Please help!

I have pretty much completed the glassing of the wing with polyester resin but for some reason there are a few small spots that won't dry. It's as if the catylist has no effect in those areas because they are still sticky - and this is 2 days after the glassing. I tried a second and third coating over these small spots and no luck. I even tried brushing on a few drops of the catylist over the spots and still no luck. Does anyone know what causes this? Should I just sand away these spots and use a patch piece of new cloth?

Thanks for the help!
Chris

Just a guess, but it sounds like you did not mix the
batch well enough.

Because the amount of catylist is so small, for polyester
it makes mixing that much more important.

Eddie Weeks
http://www.corpcomp.com/weeks1/

I agree with Eddie about mixing.
You can wipe the wet ( sticky) areas with acetone to remove the excess resin before sanding, and then patch with new glass cloth, and polyester resin.
Ron

Ok, I will be sure to mix more thoroughly in the future. I appreciate the help!

Chris

Polyester resin won't cure when applied over some epoxies (and possibly other glues ). When I say "won't cure"..this means forever I'm afraid.
The smell and compatabily problems pushed me away from polyester years ago after similar problems. I only use epoxy resins or at times. water based urethanes.
You will have to scrape, grind, gouge, whatever it takes to remove the area that is not cured. I really don't think you have a mixing problem..let us know what you find.

I have had this problem in the past, the problem was not the way I mixed the polyester but the fact that I had some epoxy (cured) on the surface that I glassed. Every spot where there was epoxy the polyester resin did not cure. This was rather confusing because I am sure that I had been able to glass with polyester over epoxy before this.
I guess I had just chosen two resins that were VERY incompatible.

The epoxy problem may be the trouble. The worst spots are along the two seams where the wing halves meet the wing center piece - epoxied together - Is it possible that I could lay down a coat of thin CA over the problem areas and attempt to glass over that, or will CA cause the resin not to cure also?

-Chris

I have heard that some CA's can have the same effect on polyester as epoxy but I don't have any first hand experience with this being a problem.
You might want to try it on a small area first just to see if it will work.
I switched to epoxy after I had that experience with polyester (just like RandyL), and have been very happy with results ever since. I use either West Systems, or EZ Lam epoxy.

Kevin,
Where do you purchase West Systems products? I've heard a lot of people say they use it, but I don't remember ever seeing it in a local hobby shop or advertised in magazines.
Thanks, Johnny

Aerospace Composites
http://www.acp-composites.com

Thanks for reminding me, I need to order some stuff from them this week!

Not sure about the CA idea or possibly using water based poly-u as an under base. Myself, I would just use epoxy resin after getting all the un cured polyester off... then continue on with epoxy resin for the remainder of the project.
I use a resin that I buy at the local hardware store. There is a bit about the product and its use on my F-4 page of my home site.

You can repair/fix your polyester or epoxy glass wet spots with CA.

Just use acetone to remove the wet spot, put a small patch of cloth in place and dribble a few drops of thin CA over the cloth. Block sand with 220 grit on a block and prime as needed.

Works for me.

Oops,

I screwed up, Aerospace Composites carries EZ-Lam, not West Systems.

I get West System from CST.
http://www.cstsales.com/

I have used West system in my business (furniture business) and also making cedar strip canoes, gallons upon gallons worth. It is THE epoxy to use many industries, started off mainly in boat building but has taken over in many others. Allways cures, ALLWAYS! Its the best epoxy and the numerous hardeners and fillers that go along with it make it a complete system.

Just go to any decent marina or boat repair shop and they will have it. I guarantee once you have used West System's epoxy system you wont use anything else.

AJC

Sounds like you have the old polyester over epoxy incompatibility concern.

You need to remove the uncured polyester by whatever means you can, first.

Patch a piece of cloth in over those areas with any finishing epoxy or CA because epoxies cure over polyester.

Z-Poxy Finishing Resin, from Pacer, cures over polyester and epoxy and is easy to sand. It doesn't have the strength of WEST Systems though.

Chris,
If you plan on priming over your glass job, and if you use a compatible polyester based primer (i.e. Duratec, etc.) can allow the uncured base resin to finally kick off and harden. It's worked for me on larger automotive fiberglass panels versus trying to sand/remove the uncured resin.

That's an interesting thought about the primer. Well, last night I rubbed the uncured spots with acetone and got rid of the stickyness. I sanded the areas and looks like I'm good to go in terms of patching. I think I will pick up some epoxy resin and patch/finish my jet with that since it sounds like that's going to be my safest bet. This is my first jet (JHH F86) and at this point I've been working on it for so long that I just want to get it finished and see if the dang thing will fly!

thanks for all the input!

Chris

I just had the same problem on the elevators of my Bobcat. The resin on the bottom of the elevator over a small amount of cured CA.

I sanded this all off after cleaning with Acetone, and patched the area with CA soaked fiberglass and sanded smooth..

Problem solved..

-Doug

Use the CA method, you will be done and working on something else while you are waiting for the Epoxy to set up!