Smooth epoxy/fiberglass layup
 

In the past, it took several fill coats and sanding or expensive vacuum bagging gear to get a smooth layup.
The "drier" you can lay up glass, the stronger it is by weight. The trouble comes when you want a smooth finish. If you sand a typical dry layup, you will sand right into the glass itself. The old solution is to add as many fill coats as necessary to cover the glass and get a sandable margin.
Recently I found this simple method to get quick results.
Lay up your glass as you normally do, them apply a film of 10 mil mylar or similar plastic over the wet epoxy, squeegee out any air bubbles and excess resin, and let cure.
Once cured you can peel off the mylar.
What the film does is compact the layup, squeeze out excess resin, and leave a surface as smooth as the mylar itself.
I have not done any large areas yet, since my current project involves only resin coating with no glass.
I used 4 once E-glass over some scraps of virola marine plywood. 4 ounce is about as heavy as you can go and achieve a transparent layup over wood.

Wet layup:
http://i810.photobucket.com/albums/z...y/epoxy001.jpg

Mylar placed over one section of glass:
http://i810.photobucket.com/albums/z...y/epoxy003.jpg

Air and excess squeezed out with plastic squeegee:
http://i810.photobucket.com/albums/z...y/epoxy004.jpg

results from previous sample. Part of the sample was left as usual with the fabric weave showing.
http://i810.photobucket.com/albums/z...y/epoxy007.jpg

That is a reflection of the trees in our yard out the window.

Another view:

http://i810.photobucket.com/albums/z...y/epoxy006.jpg

This was junk resin. You can see some small bubbles in the otherwise glass smooth surface. I think those were from the foam in the resin, I literally wrung out the paint roller to get some resin to make this sample. it was frothy white in the cup.

What you can do with it:
Bend over large radii.

What you can't do with it:
lay over a compound curve in a single piece. It will not warp in two directions.
The answer is to use strips and butt them together. This will form some small raised seams in the finish. You can cut those off with fine grit paper.

This is where I found it:
A new Technique for Epoxy-Glass
I figure this could be handy for building aeroshells, etc.

Wow! The 'finished' pics are after you removed the mylar?? A-Ma-Zing!!

The lack of a smooth finish has always been one of the reasons I disliked doing 'straight fiberglass' on the outside of a project... always thought the only way to get a decent smooth finish was to build a mold first... a bit more work than I wanted to do for a large one-off part... but this approach is so straightforward and simple... Awesome!!

Thank you for sharing!

You are welcome.
Looks like the mylar is still on there, doesn't it ?
I'll pull that other sample in the first pics in the morning and post that too.

[QUOTE=skyking;291010]A related technique, used with epoxy, is covering the layup with peel ply, which can be formed into a compound curve. This leaves a surface that permits secondary bonding without the need for sanding. But it also permits light sanding, in preparation for painting, without getting down to the glass. Sanding with 150 grit, then using a high fill primer and one sanding of that is usually enough prep for finish painting.

Bubbles might be a little easier to work out of peel ply. Both techniques can be useful for different conditions. (Peel ply replaces the fiberglass fabric weave surface with a much finer dacron weave, which is not glossy.)

Thanks Ken. I have used peel ply in the past, usually for preparing for a subsequent additional layup.

skyking ,Thanks for your in depth post on this.
I am going to try this technique on my fiberglass/foam truck camper build. Anyone have a cheap source for Mylar? I already tried the rolled polyethylene from Home Depot and it seems to stretch under the squeegee and leave a less than flat surface. Also, what was the thickness of the Mylar you used.

I purchased it at a fiberglass supply house for ~$3 a running foot, 48" wide. It seems to be about 10 Mil. I am trying out some HDPE today. If it releases as well I think I have a decent source for it. I recently purchased coroplast from a nearby vendor who also has rolls of this HDPE.

Another approach that works better than Mylar, is Glad Wrap.

It's much more flexible, is thin, and works as an excellent mold release.

Jim.

The glad wrap easily wrinkles and does not transmit a flat surface onto your job. It does work as mold release and I use it to put under parts I don't want stuck to the table.

[QUOTE=Ken Fry;291021]Ken, I have learned that peel ply is Polyester Taffeta at the discount fabric store :)
I am buying some for $2.45 per yard in 48" width to do some testing.

I have had great luck with it.

I lay up the glass, impregnate with resin, stretch the wrap over the epoxy, and tape it down beyond the wetted area to keep it tight.

And it's stretchable, so it conforms to 3D surfaces.

Works good.

If it wrinkles, then something is shifting and causing the wrinkle.

Jim.

how do you work the air out from under it? I use a plastic squeegee with the mylar and heavier films.

you can also spray with gellcoat, then PVR over the top. the PVR seals the air off so the Gellcoat will kick.

all of these methods leave a thin coat, which is great if you are dimensions are very close to final. My problem is when I am building something new, I often have to take 1/8 to 1/2 inch off to make the body right, which means I need to eat into the glass.

And for that, I sand down past where I want, then skim it with bondo, lots of elbow grease with sandpaper to make it smooth, then paint over it.

Most of this to make the plug of course as once you have a final product, you can make a mold and from then on the bondo is needed a lot less.

This wrinkling (smooth waves really) is what I found as well with the 4 mil poly . But I did not tape it down beyond the wetted area like 3 wheeler suggested. Sooo I will try again.

Hope this thread continues as these tricks and tips are hard to dig up on the web. Especially the fiberglass / foam info. By the way I think the best book I found on Fiberglass/foam is "Advanced Composite Techniques" by Zeke Smith

Rutan's Moldless Composite Construction is another pretty good one. The Gudgeon brothers have put out a magazine for years with interesting tips, too... can't think of the name, but the WEST system epoxy site would have links.

Another issue with poly film it that is is rarely smooth in the way that mylar is. Even stretched tight, its surface has little bumps and waves (near microscopic) that show up on a glossy surface.

For those interested in very lightweight with foam-cored composites, standard vacuum bagging has the disadvantage of leaving a lot of resin in the foam surface pores. If the thing you are making permits using panels as you would use thin plywood, then you can squeegee fiberglass cloth in epoxy onto a large piece of plate glass (treated with a good mold release). Then, prime one foam side with microbubbles in epoxy, which can be about half the weight of epoxy alone. Flip this onto the table over the fiberglass. Vacuum bag and cure. Peel the panel off the table. Make the second skin the same way.

The resulting panel is perfectly flat and shiny on both sides, and can be single curvature bent into place (the curvature depending upon skin thickness vs core thickness, core stiffness, etc etc.) onto a structure, such as an airplane wing (albeit not around the leading edge) maybe about from 15% on back.

A little extreme in terms of labor to save some epoxy weight.

The people who have built Vari-Eze planes have gotten pretty good at this. The idea is to get the foam nearly perfect in shape, before using any filler at all. This is right about at my patience limit -- especially on something like a wing that has to be a particular size at each point. On stuff like an autobody, if you sand too deep, just go to the other side of the car and make it too deep there too. If you need to, make up a name for that aero feature -- any German name should do. I used to have a windsurfer with an Ophibi dent or some such... to promote earlier planing. I think they just dropped the plug and didn't want to fix it.

(You can translate the stuff below for polyester -- it can be a little different, and I rarely use it, other than as Bondo) Once the shape is right, coat with microbubbles in epoxy, and lightly sand that. If there are places where you've gone through the micro, recoat and sand some more. Then lay on the cloth and squeegee on the epoxy. Unfortunately, this is when the waves show up that you didn't see when it was micro surfaced, which is flat, not glossy. I've painted things with glossy paint prior to glassing just to see the surface better. Then that can be sanded to matt to allow the epoxy to bond well. But the better the surface prior to any glass, the easier things go.

But I have never really gotten the hang of it, anyway. However, on boats, where the substrate is wood, this works more easily. One sanding after the glass goes on, followed by rolling on another coat of epoxy, followed by one more sanding is usually enough that the boat can be varnished without any filler used at all. (If you need to use filler, you simply convince yourself that you really wanted a painted boat anyway.)

BTW June sounds good. I'll reply also wherever you mentioned the trike fest.

Oh, another thing that can be helpful: When you have large areas to fill and fair with a surrounding surfaces (I've done this on sailboat keels, which are airfoil shapes that people obsess over) is to apply the first layer of filler with a notched trowel. (I think West system sells small plastic ones for this purpose.)

Then, sanding to shape is pretty easy, because you don't have to sand so much stuff. The second layer of filler fills in the valleys and the sanded ridges guide the squeegee, so very little final sanding is required.

all good points, Ken. I like the notched trowel trick.
I tried the the poly film tonight, it was a no-go for me. Not enough hands and too big a part. They don't call it cling wrap for nothing :)
somebody asked about a supply for mylar. I stopped at the wholesaler, and the best they could do was $200 for a 200' x 53" x .005!
I had hoped for better. She is checking on some 15 mil HDPE. IT *might* be stiff enough to work.

mostly what I have figured out is I can dream BIG, and throw something BIG together. Then I need to hire someone to make the waves, holes, bumps, etc all go away.
Those I hire are scared to think BIG - they can't dream of making the overall shape, but once I have a REALLY UGLY shape laid out, I can find people to sand and bondo for hours and hours for only 5 bucks an hour.

That can be a really good solution. DIYers can be their own worst enemies, at times, by failing to turn over parts of the project to others.

I generally don't weld stuff together that goes to a customer -- I just don't seem to have the level of skill anymore. Good enough for my own stuff. I find it a little hard to to turn welding over to an artiste, but admire the results.

The POC has a mix -- all the steel done by me, all the aluminum done by an artiste. Occasionally, someone will say "Wow, did you do all the welding?" and I have to fess up: "Yep, all the ones that look like wads of bubble gum. I hired out all the good-looking ones."

I can farmer weld steel - lots of penetration, lots of weld, super strong, looks like crap.

I can teach others to be a GOOD welder. One guy worked for me last year I hire to come back and weld stuff for me - he has moved on to another car builder but we are friends.

I am HORRIBLE at body work - absolutely no patience for it.

If I have time to set up and get things dialed in, I can make pretty. I will be doing that soon for my "headache rack" behind the cab. I picked up the steel yesterday. 1.5 square by 0.072, it is going to be a multipurpose mount for a ladder rack, my aeroshell, travel trailer deflector. I will have to take my time with this as it will likely be out there in the public as long as I have the truck.
Now the bumper frame is a different subject. If you want to lay on your back and criticize my welds, be my guest :D

This might be the solution, If only I could find a sample of it to try:
GBC EZLoad Nap I Educational Roll Film 3 Mil 25 x 250 Box Of 2 by Office Depot

It is 3 mil. One box of it would last me a long time.

Great idea!
The aeroshell, will it be polystyrene foam covered with glass and epoxy?

look at my truck pic. It will be 4 MM Meranti marine ply finished bright.

Funny, sounds just like me. I used to teach welding. I can easily get lots of penetration, especially on thin pipes -- blast right through all the time.

Ditto re body work... right on my patience edge.

We should work together -- we could make some really ugly stuff!

I have the bumper installed on the truck, and all the lovely welds are quite out of sight:)

How cool! Did you do it stitch-and-glue style? My POC prototype is mainly 4mm okume, skinnned in and out with 4oz glass in the central tub area, and unskinned in the unstressed areas. The stuff outside the central fuselage (fenders and wings) is Lite Ply (1/8" white poplar).

No, it has 2x2's behind the joints, cut out with a dado to leave a .75" square void. This was filled with quartersawn Sapele` to form the dark red trim wood.
I used cheap virola marine 3/8's.
I glassed the insides and back only with 4 oz. Outside is epoxy coated, and we shoot system 3 WR-LPU glossy over that this weekend with any luck at all.
If I had it do do over again, there are a ton of things I'd change. Send me a PM if you want the build pics, I am holding off posting them till it is substantially done.

I got a sample of the GBC film I linked above from Home Depot. It looks very promising! I will get some when I do my next layup, probably the glass over the aeroshell.

When I do lay ups I cover the surface with rip stop nylon or polyester fabric. On compound curves I use strips about 2 inches wide. It produces a smooth surface and makes sure that the edges of the composite are embedded in the resin, just peel off the cloth. If another layer is required you have a great surface to do a secondary layup, no sanding.

Some hints I would ad is to make sure you don't have any wrinkles in the fabric. Dont stretch the fabric as it causes the layup to distort.

Where do you get this fabric ... any fabric store ?? And thanks for posting

Search for "Polyester Taffeta"
At the fiberglass supply shops it is called peel ply. It produces a totally different effect than the mylar I posted, it leaves a flat, textured surface that does not need any sanding to go on with the next layup. The mylar leaves a mirror-like finish, for that last layer before paint. Only need a bit of sanding to provide "tooth" for the paint to stick to.
The only thing to beware of is any kind of coating it may have from a regular fabric store. That coating, if present, would mess with the bond of a successive layer.
Peel ply is useful when you lay up an area, then plan on bonding a wall or bulkhead to that surface later. Leave the peel ply on to keep it clean while you work on other things.

There is really nothing to beware of. Just go to the local fabric shop and get the color that is on sale. Rip stop is preferred but heavier polyester (dacron) works fine. I have tried smooth plastic and the surface has always needed sanding any way.

another use for polyester is to lay it out over a frame slightly heat it to get it to shrink tight and use it as a wet layup mold. In the ecomod vein I built a molded grill cover and wheel spats for my camo van. The finished result can be seen in my vehicle gallery.

Here's some very useful videos on making FRP molds and parts, using the vacuum method:

[youtube]T9bcZfY-ED0[/youtube]
[youtube]m3HXHqeHSqU[/youtube]
[youtube]qX3r4Q63brI[/youtube]

The fellow Reg Schmeiss in the videos was a member of the Edison2 X-Prize team.

Great tips. Thanks. Made my first project a while back.... was disappointed. Plan to try again.

I just stumbled across the thread. Interesting perspectives all around. Thanks, skyking!

As to the topic: My parents used this technique on craft sized projects in teh 1970s.

I think it influenced my go-to method for chemically stripping paint. Pour the stripper on and cover it with 4mil polyethylene, then squeegee it out instead of brushing. I did this on the roof of a Squareback, and when I peeled the plastic back, 70% of the paint was fused to the plastic and I was looking at the original phosphate coating on the German steel. Not so much luck with vertical surfaces but it really holds the volatiles to the task.

Citrus based strippers, not the stuff with Methyl Mercury.