 

Okay that sounds like fun. I'll build the mold and we shall give it a try. Plan to make them grey as well but clear would be awesome.

 

Importantly PAR is using Farenheit when referring to temperature. Now 300 degrees in Europe would be in Centigrade when your expensiive sheet would be smoke!.

It is important to have a smooth mould, no filler or discontinuity on the surface, hence PARs' reference to felt. This is important to keep an acceptable inner face without too much distortion. It is almost imposible to get perfect formings but you can get acceptable ones. Being aware of the problems will help. Try the technique on a bit of scrap first if you can. Also hence my note on the more expensive extruded grade acrylic which bubbles and distorts far less than the general grade available. You have to spec it with the merchant. Melt points are not too different between the two polymers - polycarbonate and acrylic.

 

WHen the time comes once the mold is done we will give it a try should be fun if nothing else. Im assuming plexa glass from the hardware store will work for practice?

 

The heat gun approach is tedious.

Make an temporary covered 'oven' of cheap plywood, and a source of warm air, as the local plastic guy does for big parts.

The 'plastic' becomes formable a long time before the wood burns, so if you see smoke, back the heat off a bit.

 

I would be tempted to use cheap PVC sheet for practice. Way cheaper, and a little bit easier to form at slightly lower temperature. It will give you the shape and look, just not the longer term durability. The stuff here in the UK is sold for cheap greenhouse glazing. I believe your US DIY stores will have it, if I'm right I think Home Depot? In UK we have B&Q as an equivalent type store.

Yes Plexiglas (US) is acrylic but here in the UK hard to get in big enough sheets except through specialist factors who also do quite a few other polymer materials.

rwatson is referring to proper commercial vacuum formers who have a number of different size elements specifically for even heating of sheet materials with special tables containing vacuum holes to suck the material shape onto the form. I have done quite a lot of formings from 0.5 to 5mm sheet for various purposes and I find transparent materials the hardest to deal with especially if you would like reasonable optical properties. The suggestion of an oven will work fine, you need about 120 deg C (don't hold me to that exact temp!) and wood chars at around 225 deg C. Try and hold the sheet only by the edges when it is being heated or it will mark. Ideally horizontally, until it starts to sag, also try and ensure heat both sides as it improves the stretch of the sheet a bit.

Your shape is simple so it should 'drape' quite well. There are lots of vacuum forming tricks you might be surprised at but they are used for quite high volume applications, like inside fridge doors.

 

Not a difficult project,if you get help for the forming.You can make a former from plywood and sand it smooth-grainy fir is not a good idea.Find a sign making company and ask them about doing the forming for you as they make lots of formed acrylic signs in most towns.As mentioned above,they are likely to use a fabric layer over your former and unless you component exceeds the available sheet size or the limitations of their oven,you will be set for a good outcome.

 

well . no I wasn't referring to vacuum formers.

I am referring to simple drape moulds encased in a plywood shell to retain and hold the heat uniformly, while an electric blower shoots hot air into the space.

 

You can't really vacuum form thick sheets. I know manufactures that can do 1/4", but most prefer much thinner stock. Besides, you don't need anything like this for a one off combing.

The obvious path is a stiff, non-corrugated board template. Maybe even some of the cheap FRP panels from Lowe's/Depot. Once the template is cut and trimmed to fit, it can be reinforced over a buck so a piece of sheet plastic can be placed over it. I'd cut a hole (~12"x24") in the middle of it to offset stresses, as it sags and starts to conform to the mold. Conversely, you could use the template and cut the sheet plastic to dimension, then heat it, so it forms the combing shape. This will leave a seam, but you can weld or glue this after it's shaped and cooled. This is probably how I'd do it, just because it easy and you don't have to try trimming it to shape after it's be molded. Lastly, sand the outboard edges with 220, progressing up through 1500 grit, wet/dry paper, preferably at a relatively slow speed, rounding the edge over as you go. As the last step, take a propane torch to the edge, after it's sanded round and lightly wave it along, which will smooth out the sanding marks and "caramelize" the edge. Be careful not to scorch or burn the edge, just a quick wave will make it look quite professionally done.