Fiberglass help

[jtrollin]

So I put the layers of fiberglass on my 10's windshield and went to start sanding it today. As I was sanding it pieces of the fiberglass started to peel off (like .5' by 3'). Some places were clearly blisters in the glass, but other places it is as if the glass never stuck in the first place.

At this point I been sanding down areas where this is occurring and removing the glass. Once this is done what do I do to make this look right and not crack in the future.

Should I remove as much as I can with a sander and start over again.

Fill it in with body filler and be done with it.

or something else.

thanks,

[Kyle Boatright]

What products are you are using? What brand and product of epoxy or polyester resin, what cloth (what weight), etc.

Also, how wet are you getting the cloth? Maybe you aren't getting enough resin in there to properly wet-out the layup.

[Ron B.]

Are you talking about the grass bonding to the alum., windscreen , or the layup itself is delaminating? The blusters are in the layup, or between the layup and alum., windscreen?
Ron

[Mike S]

In addition to Ron's and Kyle's questions above, how did you prep the surfaces you were working on, and what did you use to clean everything when you were done prepping them?

Also, was the epoxy old, if so, how had it been stored?

What did you mix the epoxy in??? I was always told not to use anything with a wax coating, like some paper bowls/cups have.

[jtrollin]

Epoxy is west systems and is new

I mixed it in a paper cup (no wax) using the pump kit and then added some black epoxy stain to make it black.

I have 10oz cloth I used. The first 6-8 layers appear to be fine, it is the last layers that did not seem to stick well. I had some issues getting the cloth to lay flat on along the curve.

I would take plastic and pour the resin on the plastic, lay the glass down fold the plastic over and work the resin in with a credit card until it was all covered in resin, then I would lay the strips up.

I prepped the aluminum and windscreen with 60 grit sand paper and then cleaned the plexy with alcohol and the aluminum with mek.

I have some delamination at the top where the glass sits on the plexy (last layer) and some in random places. I am trying to sand and pull off all the lose pieces, but not sure what to do when that is done.


I hope that answers everything

[David Shelton]

I'd sand away the suspicious fiberglass, smooth it out with a little filler, then add another fresh ply or two on top.

[Vlad]

I had delamination issue almost like yours and traced it to cold weather. I was doing windshield during winter months everything was perfect - mixture/layup/fresh west system epoxy but in a couple months it started peeling. I sanded it off completely and redid during the summertime. I see the temperature is not the case in your work.

[Mike S]

Pretty hard to determine from a distance, what the cause is.

It sounds like you did pretty much everything right, at least the stuff that has been discussed so far. The only thing I can think of, from what you have described, is if you only mixed one batch of resin, and did the entire job with it, and the final layups were starting to kick a little, thus not bonding well to the layer below??

One thing I like to do with this type of layup is to over wet it the previous layer, and lay the next layer on dry, and stipple it really good, this will wet out the layer quite well, then ad a bit more resin, another layer of glass, and repeat as needed.

For the fuse to windshield bottom layup, cutting the cloth on a 45 makes it lay flat quite nicely.

[Pat Stewart]

If its just some spots on the outer two plys I would not worry about it. I actually put a few pop rivets in the fiberglass as an extra safety measure holding the glass to the forward skin. The entire surface will get covered with west systems filler and you will do the actual sanding on the filler. Unless you have big bubbles don't spend much time sanding the glass.

[Finley Atherton]

This may not apply in your case but I had small voids/air bubbles along the length of the transition point where the fiberglass overlapped the edge of the glass layer immediately below. Subsequent sanding would break through into these voids and cause a small amount of lifting of the thin sanded glass. I see you used a relatively heavy 10 oz cloth. This tendency to form an air void could be exacerbated by using a heavy less flexible cloth.

Vans instructions say to start with the narrowest lay-up first and end with the widest. I have built a Varieze and the standard practice for multiple glass layers on inside corners (such as the lower windscreen fairing) is the opposite, starting with the widest lay-up first and ending with the narrowest on top. This avoids joggles (weak spots) in each individual lay-up and any possibility of air being trapped as described above. If I was doing my fairing again I would use the Varieze method.

As for your current predicament I would firstly remove any glass that can be EASILY pulled/sanded away. This is subjective, but if not too much has to be removed I doubt that strength would be compromised as your lay-up would be thick (and strong) because you used heavy 10 oz cloth. If you think it needs an extra layer or two then apply a thin layer of flox/epoxy mix over the area to fill any voids before adding the extra layers. If using more than one extra layer then I suggest laying up the wider strip first to avoid new voids/air bubbles.

Fin
9A